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MRI of the female pelvis
M R I of the F e m a l e P e l v i s Anne M. Kennedy, Maryellyn R. Gilfeather, and Paula J. Woodward MRI is a proven modality to evaluate the female pelvis. Excellent soft tissue contrast, sensitivity for the detection of fluid, and the multiplanar imaging capabilities of MR allow noninvasive demonstration of normal anatomy and pathological processes. Most female pelvic MRI studies are performed to answer specific questions and must, therefore, follow carefully developed protocols, which are discussed in this article. The principal MRI techniques and strategies outlined in this work include: (1) the evaluation of reproductive dysfunction, anatomic variants; (2) specific obstetrical applications; (3) oncologic evaluation and tumor staging; {4) problem solving (ie, the characterization of abnormalities detected by ultrasound); and (5) the evaluation of urethral disease.
Copyright© 1999by W,B. Saunders Company
RI IS A PROVEN modality to evaluate the
female pelvis. Excellent soft tissue contrast, M sensitivity for the detection of fluid, and the multiplanar imaging capabilities of MRI allow noninvasive demonstration of normal anatomy and pathological processes. With dedicated pelvic coils and rapid scanning techniques, pelvic MRI studies can be completed quickly with minimal patient discomfort. Most female pelvic MRI studies are performed to evaluate and stage known malignancies, define anatomy, or answer questions remaining after ultrasound or other imaging modalities have been performed. Because these are dedicated studies to answer specific questions, they need to follow a carefully developed protocol and, if possible, be supervised by a radiologist experienced in pelvic MRI. The optimal scanning parameters for evaluating the female pelvis are outlined in Table 1. This article discusses MRI techniques and problem-solving strategies for the following areas: 1. Evaluation of reproductive dysfunction, anatomic variants, and specific obstetrical applications 2. Oncologic evaluation and tumor staging 3. Specific problem solving such as the characterization of abnormalities detected by ultrasound and the evaluation of urethral disease NORMAL ANATOMY
The uterus is of homogeneous intermediate signal on Tl-weighted images; therefore, these images are not of much value for evaluating uterine
From the Department of Radiology, University of Utah Medical Center, 50 N Medical Dr, Salt Lake City, UT 84132. Address reprint requests to Anne M. Kennedy, MD, Department of Radiology, University of Utah Medical Center, 50 N Medical Dr, Salt Lake City. UT84132. Copyright © 1999 by W.B. Saunders Company 0887-2171/99/2004-0005510.00/0 214
disorders. The uterine zonal anatomy is clearly shown, however, on T2-weighted images (Fig 1). The endometrinm has high signal with T2 weighting, whereas the inner myometrium, also known as the junctional zone, has low signal. The remainder of the myometrium is of intermediate signal on T2-weighted images. The cervix, like the rest of the uterus, has intermediate signal on Tl-weighted images. On T2-weighted images, the normal cervical stroma shows low-signal intensity. Frequently, the endocervical canal is visualized as a thin, high-signal stripe (Fig 1). The ovaries show intermediate- to low-signal on Tl-weighted images. On T2-weighted images, the normal ovarian stroma has intermediate signal and the fluid-filled follicles show high-signal strength. Three distinct layers of the vagina can be identified on T2-weighted images. A central high-signal stripe is produced by secretions and marks the site of the vaginal mucosa. This stripe is most prominent in the middle of the menstrual cycle. The submucosa and muscularis (composed of both longitudinal and circular muscles) appear as a low-signal band. The adventitia, together with the vaginal venous plexus, is high in signal on T2weighted images, because of slow flow in small blood vessels. Urethral zonal anatomy is consistently displayed on T2-weighted images. Often, the lumen is identified as a central high-signal dot attributed to the presence of a small amount of urine or mucus. If this dot is not seen, the center of the urethra shows the low-signal mucosa. The submucosa has moderately high signal, and the muscularis shows lowsignal intensity.* The normal fallopian tube is too thin to be identified with MR scanning, but a hydrosalpinx can be identified as a tubular, fluid-filled structure separate from the ovary (Fig 2). Longitudinally
Seminars in Ultrasound, CT, and MRI, Vo120, No 4 (August), 1999: pp 214-230
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Table 1. Scanning Parameters for 1.5T Magnet BASICSEQUENCES TR
TE
NEX
Flip Angle
ETL
Slice Thickness
Coronal Iocalizer
8
Min
2
30 °
6, skip 0
Axial T1
400
Min
2
90 °
5 or 6, skip 1
Axial FSE T2
4000-6000
100
2 to 4
90 °
12
Sagittal FSE T2
4000-6000
100
2 to 4
90 °
8-12
TR
TE
NEX
Flip Angle
ETL
Slice Thickness
Coronal FSE T2
4000-6000
100
2 to 4
90 °
12
5 or 6, skip 1
Donut
4000-6000
100
2 to 4
90 °
12
4, skip 1
Fat Sat T1
50-150
Min
1 or 2
80 °
5-8, skip 1
FMPSPGR
100-150 or 50-150
Min
1 or 2
80 °
4 5-7, skip 1
5 or 6, skip 1
Application To check position of pelvic coil. Do with body coil in MDAs to check renal location Conventional display of anatomy Conventional display of anatomy Establish long axis of uterus, normal anatomy
ADDITIONALSEQUENCES Application Evaluate fundal contour of uterus to classify MDA (Oblique along long axis of uterus) To stage cervical cancer (Oblique plane perpendicular to long axis of cervix) To differentiate high signal blood from fat After gadolinium tissue enhancement Dynamic enhancement allows better assessment of invasiveness of endometrial cancer
Note: All patients are imaged with the pelvic coil. Frequency is anterior to posterior, The patient is instructed to have a partially full bladder. Glucagon 1 mg i.m. is given immediately before the study. Abbreviations: TR, repetition time; TE, time to echo; NEX, number of excitations; ETL, echo train length; FMPSPGR, fast multiplanar spoiled GRASS; MDA, m011erian duct anomalies; MIN, minimum, ie, shortest possible.
orientated, blunted mucosal folds specifically identify dilated fallopian tubes. High-signal loci within the dilated tube on Tl-weighted sequences suggests endometriosis as a cause of tubal obstruction. 2 BENIGN CYSTS
Benign vaginal and cervical cysts are frequently identified with MRI. It is important to be familiar with the appearances and typical locations of these common benign findings to avoid confusion with significant pathological processes,
Gartner's Duct Cyst Gartner's duct cysts develop in remnants of the wolfian duct system. They are situated anterolaterally in the upper two thirds of the vagina. On MRI, these have low-to-intermediate signal on T1-
weighted images, depending on the protein content of the cyst fluid. Gartner's duct cysts show highsignal intensity on T2-weighted images (Fig 3), occur in 1% to 2% of females, and are often incidental findings. Because they can be associated with other genitourinary anomalies, it is important to check the extended field-of-view localizer for renal abnormalities. Gartner's duct cysts can be confused clinically with urethral diverticulae. The distinction is important, as diverticulae require surgical correction, but a cyst can be managed with aspiration and sclerosis. 3 MRI can easily differentiate between these two entities.
Bartholin's Cyst Bartholin's cysts (Fig 4) occur in the posterolateral wall of the lower third of the vagina and in the
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Fig 1. Normal anatomy on FSE T2-weighted images. (A) Normal sagittal view of the uterus. This patient has a retroflexed uterus. (E, endometrium; J, junctional zone; M, myometrium) (B) Normal "donut" view. (B, bladder; C, cervix; P, parametrial fat, R, rectum) (C) Normal coronal view of the ovaries. Short white arrows indicate follicles. Long white arrows indicate intermediate signal ovarian stroma. The asterisk is a dominant follicle in the left ovary. (D) Normal urethra on axial images. The asterisk identifies the low signal mucosa, the short black arrow indicates the intermediate signal submucosa, and the long black arrow indicates the low signal muscularis.
labia. They have similar MR characteristics to Gartner's duct cysts. The diagnosis is made on the basis of the anatomic location. If they become infected, thickened walls develop and show rim enhancement with contrast administration.
Nabothian Cysts Mucous distention of endocervical glands causes nabothian cysts, which are well-circumscribed, 1to 3-mm cysts located within the cervix. When small, they are asymptomatic and easily recognized on ultrasound and MRI (Fig 5). Rarely, they can enlarge and cause confusion by appearing as a cystic adnexal mass? The signal characteristics of nabothian cysts depend on the protein content of the mucus on Tl-weighted images. They are invari-
ably high signal on T2-weighted images and well circumscribed (Fig 5). REPRODUCTIVE DYSFUNCTION
Developmental Anomalies In the female embryo, the paired mtillerian ducts join in the midline to form the uterovaginal primordium, which gives rise to the uterus, the fallopian tubes, and the upper two thirds of the vagina. The primitive germ cells migrate to the embryonic gonadal ridge. The ovaries arise from these cells and subsequently descend into the pelvis. The lower third of the vagina arises from the vaginal plate. It is, therefore, possible to have normal ovaries and external genitalia in the presence of
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Fig 2. Hydrosaipinx and normal ovary. (A) Axial FSE T2-weighted images showing uterus (U), both ovaries (O), and an extra-ovarian fluid-filled mass (H). (B) Coronal FSE T2-weighted images confirm the coiled tubular nature of the fluid-filled mass and prove that it is a hydrosalpinx.
severe developmental anomalies of the internal genital tract. In the United States, approximately 15% of couples suffer from infertility.5 The incidence of abnormal uterine development is significantly higher in patients with reproductive dysfunction than in the general population. Part of this difference is because of selection bias, but it is estimated that up to 67% of patients with mttllerian duct anomalies have some form of reproductive dysfunction. These include recurrent miscarriage, intrauterine growth retardation, and preterm labor. 6 The American Fertility and Sterility Society
Fig 3. Gartner's duct cyst. Axial FSE T2-weighted images. The white arrow indicates the pubic symphisis. Asterisk indicates a well-circumscribed, high-signal cyst in the anterolateral wall of the vagina. This is a Gartner's duct cyst. (V, vagina),
classifies mtillerian duct anomalies according to the system developed by Buttram and Gibbons in 1979, 7 which is shown in Fig 6. Management depends on the nature of the anomaly. For example, a uterine septum (class V) can be excised hysteroscopically, because the outer contour of the uterus has a normal convex shape. Surgical correction of a bicornuate uterus (class IV) requires metroplasty via an open abdominal incision. This is because the outer contour of the uterus is abnormally concave. Oblique coronal fast spin-echo (FSE) T2-weighted images along the long axis of the uterus clearly show the outer contour of the uterine fundus,
Fig 4. Bartholin's cyst, Axial FSE T2-weighted images. Well-circumscribed, high-signal cyst within the right labia is a Bartholin's cyst (*). (I, ischial tuberosity.)
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KENNEDY, GILFEATHER, AND WOODWARD
Fig 5. Nabothian cyst. Sagittal FSE T2-weighted images. B, bladder. The white arrow indicates normal, low-signal cervical stroma. Within the cervix a well-circumscribed, high-signal nabothian cyst (*) is present.
allowing accurate, noninvasive preoperative differentiation between these entities. (Fig 7) It is important to diagnose unicornuate uterus in patients undergoing assisted conception. Such patients are at increased risk for ectopic pregnancy. If ectopic pregnancy occurs, tube-sparing surgery or treatment can be performed in an attempt to preserve reproductive function. Vaginal septa that occur secondary to abnormal lateral mt~llerian duct fusion may be oriented longitudinally or vertically. These septa may cause vaginal obstruction, and, if so, the patient usually presents at menarche (Fig 7) with pelvic pain) If vaginal septa are left untreated, endometriosis may develop, which may cause chronic pelvic pain and infertility.9 Transverse vaginal septa occur as a result of failure of union of the downward-growing mUllerian duct system with the upward-growing urogenital sinus. A more severe consequence of this failure of fusion is cervical agenesis, 1°,1~ Vaginal
Fig 7. Septate uterus and obstructed vagina. Coronal FSE T2-weighted images. The long black arrows indicate the normal uterine fundal contour. This is a septate uterus with the septum extending into the vagina (short black arrow), which is obstructed. Bilateral hematocolpos (*) has occurred as a result of the vaginal obstruction.
septa are most commonly seen in association with class III mtillerian duct anomalies. Approximately 25% of mtillerian duct anomalies are associated with renal or ureteric abnormalities, with the highest incidence (up to 40%) seen in association with class II anomalies. 12 The associated renal anomalies include ipsilateral renal agenesis, ectopia, fusion, malrotation, and duplication. In MRI examinations on mtillerian anomaly patients, the coronal locaiizer is performed with the body coil, and an extended field of view that includes the kidneys should be used (Fig 8).
Other Causes of Reproductive Dysfunction Hormonal abnormalities and ovulatory dysfunction are most often diagnosed on clinical and biochemical grounds. In some cases, patients with
( Partial or complete mullarlan ageneais ) Class II Unicornuate Uterus
Class IV BIcornuate Uterus
Class V
Septate Uterus
Class III Uterus Didolphys
Class Vl Anomalies A~sociatedwith DES
Fig 6. Classification of mQIlerian duct anomalies. Diagrammatic representation of the various subclasses of mQIlerian duct anomalies. (Reprinted with permission. 34)
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Fig 8. Bicornuate uterus with associated right renal agenesis. (A) Axial FSE T2-weighted images. (R, right horn; L, left horn of bicornuate uterus.) (B} Extended field-of-view coronal Iocalizer shows absence of the right kidney. (K, left kidney.)
these conditions may undergo imaging to confirm abnormal ovarian morphology, such as is seen with polycystic ovarian disease. This diagnosis should be made cautiously, however, as patients undergoing ovarian stimulation for infertility also have abnormally enlarged ovaries with increased numbers of follicles (Fig 9). Uterine synechiae, myomata, and adenomyosis are all associated with impaired fertility. In many cases, MRI can diagnose these uterine abnormalities. Synechiae are adhesions within the uterine cavity that occur secondary to instrumentation. They are best diagnosed on hysterosalpingography. On T2-weighted MR images, they appear as low signal intensity bands traversing the high signal endometrium. ~3 Leiomyomata can impair reproductive function in a variety of ways, including tubal obstruction and prevention of implantation. They also are associated with spontaneous abortion and and pre-
term labor.14,~5In patients who are under evaluation for infertility, determining the size and location of uterine leimyomas is important to plan appropriate therapy. Intramural fibroids, which do not distort the uterine cavity or the cornua, are usually not treated surgically. Hysteroscopic resection is an option for the patient with submucosal leiomyoma, which can cause fertility problems (Fig 10). It is important to differentiate between focal adenomyosis and a submucosal leiomyoma. Both conditions present clinically with uterine enlargement, abnormal bleeding, and pain, but adenomyosis is not a cause of infertility. The only treatment currently available for adenomyosis is hysterectomy. In the infertile patient, attempted hysteroscopic resection of focal adenomyosis would not
Fig 9. Polycystic ovary. Axial FSE T2-weighted images. The ovaries are enlarged with central, low-signal stroma surrounded by multiple small peripheral immature follicles. (R, right ovary; L, left ovary.)
Fig 10. Submucosal leiomyoma. Sagittal FSE T2-weighted images. The uterus is retroflexed. A submucosal fibroid (*) deforms the endometrial cavity (E). The normal myometrium (M) is of intermediate-signal intensity.
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only be unlikely to succeed, but would also be unlikely to impact the patient's chances of successful conception. Focal adenomyosis shows lowsignal on T2-weighted images, has irregular margins and an elongated contour, and is in continuity with the junctional zone. In contrast, leiomyomata are round and generally well defined, although a variety of appearances are described. Uncomplicated leiomyomas are well circumscribed and show intermediate signal on Tl-weighted images and low signal on T2-weighted images. Degenerated leiomyomas show areas of high signal on T2weighted images (Fig 11). Endometriosis is defined as the presence of endometrial epithelium and stroma outside of the uterus. Approximately one third of patients with endometriosis have reproductive dysfunction, which in theory is related to scarring, fibrosis, and adhesion formation, all of which impair ovulation and tubal motility. The gold standard for the diagnosis of endometriosis is laparoscopy. MR has a role, however, in patients with extensive adhesions that preclude adequate laparoscopy and as a noninvasive method for evaluating response to treatment. 16 Endometriosis appears as focal areas of increased Tl-signal within the pelvic soft tissues. It is important to perform a Tl-weighted sequence with fat saturation in the evaluation of patients suspected of having endometriosis, as small implants may blend into the high-signal pelvic fat with conventional Tl-weighted images. 17,18 Endometriomas
Fig 11. Multiple uterine leiomyomata. Coronal FSE T2weighted images. Multiple leiomyomata are present; these can be subserosal (3), intramural {2), or submucosal [1). The exact location of flbroids is well shown, allowing accurate presurgical evaluation. (E, endometrium.)
KENNEDY, GILFEATHER,AND WOODWARD
Fig 12. Diffuse adenomyosis. Sagittal FSE T2-weighted images. The normal junctional zone measures less than a centimeter. In this case the junctional zone (J) was markedly increased in thickness. The normal myometrium is seen as a peripheral zone of intermediate-signal intensity. (E, endometrium.)
show high-signal on Tl-weighted images, and intermediate to low signal on T2-weighted images. The loss of signal on T2-weighted images is known as T2 shading. OBSTETRICAL MRI
Ectopic Pregnancy Although ultrasound is the principal modality used in the assessment of ectopic pregnancy, MRI can be used in difficult cases as a primary or confirmatory means of diagnosis. One such application is the diagnosis of cervical ectopic pregnancy (Fig 13). Although cervical ectopic implantation is rare, correct diagnosis is extremely important because these patients are treated medically with methotrexate rather than surgically because of the risk of hemorrhage. In a small series of patients in whom planned abortion had been unsuccessful, Kwon et all9 performed MRI to clarify the reasons for failed termination. In some cases, ectopic gestation was the cause, and these appeared as heterogenous masses on T2-weighted images. After administration of gadolinium, enhancing frond-like strands were seen that corresponded to villous structures on pathological assessment of the surgical specimens. 19It should be noted that intravenous gadolinium is normally contraindicated in pregnancy. Abdominal pregnancy is extremely rare but life threatening for both the mother and the fetus. MRI
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allow the parents the option of pregnancy termination. ONCOLOGIC IMAGING It is estimated that gynecologic cancers caused at least 25,000 deaths in 1997 (Table 2). MRI is used in patients with gynecologic malignancies to confirm diagnosis, to stage the tumor, and to establish radiation therapy ports. MRI also is used to assess response to treatment and to evaluate complications of treatment. At 6 months or more after treatment, MRI is also useful to differentiate between recurrent disease and scar tissue. 22,23 Cervical Carcinoma Fig 13. Cervical ectopic pregnancy, Sagittal FSE T2weighted images. The ectopic gestation (G) has implanted into the posterior cervical stroma. The white arrow shows a "claw" of cervical stroma extending around the gestation sac, indicating that this has embedded into the cervix and is not free within the cervical canal. M, myometrium; E, endometrium,
is quite useful in this condition. 2°,21 It assists in confirming the diagnosis of abdominal pregnancy, which can be quite difficult sonographically. Furthermore, MRI can be used to monitor involution of the adherent placenta. Placental Abnormalities
Placenta accreta, percreta, and increta represent different grades of penetration of the placenta into or through the uterine muscularis. These conditions occur in patients with prior caesarean section and either low-anterior placental location or placenta previa. The diagnosis of these potentially lethal conditions can be confirmed and the degree of placentai invasion into surrounding tissues can be accurately documented with MRI. Proper diagnosis allows for planned elective delivery at tertiary care centers. Fetal MRI
Preliminary experience suggests that MRI may also have a role to play in the assessment of fetal anomalies. Conditions such as renal agenesis are difficult to diagnose confidently with ultrasound, because of the associated profound oligohydramnios, which impairs fetal visualization. MRI can confirm the diagnosis of renal agenesis by noninvasively showing the absence of fetal kidneys. Early diagnosis of lethal fetal anomalies is essential to
Patients with cervical carcinoma present with abnormal bleeding, abnormal physical examination, or abnormalities detected on Papanicolaou smear. The staging criteria for cervical carcinoma were established by the Federation of Gynocology and Obstetrics (FIGO) on the basis of clinical examination and widely available radiologic investigative modalities, such as barium enema and intravenous pyelogram. This system was established to develop a standardized staging approach that allowed for meaningful communication among institutions worldwide (Table 3). The key issue in the management of cervical carcinoma is accurate staging, particularly in determining whether or not parametrial invasion has occurred. Once parametrial invasion occurs, the patient is not a surgical candidate, and radiation therapy is the treatment of choice. If the uterus remains in place, radioactive implants can be placed in the endometrial and cervical canals. Implants provide targeted radiation to diseased tissue while minimizing the radiation dose to adjacent structures and are preferable, therefore, to external beam irradiation. MRI is now used extensively to evaluate patients with cervical carcinoma, but the exact role of MRI is controversial. Many centers, including ours, follow the guidelines established by Hricak and Yu in 1996. 24 For tumors less than 2 cm in size, no Table 2. Estimated New Cases and Deaths Caused by Gynecological Tumors in 1997 (USA)
Ovary Endometrium Cervix Data from ref 35,
New Cases
Deaths
26,800 34,900 14,500
14,200 6,000 4,800
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Table 3. FIGO Staging of Cervical Carcinoma Stage
IA IB II
IIA liB III
IliA IIIB IV IVA IVB
Definition Carcinoma in situ Carcinoma confined to the cervix (extension to the corpus disregarded) Microinvasive Clinically invasive Carcinoma extends beyond cervix without extension to the lower third of the vagina or to the pelvic wall. No parametrial involvement Parametrial involvement Carcinoma extends to the pelvic wall and/or the lower third of the vagina; ureteral obstruction No extension to the pelvic wall Extension to the pelvic wall and/or ureteral obstruction Carcinoma extends beyond the true pelvis or involves the urinary bladder or rectum Spread to adjacent organs Distant metastases
imaging is justified. For tumors greater than 2 cm in size, MRI is the modality if choice. This approach recognizes the low probability of local extension with small tumors. In clinical stage IB disease (tumor confined to the cervix) the prevalence of bladder or rectal involvement is 0%, and the overall probability of parametrial invasion is 12%. For tumors greater than 2 cm, however, the likelihood of parametrial invasion increases to 28%. Similarly, nodal involvement increases with tumor size, and the presence of nodal metastases is of prognostic significance. With an overall accuracy of 90% to 94%, MRI is the study of choice for determining parametrial invasion of cervical cancer. 24 MRI represents a substantial improvement over traditional FIGO staging methods. When the results of clinical staging with FIGO criteria are compared with surgical staging, error rates for FIGO staging of 27% to 32% are reported in stage IB disease and up to 67% at stages II to IV.24 Furthermore, the use of MRI as the initial study obviates the use of the barium enema and intravenous pyelogram and results in a net cost saving by decreasing the number of invasive procedures and other tests required. 25When MRI findings are equivocal, other tests are used in a directed manner to answer specific questions. On T2-weighted images, the normal cervical stroma is uniformly low in signal. Cervical carcinoma appears as an area of high signal within the
low-signal stroma (Fig 14). On a short axis, or "donut" view of the cervix, a completely intact ring of cervical stroma has a 100% negative predictive value in excluding parametrial invasion. 26 The signs described in parametrial invasion are discontinuity of the normal low-signal stroma, asymmetric tumor bulge, irregular soft tissue extension into the parametrium, and thickening of the uterosacral ligaments. Unfortunately, one or more of these findings can be seen without actual parametrial involvement, which reduces the accuracy of MRI diagnosis of parametrial invasion to 94%. Extension to the pelvic side wall implies stage III disease and is characterized by the following features: vascular encasement, increased signal of muscle on T2-weighted images, obliteration of normal fat planes, and tumor mass within 3 mm of the pelvic side wall. Adenopathy is well characterized on MRI. There is an 88% accuracy rate for the detection of abnormal nodes when the diagnostic criterion of a short axis greater than 1 cm is used. The likelihood of nodal involvement in cervical carcinoma increases with the increasing size of the tumor. Gadolinium is not routinely given in the assessment of cervical carcinoma but can he of benefit if there is concern for fistula formation or the presence of necrotic nodes. The fistulous track will enhance after gadolinium administration.
Endometrial Carcinoma Endometrial carcinoma is the most gynecological malignancy, with peak occurring between the ages of 55 and Despite the fact that it is the most
common incidence 65 years. common
Fig 14. Stage liB cervical cancer, FSE T2-weighted "donut" images. A cervical carcinoma {C} entirely replaces the normal, low-signal cervical stroma. The black arrows indicate irregular extension into the parametrium on the right, confirming stage liB disease. (B, bladder; R, rectum.)
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gynecologic malignancy, it is not a leading cause of cancer deaths in women. The death rate from endometrial cancer has markedly decreased because of early diagnosis and effective therapy. Endometrial carcinoma cannot be accurately differentiated from hyperplasia and endometrial polyp on the basis of MRI alone; therefore, the role of MRI in patients with endometrial carcinoma is to provide accurate staging (Table 4). On T2-weighted images, the signal intensity of endometrial carcinoma is similar to or slightly lower than normal endometrium. Myometrial invasion is best assessed on Tl-weighted, gadolinium-enhanced sequences, as the tumor enhances less than the normal endometrium. The use of gadolinium also allows differentiation between abnormal endometrium and blood clot or debris within the endometrial lumen. The latter are nonvascular and do not show enhancement. Tumor staging depends on the depth of myometrial invasion. In the normal patient, the endometrium is surrounded by a low-signal junctional zone. If this zone is intact, invasive disease is virtually excluded. It is important to remember, however, that junctional zone thickness is decreased in postmenopausal patients. A thin junctional zone should not be mistaken for tumor invasion. The junctional zone may also be thinned by distention of the uterine cavity, either by blood, debris, or a polypoid tumor. If the junctional zone is not well seen, invasion is assessed by the appearance of the endometrium-myometrium interface, which normally is smooth. An irregular interface suggests invasion of the myometrium. Invasion is considered superficial when only the inner half of the myometrium is involved and is considered deep when tumor extends to the outer half as well (Fig 15). The goals of MRI staging in endometrial carciTable 4. FIGO Staging of Endometrial Carcinoma Stage O IA IB IC II Ill IVA IVB
Definition Carcinoma in situ Tumor limited to the endometrium Invasion of less than half of the myometrium Invasion of more than half of the myometrium Invasion of the cervix, but no extent into periuterine tissue Tumor extends beyond the uterus, but not outside the true pelvis Tumor invades bladder, rectum, or extends beyond the true pelvis Distant metastases
Fig 15, Endometrial carcinoma. Coronal FSE T2-weighted images, A Foley catheter is in the urinary bladder, The white arrows show invasion of the myometrium by less than 50% indicating superficial invasion,
noma are to accurately delineate the relationship of the tumor to the myometrium and cervix; to detect local invasion of the vagina, bladder, and rectum; and to evaluate for adenopathy. The staging accuracy of MRI for endometrial carcinoma is 74% with stage I disease and 89% in detecting superficial invasion. The likelihood of nodal involvement in endometrial carcinoma correlates with the depth of invasion of the tumor. This is in contrast to patients with cervical carcinoma, in whom the likelihood of adenopathy increases with the size of the primary tumor. 26 Ovarian Carcinoma
Although the incidence of ovarian carcinoma is less than that of endometrial carcinoma, it is the leading cause of death from gynecologic malignancy. This is largely because of the late stage of tumor development at the time of presentation. Seventy-five percent of patients have disease beyond the ovaries, and 60% have spread of disease beyond the pelvis at the time of diagnosis. 27 Only about 30% of patients are considered surgically curable by total abdominal hysterectomy and bilateral salpingo-oophorectomy. Ovarian malignancies are classified according to the cell type of origin. They are divided into epithelial (70%), stromal (5% to 10%), and germcell (15%) tumors. Metastases account for 5% to 10% of ovarian tumors. Epithelial tumors are most
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Table 5. Summary of FIGO Criteria for Staging Ovarian Cancer Stage I Stage II Stage III
Stage IV
Fig 16. Mucinous cystadenoma of the left ovary. Axial FSE T2-weighted images. The uterus is surgically absent. White arrows indicate a large, fluid-filled mass with multiple fine septations. (R, right ovary.)
common, and those appear as complex cystic masses on MRI. They show intermediate signal intensity on Tl-weighted images but sometimes contain layering debris or hemorrhage that has high T1 signal. They also show high signal on T2weighted images and may have septations, papillary excrecences, and/or solid components. The differentiation between benign and malignant ovarian epithelial tumors is based on morphology. Malignancy is more likely in the presence of papillary excrecences, irregular septations, and complex internal architecture (Figs 16 and 17). FIGO staging criteria for ovarian carcinoma
Tumor limited to the ovary Tumor involving one or both ovaries with pelvic extension Tumor involving one or both ovaries with intraperitoneal metastases outside the pelvis and/or positive retroperitoneal or inguinal nodes, including superficial liver metastases; tumor limited to the true pelvis with histologically proved malignant extension to small bowel or omentum Tumor involving one or both ovaries with distant metastasis, parenchymalliver metastasis, malignant pleural effusion
(Table 5) were established on the basis of laparotomy findings. MRI is accurate in ovarian carcinoma staging, with published rates as high as 83%. 26 One area in which MRI has an advantage over other imaging modalities is in the demonstration of peritoneal implants. These are most common in the right paracolic gutter, and may extend cephalad to beneath the right hemidiaphragm. Particular attention for metastases should also be given to the rectovesical pouch and the greater omentum. Axial gadolinium-enhanced, T 1-weighted images with fat saturation are helpful in showing peritoneal implants, evaluating for nodal necrosis, and differentiating between papillary projections and adherent clot in the ovarian mass.
Fig 17. Ovarian stromal cancer, (A) Sagittal FSE T2-weighted images show a large mass with mixed cystic and solid components, No normal ovary was identified on this side. (B) Coronal FSE T2-weighted images confirm the presence of a complex solid mass, Note the differences in appearances between this carcinoma and the benign ovarian mass shown in Fig 16. (C, cervix; B, bladder,)
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Fallopian Tube Carcinomas Carcinomas of the fallopian tubes are rare adenocarcinomas that appear as solid masses showing low-signal intensity on Tl-weighted images, high signal on T2-weighted images, and enhancement with gadolinium. They often present sonographically as an adnexal mass, making it difficult to differentiate between this tumor and an ovarian primary. MRI can aid in this differentiation, because its multiplanar imaging capabilities enable visualization of a normal adjacent ovary. 27
Vagina Vaginal carcinoma is an uncommon tumor, representing only 1% to 2% of female genital tract carcinomas. The majority of vaginal tumors result from local spread of cervical or uterine tumors. 8 Patients with vaginal carcinoma usually present with painless vaginal bleeding. There are 2 main subtypes of primary vaginal tumors. Squamous carcinomas constitute more than 90%. These tend to arise in the posterior wall of the proximal third of the vagina. Clear cell carcinoma of the vagina is a subtype of adenocarcinoma that occurs in daughters of women exposed to diethylstilbestrol (DES) during pregnancy. DES was widely prescribed for pregnant women in the United States from 1947 to 1971. It continued to be sold in the rest of the world into the late 1980s. There are an estimated 10 million DES mothers and daughters in the United States today. Clear cell carcinomas arise in young women, usually less than 35 years of age, and usually are located in the anterior wall of the proximal third of the vagina. Approximately one in a thousand women exposed to DES in utero develops this tumor. Alternative differential considerations for vaginal tumors include melanoma and sarcoma botyroides (in infants).
Vulvar Carcinomas Five percent of genital tract malignancies are vulvar primary tumor. These are easily diagnosed clinically, but MRI can be used to define the extent of the soft-tissue mass and to look for nodal involvement (Fig 18). MRI AS A PROBLEM SOLVER
The Adnexal Mass One of the most common diagnostic dilemmas in pelvic imaging of women is the adnexal mass.
Fig 18. Vulvar carcinoma. (A) Axial FSE T2-weighted images. The white arrows indicate an intermediate-signal mass in the right side of the vulva extending into the vagina. This was biopsied and proved to be a squamous carcinoma. (B} Axial FSE T2-weighted images. The normal left labia is indicated by the large arrow. The small arrows delineate a complex mass in the right vulva, which was biopsied and proved to be a sarcoma.
Simple cysts are beautifully shown on ultrasound, but characterizing a part cyst-part solid mass can be challenging. Less than 10% of complex adnexal masses are malignant, with a ratio of 11 benign masses to 1 malignant mass surgically removed. 28 MRI allows more detailed assessment of these lesions, and in some cases provides a specific diagnosis that obviates surgery. In 1994, Schwartz et al29 reviewed the impact of MRI on adnexal mass treatment decisions. Of 49 patients originally scheduled for surgery, 73% either did not have surgery or had a less invasive procedure after MRI evaluation. The change in management had no adverse effect on patient outcome, but the net cost savings were in
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excess of $1700 for each patient in whom surgery was avoided. 29 Some of the specific uses of MRI in evaluating pelvic masses are discussed later in this article. If an adnexal mass appears bright on Tl-weighted images, a Tl-weighted sequence with fat saturation should be performed. This clearly distinguishes fat (which will lose signal on fat saturation sequences) from blood products (which will remain bright on fat saturation sequences) (Fig 19). The ability to easily perform fat saturation can confirm the diagnosis of a fat-containing teratoma. Lesions containing blood products include
KENNEDY, GILFEATHER, AND WOODWARD
hemorrhagic cysts and endometriomas. Recurrent episodes of bleeding in an endometrioma results in very high local concentrations of iron, much greater than would occur in a simple hemorrhagic cyst. There are no definite distinguishing features between benign and malignant ovarian masses. The addition of a gadolinium-enhanced, Tl-weighted sequences with fat saturation, however, aids in detection of peritoneal implants and necrotic lymph nodes. These findings are seen only with malignancy. It can occasionally be difficult to determine the
Fig 19. Endometrioma. (A) Axial Tl-weighted images show a high-signal mass (E) in the expected location of the left ovary. (B) Axial FSE T2-weighted images show the normal uterus (U). The mass that was high signal on T1 shows loss of signal and some heterogeneity on T2-weighted sequence. (C) Axial T1-weighted images with fat saturation. The high-signal mass does not lose signal, confirming that it is not fatty in nature but represents blood products consistent with an endometrioma.
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origin of large pelvic masses with ultrasound. Differentiation between a pedunculated serosal fibroid and a solid ovarian mass is crucial, particularly in a patient who wishes to preserve fertility. The multiplanar capability of MR/can help determine the origin of a pelvic mass in difficult cases, as shown in Fig 20. Pelvic Pain
Chronic pelvic pain is defined as pain persisting for longer than 6 months. Patients with this condition are often subjected to extensive investigations and psychological analysis and may undergo total abdominal hysterectomy and bilateral salpingooophrectomy without symptomatic relief. M R / i s of diagnostic benefit in pelvic pain patients in two ways: First, MRI provides noninvasive assessment of the bladder, urethra, rectum, and genital tract, second, MR/helps to identify unrecognized sources of pain such as pelvic venous congestion and peritoneal inclusion cysts. Enlarged parametriai and pelvic veins seen in a patient with chronic pelvic pain suggest the diagnosis of pelvic venous congestion. Patients with this finding can be referred to the appropriate specialist for careful clinical assessment and consideration for pelvic venous mapping. 3° Medical treatment is available for women with pelvic venous congestion, enabling them to avoid unnecessary invasive procedures and surgery (Fig 21). Fig 21. Pelvic venous congestion. (A) Axial Tl-weighted images. Bilateral serpiginous structures are identified in the parametrial fat (white arrows). (B) Axial FSE T2-weighted images confirm the serpiginous nature of enlarged vessels. This patient had a hysterectomy, and the presence of such enlarged vessels despite hysterectomy is strongly suggestive of pelvic venous congestion.
Fig 20. Pedunculated leiomyoma. Coronal FSET2-weighted images. A large pedunculated leiomyoma (P) is clearly shown to be separate from the ovaries (O) and the uterus (U). Incidental note is made of the presence of a submucosal myoma (S) within the uterus.
Peritoneal inclusion cysts (also known as peritoneal pseudocyst) result from entrapment of ovarian secretions by peritoneal adhesions. They occur in women of reproductive capacity with a past history of surgery or peritoneal inflammation. The appearance of these cysts has been well described in the imaging literature. 3~,32 The diagnostic features include the following: (1) a history of surgery or pelvic inflammation; (2) a cyst without mass effect; (3) cyst "walls" formed by adjacent normal structures; and (4) an ovary that is either part of the "wall" or is suspended within a network of adhesions.
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Fig 22, Peritoneal inclusion cyst, Sagittal FSE T2-weighted images. White arrows indicate the ovary surrounded by a septated fluid collection in this patient with a history of multiple urologic surgeries,
The fluid retained in a peritoneal inclusion cyst is serous; therefore, it has low signal on Tl-weighted images and high signal on T2-weighted images. It is important to recognize a peritoneal inclusion cyst (Fig 22) as a benign condition that can be treated with aspiration of fluid and ovarian suppression. Surgery is not indicated for these cysts. Adenomyosis is characterized by the presence
Fig 24. Urethral diverticulum complicated by stone formation. (A) Axial FSE T2-weighted images obtained with the endovaginal coil, The urethral lumen is marked by a Foley catheter containing high-signal urine (F), The low-signal mass (*) surrounding the Foley catheter is a stone within a urethral diverticulum, (B) Sagittal FSE T2-weighted images of same patient as (A). Foley catheter can be seen within the urethra, The urethral diverticulum contains a stone (*).
Fig 23. Urethral diverticulum, Axial FSE T2 images obtained with an endovaginal coil. The urethra (U) is surrounded by high-signal intensity diverticulae (*),
of endometrial tissue within the myometrium. Symptoms of this condition include chronic pelvic pain. Diffuse adenomyosis is diagnosed on MRI when the junctional zone on T2-weighted images measures greater than 1 cm (Fig 12). Focal adenomyosis has been discussed above as a differential consideration for submucosal leiornyoma.
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Urethral Disease Urethral disease processes in women can present with nonspecific symptoms. Patients with urethral disease are often misdiagnosed as having urinary tract infections and therefore take repeated courses of antibiotic without symptomatic relief. Urethral diverticulae are most common in the mid-urethra and occur more often on the posterior wall than the anterior wall. Urethral diverticulae are thought to result from inflammation and trauma of the periurethral glands, leading to local glandular dilatation. The diverticula are often distended with urine; therefore, they have low signal on T1 and high signal on T2-weighted images 1 (Fig 23). Complications of urethral diverticula, such as stone formation and tumor, are readily demonstrable with M R / ( F i g 24). Although voiding cystourethrograms and plain radiographic studies can occasionally show urethral diverticula, MRI has several advantages compared with these studies: it is noninvasive, there is no requirement for the patient to urinate, and the anatomic relations of the cysts to surrounding structures are well shown. A developing role for MRI in gynecological
urology is the evaluation of patients with stress incontinence. By using fast MRI scanning techniques, supine and prone resting and straining images can be performed. Rapid scanning allows physiological information to be obtained in addition to the anatomic information. Complications of implantable sphincter devices for urinary incontinence also can be evaluated with MR/. With these devices, the urethra is subject to erosion, fistula formation, and periurethral abscess. 33
CONCLUSION M R / i s a safe, noninvasive, and effective diagnostic tool to evaluate the female pelvis. The ability of MRI to concisely define anatomy and disease is unequalled by any other imaging modality. The cost-effectiveness of MRI has been proven in the assessment of cervical carcinoma and the evaluation of adnexal masses. As a radiologist, it is exciting to see our involvement with M R / i m p r o v ing diagnostic accuracy, resulting in the selection of appropriate treatment methods and the avoidance of unnecessary surgery.
REFERENCES
1. Kim B, Hricak H, Tanagho EA: Diagnosis of urethral diverticulae in women: Value of MR imaging. AJR Am J Roentgenol 161:809-815, 1993 2. OutwaterEK, SiegelmanES, ChiowanichP, et al: Dilated fallopiantubes:MR imagingcharacteristics.Radiology208:463469, 1998 3. Abd-Rabbo MS, Atta MA: Aspiration and tetracycline sclerotherapy: A novel method for managementof vaginal and vulvalGartnercysts. Int J GynaecolObstet 35:235-237, 1991 4. TogashiK, Noma S, Ozasa H: CT and MR demonstration of Nabothiancysts mimickinga cystic adnexal mass. J Comput Assist Tomogr 11:1091-1092, 1987 5. ClarkRL, KeefeB: Infertility:lmagingofthe female. Urol Radiol 11:233-237, 1989 6. ButtramVC: Mulleriananomaliesand their management. Fertil Steri140:159-163, 1983 7. Buttram VS, Gibbons WE: MnllerianAnomalies:A proposed classification (An analysis of 144 cases). Fertil Steril 42:40-46, 1979 8. Siegelman ES, Outwater EK, Banner MP, et al: High resolution MR imaging of the vagina. Radiographics 17:11831203, 1997 9. Lin CC, Chen AC, Chen TY: Double uterus with an obstructed bemivaginaand ipsilateralrenal agenesis: Report of 5 cases and a review of the literature. J Formos Med Assoc 90:195-201, 1991 10. Markham SM, ParmleyTH, MurphyAA, et al: Cervical
agenesis combined with vaginal agenesis diagnosed by magnetic resonanceimaging.Fertil Steri148:143-145, 1987 11. Bakrl YN, A1-SugairA, Hugusson C: Bicornuate nonfused rudimentary horns with functioning endometria and complete cervical-vaginalagenesis:Magneticresonancediagnosis. Fertil Steri158:620-621, 1992 12. Brody JM, Koelliker SL, Fishman GN: Unicornuate uterus: Imaging appearance, associated anomalies,and clinical implications.AJR Am J Roentgenol171:1341-1647, 1998 13. WoodwardPJ, WagnerBJ, FarleyTE: MR imagingin the evaluation of female infertility. Radiographics 13:293-310, 1993 14. McCarthy S: MR imaging of the uterus. Radiology 171:321-322, 1989 15. Dudiak CM, qharnerDA, Patel SK: Uterine leiomyomas in the infertile patient, preoperative localization with MR imaging versus ultrasoundand hysterosalpingography.Radiology 167:627-630,1988 16. Bis KG, Vrachliotis TG, Agrawal R, et al: Pelvic endometriosis:MR imagingspectrumwithlaparoscopiccorrelation and diagnosticpitfalls.Radiographics 17:639-655, 1997 17. Outwater EK, Dunton CJ: Imaging of the ovary and adnexa: Clinical issues and applications of MR imaging. Radiology 194:i- 18, 1995 18. Arrive L, ttricak H, Martin MC: Pelvic endometriosis: MR imaging.Radiology 171:687-692, 1989
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19. Ha HK, Jung J, Kang SJ, et al: MR imaging in the diagnosis of rare forms of ectopic pregnancy. AJR Am J Roentgenol 160:1229-1232, 1993 20. Hall JM, Manning N, Moore NR, et al: Antenatal diagnosis of a late abdominal pregnancy using ultrasound and magnetic resonance imaging: A case report of successful outcome. Ultrasound Obstet Gynecol 7:289-292, 1996 21. Wagner A, Burchardt AJ. MR Imaging in advanced abdominal pregnancy. A case report of fetal death. Acta Radiol 36:193-195, 1995 22. Sugimura K, Carrington BM, Quivey JM, et al: Post irradiation changes in the pelvis: Assessment with MR imaging. Radiology 175:805-813, 1990 23. Ebner K, Kressel HY, Mintz MC, et al: Tumor recurrence versus fibrosis in the female pelvis: Differentiation with MR imaging at 1.5 T. Radiology 166:333-340, 1988 24. Hricak H, Yu KK: Radiology in invasive cervical cancer. AJR Am J Roentgenol 167:1101-1108, 1996 25. Hricak H, Powell CB, Yu KK, et al: Invasive cervical cancer: Role of MR imaging in pretreatment work up---cost minimization and diagnostic efficacy analysis. Radiology 198: 403-409, 1996 26. Patel VH, Somers S: MR imaging of the female pelvis: Current perspectives in review of genital tract congenital anomalies and benign and malignant diseases. Crit Rev Diagn Imaging 38:417-499, 1997
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27. Troiano RN, McCarthey S: Magnetic resonance imaging evaluation of adnexal masses. Semin Ultrasound CT MR 15:38-48, 1994 28. JainKA: Magnetic resonance imaging of ovarian masses. The Radiologist 2:259-268, 1995 29. Schwartz LB, Panageas E, Lange R, et al: Female pelvis: Impact of MR imaging on treatment decisions and net cost analysis. Radiology 192:55-60, 1994 30. Palter SF, Olive DL: Office microlaparoscopy under local anaesthesia for chronic pelvic pain. J Am Assoc Gynecol Laparosc 3:359-364, 1996 31. Sohaey R, Gardener T, Woodward PJ, et al: Sonographic diagnosis of peritoneal inclusion cysts. J Ultrasound Med 14:913-917, 1995 32. Kurachi H, Murakami T, Nakamura H, et al: Imaging of peritoneal psendocysts: Value of MR imaging compared with sonography and CT. AIR Am J Roentgenol 160:589-591, 1993 33. Siegelman ES, Banner MP, Ramchamdani P, et al: Multicoil MR imaging of symptomatic female urethral and periurethral disease. Radiographics 17:349-365, 1997 34. Wagner BJ, Woodward PJ: Magnetic resonance evaluation of congenital uterine anomalies. Semin Ultrasound CT MR 15:4-17, 1994 35. American Cancer Society: Cancer Facts & Figures-1997. New York, NY, American Cancer Society, 1997.
Copyright© 1999by W,B. Saunders Company
RI IS A PROVEN modality to evaluate the
female pelvis. Excellent soft tissue contrast, M sensitivity for the detection of fluid, and the multiplanar imaging capabilities of MRI allow noninvasive demonstration of normal anatomy and pathological processes. With dedicated pelvic coils and rapid scanning techniques, pelvic MRI studies can be completed quickly with minimal patient discomfort. Most female pelvic MRI studies are performed to evaluate and stage known malignancies, define anatomy, or answer questions remaining after ultrasound or other imaging modalities have been performed. Because these are dedicated studies to answer specific questions, they need to follow a carefully developed protocol and, if possible, be supervised by a radiologist experienced in pelvic MRI. The optimal scanning parameters for evaluating the female pelvis are outlined in Table 1. This article discusses MRI techniques and problem-solving strategies for the following areas: 1. Evaluation of reproductive dysfunction, anatomic variants, and specific obstetrical applications 2. Oncologic evaluation and tumor staging 3. Specific problem solving such as the characterization of abnormalities detected by ultrasound and the evaluation of urethral disease NORMAL ANATOMY
The uterus is of homogeneous intermediate signal on Tl-weighted images; therefore, these images are not of much value for evaluating uterine
From the Department of Radiology, University of Utah Medical Center, 50 N Medical Dr, Salt Lake City, UT 84132. Address reprint requests to Anne M. Kennedy, MD, Department of Radiology, University of Utah Medical Center, 50 N Medical Dr, Salt Lake City. UT84132. Copyright © 1999 by W.B. Saunders Company 0887-2171/99/2004-0005510.00/0 214
disorders. The uterine zonal anatomy is clearly shown, however, on T2-weighted images (Fig 1). The endometrinm has high signal with T2 weighting, whereas the inner myometrium, also known as the junctional zone, has low signal. The remainder of the myometrium is of intermediate signal on T2-weighted images. The cervix, like the rest of the uterus, has intermediate signal on Tl-weighted images. On T2-weighted images, the normal cervical stroma shows low-signal intensity. Frequently, the endocervical canal is visualized as a thin, high-signal stripe (Fig 1). The ovaries show intermediate- to low-signal on Tl-weighted images. On T2-weighted images, the normal ovarian stroma has intermediate signal and the fluid-filled follicles show high-signal strength. Three distinct layers of the vagina can be identified on T2-weighted images. A central high-signal stripe is produced by secretions and marks the site of the vaginal mucosa. This stripe is most prominent in the middle of the menstrual cycle. The submucosa and muscularis (composed of both longitudinal and circular muscles) appear as a low-signal band. The adventitia, together with the vaginal venous plexus, is high in signal on T2weighted images, because of slow flow in small blood vessels. Urethral zonal anatomy is consistently displayed on T2-weighted images. Often, the lumen is identified as a central high-signal dot attributed to the presence of a small amount of urine or mucus. If this dot is not seen, the center of the urethra shows the low-signal mucosa. The submucosa has moderately high signal, and the muscularis shows lowsignal intensity.* The normal fallopian tube is too thin to be identified with MR scanning, but a hydrosalpinx can be identified as a tubular, fluid-filled structure separate from the ovary (Fig 2). Longitudinally
Seminars in Ultrasound, CT, and MRI, Vo120, No 4 (August), 1999: pp 214-230
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Table 1. Scanning Parameters for 1.5T Magnet BASICSEQUENCES TR
TE
NEX
Flip Angle
ETL
Slice Thickness
Coronal Iocalizer
8
Min
2
30 °
6, skip 0
Axial T1
400
Min
2
90 °
5 or 6, skip 1
Axial FSE T2
4000-6000
100
2 to 4
90 °
12
Sagittal FSE T2
4000-6000
100
2 to 4
90 °
8-12
TR
TE
NEX
Flip Angle
ETL
Slice Thickness
Coronal FSE T2
4000-6000
100
2 to 4
90 °
12
5 or 6, skip 1
Donut
4000-6000
100
2 to 4
90 °
12
4, skip 1
Fat Sat T1
50-150
Min
1 or 2
80 °
5-8, skip 1
FMPSPGR
100-150 or 50-150
Min
1 or 2
80 °
4 5-7, skip 1
5 or 6, skip 1
Application To check position of pelvic coil. Do with body coil in MDAs to check renal location Conventional display of anatomy Conventional display of anatomy Establish long axis of uterus, normal anatomy
ADDITIONALSEQUENCES Application Evaluate fundal contour of uterus to classify MDA (Oblique along long axis of uterus) To stage cervical cancer (Oblique plane perpendicular to long axis of cervix) To differentiate high signal blood from fat After gadolinium tissue enhancement Dynamic enhancement allows better assessment of invasiveness of endometrial cancer
Note: All patients are imaged with the pelvic coil. Frequency is anterior to posterior, The patient is instructed to have a partially full bladder. Glucagon 1 mg i.m. is given immediately before the study. Abbreviations: TR, repetition time; TE, time to echo; NEX, number of excitations; ETL, echo train length; FMPSPGR, fast multiplanar spoiled GRASS; MDA, m011erian duct anomalies; MIN, minimum, ie, shortest possible.
orientated, blunted mucosal folds specifically identify dilated fallopian tubes. High-signal loci within the dilated tube on Tl-weighted sequences suggests endometriosis as a cause of tubal obstruction. 2 BENIGN CYSTS
Benign vaginal and cervical cysts are frequently identified with MRI. It is important to be familiar with the appearances and typical locations of these common benign findings to avoid confusion with significant pathological processes,
Gartner's Duct Cyst Gartner's duct cysts develop in remnants of the wolfian duct system. They are situated anterolaterally in the upper two thirds of the vagina. On MRI, these have low-to-intermediate signal on T1-
weighted images, depending on the protein content of the cyst fluid. Gartner's duct cysts show highsignal intensity on T2-weighted images (Fig 3), occur in 1% to 2% of females, and are often incidental findings. Because they can be associated with other genitourinary anomalies, it is important to check the extended field-of-view localizer for renal abnormalities. Gartner's duct cysts can be confused clinically with urethral diverticulae. The distinction is important, as diverticulae require surgical correction, but a cyst can be managed with aspiration and sclerosis. 3 MRI can easily differentiate between these two entities.
Bartholin's Cyst Bartholin's cysts (Fig 4) occur in the posterolateral wall of the lower third of the vagina and in the
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Fig 1. Normal anatomy on FSE T2-weighted images. (A) Normal sagittal view of the uterus. This patient has a retroflexed uterus. (E, endometrium; J, junctional zone; M, myometrium) (B) Normal "donut" view. (B, bladder; C, cervix; P, parametrial fat, R, rectum) (C) Normal coronal view of the ovaries. Short white arrows indicate follicles. Long white arrows indicate intermediate signal ovarian stroma. The asterisk is a dominant follicle in the left ovary. (D) Normal urethra on axial images. The asterisk identifies the low signal mucosa, the short black arrow indicates the intermediate signal submucosa, and the long black arrow indicates the low signal muscularis.
labia. They have similar MR characteristics to Gartner's duct cysts. The diagnosis is made on the basis of the anatomic location. If they become infected, thickened walls develop and show rim enhancement with contrast administration.
Nabothian Cysts Mucous distention of endocervical glands causes nabothian cysts, which are well-circumscribed, 1to 3-mm cysts located within the cervix. When small, they are asymptomatic and easily recognized on ultrasound and MRI (Fig 5). Rarely, they can enlarge and cause confusion by appearing as a cystic adnexal mass? The signal characteristics of nabothian cysts depend on the protein content of the mucus on Tl-weighted images. They are invari-
ably high signal on T2-weighted images and well circumscribed (Fig 5). REPRODUCTIVE DYSFUNCTION
Developmental Anomalies In the female embryo, the paired mtillerian ducts join in the midline to form the uterovaginal primordium, which gives rise to the uterus, the fallopian tubes, and the upper two thirds of the vagina. The primitive germ cells migrate to the embryonic gonadal ridge. The ovaries arise from these cells and subsequently descend into the pelvis. The lower third of the vagina arises from the vaginal plate. It is, therefore, possible to have normal ovaries and external genitalia in the presence of
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Fig 2. Hydrosaipinx and normal ovary. (A) Axial FSE T2-weighted images showing uterus (U), both ovaries (O), and an extra-ovarian fluid-filled mass (H). (B) Coronal FSE T2-weighted images confirm the coiled tubular nature of the fluid-filled mass and prove that it is a hydrosalpinx.
severe developmental anomalies of the internal genital tract. In the United States, approximately 15% of couples suffer from infertility.5 The incidence of abnormal uterine development is significantly higher in patients with reproductive dysfunction than in the general population. Part of this difference is because of selection bias, but it is estimated that up to 67% of patients with mttllerian duct anomalies have some form of reproductive dysfunction. These include recurrent miscarriage, intrauterine growth retardation, and preterm labor. 6 The American Fertility and Sterility Society
Fig 3. Gartner's duct cyst. Axial FSE T2-weighted images. The white arrow indicates the pubic symphisis. Asterisk indicates a well-circumscribed, high-signal cyst in the anterolateral wall of the vagina. This is a Gartner's duct cyst. (V, vagina),
classifies mtillerian duct anomalies according to the system developed by Buttram and Gibbons in 1979, 7 which is shown in Fig 6. Management depends on the nature of the anomaly. For example, a uterine septum (class V) can be excised hysteroscopically, because the outer contour of the uterus has a normal convex shape. Surgical correction of a bicornuate uterus (class IV) requires metroplasty via an open abdominal incision. This is because the outer contour of the uterus is abnormally concave. Oblique coronal fast spin-echo (FSE) T2-weighted images along the long axis of the uterus clearly show the outer contour of the uterine fundus,
Fig 4. Bartholin's cyst, Axial FSE T2-weighted images. Well-circumscribed, high-signal cyst within the right labia is a Bartholin's cyst (*). (I, ischial tuberosity.)
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KENNEDY, GILFEATHER, AND WOODWARD
Fig 5. Nabothian cyst. Sagittal FSE T2-weighted images. B, bladder. The white arrow indicates normal, low-signal cervical stroma. Within the cervix a well-circumscribed, high-signal nabothian cyst (*) is present.
allowing accurate, noninvasive preoperative differentiation between these entities. (Fig 7) It is important to diagnose unicornuate uterus in patients undergoing assisted conception. Such patients are at increased risk for ectopic pregnancy. If ectopic pregnancy occurs, tube-sparing surgery or treatment can be performed in an attempt to preserve reproductive function. Vaginal septa that occur secondary to abnormal lateral mt~llerian duct fusion may be oriented longitudinally or vertically. These septa may cause vaginal obstruction, and, if so, the patient usually presents at menarche (Fig 7) with pelvic pain) If vaginal septa are left untreated, endometriosis may develop, which may cause chronic pelvic pain and infertility.9 Transverse vaginal septa occur as a result of failure of union of the downward-growing mUllerian duct system with the upward-growing urogenital sinus. A more severe consequence of this failure of fusion is cervical agenesis, 1°,1~ Vaginal
Fig 7. Septate uterus and obstructed vagina. Coronal FSE T2-weighted images. The long black arrows indicate the normal uterine fundal contour. This is a septate uterus with the septum extending into the vagina (short black arrow), which is obstructed. Bilateral hematocolpos (*) has occurred as a result of the vaginal obstruction.
septa are most commonly seen in association with class III mtillerian duct anomalies. Approximately 25% of mtillerian duct anomalies are associated with renal or ureteric abnormalities, with the highest incidence (up to 40%) seen in association with class II anomalies. 12 The associated renal anomalies include ipsilateral renal agenesis, ectopia, fusion, malrotation, and duplication. In MRI examinations on mtillerian anomaly patients, the coronal locaiizer is performed with the body coil, and an extended field of view that includes the kidneys should be used (Fig 8).
Other Causes of Reproductive Dysfunction Hormonal abnormalities and ovulatory dysfunction are most often diagnosed on clinical and biochemical grounds. In some cases, patients with
( Partial or complete mullarlan ageneais ) Class II Unicornuate Uterus
Class IV BIcornuate Uterus
Class V
Septate Uterus
Class III Uterus Didolphys
Class Vl Anomalies A~sociatedwith DES
Fig 6. Classification of mQIlerian duct anomalies. Diagrammatic representation of the various subclasses of mQIlerian duct anomalies. (Reprinted with permission. 34)
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Fig 8. Bicornuate uterus with associated right renal agenesis. (A) Axial FSE T2-weighted images. (R, right horn; L, left horn of bicornuate uterus.) (B} Extended field-of-view coronal Iocalizer shows absence of the right kidney. (K, left kidney.)
these conditions may undergo imaging to confirm abnormal ovarian morphology, such as is seen with polycystic ovarian disease. This diagnosis should be made cautiously, however, as patients undergoing ovarian stimulation for infertility also have abnormally enlarged ovaries with increased numbers of follicles (Fig 9). Uterine synechiae, myomata, and adenomyosis are all associated with impaired fertility. In many cases, MRI can diagnose these uterine abnormalities. Synechiae are adhesions within the uterine cavity that occur secondary to instrumentation. They are best diagnosed on hysterosalpingography. On T2-weighted MR images, they appear as low signal intensity bands traversing the high signal endometrium. ~3 Leiomyomata can impair reproductive function in a variety of ways, including tubal obstruction and prevention of implantation. They also are associated with spontaneous abortion and and pre-
term labor.14,~5In patients who are under evaluation for infertility, determining the size and location of uterine leimyomas is important to plan appropriate therapy. Intramural fibroids, which do not distort the uterine cavity or the cornua, are usually not treated surgically. Hysteroscopic resection is an option for the patient with submucosal leiomyoma, which can cause fertility problems (Fig 10). It is important to differentiate between focal adenomyosis and a submucosal leiomyoma. Both conditions present clinically with uterine enlargement, abnormal bleeding, and pain, but adenomyosis is not a cause of infertility. The only treatment currently available for adenomyosis is hysterectomy. In the infertile patient, attempted hysteroscopic resection of focal adenomyosis would not
Fig 9. Polycystic ovary. Axial FSE T2-weighted images. The ovaries are enlarged with central, low-signal stroma surrounded by multiple small peripheral immature follicles. (R, right ovary; L, left ovary.)
Fig 10. Submucosal leiomyoma. Sagittal FSE T2-weighted images. The uterus is retroflexed. A submucosal fibroid (*) deforms the endometrial cavity (E). The normal myometrium (M) is of intermediate-signal intensity.
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only be unlikely to succeed, but would also be unlikely to impact the patient's chances of successful conception. Focal adenomyosis shows lowsignal on T2-weighted images, has irregular margins and an elongated contour, and is in continuity with the junctional zone. In contrast, leiomyomata are round and generally well defined, although a variety of appearances are described. Uncomplicated leiomyomas are well circumscribed and show intermediate signal on Tl-weighted images and low signal on T2-weighted images. Degenerated leiomyomas show areas of high signal on T2weighted images (Fig 11). Endometriosis is defined as the presence of endometrial epithelium and stroma outside of the uterus. Approximately one third of patients with endometriosis have reproductive dysfunction, which in theory is related to scarring, fibrosis, and adhesion formation, all of which impair ovulation and tubal motility. The gold standard for the diagnosis of endometriosis is laparoscopy. MR has a role, however, in patients with extensive adhesions that preclude adequate laparoscopy and as a noninvasive method for evaluating response to treatment. 16 Endometriosis appears as focal areas of increased Tl-signal within the pelvic soft tissues. It is important to perform a Tl-weighted sequence with fat saturation in the evaluation of patients suspected of having endometriosis, as small implants may blend into the high-signal pelvic fat with conventional Tl-weighted images. 17,18 Endometriomas
Fig 11. Multiple uterine leiomyomata. Coronal FSE T2weighted images. Multiple leiomyomata are present; these can be subserosal (3), intramural {2), or submucosal [1). The exact location of flbroids is well shown, allowing accurate presurgical evaluation. (E, endometrium.)
KENNEDY, GILFEATHER,AND WOODWARD
Fig 12. Diffuse adenomyosis. Sagittal FSE T2-weighted images. The normal junctional zone measures less than a centimeter. In this case the junctional zone (J) was markedly increased in thickness. The normal myometrium is seen as a peripheral zone of intermediate-signal intensity. (E, endometrium.)
show high-signal on Tl-weighted images, and intermediate to low signal on T2-weighted images. The loss of signal on T2-weighted images is known as T2 shading. OBSTETRICAL MRI
Ectopic Pregnancy Although ultrasound is the principal modality used in the assessment of ectopic pregnancy, MRI can be used in difficult cases as a primary or confirmatory means of diagnosis. One such application is the diagnosis of cervical ectopic pregnancy (Fig 13). Although cervical ectopic implantation is rare, correct diagnosis is extremely important because these patients are treated medically with methotrexate rather than surgically because of the risk of hemorrhage. In a small series of patients in whom planned abortion had been unsuccessful, Kwon et all9 performed MRI to clarify the reasons for failed termination. In some cases, ectopic gestation was the cause, and these appeared as heterogenous masses on T2-weighted images. After administration of gadolinium, enhancing frond-like strands were seen that corresponded to villous structures on pathological assessment of the surgical specimens. 19It should be noted that intravenous gadolinium is normally contraindicated in pregnancy. Abdominal pregnancy is extremely rare but life threatening for both the mother and the fetus. MRI
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allow the parents the option of pregnancy termination. ONCOLOGIC IMAGING It is estimated that gynecologic cancers caused at least 25,000 deaths in 1997 (Table 2). MRI is used in patients with gynecologic malignancies to confirm diagnosis, to stage the tumor, and to establish radiation therapy ports. MRI also is used to assess response to treatment and to evaluate complications of treatment. At 6 months or more after treatment, MRI is also useful to differentiate between recurrent disease and scar tissue. 22,23 Cervical Carcinoma Fig 13. Cervical ectopic pregnancy, Sagittal FSE T2weighted images. The ectopic gestation (G) has implanted into the posterior cervical stroma. The white arrow shows a "claw" of cervical stroma extending around the gestation sac, indicating that this has embedded into the cervix and is not free within the cervical canal. M, myometrium; E, endometrium,
is quite useful in this condition. 2°,21 It assists in confirming the diagnosis of abdominal pregnancy, which can be quite difficult sonographically. Furthermore, MRI can be used to monitor involution of the adherent placenta. Placental Abnormalities
Placenta accreta, percreta, and increta represent different grades of penetration of the placenta into or through the uterine muscularis. These conditions occur in patients with prior caesarean section and either low-anterior placental location or placenta previa. The diagnosis of these potentially lethal conditions can be confirmed and the degree of placentai invasion into surrounding tissues can be accurately documented with MRI. Proper diagnosis allows for planned elective delivery at tertiary care centers. Fetal MRI
Preliminary experience suggests that MRI may also have a role to play in the assessment of fetal anomalies. Conditions such as renal agenesis are difficult to diagnose confidently with ultrasound, because of the associated profound oligohydramnios, which impairs fetal visualization. MRI can confirm the diagnosis of renal agenesis by noninvasively showing the absence of fetal kidneys. Early diagnosis of lethal fetal anomalies is essential to
Patients with cervical carcinoma present with abnormal bleeding, abnormal physical examination, or abnormalities detected on Papanicolaou smear. The staging criteria for cervical carcinoma were established by the Federation of Gynocology and Obstetrics (FIGO) on the basis of clinical examination and widely available radiologic investigative modalities, such as barium enema and intravenous pyelogram. This system was established to develop a standardized staging approach that allowed for meaningful communication among institutions worldwide (Table 3). The key issue in the management of cervical carcinoma is accurate staging, particularly in determining whether or not parametrial invasion has occurred. Once parametrial invasion occurs, the patient is not a surgical candidate, and radiation therapy is the treatment of choice. If the uterus remains in place, radioactive implants can be placed in the endometrial and cervical canals. Implants provide targeted radiation to diseased tissue while minimizing the radiation dose to adjacent structures and are preferable, therefore, to external beam irradiation. MRI is now used extensively to evaluate patients with cervical carcinoma, but the exact role of MRI is controversial. Many centers, including ours, follow the guidelines established by Hricak and Yu in 1996. 24 For tumors less than 2 cm in size, no Table 2. Estimated New Cases and Deaths Caused by Gynecological Tumors in 1997 (USA)
Ovary Endometrium Cervix Data from ref 35,
New Cases
Deaths
26,800 34,900 14,500
14,200 6,000 4,800
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Table 3. FIGO Staging of Cervical Carcinoma Stage
IA IB II
IIA liB III
IliA IIIB IV IVA IVB
Definition Carcinoma in situ Carcinoma confined to the cervix (extension to the corpus disregarded) Microinvasive Clinically invasive Carcinoma extends beyond cervix without extension to the lower third of the vagina or to the pelvic wall. No parametrial involvement Parametrial involvement Carcinoma extends to the pelvic wall and/or the lower third of the vagina; ureteral obstruction No extension to the pelvic wall Extension to the pelvic wall and/or ureteral obstruction Carcinoma extends beyond the true pelvis or involves the urinary bladder or rectum Spread to adjacent organs Distant metastases
imaging is justified. For tumors greater than 2 cm in size, MRI is the modality if choice. This approach recognizes the low probability of local extension with small tumors. In clinical stage IB disease (tumor confined to the cervix) the prevalence of bladder or rectal involvement is 0%, and the overall probability of parametrial invasion is 12%. For tumors greater than 2 cm, however, the likelihood of parametrial invasion increases to 28%. Similarly, nodal involvement increases with tumor size, and the presence of nodal metastases is of prognostic significance. With an overall accuracy of 90% to 94%, MRI is the study of choice for determining parametrial invasion of cervical cancer. 24 MRI represents a substantial improvement over traditional FIGO staging methods. When the results of clinical staging with FIGO criteria are compared with surgical staging, error rates for FIGO staging of 27% to 32% are reported in stage IB disease and up to 67% at stages II to IV.24 Furthermore, the use of MRI as the initial study obviates the use of the barium enema and intravenous pyelogram and results in a net cost saving by decreasing the number of invasive procedures and other tests required. 25When MRI findings are equivocal, other tests are used in a directed manner to answer specific questions. On T2-weighted images, the normal cervical stroma is uniformly low in signal. Cervical carcinoma appears as an area of high signal within the
low-signal stroma (Fig 14). On a short axis, or "donut" view of the cervix, a completely intact ring of cervical stroma has a 100% negative predictive value in excluding parametrial invasion. 26 The signs described in parametrial invasion are discontinuity of the normal low-signal stroma, asymmetric tumor bulge, irregular soft tissue extension into the parametrium, and thickening of the uterosacral ligaments. Unfortunately, one or more of these findings can be seen without actual parametrial involvement, which reduces the accuracy of MRI diagnosis of parametrial invasion to 94%. Extension to the pelvic side wall implies stage III disease and is characterized by the following features: vascular encasement, increased signal of muscle on T2-weighted images, obliteration of normal fat planes, and tumor mass within 3 mm of the pelvic side wall. Adenopathy is well characterized on MRI. There is an 88% accuracy rate for the detection of abnormal nodes when the diagnostic criterion of a short axis greater than 1 cm is used. The likelihood of nodal involvement in cervical carcinoma increases with the increasing size of the tumor. Gadolinium is not routinely given in the assessment of cervical carcinoma but can he of benefit if there is concern for fistula formation or the presence of necrotic nodes. The fistulous track will enhance after gadolinium administration.
Endometrial Carcinoma Endometrial carcinoma is the most gynecological malignancy, with peak occurring between the ages of 55 and Despite the fact that it is the most
common incidence 65 years. common
Fig 14. Stage liB cervical cancer, FSE T2-weighted "donut" images. A cervical carcinoma {C} entirely replaces the normal, low-signal cervical stroma. The black arrows indicate irregular extension into the parametrium on the right, confirming stage liB disease. (B, bladder; R, rectum.)
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gynecologic malignancy, it is not a leading cause of cancer deaths in women. The death rate from endometrial cancer has markedly decreased because of early diagnosis and effective therapy. Endometrial carcinoma cannot be accurately differentiated from hyperplasia and endometrial polyp on the basis of MRI alone; therefore, the role of MRI in patients with endometrial carcinoma is to provide accurate staging (Table 4). On T2-weighted images, the signal intensity of endometrial carcinoma is similar to or slightly lower than normal endometrium. Myometrial invasion is best assessed on Tl-weighted, gadolinium-enhanced sequences, as the tumor enhances less than the normal endometrium. The use of gadolinium also allows differentiation between abnormal endometrium and blood clot or debris within the endometrial lumen. The latter are nonvascular and do not show enhancement. Tumor staging depends on the depth of myometrial invasion. In the normal patient, the endometrium is surrounded by a low-signal junctional zone. If this zone is intact, invasive disease is virtually excluded. It is important to remember, however, that junctional zone thickness is decreased in postmenopausal patients. A thin junctional zone should not be mistaken for tumor invasion. The junctional zone may also be thinned by distention of the uterine cavity, either by blood, debris, or a polypoid tumor. If the junctional zone is not well seen, invasion is assessed by the appearance of the endometrium-myometrium interface, which normally is smooth. An irregular interface suggests invasion of the myometrium. Invasion is considered superficial when only the inner half of the myometrium is involved and is considered deep when tumor extends to the outer half as well (Fig 15). The goals of MRI staging in endometrial carciTable 4. FIGO Staging of Endometrial Carcinoma Stage O IA IB IC II Ill IVA IVB
Definition Carcinoma in situ Tumor limited to the endometrium Invasion of less than half of the myometrium Invasion of more than half of the myometrium Invasion of the cervix, but no extent into periuterine tissue Tumor extends beyond the uterus, but not outside the true pelvis Tumor invades bladder, rectum, or extends beyond the true pelvis Distant metastases
Fig 15, Endometrial carcinoma. Coronal FSE T2-weighted images, A Foley catheter is in the urinary bladder, The white arrows show invasion of the myometrium by less than 50% indicating superficial invasion,
noma are to accurately delineate the relationship of the tumor to the myometrium and cervix; to detect local invasion of the vagina, bladder, and rectum; and to evaluate for adenopathy. The staging accuracy of MRI for endometrial carcinoma is 74% with stage I disease and 89% in detecting superficial invasion. The likelihood of nodal involvement in endometrial carcinoma correlates with the depth of invasion of the tumor. This is in contrast to patients with cervical carcinoma, in whom the likelihood of adenopathy increases with the size of the primary tumor. 26 Ovarian Carcinoma
Although the incidence of ovarian carcinoma is less than that of endometrial carcinoma, it is the leading cause of death from gynecologic malignancy. This is largely because of the late stage of tumor development at the time of presentation. Seventy-five percent of patients have disease beyond the ovaries, and 60% have spread of disease beyond the pelvis at the time of diagnosis. 27 Only about 30% of patients are considered surgically curable by total abdominal hysterectomy and bilateral salpingo-oophorectomy. Ovarian malignancies are classified according to the cell type of origin. They are divided into epithelial (70%), stromal (5% to 10%), and germcell (15%) tumors. Metastases account for 5% to 10% of ovarian tumors. Epithelial tumors are most
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Table 5. Summary of FIGO Criteria for Staging Ovarian Cancer Stage I Stage II Stage III
Stage IV
Fig 16. Mucinous cystadenoma of the left ovary. Axial FSE T2-weighted images. The uterus is surgically absent. White arrows indicate a large, fluid-filled mass with multiple fine septations. (R, right ovary.)
common, and those appear as complex cystic masses on MRI. They show intermediate signal intensity on Tl-weighted images but sometimes contain layering debris or hemorrhage that has high T1 signal. They also show high signal on T2weighted images and may have septations, papillary excrecences, and/or solid components. The differentiation between benign and malignant ovarian epithelial tumors is based on morphology. Malignancy is more likely in the presence of papillary excrecences, irregular septations, and complex internal architecture (Figs 16 and 17). FIGO staging criteria for ovarian carcinoma
Tumor limited to the ovary Tumor involving one or both ovaries with pelvic extension Tumor involving one or both ovaries with intraperitoneal metastases outside the pelvis and/or positive retroperitoneal or inguinal nodes, including superficial liver metastases; tumor limited to the true pelvis with histologically proved malignant extension to small bowel or omentum Tumor involving one or both ovaries with distant metastasis, parenchymalliver metastasis, malignant pleural effusion
(Table 5) were established on the basis of laparotomy findings. MRI is accurate in ovarian carcinoma staging, with published rates as high as 83%. 26 One area in which MRI has an advantage over other imaging modalities is in the demonstration of peritoneal implants. These are most common in the right paracolic gutter, and may extend cephalad to beneath the right hemidiaphragm. Particular attention for metastases should also be given to the rectovesical pouch and the greater omentum. Axial gadolinium-enhanced, T 1-weighted images with fat saturation are helpful in showing peritoneal implants, evaluating for nodal necrosis, and differentiating between papillary projections and adherent clot in the ovarian mass.
Fig 17. Ovarian stromal cancer, (A) Sagittal FSE T2-weighted images show a large mass with mixed cystic and solid components, No normal ovary was identified on this side. (B) Coronal FSE T2-weighted images confirm the presence of a complex solid mass, Note the differences in appearances between this carcinoma and the benign ovarian mass shown in Fig 16. (C, cervix; B, bladder,)
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Fallopian Tube Carcinomas Carcinomas of the fallopian tubes are rare adenocarcinomas that appear as solid masses showing low-signal intensity on Tl-weighted images, high signal on T2-weighted images, and enhancement with gadolinium. They often present sonographically as an adnexal mass, making it difficult to differentiate between this tumor and an ovarian primary. MRI can aid in this differentiation, because its multiplanar imaging capabilities enable visualization of a normal adjacent ovary. 27
Vagina Vaginal carcinoma is an uncommon tumor, representing only 1% to 2% of female genital tract carcinomas. The majority of vaginal tumors result from local spread of cervical or uterine tumors. 8 Patients with vaginal carcinoma usually present with painless vaginal bleeding. There are 2 main subtypes of primary vaginal tumors. Squamous carcinomas constitute more than 90%. These tend to arise in the posterior wall of the proximal third of the vagina. Clear cell carcinoma of the vagina is a subtype of adenocarcinoma that occurs in daughters of women exposed to diethylstilbestrol (DES) during pregnancy. DES was widely prescribed for pregnant women in the United States from 1947 to 1971. It continued to be sold in the rest of the world into the late 1980s. There are an estimated 10 million DES mothers and daughters in the United States today. Clear cell carcinomas arise in young women, usually less than 35 years of age, and usually are located in the anterior wall of the proximal third of the vagina. Approximately one in a thousand women exposed to DES in utero develops this tumor. Alternative differential considerations for vaginal tumors include melanoma and sarcoma botyroides (in infants).
Vulvar Carcinomas Five percent of genital tract malignancies are vulvar primary tumor. These are easily diagnosed clinically, but MRI can be used to define the extent of the soft-tissue mass and to look for nodal involvement (Fig 18). MRI AS A PROBLEM SOLVER
The Adnexal Mass One of the most common diagnostic dilemmas in pelvic imaging of women is the adnexal mass.
Fig 18. Vulvar carcinoma. (A) Axial FSE T2-weighted images. The white arrows indicate an intermediate-signal mass in the right side of the vulva extending into the vagina. This was biopsied and proved to be a squamous carcinoma. (B} Axial FSE T2-weighted images. The normal left labia is indicated by the large arrow. The small arrows delineate a complex mass in the right vulva, which was biopsied and proved to be a sarcoma.
Simple cysts are beautifully shown on ultrasound, but characterizing a part cyst-part solid mass can be challenging. Less than 10% of complex adnexal masses are malignant, with a ratio of 11 benign masses to 1 malignant mass surgically removed. 28 MRI allows more detailed assessment of these lesions, and in some cases provides a specific diagnosis that obviates surgery. In 1994, Schwartz et al29 reviewed the impact of MRI on adnexal mass treatment decisions. Of 49 patients originally scheduled for surgery, 73% either did not have surgery or had a less invasive procedure after MRI evaluation. The change in management had no adverse effect on patient outcome, but the net cost savings were in
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excess of $1700 for each patient in whom surgery was avoided. 29 Some of the specific uses of MRI in evaluating pelvic masses are discussed later in this article. If an adnexal mass appears bright on Tl-weighted images, a Tl-weighted sequence with fat saturation should be performed. This clearly distinguishes fat (which will lose signal on fat saturation sequences) from blood products (which will remain bright on fat saturation sequences) (Fig 19). The ability to easily perform fat saturation can confirm the diagnosis of a fat-containing teratoma. Lesions containing blood products include
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hemorrhagic cysts and endometriomas. Recurrent episodes of bleeding in an endometrioma results in very high local concentrations of iron, much greater than would occur in a simple hemorrhagic cyst. There are no definite distinguishing features between benign and malignant ovarian masses. The addition of a gadolinium-enhanced, Tl-weighted sequences with fat saturation, however, aids in detection of peritoneal implants and necrotic lymph nodes. These findings are seen only with malignancy. It can occasionally be difficult to determine the
Fig 19. Endometrioma. (A) Axial Tl-weighted images show a high-signal mass (E) in the expected location of the left ovary. (B) Axial FSE T2-weighted images show the normal uterus (U). The mass that was high signal on T1 shows loss of signal and some heterogeneity on T2-weighted sequence. (C) Axial T1-weighted images with fat saturation. The high-signal mass does not lose signal, confirming that it is not fatty in nature but represents blood products consistent with an endometrioma.
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origin of large pelvic masses with ultrasound. Differentiation between a pedunculated serosal fibroid and a solid ovarian mass is crucial, particularly in a patient who wishes to preserve fertility. The multiplanar capability of MR/can help determine the origin of a pelvic mass in difficult cases, as shown in Fig 20. Pelvic Pain
Chronic pelvic pain is defined as pain persisting for longer than 6 months. Patients with this condition are often subjected to extensive investigations and psychological analysis and may undergo total abdominal hysterectomy and bilateral salpingooophrectomy without symptomatic relief. M R / i s of diagnostic benefit in pelvic pain patients in two ways: First, MRI provides noninvasive assessment of the bladder, urethra, rectum, and genital tract, second, MR/helps to identify unrecognized sources of pain such as pelvic venous congestion and peritoneal inclusion cysts. Enlarged parametriai and pelvic veins seen in a patient with chronic pelvic pain suggest the diagnosis of pelvic venous congestion. Patients with this finding can be referred to the appropriate specialist for careful clinical assessment and consideration for pelvic venous mapping. 3° Medical treatment is available for women with pelvic venous congestion, enabling them to avoid unnecessary invasive procedures and surgery (Fig 21). Fig 21. Pelvic venous congestion. (A) Axial Tl-weighted images. Bilateral serpiginous structures are identified in the parametrial fat (white arrows). (B) Axial FSE T2-weighted images confirm the serpiginous nature of enlarged vessels. This patient had a hysterectomy, and the presence of such enlarged vessels despite hysterectomy is strongly suggestive of pelvic venous congestion.
Fig 20. Pedunculated leiomyoma. Coronal FSET2-weighted images. A large pedunculated leiomyoma (P) is clearly shown to be separate from the ovaries (O) and the uterus (U). Incidental note is made of the presence of a submucosal myoma (S) within the uterus.
Peritoneal inclusion cysts (also known as peritoneal pseudocyst) result from entrapment of ovarian secretions by peritoneal adhesions. They occur in women of reproductive capacity with a past history of surgery or peritoneal inflammation. The appearance of these cysts has been well described in the imaging literature. 3~,32 The diagnostic features include the following: (1) a history of surgery or pelvic inflammation; (2) a cyst without mass effect; (3) cyst "walls" formed by adjacent normal structures; and (4) an ovary that is either part of the "wall" or is suspended within a network of adhesions.
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Fig 22, Peritoneal inclusion cyst, Sagittal FSE T2-weighted images. White arrows indicate the ovary surrounded by a septated fluid collection in this patient with a history of multiple urologic surgeries,
The fluid retained in a peritoneal inclusion cyst is serous; therefore, it has low signal on Tl-weighted images and high signal on T2-weighted images. It is important to recognize a peritoneal inclusion cyst (Fig 22) as a benign condition that can be treated with aspiration of fluid and ovarian suppression. Surgery is not indicated for these cysts. Adenomyosis is characterized by the presence
Fig 24. Urethral diverticulum complicated by stone formation. (A) Axial FSE T2-weighted images obtained with the endovaginal coil, The urethral lumen is marked by a Foley catheter containing high-signal urine (F), The low-signal mass (*) surrounding the Foley catheter is a stone within a urethral diverticulum, (B) Sagittal FSE T2-weighted images of same patient as (A). Foley catheter can be seen within the urethra, The urethral diverticulum contains a stone (*).
Fig 23. Urethral diverticulum, Axial FSE T2 images obtained with an endovaginal coil. The urethra (U) is surrounded by high-signal intensity diverticulae (*),
of endometrial tissue within the myometrium. Symptoms of this condition include chronic pelvic pain. Diffuse adenomyosis is diagnosed on MRI when the junctional zone on T2-weighted images measures greater than 1 cm (Fig 12). Focal adenomyosis has been discussed above as a differential consideration for submucosal leiornyoma.
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Urethral Disease Urethral disease processes in women can present with nonspecific symptoms. Patients with urethral disease are often misdiagnosed as having urinary tract infections and therefore take repeated courses of antibiotic without symptomatic relief. Urethral diverticulae are most common in the mid-urethra and occur more often on the posterior wall than the anterior wall. Urethral diverticulae are thought to result from inflammation and trauma of the periurethral glands, leading to local glandular dilatation. The diverticula are often distended with urine; therefore, they have low signal on T1 and high signal on T2-weighted images 1 (Fig 23). Complications of urethral diverticula, such as stone formation and tumor, are readily demonstrable with M R / ( F i g 24). Although voiding cystourethrograms and plain radiographic studies can occasionally show urethral diverticula, MRI has several advantages compared with these studies: it is noninvasive, there is no requirement for the patient to urinate, and the anatomic relations of the cysts to surrounding structures are well shown. A developing role for MRI in gynecological
urology is the evaluation of patients with stress incontinence. By using fast MRI scanning techniques, supine and prone resting and straining images can be performed. Rapid scanning allows physiological information to be obtained in addition to the anatomic information. Complications of implantable sphincter devices for urinary incontinence also can be evaluated with MR/. With these devices, the urethra is subject to erosion, fistula formation, and periurethral abscess. 33
CONCLUSION M R / i s a safe, noninvasive, and effective diagnostic tool to evaluate the female pelvis. The ability of MRI to concisely define anatomy and disease is unequalled by any other imaging modality. The cost-effectiveness of MRI has been proven in the assessment of cervical carcinoma and the evaluation of adnexal masses. As a radiologist, it is exciting to see our involvement with M R / i m p r o v ing diagnostic accuracy, resulting in the selection of appropriate treatment methods and the avoidance of unnecessary surgery.
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