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Magnetic resonance imaging of maxillary cancer — possibility of detecting bone destruction
Oral Oncology 36 (2000) 499±507
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Magnetic resonance imaging of maxillary cancer Ð possibility of detecting bone destruction Y. Ariyoshi *, M. Shimahara Department of Oral Surgery, Osaka Medical College, 2-7, Daigaku-machi, Takatsuki city, Osaka, 569-8686, Japan Received 2 March 2000; accepted 2 April 2000
Abstract The purpose of this study was to evaluate the detectability of bone destruction of maxillary cancer with magnetic resonance imaging (MRI) using 14 cases of squamous cell carcinoma of the upper jaw. The detectability of bone destruction including the degree of spread to adjacent soft tissues was evaluated and compared to that of clinical examination, computed tomography (CT) and conventional X-ray ®lms. MRI could show bone destruction of each bony part almost equally with CT, but dierentiation among simple bone defects, bone expansion and bone destruction was dicult on MRI. The pattern of bone destruction of alveolus that could be detected on conventional X-ray examinations, could not be assessed on either CT or MRI. Soft tissue in®ltration of the tumour was more clearly detected on MRI compared with CT and conventional X-ray ®lms. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Magnetic resonance imaging (MRI); Computed tomography (CT); Bone destruction; Maxillary cancer
1. Introduction Clinical examination of malignant tumours of the oral cavity is relatively easy, as except for patients with severe trismus, it is possible to inspect and palpate the tumour directly. However, in some patients with maxillary cancer involving the upper gingiva and the antrum, it would be dicult to assess the extension of the tumour without diagnostic imaging. If the tumour is localized or extends to the antrum and/or nasal cavity, it can not be inspected and palpated directly. In the case of gingival cancer, detection of whether or not the tumour spreads to the antrum is important, because it will aect the treatment planning and prognosis. Although we routinely use, in addition to clinical examinations, orthopantomogram, Waters view, postero-anterior view (PA) and periapical view for the ®rst choice of examination in cases of suspected malignancy of the upper jaw, there have been many cases in which it was dicult to assess the condition. These mainly involved the inner structures of the aected * Corresponding author. Tel.: +81-66-726-83-1221; fax: +81-66726-84-6538. E-mail address: y-ariyoshi@Safe- mail.ne.jp (Y. Ariyoshi).
antrum and invasion into adjacent structures including infratemporal fossa and/or cranial base. Currently, because of their superior spatial resolution and soft tissue contrast resolution, magnetic resonance imaging (MRI) and computed tomography (CT) have been used to examine the maxilla and paranasal sinuses, which form a complex system of bone, soft tissue and air. In this study, we retrospectively reviewed the ®ndings of MRI to assess its potential utility for diagnosing squamous cell carcinoma of the maxillary region, in particular whether bone destruction is present. 2. Material and methods The subjects of this study were 14 patients with squamous cell carcinoma of the maxillary region including the maxillary gingiva, alveolar bone and maxillary antrum. In this study, carcinoma which originated in the hard palate was excluded. The TNM classi®cation of carcinoma of the oral cavity was used to assess the tumour stage [1], but in extensive cases, especially in a T4 tumour, it was dicult clinically to de®ne whether the tumour originated in the gingiva or the antrum; we did not make this dierentiation in the current study
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examination, T1-weighted (TR/TE/excitations=200-400 /20/1) and T2-weighted (TR/TE/excitations=2000/70/1) or Fast SE T2-weighted (TR/TE/echo train length/excitations=4000/85-105/11-12/4) axial spin echo imagings were obtained. These studies were followed by static (TR/ TE/excitations=200-400/20/1) or dynamic (TR/TE/ excitations=200/20/1) enhanced studies obtained with spin echo sequences. Gd-DTPA (0.1 mmol/kg body weight) was used as the contrast medium. In Case Nos. 5, 9, 10 and 11, fat suppressed images (CHESS) were obtained after the above mentioned enhanced studies. The non-enhanced and/or enhanced CT examinations were performed almost simultaneously with MRI. The CT systems used in this study were Xvigor or Xforce (Toshiba). In CT, axial images of 3±5 mm in slice thickness were taken with 400 mA, 120 kVp. Direct coronal scanning was not performed because the required hyperextension of the neck was frequently too
(extensive maxillary tumour). A clinical T4 tumour was de®ned as a tumour which had clinically invaded skin and/or orbita, or which induced trismus without apparent in¯ammatory signs (Table 1). The most common clinical symptoms, except for palpable mass formation and/or ulceration of the aected alveolar process which was demonstrated in all cases, was mass formation in the cheek followed by trismus, proptosis, dipropia and nasal obstruction. No patients suered from neurological symptoms such as paralysis of the infraorbital region (Table 2). The MRI examinations were performed using a superconducting magnet (SIGNA, Performance Plus or Advantage, General Electric) operating at 1.5 Tesla. The head coil had a diameter of 28 cm. All sequences were performed with a slice thickness of 5.0 mm with a 0±1 mm intersection gap, a 256192 imaging matrix and a ®eld of view of 26 cm. According to our routine Table 1 Summary of 14 cases of maxillary cancer Case No.
Age
Sex
Location
T factor (clinical)
Clinical appearance (oral symptoms)
1 2 3 4 5 6 7 8 9 10 11 12 13 14
51 62 52 73 48 53 71 61 62 66 58 64 63 68
M M M F M M M M M F M M F F
Extensive Extensive Extensive Gingiva Gingiva Gingiva Gingiva Gingiva Gingiva Gingiva Gingiva Gingiva Gingiva Intraosseous
T4 T4 T4 T4 T3 T3 T3 T2 T2 T2 T2 T2 T2 T3
Granular Expansive Expansive Expansive Expansive Ulcerative Granular Granular Ulcerative Granular Ulcerative Granular Granular Expansive
Table 2 Clinical symptomsa Case No.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 a
Nasal symptoms
Orbital symptoms
Movement of mandible
Cheek
Nasal obstruction
Nasal discharge
Epistaxis
Proptosis
Dipropia
Trismus
Paralysis mass formation
+ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
ÿ ÿ + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
ÿ ÿ + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
+ ÿ ÿ + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
(+), symptom was presented; (ÿ), symptom was not presented.
+ + + + + ÿ + ÿ ÿ + ÿ ÿ ÿ ÿ
Y. Ariyoshi, M. Shimahara / Oral Oncology 36 (2000) 499±507
dicult for many patients who were either elderly or had an associated neck mass. MRI and CT were performed within 1 week or less. First of all, because direct visualization of thin cortical bone is, in general, dicult on MRI, we tried to assess the possibility of visualizing it using non-aected contralateral side. Speci®cally, the alveolar process was divided into six portions, bone marrow of tuberosity of maxilla, crotical bone of tuberosity, and the buccal and palatal cortex which were subdivided into posterior and anterior portions at the point of the canine. In addition, each non-aected antral wall was estimated its visualization independently. The MRI ®ndings of aected side were reviewed to establish whether or not bone destruction was present, and if present, its degree. The presence and degree of bone destruction were compared to that of CT and conventional X-ray ®lms, and in addition, if possible, surgical ®ndings. Conventional X-ray examinations which included Waters view, PA view and orthopantomogram were reviewed and the bone destruction of each radiological landmark was analyzed. Namely, in this study, the zygomatico±alveolar line, inferior border of the orbit and nasal wall were assessed on Waters view and PA view. The alveolar process, tuberosity of maxilla, panoramic innominate line [2], inferior border of antrum and nasal wall were assessed on orthopantomogram. Destruction of anterior wall was not assessed on conventional X-ray examination, because lateral view were not obtained. In this study, periapical view was not
501
used for assessing bone destruction. On conventional Xray examinations, evaluation of bone defect of each radiological landmark was recorded as present (+) or absent (ÿ). The MRI and CT ®ndings on maxillary cancer were evaluated as follows: the maxilla were subdivided into a portion of the process and four parts of the bony walls, namely, the alveolar process, anterior wall, posterior wall, nasal wall and infraorbital wall, respectively. In this study, the alveolar process was de®ned as the bony structure including the tooth-bearing area and lying under the inferior border of the antrum, and it was subdivided into three portions (tuberosity, buccal and palatal cortical bone). Each portion was evaluated independently as to the degree of bone destruction including invasion of surrounding soft tissues using four point system (Table 3). All cases were interpreted by two authors (Y.A., M.S.): agreement was reached on each case as to the detection of bone destruction. 3. Results 3.1. Direct visualization of normal maxillary bony structures on MRI For the alveolar process, 12 cases could be used to assess normal structures, except for two cases in which marked dental metal artifacts degraded the images. In all 12 cases, the tuberosity of maxilla was demonstrated
Table 3 The four point system for detecting bone destruction (CT and MRI)a Location/score
Description
Alveolar process 1 2 3 4
(P=palatal cortical plate, B=buccal cortical plate, T=tuberosity of maxilla, I=inferior border of antrum) No bone defect Only bone defect Bone destruction with invading surrounding structures and/or marrow space Apparent invasion to surrounding structures (bone destruction of palate, invasion to masticatory muscles)
Anterior wall 1 2 3 4
No bone defect Only bone defect Bone destruction with invading under facial muscles Bone destruction with invading subcutaneous fat
Posterior wall 1 2 3 4
No bone defect Only bone defect without invasion to the infratemporal fat plane Bone destruction with invasion to infratemporal fat plane Bone destruction with invasion to masticatory muscles and/or obliteration of infratemporal fat plane
Nasal wall and infraorbital wall 1 2 3 4
No bone defect Only bone defect without protrusion to nasal cavity or orbit Bone destruction with protrusion to nasal cavity or orbit slightly Bone destruction with protrusion to nasal cavity or orbit extensively
a
Conventional X-ray examination: +, bone defect is presented; ÿ, bone defect is not presented.
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by high signal intensity on T1 weighted images. A signal void from the cortical bone was detected in nine cases in the tuberosity (75.0%), 11 cases in the buccal molar region (91.7%), two cases in the labial incisor region (16.7%), ®ve cases in the palatal molar region (41.7%) and no cases on palatal incisor region (0%), respectively. In addition, signal void from the pterygoid plate was detected in four out of 12 cases (33.3%). Direct visualization of normal anterior, posterior, nasal and infraorbital wall was extremely dicult. A portion of the cortical bone of in¯ammed antrum was visualized as a signal void between the high signal of edematous antral mucosa and surrounding high signal fat tissue (posterior wall, infraorbital wall on sagittal scan) or a relatively low signal of the musculature (anterior wall), especially T2 weighted and enhanced scans. For non-in¯ammed antrum, direct visualization of each antral wall was impossible (Fig. 1). 3.2. Imaging analysis of maxillary cancer 3.2.1. Alveolar process including inferior border of antrum On conventional X-ray examination, in all cases except for Cases Nos. 9 and 13, bone destruction of alveolar process was demonstrated on orthopantomogram. In these 12 cases, bone destruction was localized in alveolar
process in two cases, and in alveolar process and tuberosity of the maxilla in three cases. In another seven cases the inferior border of the antrum was destructed and tumour invasion of the antrum was suspected on conventional X-ray examinations. For buccal and palatal cortical bone, extensive bone destruction was detected equally by both CT and MRI, but MRI could not detect simple bone defects that could be detected on CT (Case Nos. 4, 9, 12 and 13). In Case No. 10, it was impossible to assess bone destruction of the alveolus using either CT or MRI, because marked metal artifact caused by dental ®llings obscured the aected alveolar process. On the tuberosity of the maxilla, MRI could detect bone destruction almost equally with CT. In Case No. 8, CT could depict cortical bone on tuberosity, but on MRI, because the high signal intensity of the tuberosity and signal void of cortical bone was obliterated, we misdiagnosed that a bone defect was present. In Case No. 6, tumour in®ltration to the masticatory musculature was suspected on MRI due to an abnormally high signal intensity of the pterygold muscles on T2 weighted images, while CT could depict only a cortical bone defect without in®ltration to the musculature. As we obtained only axial CT, direct assessment of inferior border of the antrum was dicult on CT. Coronal and sagittal MRI also did not depict inferior border of the antrum directly. Conventional
Fig. 1. (a) T1 weighted image (Gd-enhanced), (b) CT (bone level), (c) T1 weighted image, (d) T2 weighted image, (e) CT (bone level). Bone marrow of the tuberosity of maxilla showed high signal intensity on Gd-enhanced T1 weighted image (arrow head). Note the signal void that indicates the cortex of molar region (large arrow) and pterygoid plate (small arrow). Although CT scan could depict the thin antral wall, MRI could not depict it.
Y. Ariyoshi, M. Shimahara / Oral Oncology 36 (2000) 499±507
X-ray examinations, including orthopantomogram, were the only modality to depict the inferior border of the antrum directly (Fig. 2, Table 4). 3.2.2. Antral wall including anterior, nasal, orbital and posterior wall On anterior, nasal and orbital wall, although direct visualization of the thin bony walls was dicult on MRI, the results of scores were almost equal to CT. In Case Nos. 2 and 4, MRI was more sensitive than conventional X-ray examination for assessing nasal-wall bone destruction, if the result of CT is used as the gold standard (Fig. 3, Table 5). Lateral bone destruction was assessed using zygomatico±alveolar line on PA and Waters view in addition to the panoramic innominate line, and posterior bone destruction was assessed using the posterior border of the antrum on orthopantomogram. According to these radiological landmarks, the presence of lateral bone destruction was detected in Case Nos. 1, 4 and
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5. In the lateral portion, MRI could also depict bone destruction, together with its degree, equally with CT and conventional X-ray ®lms. For the posterior wall, MRI could also detect bone destruction equally with CT and conventional X-ray examinations. In addition, MRI could more clearly delineate tumour in®ltration to the masticatory muscles, which showed high signal intensities compared to the contralateral normal muscles on T2 weighted images, and abnormal enhancement patterns of these muscles. CT could delineate tumour in®ltration to the masticatory muscles due to the swelling and abnormal enhancement of those muscles, and in addition, destruction of the pterygoid plate (Fig. 4, Table 6). 4. Discussion Clinical assessment including tumour staging of gingival cancer of the maxilla whether or not the tumour is
Fig. 2. Case No.13 (a) orthopantomogram, (b) CT scan, (c) Tl weighted image, (d) T2 weighted image, (e) Gd-enhanced T1 weighted image. On orthopantomogram and CT scan, the tuberosity of maxilla was destructed. MRI could equally depict bone destruction of tuberosity and palatal cortex. On TI weighted image, bone marrow of the tuberosity was replaced by a tumour which demonstrated as a low signal mass lesion. On T2 weighted and enhanced T1 weighted images, this mass lesion was depicted as a high signal and enhanced mass, respectively. MRI could clearly demonstrate the normal shape and signal intensity of the pterygoid muscle, indicating no tumour invasion.
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Table 4 Results of imaging analysis (alveolar process) Case No.
Alveolar process Conventional X-ray (orthopantomogram)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 a
+ + + + + + + + ÿ + + + ÿ +
Tuberosity of Maxilla (T) CT
MRI
B
P
B
P
4 4 4 2 4 2 3 1 2 1 1 2 2 2
4 4 4 3 4 2 4 2 1 / 3 3 3 3
4 4 4 1 4 3 3 1 1 / 1 1 1 2
4 4 4 3 4 3 4 2 1 / 3 3 3 3
Inferior border of antrum (I)
Conventional X-ray
CT
MRI
Conventional X-ray
CT
MRI
+ ÿ ÿ + + + + ÿ ÿ ÿ + + ÿ +
4 1 1 4 3 2 4 1 1 / 2 2 2 2
4 1 1 4 3 4 4 2 1 / 2 2 2 2
+ + + + + + + ÿ ÿ ÿ ÿ ÿ ÿ ÿ
2 2 2 2 /a 2 2 1 2 / 1 1 1 1
2 2 2 2 1 2 1 2 1 / 1 1 1 1
Estimation was impossible.
Fig. 3. Case No.3 (a) Orthopantomograrn, (b) CT scan, (c) T1 weighted axial image, (d) Gd-enhanced T1 weighted coronal image. On orthopantomogram, apparent bone destruction was demonstrated on the nasal wall and alveolar process, and destruction of the inferior border of the orbita was suspected (a). On CT, nasal wall and anterior wall was destructed and tumor invasion to the subcutaneous fat and nasal choncha was demonstrated (b). MRI could demonstrate the bone destruction of anterior and nasal wall. The presence of signal void of posterior wall and zygomatic process of maxilla indicated that bone destruction was not present (c). Left nasal choncha was destructed. Tumour invasion to orbital cavity was suspected in the medial portion (d).
spreading to the antrum is dicult without diagnostic imagings. Once a tumour has in®ltrated the antrum, tumour extension can not be visualized directly. In addition, in extensive cases, it is dicult to detect whether the tumour originates in the gingival or antral mucosa, which aects tumour staging. We routinely used, in addition to conventional X-ray examinations, MRI and CT to detect tumour localization and
tumour spread to adjacent soft tissues when clinical and histopathological diagnoses of malignancy of maxillary region were made. In general, CT and MRI each have advantages and disadvantages for assessing sinonasal tumors, but tend to be complementary [3]. The most signi®cant disadvantage of MRI is the lack of a signal from dense bone or calcium. In this study, this disadvantage of MRI was compared to CT, which has the
Y. Ariyoshi, M. Shimahara / Oral Oncology 36 (2000) 499±507
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Table 5 Results of imaging analysis (anterior wall, nasal wall, orbital wall) Anterior wall
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Nasal wall
Orbital wall
CT
MRI
Conventional X-ray
CT
MRI
Convential X-ray
CT
MRI
2 1 4 3 3 1 1 1 1 1 1 1 1 1
2 1 4 3 3 1 1 1 1 1 1 1 1 1
+ ÿ + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
3 2 4 3 1 2 1 1 1 1 1 1 1 1
3 3 4 3 1 1 1 1 1 1 1 1 1 1
ÿ + + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
1 3 3 1 1 1 1 1 1 1 1 1 1 1
1 3 3 1 1 1 1 1 1 1 1 1 1 1
advantage of superior detail of bone delineation. In this study, direct visualization of thin cortical bone on nonaected normal side was very dicult on MRI, but in the portions that had relatively thick cortical bone, especially in the buccal and palatal alveolar molar regions, cortical bone could be delineated as no-signal linear zone. This result indicated both the potential and limitation of MRI for delineating bone detail. To resolve these issues, further large series will be required. When the tumour has localized in the alveolus, conventional X-ray examinations including orthopantomogram were the most useful modality to detect bone destruction. The results of the current study indicated that CT could detect bone destruction that could not be detected on conventional X-ray examinations, and MRI could detect bone destruction almost equally with conventional X-ray examinations. Epstein et al. [4] reported that 65 and 75% of bone destruction could be assessed on orthopantomogram and CT, respectively. However, concerning the mode of bone destruction that would indicate the prognosis [5], conventional X-ray examinations were the most useful modality. In addition, the relationship between tumour and tooth, for example the `Floating Tooth' that is one of the characteristic appearance of malignancy on conventional X-ray examinations could not be detected either by CT or MRI in this study. In general, MRI has an advantage over CT concerning metal artifact [3]. However, in Case No. 10, dental ®llings caused marked metal artifact not only on CT but also on MRI. Conventional X-ray ®lms were not aected by this artifact. Such artifacts will degrade CT and MRI examinations of minimal bone destruction when the tooth-bearing area is within the region of interest. From these results, we think that a combination of CT and conventional X-ray examinations is the best mod-
ality for detecting the presence of alveolar bone destruction. Especially, if there are no dental ®llings, CT is the most useful modality. In the recent years, volume data obtained by helical CT have been used to evaluate the mandibular and maxillary pathology [6]. This system uses axial CT information to reconstruct true cross-sectional and panoramic views. By the use of this program, the disadvantages of CT can be resolved and further accurate information may be obtained as to whether or not alveolar bone destruction, in addition to the inferior border of antrum, is present. The MRI and CT appearance of neoplasms which aected the paranasal sinuses and nasal cavity have been reported in many articles [7±13]. Virapongse et al. [7] reported that bone destruction seen on CT was always detectable on MRI, although CT was superior in resolving bone detail. In addition, on MRI the bony anatomy is best visualized on T1 weighted images where bone is shown `in relief ' due to the absence of signal. Lund et al. [8] reported that the accuracy of CT scanning in determining tumour spread and tumour erosion of the cribriform plate, posterior wall of the maxillary sinus, and the medial orbital wall corresponded accurately with intraoperative and histologic ®ndings. To assess the presence and degree of orbital extension, direct coronal scanning is mandatory. In addition, they also reported that it was possible to show simple expansion of the posterior antral wall; expansion with early erosion, or direct invasion of the soft tissues and musculature. In the current study, CT could delineate bone detail and could dierentiate bone destruction from bone expansion, but MRI could not dierentiate them at the same level for CT. Conversely, due to the excellent contrast resolution of MRI, once a tumour in®ltrated to the surrounding soft tissues, MRI had the advantage over CT for detecting its presence. However,
506
Y. Ariyoshi, M. Shimahara / Oral Oncology 36 (2000) 499±507
Fig. 4. Case No.1 (a) Waters view, (b) CT scan, (c) T1 weighted axial image, (d) T2 weighted axial image, (e) Gd-enhanced T1 weighted axial image. On Watersview zygomatico-alveolar line was obliterated (arrow). Lateral portion of the antrum showed decreased radiolucency (a). Maxillary bone was destructed including alveolar process, palatal bone, lateral portion and posterior wall of antrum. Tumour invasion to the masticatory muscles was clearly demonstrated (b). Tumour mass was demonstrated as low signal, intermediate signal and enhanced mass on T1 weighted, T2 weighted and enhanced T1 weighted image, respectively. Note the obliteration of high signal of tuberosity, signal void of buccal and palatal cortical plate of alveolar process. In addition, abnormal shape and signal intensity of pterygoid muscle are visible (c, d, e).
it is important to note that secondary in¯ammation could show almost equal sign to tumour in®ltration. Hunink et al. [9] compared detectability of the nose and paranasal sinuses, the nasopharynx and the parapharyngeal space tumour spread between CT and MRI using ROC methodology. They subdivided the extension of tumours originating in the maxillary sinus into ®ve compartments that had practical consequences for the treatment choice. They concluded that CT and MR imaging did not appear to dier signi®cantly for staging tumours of the nasal cavity and paranasal sinuses. In addition, tumours involving predominantly soft tissues and relatively large bony structures (that is the maxilla, cheek, orbit, ethmoid and frontal sinuses), MRI per-
forms better than CT, while for tumours that involve many thin bony structures (that is the medial wall of the maxillary sinuses, the nasal cavity, palate, middle cranial fossa, cribriform plate, clivus and skull base), CT performs better than MRI. In a comparative study of MRI and CT for evaluation of maxillary and mandibular tumours, MRI was competitive with CT in assessing loss of cortical margins and bony expansion, while MRI was superior in demonstrating replacement of marrow fat and the extra-osseous extension of the neoplasm [14]. In our series, bone destruction of antral wall that could be detected on CT was also detected on MRI, except for the bony part that was the nasal wall on Case No. 6. The diculty of evaluating the nasal
Y. Ariyoshi, M. Shimahara / Oral Oncology 36 (2000) 499±507 Table 6 Results of imaging analysis (posterior wall including lateral portion) Case No.
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Conventional X-ray Posterior wall
Zygomatico alveolar line
Panoramic innominate line
+ ÿ ÿ + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
+ ÿ ÿ + + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
+ ÿ ÿ + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
CT
MRI
4 1 1 3 3 1 1 1 1 1 1 1 1 1
4 1 1 3 3 1 1 1 1 1 1 1 1 1
wall on MRI was due to the fact that direct visualization of the thin nasal wall was impossible on MRI. In addition, the nasal wall has complex structures compared to other walls such as a presentation of ostium. Beltran et al. [15] analyzed the increased signal intensity on T2 weighted images in skeletal muscle adjacent to neoplasms. They reported that the area of this increased signal intensity revealed edema more often than malignant tumour in®ltration. In this study, increasing signal intensity of pterygoid muscles on T2 weighted images was observed in ®ve cases. In one case (Case No. 5), tumour in®ltration was detected histopathologically, but another case (Case No. 7) only in¯ammatory reaction was observed. In another three cases (Case Nos. 1, 4 and 6), because radical operation could not be performed, we could not obtain histopathological diagnosis as a gold standard as to whether or not tumour in®ltration to the soft tissues was present. Clinical examination of these cases indicated that soft tissue in®ltration of the tumour was presented in Case Nos. 1 and 4. and uncertain in Case No. 6. This result indicated that, concerning the presentation of bone destruction, CT and MRI could detect in almost equal degrees. Diagnosis of MRI is not direct delineation of cortical bone and the speci®city of soft tissue in®ltration is low. We routinely performed dynamic enhanced studies for examining head and neck cancer [16], because this technique has the ability to improve qualitative evaluation of the mass lesions and abnormal structures [17,18]. It should be used in cases where tumour extension over the bony wall is suspected. Further studies concerning the correlation between MRI and histopathological ®ndings are necessary.
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Magnetic resonance imaging of maxillary cancer Ð possibility of detecting bone destruction Y. Ariyoshi *, M. Shimahara Department of Oral Surgery, Osaka Medical College, 2-7, Daigaku-machi, Takatsuki city, Osaka, 569-8686, Japan Received 2 March 2000; accepted 2 April 2000
Abstract The purpose of this study was to evaluate the detectability of bone destruction of maxillary cancer with magnetic resonance imaging (MRI) using 14 cases of squamous cell carcinoma of the upper jaw. The detectability of bone destruction including the degree of spread to adjacent soft tissues was evaluated and compared to that of clinical examination, computed tomography (CT) and conventional X-ray ®lms. MRI could show bone destruction of each bony part almost equally with CT, but dierentiation among simple bone defects, bone expansion and bone destruction was dicult on MRI. The pattern of bone destruction of alveolus that could be detected on conventional X-ray examinations, could not be assessed on either CT or MRI. Soft tissue in®ltration of the tumour was more clearly detected on MRI compared with CT and conventional X-ray ®lms. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Magnetic resonance imaging (MRI); Computed tomography (CT); Bone destruction; Maxillary cancer
1. Introduction Clinical examination of malignant tumours of the oral cavity is relatively easy, as except for patients with severe trismus, it is possible to inspect and palpate the tumour directly. However, in some patients with maxillary cancer involving the upper gingiva and the antrum, it would be dicult to assess the extension of the tumour without diagnostic imaging. If the tumour is localized or extends to the antrum and/or nasal cavity, it can not be inspected and palpated directly. In the case of gingival cancer, detection of whether or not the tumour spreads to the antrum is important, because it will aect the treatment planning and prognosis. Although we routinely use, in addition to clinical examinations, orthopantomogram, Waters view, postero-anterior view (PA) and periapical view for the ®rst choice of examination in cases of suspected malignancy of the upper jaw, there have been many cases in which it was dicult to assess the condition. These mainly involved the inner structures of the aected * Corresponding author. Tel.: +81-66-726-83-1221; fax: +81-66726-84-6538. E-mail address: y-ariyoshi@Safe- mail.ne.jp (Y. Ariyoshi).
antrum and invasion into adjacent structures including infratemporal fossa and/or cranial base. Currently, because of their superior spatial resolution and soft tissue contrast resolution, magnetic resonance imaging (MRI) and computed tomography (CT) have been used to examine the maxilla and paranasal sinuses, which form a complex system of bone, soft tissue and air. In this study, we retrospectively reviewed the ®ndings of MRI to assess its potential utility for diagnosing squamous cell carcinoma of the maxillary region, in particular whether bone destruction is present. 2. Material and methods The subjects of this study were 14 patients with squamous cell carcinoma of the maxillary region including the maxillary gingiva, alveolar bone and maxillary antrum. In this study, carcinoma which originated in the hard palate was excluded. The TNM classi®cation of carcinoma of the oral cavity was used to assess the tumour stage [1], but in extensive cases, especially in a T4 tumour, it was dicult clinically to de®ne whether the tumour originated in the gingiva or the antrum; we did not make this dierentiation in the current study
1368-8375/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S1368-8375(00)00041-5
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examination, T1-weighted (TR/TE/excitations=200-400 /20/1) and T2-weighted (TR/TE/excitations=2000/70/1) or Fast SE T2-weighted (TR/TE/echo train length/excitations=4000/85-105/11-12/4) axial spin echo imagings were obtained. These studies were followed by static (TR/ TE/excitations=200-400/20/1) or dynamic (TR/TE/ excitations=200/20/1) enhanced studies obtained with spin echo sequences. Gd-DTPA (0.1 mmol/kg body weight) was used as the contrast medium. In Case Nos. 5, 9, 10 and 11, fat suppressed images (CHESS) were obtained after the above mentioned enhanced studies. The non-enhanced and/or enhanced CT examinations were performed almost simultaneously with MRI. The CT systems used in this study were Xvigor or Xforce (Toshiba). In CT, axial images of 3±5 mm in slice thickness were taken with 400 mA, 120 kVp. Direct coronal scanning was not performed because the required hyperextension of the neck was frequently too
(extensive maxillary tumour). A clinical T4 tumour was de®ned as a tumour which had clinically invaded skin and/or orbita, or which induced trismus without apparent in¯ammatory signs (Table 1). The most common clinical symptoms, except for palpable mass formation and/or ulceration of the aected alveolar process which was demonstrated in all cases, was mass formation in the cheek followed by trismus, proptosis, dipropia and nasal obstruction. No patients suered from neurological symptoms such as paralysis of the infraorbital region (Table 2). The MRI examinations were performed using a superconducting magnet (SIGNA, Performance Plus or Advantage, General Electric) operating at 1.5 Tesla. The head coil had a diameter of 28 cm. All sequences were performed with a slice thickness of 5.0 mm with a 0±1 mm intersection gap, a 256192 imaging matrix and a ®eld of view of 26 cm. According to our routine Table 1 Summary of 14 cases of maxillary cancer Case No.
Age
Sex
Location
T factor (clinical)
Clinical appearance (oral symptoms)
1 2 3 4 5 6 7 8 9 10 11 12 13 14
51 62 52 73 48 53 71 61 62 66 58 64 63 68
M M M F M M M M M F M M F F
Extensive Extensive Extensive Gingiva Gingiva Gingiva Gingiva Gingiva Gingiva Gingiva Gingiva Gingiva Gingiva Intraosseous
T4 T4 T4 T4 T3 T3 T3 T2 T2 T2 T2 T2 T2 T3
Granular Expansive Expansive Expansive Expansive Ulcerative Granular Granular Ulcerative Granular Ulcerative Granular Granular Expansive
Table 2 Clinical symptomsa Case No.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 a
Nasal symptoms
Orbital symptoms
Movement of mandible
Cheek
Nasal obstruction
Nasal discharge
Epistaxis
Proptosis
Dipropia
Trismus
Paralysis mass formation
+ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
ÿ ÿ + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
ÿ ÿ + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
+ ÿ ÿ + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
(+), symptom was presented; (ÿ), symptom was not presented.
+ + + + + ÿ + ÿ ÿ + ÿ ÿ ÿ ÿ
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dicult for many patients who were either elderly or had an associated neck mass. MRI and CT were performed within 1 week or less. First of all, because direct visualization of thin cortical bone is, in general, dicult on MRI, we tried to assess the possibility of visualizing it using non-aected contralateral side. Speci®cally, the alveolar process was divided into six portions, bone marrow of tuberosity of maxilla, crotical bone of tuberosity, and the buccal and palatal cortex which were subdivided into posterior and anterior portions at the point of the canine. In addition, each non-aected antral wall was estimated its visualization independently. The MRI ®ndings of aected side were reviewed to establish whether or not bone destruction was present, and if present, its degree. The presence and degree of bone destruction were compared to that of CT and conventional X-ray ®lms, and in addition, if possible, surgical ®ndings. Conventional X-ray examinations which included Waters view, PA view and orthopantomogram were reviewed and the bone destruction of each radiological landmark was analyzed. Namely, in this study, the zygomatico±alveolar line, inferior border of the orbit and nasal wall were assessed on Waters view and PA view. The alveolar process, tuberosity of maxilla, panoramic innominate line [2], inferior border of antrum and nasal wall were assessed on orthopantomogram. Destruction of anterior wall was not assessed on conventional X-ray examination, because lateral view were not obtained. In this study, periapical view was not
501
used for assessing bone destruction. On conventional Xray examinations, evaluation of bone defect of each radiological landmark was recorded as present (+) or absent (ÿ). The MRI and CT ®ndings on maxillary cancer were evaluated as follows: the maxilla were subdivided into a portion of the process and four parts of the bony walls, namely, the alveolar process, anterior wall, posterior wall, nasal wall and infraorbital wall, respectively. In this study, the alveolar process was de®ned as the bony structure including the tooth-bearing area and lying under the inferior border of the antrum, and it was subdivided into three portions (tuberosity, buccal and palatal cortical bone). Each portion was evaluated independently as to the degree of bone destruction including invasion of surrounding soft tissues using four point system (Table 3). All cases were interpreted by two authors (Y.A., M.S.): agreement was reached on each case as to the detection of bone destruction. 3. Results 3.1. Direct visualization of normal maxillary bony structures on MRI For the alveolar process, 12 cases could be used to assess normal structures, except for two cases in which marked dental metal artifacts degraded the images. In all 12 cases, the tuberosity of maxilla was demonstrated
Table 3 The four point system for detecting bone destruction (CT and MRI)a Location/score
Description
Alveolar process 1 2 3 4
(P=palatal cortical plate, B=buccal cortical plate, T=tuberosity of maxilla, I=inferior border of antrum) No bone defect Only bone defect Bone destruction with invading surrounding structures and/or marrow space Apparent invasion to surrounding structures (bone destruction of palate, invasion to masticatory muscles)
Anterior wall 1 2 3 4
No bone defect Only bone defect Bone destruction with invading under facial muscles Bone destruction with invading subcutaneous fat
Posterior wall 1 2 3 4
No bone defect Only bone defect without invasion to the infratemporal fat plane Bone destruction with invasion to infratemporal fat plane Bone destruction with invasion to masticatory muscles and/or obliteration of infratemporal fat plane
Nasal wall and infraorbital wall 1 2 3 4
No bone defect Only bone defect without protrusion to nasal cavity or orbit Bone destruction with protrusion to nasal cavity or orbit slightly Bone destruction with protrusion to nasal cavity or orbit extensively
a
Conventional X-ray examination: +, bone defect is presented; ÿ, bone defect is not presented.
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by high signal intensity on T1 weighted images. A signal void from the cortical bone was detected in nine cases in the tuberosity (75.0%), 11 cases in the buccal molar region (91.7%), two cases in the labial incisor region (16.7%), ®ve cases in the palatal molar region (41.7%) and no cases on palatal incisor region (0%), respectively. In addition, signal void from the pterygoid plate was detected in four out of 12 cases (33.3%). Direct visualization of normal anterior, posterior, nasal and infraorbital wall was extremely dicult. A portion of the cortical bone of in¯ammed antrum was visualized as a signal void between the high signal of edematous antral mucosa and surrounding high signal fat tissue (posterior wall, infraorbital wall on sagittal scan) or a relatively low signal of the musculature (anterior wall), especially T2 weighted and enhanced scans. For non-in¯ammed antrum, direct visualization of each antral wall was impossible (Fig. 1). 3.2. Imaging analysis of maxillary cancer 3.2.1. Alveolar process including inferior border of antrum On conventional X-ray examination, in all cases except for Cases Nos. 9 and 13, bone destruction of alveolar process was demonstrated on orthopantomogram. In these 12 cases, bone destruction was localized in alveolar
process in two cases, and in alveolar process and tuberosity of the maxilla in three cases. In another seven cases the inferior border of the antrum was destructed and tumour invasion of the antrum was suspected on conventional X-ray examinations. For buccal and palatal cortical bone, extensive bone destruction was detected equally by both CT and MRI, but MRI could not detect simple bone defects that could be detected on CT (Case Nos. 4, 9, 12 and 13). In Case No. 10, it was impossible to assess bone destruction of the alveolus using either CT or MRI, because marked metal artifact caused by dental ®llings obscured the aected alveolar process. On the tuberosity of the maxilla, MRI could detect bone destruction almost equally with CT. In Case No. 8, CT could depict cortical bone on tuberosity, but on MRI, because the high signal intensity of the tuberosity and signal void of cortical bone was obliterated, we misdiagnosed that a bone defect was present. In Case No. 6, tumour in®ltration to the masticatory musculature was suspected on MRI due to an abnormally high signal intensity of the pterygold muscles on T2 weighted images, while CT could depict only a cortical bone defect without in®ltration to the musculature. As we obtained only axial CT, direct assessment of inferior border of the antrum was dicult on CT. Coronal and sagittal MRI also did not depict inferior border of the antrum directly. Conventional
Fig. 1. (a) T1 weighted image (Gd-enhanced), (b) CT (bone level), (c) T1 weighted image, (d) T2 weighted image, (e) CT (bone level). Bone marrow of the tuberosity of maxilla showed high signal intensity on Gd-enhanced T1 weighted image (arrow head). Note the signal void that indicates the cortex of molar region (large arrow) and pterygoid plate (small arrow). Although CT scan could depict the thin antral wall, MRI could not depict it.
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X-ray examinations, including orthopantomogram, were the only modality to depict the inferior border of the antrum directly (Fig. 2, Table 4). 3.2.2. Antral wall including anterior, nasal, orbital and posterior wall On anterior, nasal and orbital wall, although direct visualization of the thin bony walls was dicult on MRI, the results of scores were almost equal to CT. In Case Nos. 2 and 4, MRI was more sensitive than conventional X-ray examination for assessing nasal-wall bone destruction, if the result of CT is used as the gold standard (Fig. 3, Table 5). Lateral bone destruction was assessed using zygomatico±alveolar line on PA and Waters view in addition to the panoramic innominate line, and posterior bone destruction was assessed using the posterior border of the antrum on orthopantomogram. According to these radiological landmarks, the presence of lateral bone destruction was detected in Case Nos. 1, 4 and
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5. In the lateral portion, MRI could also depict bone destruction, together with its degree, equally with CT and conventional X-ray ®lms. For the posterior wall, MRI could also detect bone destruction equally with CT and conventional X-ray examinations. In addition, MRI could more clearly delineate tumour in®ltration to the masticatory muscles, which showed high signal intensities compared to the contralateral normal muscles on T2 weighted images, and abnormal enhancement patterns of these muscles. CT could delineate tumour in®ltration to the masticatory muscles due to the swelling and abnormal enhancement of those muscles, and in addition, destruction of the pterygoid plate (Fig. 4, Table 6). 4. Discussion Clinical assessment including tumour staging of gingival cancer of the maxilla whether or not the tumour is
Fig. 2. Case No.13 (a) orthopantomogram, (b) CT scan, (c) Tl weighted image, (d) T2 weighted image, (e) Gd-enhanced T1 weighted image. On orthopantomogram and CT scan, the tuberosity of maxilla was destructed. MRI could equally depict bone destruction of tuberosity and palatal cortex. On TI weighted image, bone marrow of the tuberosity was replaced by a tumour which demonstrated as a low signal mass lesion. On T2 weighted and enhanced T1 weighted images, this mass lesion was depicted as a high signal and enhanced mass, respectively. MRI could clearly demonstrate the normal shape and signal intensity of the pterygoid muscle, indicating no tumour invasion.
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Table 4 Results of imaging analysis (alveolar process) Case No.
Alveolar process Conventional X-ray (orthopantomogram)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 a
+ + + + + + + + ÿ + + + ÿ +
Tuberosity of Maxilla (T) CT
MRI
B
P
B
P
4 4 4 2 4 2 3 1 2 1 1 2 2 2
4 4 4 3 4 2 4 2 1 / 3 3 3 3
4 4 4 1 4 3 3 1 1 / 1 1 1 2
4 4 4 3 4 3 4 2 1 / 3 3 3 3
Inferior border of antrum (I)
Conventional X-ray
CT
MRI
Conventional X-ray
CT
MRI
+ ÿ ÿ + + + + ÿ ÿ ÿ + + ÿ +
4 1 1 4 3 2 4 1 1 / 2 2 2 2
4 1 1 4 3 4 4 2 1 / 2 2 2 2
+ + + + + + + ÿ ÿ ÿ ÿ ÿ ÿ ÿ
2 2 2 2 /a 2 2 1 2 / 1 1 1 1
2 2 2 2 1 2 1 2 1 / 1 1 1 1
Estimation was impossible.
Fig. 3. Case No.3 (a) Orthopantomograrn, (b) CT scan, (c) T1 weighted axial image, (d) Gd-enhanced T1 weighted coronal image. On orthopantomogram, apparent bone destruction was demonstrated on the nasal wall and alveolar process, and destruction of the inferior border of the orbita was suspected (a). On CT, nasal wall and anterior wall was destructed and tumor invasion to the subcutaneous fat and nasal choncha was demonstrated (b). MRI could demonstrate the bone destruction of anterior and nasal wall. The presence of signal void of posterior wall and zygomatic process of maxilla indicated that bone destruction was not present (c). Left nasal choncha was destructed. Tumour invasion to orbital cavity was suspected in the medial portion (d).
spreading to the antrum is dicult without diagnostic imagings. Once a tumour has in®ltrated the antrum, tumour extension can not be visualized directly. In addition, in extensive cases, it is dicult to detect whether the tumour originates in the gingival or antral mucosa, which aects tumour staging. We routinely used, in addition to conventional X-ray examinations, MRI and CT to detect tumour localization and
tumour spread to adjacent soft tissues when clinical and histopathological diagnoses of malignancy of maxillary region were made. In general, CT and MRI each have advantages and disadvantages for assessing sinonasal tumors, but tend to be complementary [3]. The most signi®cant disadvantage of MRI is the lack of a signal from dense bone or calcium. In this study, this disadvantage of MRI was compared to CT, which has the
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Table 5 Results of imaging analysis (anterior wall, nasal wall, orbital wall) Anterior wall
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Nasal wall
Orbital wall
CT
MRI
Conventional X-ray
CT
MRI
Convential X-ray
CT
MRI
2 1 4 3 3 1 1 1 1 1 1 1 1 1
2 1 4 3 3 1 1 1 1 1 1 1 1 1
+ ÿ + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
3 2 4 3 1 2 1 1 1 1 1 1 1 1
3 3 4 3 1 1 1 1 1 1 1 1 1 1
ÿ + + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
1 3 3 1 1 1 1 1 1 1 1 1 1 1
1 3 3 1 1 1 1 1 1 1 1 1 1 1
advantage of superior detail of bone delineation. In this study, direct visualization of thin cortical bone on nonaected normal side was very dicult on MRI, but in the portions that had relatively thick cortical bone, especially in the buccal and palatal alveolar molar regions, cortical bone could be delineated as no-signal linear zone. This result indicated both the potential and limitation of MRI for delineating bone detail. To resolve these issues, further large series will be required. When the tumour has localized in the alveolus, conventional X-ray examinations including orthopantomogram were the most useful modality to detect bone destruction. The results of the current study indicated that CT could detect bone destruction that could not be detected on conventional X-ray examinations, and MRI could detect bone destruction almost equally with conventional X-ray examinations. Epstein et al. [4] reported that 65 and 75% of bone destruction could be assessed on orthopantomogram and CT, respectively. However, concerning the mode of bone destruction that would indicate the prognosis [5], conventional X-ray examinations were the most useful modality. In addition, the relationship between tumour and tooth, for example the `Floating Tooth' that is one of the characteristic appearance of malignancy on conventional X-ray examinations could not be detected either by CT or MRI in this study. In general, MRI has an advantage over CT concerning metal artifact [3]. However, in Case No. 10, dental ®llings caused marked metal artifact not only on CT but also on MRI. Conventional X-ray ®lms were not aected by this artifact. Such artifacts will degrade CT and MRI examinations of minimal bone destruction when the tooth-bearing area is within the region of interest. From these results, we think that a combination of CT and conventional X-ray examinations is the best mod-
ality for detecting the presence of alveolar bone destruction. Especially, if there are no dental ®llings, CT is the most useful modality. In the recent years, volume data obtained by helical CT have been used to evaluate the mandibular and maxillary pathology [6]. This system uses axial CT information to reconstruct true cross-sectional and panoramic views. By the use of this program, the disadvantages of CT can be resolved and further accurate information may be obtained as to whether or not alveolar bone destruction, in addition to the inferior border of antrum, is present. The MRI and CT appearance of neoplasms which aected the paranasal sinuses and nasal cavity have been reported in many articles [7±13]. Virapongse et al. [7] reported that bone destruction seen on CT was always detectable on MRI, although CT was superior in resolving bone detail. In addition, on MRI the bony anatomy is best visualized on T1 weighted images where bone is shown `in relief ' due to the absence of signal. Lund et al. [8] reported that the accuracy of CT scanning in determining tumour spread and tumour erosion of the cribriform plate, posterior wall of the maxillary sinus, and the medial orbital wall corresponded accurately with intraoperative and histologic ®ndings. To assess the presence and degree of orbital extension, direct coronal scanning is mandatory. In addition, they also reported that it was possible to show simple expansion of the posterior antral wall; expansion with early erosion, or direct invasion of the soft tissues and musculature. In the current study, CT could delineate bone detail and could dierentiate bone destruction from bone expansion, but MRI could not dierentiate them at the same level for CT. Conversely, due to the excellent contrast resolution of MRI, once a tumour in®ltrated to the surrounding soft tissues, MRI had the advantage over CT for detecting its presence. However,
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Fig. 4. Case No.1 (a) Waters view, (b) CT scan, (c) T1 weighted axial image, (d) T2 weighted axial image, (e) Gd-enhanced T1 weighted axial image. On Watersview zygomatico-alveolar line was obliterated (arrow). Lateral portion of the antrum showed decreased radiolucency (a). Maxillary bone was destructed including alveolar process, palatal bone, lateral portion and posterior wall of antrum. Tumour invasion to the masticatory muscles was clearly demonstrated (b). Tumour mass was demonstrated as low signal, intermediate signal and enhanced mass on T1 weighted, T2 weighted and enhanced T1 weighted image, respectively. Note the obliteration of high signal of tuberosity, signal void of buccal and palatal cortical plate of alveolar process. In addition, abnormal shape and signal intensity of pterygoid muscle are visible (c, d, e).
it is important to note that secondary in¯ammation could show almost equal sign to tumour in®ltration. Hunink et al. [9] compared detectability of the nose and paranasal sinuses, the nasopharynx and the parapharyngeal space tumour spread between CT and MRI using ROC methodology. They subdivided the extension of tumours originating in the maxillary sinus into ®ve compartments that had practical consequences for the treatment choice. They concluded that CT and MR imaging did not appear to dier signi®cantly for staging tumours of the nasal cavity and paranasal sinuses. In addition, tumours involving predominantly soft tissues and relatively large bony structures (that is the maxilla, cheek, orbit, ethmoid and frontal sinuses), MRI per-
forms better than CT, while for tumours that involve many thin bony structures (that is the medial wall of the maxillary sinuses, the nasal cavity, palate, middle cranial fossa, cribriform plate, clivus and skull base), CT performs better than MRI. In a comparative study of MRI and CT for evaluation of maxillary and mandibular tumours, MRI was competitive with CT in assessing loss of cortical margins and bony expansion, while MRI was superior in demonstrating replacement of marrow fat and the extra-osseous extension of the neoplasm [14]. In our series, bone destruction of antral wall that could be detected on CT was also detected on MRI, except for the bony part that was the nasal wall on Case No. 6. The diculty of evaluating the nasal
Y. Ariyoshi, M. Shimahara / Oral Oncology 36 (2000) 499±507 Table 6 Results of imaging analysis (posterior wall including lateral portion) Case No.
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Conventional X-ray Posterior wall
Zygomatico alveolar line
Panoramic innominate line
+ ÿ ÿ + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
+ ÿ ÿ + + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
+ ÿ ÿ + ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ
CT
MRI
4 1 1 3 3 1 1 1 1 1 1 1 1 1
4 1 1 3 3 1 1 1 1 1 1 1 1 1
wall on MRI was due to the fact that direct visualization of the thin nasal wall was impossible on MRI. In addition, the nasal wall has complex structures compared to other walls such as a presentation of ostium. Beltran et al. [15] analyzed the increased signal intensity on T2 weighted images in skeletal muscle adjacent to neoplasms. They reported that the area of this increased signal intensity revealed edema more often than malignant tumour in®ltration. In this study, increasing signal intensity of pterygoid muscles on T2 weighted images was observed in ®ve cases. In one case (Case No. 5), tumour in®ltration was detected histopathologically, but another case (Case No. 7) only in¯ammatory reaction was observed. In another three cases (Case Nos. 1, 4 and 6), because radical operation could not be performed, we could not obtain histopathological diagnosis as a gold standard as to whether or not tumour in®ltration to the soft tissues was present. Clinical examination of these cases indicated that soft tissue in®ltration of the tumour was presented in Case Nos. 1 and 4. and uncertain in Case No. 6. This result indicated that, concerning the presentation of bone destruction, CT and MRI could detect in almost equal degrees. Diagnosis of MRI is not direct delineation of cortical bone and the speci®city of soft tissue in®ltration is low. We routinely performed dynamic enhanced studies for examining head and neck cancer [16], because this technique has the ability to improve qualitative evaluation of the mass lesions and abnormal structures [17,18]. It should be used in cases where tumour extension over the bony wall is suspected. Further studies concerning the correlation between MRI and histopathological ®ndings are necessary.
507
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