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Single film inclined angioplacentography in the diagnosis of placenta praevia
clin. RadioL (1968) 19, 59-64
sINGLE FILM INCLINED
ANGIOPLACENTOGRAPHY OF PLACENTA PRAEVIA
IN THE DIAGNOSIS
H. HERLINGER From the St. James's Hospital, Leeds'
The author describes a simple tilting device which allows a single film anteroposterior radiographic method of angioplacentography. The central ray is angled craniad and aligned through a plane which separates the 2 segments of the uterus. In 80 examinations, there were no false negative diagnoses, a diagnostic accuracy of 97.5 % was achieved and the radiation dose to the foetal gonads was very greatly reduced.
TIlE boundary between the upper and the lower All authors have agreed on the sacral promontsegments of the uterus can be considered as the ory as the posterior landmark for the intersegmental intersection of an imaginary intersegmental plane plane. Most of them have placed the intersection and the uterine wall. Accuracy in defining the level of the plane with the anterior uterine wall at a of this plane is restricted because (a) the boundary slightly greater distance from the external os, may be unsharp even on direct inspection; (b) thereby acting in accordance with the principle of painless contractions during the 3rd trimester of diagnostic safety. Brink (1960), Basson and pregnancy lengthen the lower segment and will DeVilliers (1963) and Ainsworth and Gillman increase the distance of the intersegmental boundary (1964) presented the intersegmental plane as a line from the external os to an unpredictable degree; between promontory and the 2 anterior superior and (c) direct roentgen visualisation is impossible. iliac spines as shown in the lateral or 5° off-lateral It therefore becomes necessary to use fixed points view. Borell, Fernstroem and Ohlson (1963) used of the bony pelvis in substitution for the changing a line which extends from the promontory through intersegmental boundary. It is evident that the a point 5 cm. above the symphysis pubis. It can boundary can not be defined with the same degree be shown that both methods of placing the interof precision as the lower edge of the placenta segmental plane are combined by a line which when shown by aortography. The following extends from the promontory to the lowest point considerations become important: on the 2 anterior superior iliac spines. The distance (1) Placenta praevia is best treated in hospital. from external os to the intersection with the anterior The danger is of repeated and increasingly uterine wall was found to be about 20 % greater severe bleeding, and the aim is deferment of than that between promontory and external os, this delivery until foetal maturity has been reached. being the geometrical basis of the principle of Cases of ante-partum haemorrhage not due to diagnostic safety. A posterior extension of this placenta praevia can usually be discharged to the line wilI reach the surface 1 cm. above the posterior care of ante-natal clinics. Early diagnosis and superior iliac spines (Fig. 1). patient disposal are of economic and social The Lateral View importance. (2) A false negative diagnosis must be avoided as it The first 15 angioplacentograms at this hospital may have fatal consequences. In view of the were done in the manner described by Ainsworth inherent inaccuracy of intersegmental boundary and Gillman (1964) with a vertical ray exposure determination, it becomes necessary to place the of the supine patient. It was found that in 6 of the bony landmarks at a somewhat high level, 15 patients a further lateral view became necessary, thereby accepting a small proportion of false mostly to make clear an anterior insertion of a positive findings. normal placenta (see Fig. 4a). Such lateral views 59
60
CLINICAL
RADIOLOGY
Fro. 2 The tilting device *. A--perspex strip which is to be placed under patient's back. B--perspex rod to lie against the lowest point of the anterior superior iliac spine. C--rotating anal which can be made firm at the required degree of angulation. *Obtainable from Cuthbert Andrews of Bushey, Herts. Fro. 1 Lateral view of pelvis. Forceps marks external os (A). Adjusted superimposed position of posterior superior iliac spines at B and of lowest point on anterior superior iliac spines at C. Line from promontory (D) through C represents the intersegmental plane, its backward continuation passing 1 cm. above B. The plane intersects the anterior uterine wall at E. Distances AD, AE, and symphysis pubis (F) to intersegmental plane are given as true values.
seem inadvisable in angioplacentography for the following reasons. (a) A very high foetal gonad dose results. Unsharpness due to scatter and movement blur is not unusual, at times making a further exposure necessary. (b) The placenta is supplied by either or both uterine arteries. It can be shown that, in the lateral decubitus and with injection at normal hand pressure, contrast medium may only flow into the dependent common iliac artery and thus fail to outline the whole of the placenta. TILTING DEVICE Lateral views were avoided after the construction of a simple device (Fig. 2) which enables the operator to angle the x-ray tube in order to align the central ray through the intersegmental' plane.* A perspex strip incorporating a lead wire is introduced under the patient's back, its lower border placed at the level of the usually palpable posterior superior iliac spines. The strip is attached to the base of a half-disk which adheres to the table top by rubber suckers. An arm projects beyond the half-disk and swivels through a plane which is in line with the long axis of the table and at right * Device obtainable f r o m C u t h b e r t A n d r e w s of Bushey,
Herts.
FIC. 3 Lateral pelvis, patient supine, hips flexed slightly. Intersegmental plane and perpendicular to table top form a caudad angle of 25 °. ( A = adjusted superimposed anterior superior iliac spines; B = promontory.)
angles to the table top. It can be made firm at any~ required angulation and carries a short, adjustable, lead wire tipped perspex rod which is placed against the lowest point of the anterior superior iliac spine opposite the side to be catheterised. When positioned in this way, the 2 lead wires mark the anterior and posterior levels of the intersegmental plane which is represented by the
INCLINED
ANGIOPLACENTOGRAPHY
I N T H E D I A G N O S I S OF P L A C E N T A
tilted connecting arm. A scale on the upper surface of the half-disk shows the angle between this plane and a perpendicular to the table top. The x-ray tube is tilted craniad by the same angle, with the central ray directed through the level of the wire in the tip of the upper rod. The 2 wires will become superimposed across the middle of the x-ray film where they represent the intersegmental plane seen tangentially. Continued use of the tilting device in this way made it clear that an angle of 25 ° was obtained whenever lumbar lordosis was slight (Fig. 3). When lordosis was more pronounced, the lumbar curve could usually be flattened by placing a pillow beneath the patient's knees, slight flexion of the hips not causing any difficulty with the subsequent catheterisation of the common femoral artery. In
PRAEVIA
61
the large majority of cases it became thus possible to pre-set the angle of the device to 256 in a caudad direction, POsition the posterior strip without palpation and then apply the anterior rod to the lowest point on the anterior superior iliac spine. In cases where lordosis could not be corrected a slightly greater angle was needed, so far not in excess of 30 °. This method makes it possibl e to distinguish placenta praevia from normal insertion by a single antero-posterior radiograph. If the lower border of the placenta is projected entirely above the marker line across the film, a normal upper segment insertion has been demonstrated (Fig. 4b). If the placental edge extends across the lead line, a placenta praevia exists, the extent of the crossover indicating its degree (Figs. 5, 6).
FIG. 5 Placental edge across lead line. Placenta praevia grade 1 diagnosed and confirmed at examination under anaesthetic before induction of labour at 38 weeks.
Fro. 4
FIG. 6 Placenta praevia grade 3 or 4 diagnosed. Central placenta praevia found at Caesarian section.
62
CLINICAL
TECHNIQUE Position of tilting device, angle and centering (Fig. 7) are checked by the radiologist. A preliminary film is unnecessary. A scale on the vertical arm of the tilting device measures the thickness of tissue to be traversed by the central ray. Table 1 relates a range of thickness readings to exposure factors required for a 3-phase generator unit in this department. Brief experience with a given set will make it possible to adapt this scale. A teflon catheter is introduced by conventional transfemoral method and its tip advanced in accordance with the patient's height: 23 cm. if 5 ft. tall; 0-5 cm. is added for every 1 inch over 5 feet. With the catheter tip thus above the bi-
FIe. 7 Tilting device p o s i t i o n e d , t u b e a n g l e d a n d centered. P a t i e n t ' s hips a r e flexed slightly to flatten t h e l u m b a r lordosis.
TABLE 1 X-RAY EXPOSURES RELATED TO TXSSUE THICKNESS Distance shown o n Device 14 15 16 17 18 19 20
cms. cms. cms. cms. cms. cms. cms.
k.v.
T i m e in sec.
76 78 80 82 82 86 86
"12 "12 "16 "16 "20 '20 '24
All a t 400 m A . , F F D 40 ins. I l f o r d F a s t T u n g s t a t e Screens, K o d a k Blue B r a n d Film.
RADIOLOGY
furcation of the aorta, 30 to 40 ml. of contrast medium are injected by means of a Gidlund pump, at a pressure of 2 kg./sq, cm., the exposure of a 14 in. sq. film being made 2 seconds after the end of the injection. Sixty per cent meglumine iothalamat¢ (Conray 280) was found to be the best tolerated medium, giving only little subjective discomfort and being only exceptionally attended with uterine activity or accelerated foetal movement. The catheter is left in situ until the film has been viewed. Injection and exposure are repeated in the following unusual circumstances: (a) Film technically inadequate; (b) Exposure too early and placental sinusoids as yet insufficiently filled. It is important to reject such a film as it may misrepresent the lower edge of the placenta and will make a false negative diagnosis possible; (c) Non-visualisation of the placenta, which occured in 4 patients. In a patient 2 weeks from term, the exposure coincided with an obvious contraction of the uterus which may have prevented the filling of the sinusoids. Ainsworth and Gillman have referred to this possible difficulty close to the end of pregnancy, at a time when the need for angioplacentography is in doubt. In the other 3 patients it was assumed that the placenta was high in the fundus, its lower edge completely hidden by the foetus. TNs was confirmed by re-injection and a vertical ray film. DISCUSSION Two characteristics of the inclined method may seem to be disadvantageous. (1) Placenta not shown in tote. The demonstration of the entire placenta may be aesthetically pleasing but is unnecessary in this context, as only the lower edge matters in the diagnosis of placenta praevia. (2) Anterior or posterior insertion. The inclined film can not distinguish between them. Stallworthy 0951) stressed the significance of the 'dangerous placenta', a low-lying, grade 1 or 2 placenta praevia of posterior insertion. Bevis (1954) believes that a posterior placenta praevia may cause cephalo-pdvic disproportion but remarks that this was not a universally accepted opinion. At this hospital, Redman 0955) emphasises that he looks to the radiologist purely for the affirmation or exclusion of a placenta praevia and is not interested in its exact position. If a positive diagnosis is made in this way, his patients are kept in hospital and treated conservatively as long as possible. At 36 weeks they are taken to the operating theatre for an examination under general anaesthetic to decide
INCLINED
ANGIOPLACENTOGRAPHY
IN THE DIAGNOSIS
whether induction or Caesarian section should follow. X-ray information as to the degree of placenta praevia may give a useful indication of the likelihood of success of expectant therapy. In addition, Pedowitz (1965) was able to reject the concept that lower segment Caesarian section was contra-indicated in an anteriorly inserted placenta praevia. Where clinical judgement or circumstances will still make necessary the distinction between an anterior and posterior placement of a placenta praevia, a 2nd film will be required. This should be done with a vertical ray centered at the level of the posterior rod of the tilting device which has remained in place. This projection will cause parallactic separation of the 2 lead markers on the film, the placental edge remaining close to the marker nearest to it, e.g. the short marker if anteriorly inserted. Figure 4b followed by 4a illustrates the principle of this method. RESULTS The following appearances on the film make clear the correctness of the procedure: (a)The wire line across the middle of the film will be projected over the upper edge of the sacrum. (b) The short wire will be superimposed on the long wire. (c) The placental edge will be well filled and clearly seen. The diagnoses, confidently based on these features in 80 patients are set out in Table 2. Clinical verification was obtained by uneventful delivery or by findings at Caesarian section or manual examination. Correctness of diagnosis in respect of placenta praevia in this series can be expressed as being 97.5 ~. More important is the absence of false negative diagnoses, a fact safeguarded by the occurrence of two false positive findings. Reduced Radiation Dose As a result of craniad angulation and low centering, the greater bulk of the uterus is avoided by the x-ray beam in the inclined view. The use of TABLE 2 FINDINGS IN 80 CASES OF ANTEPARTUMHAEMORRHAGE
X-ray Diagnosis
Normal Insertion 66 Final Clinical Diagnos!s [. 68 X-ray Diagnosis Evaluation
Placenta Praevia3-4 Grade 1-2 Grade 11 3 9 3
False Positive False Negative
2 nil
nil nil
OF P L A C E N T A
PRAEVIA
63
a 14 in. sq. film, centered as described and coned to within its borders, will avoid the direct irradiation of the foetal gonads in the case of vertex presentation. Dr. A. E. Chester has measured the foetal gonad dose during inclined exposures and has found an average reading of 15 mR. Allowing for the occasionally required additional vertical ray film and for the incidence of breech presentation, the average foetal gonad dose of the inclined method will amount to only 18 mR. COMPARISON WITH OTHER METHODS Lateral Method.--This examination is based on a single lateral view taken at the end of the injection into the aorta. An average foetal gonad dose of 360 mR results, i.e. 20 times that of the inclined method. Conventional Examination (Ainsworth and Gillman).--Dr. Chester obtained an average foetal gonad dose reading of 80 mR during vertical ray A.P. exposures, using 17 by 14 in. sq. films. On the assumption of one lateral view being required for each four A.P. film examinations, an average gonad dose of 170 mR ensues, i.e. about 10 times the dose in the inclined form of angioplacentography. Oblique Examination.--This single film procedure is attended by a foetal gonad dose of 75 mR, only four times that of the inclined method. A disadvantage is that film diagnosis will have to rely on judgement and experience. Furthermore, the need to outline the external os of the uterus by the introduction of a speculum will render the method unacceptable to most obstetricians. Isotopic Localisation.--Where isotope scanning facilities are available, angioplacentography wilt survive only if sufficiently modified to reduce foetal radiation dosages to the extent achieved by the inclined method. At the present time, angioplacentography is the more accurate procedure for distinguishing between a low normal insertion and a low-grade placenta praevia. CONCLUSIONS The lowering of the foetal radiation dose to the dosage range of radio-isotope placentography is the most important feature of the method introduced in this paper. Such reduction can be obtained without loss of achievable accuracy. There are few instances in radiology where the outcome of an examination affects the patient's disposal in such a direct manner and where it is possible to present a clear choice between only 2
64
CLINICAL RADIOLOGY
d i a g n o s t i c alternatives. T h e single film o b t a i n e d by the inclined method of angioplacentography b e a r s t e s t i m o n y to t h e a d e q u a c y o f the p r o c e d u r e a n d m a k e s o b v i o u s the d i a g n o s i s w h i c h derives f r o m it. Acknowledgement.--Gratitude is expressed to radiographers in the main x-ray department and to members of the medical photography unit at St. James's Hospital in Leeds. Dr. A. E. Chester, Chief Physicist of the Leeds Regional Medical Physics Unit is thanked for measuring foetal radiation. Since submission of this paper, angioplacentographies done by this method have increased to a total of 116.
REFERENCES An~SWORT~, J. & GILLMAN,P. W. (1964). Proc. R. Soc. Med., 57, 697. BASSON, J. M. N. & DrVmLtERS, J. N. (1963). Clin. Radiol., 14, 230. BEVIS,D. C. A. (1964). Proc. R. Soc. Med., 57, 700. BORrLL, U., F~RNSTROrM, I. & OHLSON, L. (1963). Amer. J. Obstet. Gynec., 86, 535. BRINK, D., (1960). J. Obstet. Gynaec. Brit. Cwlth., 67, 437. CheSTER, A. E. (1966). Personal communication. FrRNSTRO~M, I. (1955). Acta. Radiol., Suppl., 122. PEOOWXVZ,P. (1965). Amer. J. Obstet. Gynec., 93, 16. REDMAN, T. F. (1966). Personal commtmication. STALLWORTrtY,J. (1951). Amer. J. Obstet. Gynec., 61, 720. SUTTON,D. (1966). Brit. J. Radiol., 39, 47.
NOTICES CHRISTIE HOSPITAL AND H O L T RADIUM INSTITUTE VISITOR'S COURSES ONE week Visitors' Courses are held at the Christie Hospital twice a year, in November and May. These courses are primarily intended for visitors from this country and overseas who already have some knowledge of radiotherapy but who wish to see current methods and techniques being used in Manchester. They may be useful for D.M.R.T. and F.F.R. examination candidates but are not meant to be revision courses for either examination. During these courses there will be a full programme of talks, discussions and demonstrations by all the consultant radiotherapy staff of the hospital, which will include ail the common varieties of disease treated by radiotherapy. The formal cOurse will last five days beginning on the first Mondays in November and May. Visitors may, if they wish, remain for one further Week to attend normal Out-patient, x-ray therapy, Radium Theatre and Mould Room work. No fee is asked for these courses but numbers will be
limited. Prospective visitors are asked to write to Dr. E. C. Easson, Director of Radiotherapy, Christie H0spital, Withington, Manchester, 20, preferably at least one month in advance for further particulars.
CONFERENCE O N THYROID CANCERS A mETING on thyroid cancers will be held in Lausanne (Switzerland) from 8th to 10th May, 1968. Organized by the International union against cancer, it will gather together specialists of several countries who will examine this problem under its various aspects: epidemiology, functional activity, experimental research, results of therapy. The basis of a clinical and pathological classification will be issued from this conference. Those interested should contact Professor G. Candardjis, Institut universitaire de radiologie m6dicale, H6pital cantonal, 1000 Lausanne (Switzerland), or to Union internationale contre le cancer (UICC), Rue du Conseil-G6n6rat 3, 1200 Geneve (Switzerland).
sINGLE FILM INCLINED
ANGIOPLACENTOGRAPHY OF PLACENTA PRAEVIA
IN THE DIAGNOSIS
H. HERLINGER From the St. James's Hospital, Leeds'
The author describes a simple tilting device which allows a single film anteroposterior radiographic method of angioplacentography. The central ray is angled craniad and aligned through a plane which separates the 2 segments of the uterus. In 80 examinations, there were no false negative diagnoses, a diagnostic accuracy of 97.5 % was achieved and the radiation dose to the foetal gonads was very greatly reduced.
TIlE boundary between the upper and the lower All authors have agreed on the sacral promontsegments of the uterus can be considered as the ory as the posterior landmark for the intersegmental intersection of an imaginary intersegmental plane plane. Most of them have placed the intersection and the uterine wall. Accuracy in defining the level of the plane with the anterior uterine wall at a of this plane is restricted because (a) the boundary slightly greater distance from the external os, may be unsharp even on direct inspection; (b) thereby acting in accordance with the principle of painless contractions during the 3rd trimester of diagnostic safety. Brink (1960), Basson and pregnancy lengthen the lower segment and will DeVilliers (1963) and Ainsworth and Gillman increase the distance of the intersegmental boundary (1964) presented the intersegmental plane as a line from the external os to an unpredictable degree; between promontory and the 2 anterior superior and (c) direct roentgen visualisation is impossible. iliac spines as shown in the lateral or 5° off-lateral It therefore becomes necessary to use fixed points view. Borell, Fernstroem and Ohlson (1963) used of the bony pelvis in substitution for the changing a line which extends from the promontory through intersegmental boundary. It is evident that the a point 5 cm. above the symphysis pubis. It can boundary can not be defined with the same degree be shown that both methods of placing the interof precision as the lower edge of the placenta segmental plane are combined by a line which when shown by aortography. The following extends from the promontory to the lowest point considerations become important: on the 2 anterior superior iliac spines. The distance (1) Placenta praevia is best treated in hospital. from external os to the intersection with the anterior The danger is of repeated and increasingly uterine wall was found to be about 20 % greater severe bleeding, and the aim is deferment of than that between promontory and external os, this delivery until foetal maturity has been reached. being the geometrical basis of the principle of Cases of ante-partum haemorrhage not due to diagnostic safety. A posterior extension of this placenta praevia can usually be discharged to the line wilI reach the surface 1 cm. above the posterior care of ante-natal clinics. Early diagnosis and superior iliac spines (Fig. 1). patient disposal are of economic and social The Lateral View importance. (2) A false negative diagnosis must be avoided as it The first 15 angioplacentograms at this hospital may have fatal consequences. In view of the were done in the manner described by Ainsworth inherent inaccuracy of intersegmental boundary and Gillman (1964) with a vertical ray exposure determination, it becomes necessary to place the of the supine patient. It was found that in 6 of the bony landmarks at a somewhat high level, 15 patients a further lateral view became necessary, thereby accepting a small proportion of false mostly to make clear an anterior insertion of a positive findings. normal placenta (see Fig. 4a). Such lateral views 59
60
CLINICAL
RADIOLOGY
Fro. 2 The tilting device *. A--perspex strip which is to be placed under patient's back. B--perspex rod to lie against the lowest point of the anterior superior iliac spine. C--rotating anal which can be made firm at the required degree of angulation. *Obtainable from Cuthbert Andrews of Bushey, Herts. Fro. 1 Lateral view of pelvis. Forceps marks external os (A). Adjusted superimposed position of posterior superior iliac spines at B and of lowest point on anterior superior iliac spines at C. Line from promontory (D) through C represents the intersegmental plane, its backward continuation passing 1 cm. above B. The plane intersects the anterior uterine wall at E. Distances AD, AE, and symphysis pubis (F) to intersegmental plane are given as true values.
seem inadvisable in angioplacentography for the following reasons. (a) A very high foetal gonad dose results. Unsharpness due to scatter and movement blur is not unusual, at times making a further exposure necessary. (b) The placenta is supplied by either or both uterine arteries. It can be shown that, in the lateral decubitus and with injection at normal hand pressure, contrast medium may only flow into the dependent common iliac artery and thus fail to outline the whole of the placenta. TILTING DEVICE Lateral views were avoided after the construction of a simple device (Fig. 2) which enables the operator to angle the x-ray tube in order to align the central ray through the intersegmental' plane.* A perspex strip incorporating a lead wire is introduced under the patient's back, its lower border placed at the level of the usually palpable posterior superior iliac spines. The strip is attached to the base of a half-disk which adheres to the table top by rubber suckers. An arm projects beyond the half-disk and swivels through a plane which is in line with the long axis of the table and at right * Device obtainable f r o m C u t h b e r t A n d r e w s of Bushey,
Herts.
FIC. 3 Lateral pelvis, patient supine, hips flexed slightly. Intersegmental plane and perpendicular to table top form a caudad angle of 25 °. ( A = adjusted superimposed anterior superior iliac spines; B = promontory.)
angles to the table top. It can be made firm at any~ required angulation and carries a short, adjustable, lead wire tipped perspex rod which is placed against the lowest point of the anterior superior iliac spine opposite the side to be catheterised. When positioned in this way, the 2 lead wires mark the anterior and posterior levels of the intersegmental plane which is represented by the
INCLINED
ANGIOPLACENTOGRAPHY
I N T H E D I A G N O S I S OF P L A C E N T A
tilted connecting arm. A scale on the upper surface of the half-disk shows the angle between this plane and a perpendicular to the table top. The x-ray tube is tilted craniad by the same angle, with the central ray directed through the level of the wire in the tip of the upper rod. The 2 wires will become superimposed across the middle of the x-ray film where they represent the intersegmental plane seen tangentially. Continued use of the tilting device in this way made it clear that an angle of 25 ° was obtained whenever lumbar lordosis was slight (Fig. 3). When lordosis was more pronounced, the lumbar curve could usually be flattened by placing a pillow beneath the patient's knees, slight flexion of the hips not causing any difficulty with the subsequent catheterisation of the common femoral artery. In
PRAEVIA
61
the large majority of cases it became thus possible to pre-set the angle of the device to 256 in a caudad direction, POsition the posterior strip without palpation and then apply the anterior rod to the lowest point on the anterior superior iliac spine. In cases where lordosis could not be corrected a slightly greater angle was needed, so far not in excess of 30 °. This method makes it possibl e to distinguish placenta praevia from normal insertion by a single antero-posterior radiograph. If the lower border of the placenta is projected entirely above the marker line across the film, a normal upper segment insertion has been demonstrated (Fig. 4b). If the placental edge extends across the lead line, a placenta praevia exists, the extent of the crossover indicating its degree (Figs. 5, 6).
FIG. 5 Placental edge across lead line. Placenta praevia grade 1 diagnosed and confirmed at examination under anaesthetic before induction of labour at 38 weeks.
Fro. 4
FIG. 6 Placenta praevia grade 3 or 4 diagnosed. Central placenta praevia found at Caesarian section.
62
CLINICAL
TECHNIQUE Position of tilting device, angle and centering (Fig. 7) are checked by the radiologist. A preliminary film is unnecessary. A scale on the vertical arm of the tilting device measures the thickness of tissue to be traversed by the central ray. Table 1 relates a range of thickness readings to exposure factors required for a 3-phase generator unit in this department. Brief experience with a given set will make it possible to adapt this scale. A teflon catheter is introduced by conventional transfemoral method and its tip advanced in accordance with the patient's height: 23 cm. if 5 ft. tall; 0-5 cm. is added for every 1 inch over 5 feet. With the catheter tip thus above the bi-
FIe. 7 Tilting device p o s i t i o n e d , t u b e a n g l e d a n d centered. P a t i e n t ' s hips a r e flexed slightly to flatten t h e l u m b a r lordosis.
TABLE 1 X-RAY EXPOSURES RELATED TO TXSSUE THICKNESS Distance shown o n Device 14 15 16 17 18 19 20
cms. cms. cms. cms. cms. cms. cms.
k.v.
T i m e in sec.
76 78 80 82 82 86 86
"12 "12 "16 "16 "20 '20 '24
All a t 400 m A . , F F D 40 ins. I l f o r d F a s t T u n g s t a t e Screens, K o d a k Blue B r a n d Film.
RADIOLOGY
furcation of the aorta, 30 to 40 ml. of contrast medium are injected by means of a Gidlund pump, at a pressure of 2 kg./sq, cm., the exposure of a 14 in. sq. film being made 2 seconds after the end of the injection. Sixty per cent meglumine iothalamat¢ (Conray 280) was found to be the best tolerated medium, giving only little subjective discomfort and being only exceptionally attended with uterine activity or accelerated foetal movement. The catheter is left in situ until the film has been viewed. Injection and exposure are repeated in the following unusual circumstances: (a) Film technically inadequate; (b) Exposure too early and placental sinusoids as yet insufficiently filled. It is important to reject such a film as it may misrepresent the lower edge of the placenta and will make a false negative diagnosis possible; (c) Non-visualisation of the placenta, which occured in 4 patients. In a patient 2 weeks from term, the exposure coincided with an obvious contraction of the uterus which may have prevented the filling of the sinusoids. Ainsworth and Gillman have referred to this possible difficulty close to the end of pregnancy, at a time when the need for angioplacentography is in doubt. In the other 3 patients it was assumed that the placenta was high in the fundus, its lower edge completely hidden by the foetus. TNs was confirmed by re-injection and a vertical ray film. DISCUSSION Two characteristics of the inclined method may seem to be disadvantageous. (1) Placenta not shown in tote. The demonstration of the entire placenta may be aesthetically pleasing but is unnecessary in this context, as only the lower edge matters in the diagnosis of placenta praevia. (2) Anterior or posterior insertion. The inclined film can not distinguish between them. Stallworthy 0951) stressed the significance of the 'dangerous placenta', a low-lying, grade 1 or 2 placenta praevia of posterior insertion. Bevis (1954) believes that a posterior placenta praevia may cause cephalo-pdvic disproportion but remarks that this was not a universally accepted opinion. At this hospital, Redman 0955) emphasises that he looks to the radiologist purely for the affirmation or exclusion of a placenta praevia and is not interested in its exact position. If a positive diagnosis is made in this way, his patients are kept in hospital and treated conservatively as long as possible. At 36 weeks they are taken to the operating theatre for an examination under general anaesthetic to decide
INCLINED
ANGIOPLACENTOGRAPHY
IN THE DIAGNOSIS
whether induction or Caesarian section should follow. X-ray information as to the degree of placenta praevia may give a useful indication of the likelihood of success of expectant therapy. In addition, Pedowitz (1965) was able to reject the concept that lower segment Caesarian section was contra-indicated in an anteriorly inserted placenta praevia. Where clinical judgement or circumstances will still make necessary the distinction between an anterior and posterior placement of a placenta praevia, a 2nd film will be required. This should be done with a vertical ray centered at the level of the posterior rod of the tilting device which has remained in place. This projection will cause parallactic separation of the 2 lead markers on the film, the placental edge remaining close to the marker nearest to it, e.g. the short marker if anteriorly inserted. Figure 4b followed by 4a illustrates the principle of this method. RESULTS The following appearances on the film make clear the correctness of the procedure: (a)The wire line across the middle of the film will be projected over the upper edge of the sacrum. (b) The short wire will be superimposed on the long wire. (c) The placental edge will be well filled and clearly seen. The diagnoses, confidently based on these features in 80 patients are set out in Table 2. Clinical verification was obtained by uneventful delivery or by findings at Caesarian section or manual examination. Correctness of diagnosis in respect of placenta praevia in this series can be expressed as being 97.5 ~. More important is the absence of false negative diagnoses, a fact safeguarded by the occurrence of two false positive findings. Reduced Radiation Dose As a result of craniad angulation and low centering, the greater bulk of the uterus is avoided by the x-ray beam in the inclined view. The use of TABLE 2 FINDINGS IN 80 CASES OF ANTEPARTUMHAEMORRHAGE
X-ray Diagnosis
Normal Insertion 66 Final Clinical Diagnos!s [. 68 X-ray Diagnosis Evaluation
Placenta Praevia3-4 Grade 1-2 Grade 11 3 9 3
False Positive False Negative
2 nil
nil nil
OF P L A C E N T A
PRAEVIA
63
a 14 in. sq. film, centered as described and coned to within its borders, will avoid the direct irradiation of the foetal gonads in the case of vertex presentation. Dr. A. E. Chester has measured the foetal gonad dose during inclined exposures and has found an average reading of 15 mR. Allowing for the occasionally required additional vertical ray film and for the incidence of breech presentation, the average foetal gonad dose of the inclined method will amount to only 18 mR. COMPARISON WITH OTHER METHODS Lateral Method.--This examination is based on a single lateral view taken at the end of the injection into the aorta. An average foetal gonad dose of 360 mR results, i.e. 20 times that of the inclined method. Conventional Examination (Ainsworth and Gillman).--Dr. Chester obtained an average foetal gonad dose reading of 80 mR during vertical ray A.P. exposures, using 17 by 14 in. sq. films. On the assumption of one lateral view being required for each four A.P. film examinations, an average gonad dose of 170 mR ensues, i.e. about 10 times the dose in the inclined form of angioplacentography. Oblique Examination.--This single film procedure is attended by a foetal gonad dose of 75 mR, only four times that of the inclined method. A disadvantage is that film diagnosis will have to rely on judgement and experience. Furthermore, the need to outline the external os of the uterus by the introduction of a speculum will render the method unacceptable to most obstetricians. Isotopic Localisation.--Where isotope scanning facilities are available, angioplacentography wilt survive only if sufficiently modified to reduce foetal radiation dosages to the extent achieved by the inclined method. At the present time, angioplacentography is the more accurate procedure for distinguishing between a low normal insertion and a low-grade placenta praevia. CONCLUSIONS The lowering of the foetal radiation dose to the dosage range of radio-isotope placentography is the most important feature of the method introduced in this paper. Such reduction can be obtained without loss of achievable accuracy. There are few instances in radiology where the outcome of an examination affects the patient's disposal in such a direct manner and where it is possible to present a clear choice between only 2
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CLINICAL RADIOLOGY
d i a g n o s t i c alternatives. T h e single film o b t a i n e d by the inclined method of angioplacentography b e a r s t e s t i m o n y to t h e a d e q u a c y o f the p r o c e d u r e a n d m a k e s o b v i o u s the d i a g n o s i s w h i c h derives f r o m it. Acknowledgement.--Gratitude is expressed to radiographers in the main x-ray department and to members of the medical photography unit at St. James's Hospital in Leeds. Dr. A. E. Chester, Chief Physicist of the Leeds Regional Medical Physics Unit is thanked for measuring foetal radiation. Since submission of this paper, angioplacentographies done by this method have increased to a total of 116.
REFERENCES An~SWORT~, J. & GILLMAN,P. W. (1964). Proc. R. Soc. Med., 57, 697. BASSON, J. M. N. & DrVmLtERS, J. N. (1963). Clin. Radiol., 14, 230. BEVIS,D. C. A. (1964). Proc. R. Soc. Med., 57, 700. BORrLL, U., F~RNSTROrM, I. & OHLSON, L. (1963). Amer. J. Obstet. Gynec., 86, 535. BRINK, D., (1960). J. Obstet. Gynaec. Brit. Cwlth., 67, 437. CheSTER, A. E. (1966). Personal communication. FrRNSTRO~M, I. (1955). Acta. Radiol., Suppl., 122. PEOOWXVZ,P. (1965). Amer. J. Obstet. Gynec., 93, 16. REDMAN, T. F. (1966). Personal commtmication. STALLWORTrtY,J. (1951). Amer. J. Obstet. Gynec., 61, 720. SUTTON,D. (1966). Brit. J. Radiol., 39, 47.
NOTICES CHRISTIE HOSPITAL AND H O L T RADIUM INSTITUTE VISITOR'S COURSES ONE week Visitors' Courses are held at the Christie Hospital twice a year, in November and May. These courses are primarily intended for visitors from this country and overseas who already have some knowledge of radiotherapy but who wish to see current methods and techniques being used in Manchester. They may be useful for D.M.R.T. and F.F.R. examination candidates but are not meant to be revision courses for either examination. During these courses there will be a full programme of talks, discussions and demonstrations by all the consultant radiotherapy staff of the hospital, which will include ail the common varieties of disease treated by radiotherapy. The formal cOurse will last five days beginning on the first Mondays in November and May. Visitors may, if they wish, remain for one further Week to attend normal Out-patient, x-ray therapy, Radium Theatre and Mould Room work. No fee is asked for these courses but numbers will be
limited. Prospective visitors are asked to write to Dr. E. C. Easson, Director of Radiotherapy, Christie H0spital, Withington, Manchester, 20, preferably at least one month in advance for further particulars.
CONFERENCE O N THYROID CANCERS A mETING on thyroid cancers will be held in Lausanne (Switzerland) from 8th to 10th May, 1968. Organized by the International union against cancer, it will gather together specialists of several countries who will examine this problem under its various aspects: epidemiology, functional activity, experimental research, results of therapy. The basis of a clinical and pathological classification will be issued from this conference. Those interested should contact Professor G. Candardjis, Institut universitaire de radiologie m6dicale, H6pital cantonal, 1000 Lausanne (Switzerland), or to Union internationale contre le cancer (UICC), Rue du Conseil-G6n6rat 3, 1200 Geneve (Switzerland).