Magnetic resonance imaging in the late post-operative assessment of coarctation of the aorta

Clinical Radiology (1988) 39,673-689

Abstracts Abstracts of papers presented at the Royal College of Radiologists Annual Scientific Meeting held on 7-10 September 1988 at the University of Exeter, Devon DIAGNOSTIC

RADIOLOGY

ACCURACY OF STAGING BLADDER CARCINOMA BY MAGNETIC RESONANCE IMAGING R. J. JOHNSON, J. P. R. JENKINS, R. J. BARNARD, G. READ and I. ISHERWOOD

University of Manchester and Christie Hospital, Manchester The aim of this study was to determine the accuracy of magnetic resonance imaging (MRI) in staging bladder carcinoma. Thirty-five patients (age range 46-77 years) were studied by cystoscopy with examination under anaesthesia (EUA) and MRI. Thirtyone had proven bladder carcinoma and in the remaining four this diagnosis was suspected on cystoscopy and EUA. Nine patients subsequently underwent cystectomy or laparotomy. MRI was performed on a 0.26 T Picker International superconducting magnet system using a variety of spin-echo sequences and imaging planes. A tumour was classified on MRI according to the TNM coding. Thirty-one patients with proven bladder carcinoma were clearly identified on MRI and classified as: 14, T3a; 11, T3b; and six T4 lesions. It was not possible to distinguish T1 or T2 from T3a lesions on MRI. In the remaining four where tumour was suspected on EUA and cystoscopy, this was not confirmed on MRI. Biopsy was negative on all four, including one cystectomy. Of the nine patients who have since undergone cystectomy or laparotomy, agreement with MRI staging was recorded in eight. For the group as a whole there was good concordance between those who are now disease-free with T3a tumours on MRI and those with T3b or T4 lesions who have since developed recurrence and/or died. MRI has proved accurate in staging bladder carcinoma particularly T3a, T3b and T4 lesions, but cannot, at present, distinguish T1 or T2 from T3a tumours.

A COMPARISON OF CT AND MRI FOR STAGING BLADDER CANCER J. E. HUSBAND, M. P. WILLIAMS, C. W. HERON and G. R. CHERRYMAN

Royal Marsden Hospital, Sutton, Surrey Although CT has been shown to be a valuable method for staging bladder cancer with accuracy rates ranging from 60-90%, magnetic resonance imaging has potential advantages. These include superior contrast resolution, the ability to obtain images in multiple planes and to vary the imaging sequences to emphasise different tissue characteristics. We have compared the results of CT and MRI for staging 30 patients with bladder cancer at 1.5 T. Although MRI frequently demonstrates extravesical tumour spread more elegantly than CT, no patient was upstaged by MRI with respect to tumour spread beyond the bladder wall. In two patients CT demonstrated the turnout which was not seen on the MRI images due to artefacts. Three patients were overstaged by both techniques due to the inability to distinguish tumour from oedema following cystoscopy. The results of our study have not shown any significant difference between the accuracies of the two techniques. These results, together with those from other institutions, will be discussed with particular reference to the role of MRI in clinical practice.

APPLICATION OF FLOW MEASUREMENTS BY MAGNETIC RESONANCE PHASE MAPPING TO CONGENITAL HEART DISEASE R. S. O. REES, D. N. FIRMIN, S. R. UNDERWOOD, R. H. MOHIADDIN, R. H. KLIPSTEIN, J. SOMERVILLE and D. B. LONGMORE

National Heart and Chest Hospitals, London Quantitative measurements of flow can be acquired from magnetic resonance images using phase mapping, dependent on the fact that a magnetic resonance signal has both amplitude and phase and that

phase can be encoded to give a measure of flow velocity. Stationary tissues have zero phase and are shown as mid-grey, but flowing blood has a phase shift that is displayed as either a darker or lighter shade depending upon its direction and velocity. Flow measurements in the aorta and pulmonary trunk have been validated in-vivo by comparing them with right and left ventricular stroke volume measurements by magnetic resonance, and found to be accurate to within 6%. Flow measurements in the aorta, pulmonary trunk and hilar pulmonary arteries have been obtained in 10 patients with shunts, including atrial and ventricular septal defects, patent ductus and truncus arteriosus. In three of the patients, with pulmonary hypertension, the resultant figures were used as a basis to decide on operability. Coronary flow was measured in a further patient with origin of the left coronary artery from the pulmonary trunk, and this provided a direct measurement of the left-to-right shunt through the coronary circulation. Flow measurements by magnetic resonance phase mapping can provide physiological data which is not otherwise obtainable noninvasively.

ASSESSMENT OF MITRAL AND AORTIC VALVE DISEASE USING CINE-FLOW MAGNETIC RESONANCE IMAGING L. MITCHELL, J. P. R. JENKINS, Y. WATSON, D. J. ROWLANDS and I. ISHERWOOD

University of Manchester, Manchester The purpose of this study was to assess the ability of magnetic resonance imaging (MRI) to diagnose and grade valvular heart disease using a cine-flow technique utilising the FEER (field echo even rephasing) sequence. This sequence gives a high signal from coherently flowing blood at different phases of the cardiac cycle. Turbulence in jets of stenosis or regurgitation produce areas of signal loss. Sixty-eight valves were assessed in 40 patients who had undergone cardiac catheterisation and four volunteers. MRI was performed on a 0.26 T Picker International superconducting magnet system. All stenotic valves showed signal loss distal to the valve as did five patients with aortic sclerosis. All haemodynamically significant cases of reflux showed signal loss proximal to the valve. Reflux was graded qualitatively by size of area of signal loss. This correlated well with grading at cardiac catheterisation. Measurement of length of signal loss distal to the aortic valve allowed discrimination between stenosis and sclerosis. In stenosis this measurement correlated directly with pressure gradient. In mitral stenosis the maximum area of signal loss was expressed as a percentage of left ventricular cross-sectional area. This showed good concordance with pressure measurements and permitted grading of severity. Theseresults indicate that valvular heart disease can be accurately diagnosed and graded by cine-flow MRI.

MAGNETIC RESONANCE IMAGING IN THE LATE POSTOPERATIVE ASSESSMENT OF COARCTATION OF THE AORTA R. S. O. REES, J. SOMERVILLE, C. WARD, J. MARTINEZ, S. R. UNDERWOOD and D. B. LONGMORE

The National Heart and Chest Hospitals, London Thirty-five patients have been studied by magnetic resonance imaging 2 to 29 years after repair of coarctation of the aorta. Their ages, which at operation ranged from under 1 year to 68 years (mean 11), were between 5 and 74 years (mean 26). The operative techniques used for the coarctation repair were Dacron patch (12 patients), patch angioplasty using internal mammary or subclavian artery (five patients), end-to-end anastomosis (eight patients) and Dacron by-pass conduit (one patient). In the remaining nine patients the exact technique was uncertain. Re-operation to the isthmal area had been performed in four patients, one for resection of aneurysm and three for restenosis using a Dacron patch in two and a by-pass conduit in one. Measurements of isthmal gradients were available on catheter data in 12 patients and by Doppler echocardiography in a further 16.

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CLINICAL RADIOLOGY

Measurements of aortic diameter on the M R images were obtained of the mid-ascending aorta and of the descending aorta in the same transverse slice. The minimal diameter of the isthmus was also measured and the severity of the stenosis was expressed as a ratio of the isthmal diameter to the mean diameters of the ascending and descending aorta. Six patients had gradients at catheterisation varying between 10 and 55 mmHg, and seven others had significant gradients on Doppler echocardiography: in these 13, the isthmal/aortic diameter ratio varied between 0.18 and 0.15 (mean 0.38). Fifteen patients had no gradient on Doppler or at catheterisation, of whom two had an aneurysm at the isthmus. The other 13 had isthmal/aortic diameter ratios of between 0.48 and 0.95 (mean 0.70). Of the remaining seven patients with no gradient measurements, all had ratios above 0.5 (mean 0.65) and were regarded as having a successful result. Three patients were found to have an aneurysm at the site of the Dacron patch inserted 17 and 18 years previously. In morphology they were different, one being saccular, one fusiform, and one was a dissection. Two have been resected and the patient with the dissection has been treated conservatively as a second scan showed no change over a period of a year. These results show that M R tomographic spin-echo images in transverse and oblique planes provide a reliable method of demonstrating aortic anatomy non-invasively and can confirm or exclude the presence of an aneurysm. Re-stenosis at the site of the repair can be predicted when the isthmal/aortic diameter ratio is below 0.5. MAGNETIC RESONANCE IMAGING OF STRESSED ANTERIOR CRUCIATE LIGAMENTS A. M. R I J K E and T. H. G O I T Z

University of Virginia Medical Center, Charlottesville, Va. 22908 USA In t h e diagnostic analysis of anterior cruciate ligament (ACL) injury, magnetic resonance imaging can provide conclusive evidence in cases of a complete rupture and in most cases of intact cruciates, but partial tears cannot be diagnosed with confidence. Poor visualisation, a wavy appearance of the anterior margin, or an increased low signal intensity at its origin may raise the suspicion of an A C L tear, but correlation with functional status has proved elusive. We have used a stress apparatus made of wood and epoxy that can maintain a 15 kPa pressure, applied to the posterior-upper aspects of the lower leg, throughout the 16 min scanning time. T~-weighted sagittal F L A S H and FISP sequences, using 1.5 mm slice thickness, show an elevation of the A C L in all cases for which a partial tear was subsequently confirmed by surgery. This information was correlated with the results of the physical examination and has assisted our orthopedic surgeons in their decision between conservative treatment and intra- or extra-articular reconstruction.

THE URETERIC CALCULUS AN ALTERNATIVE APPROACH TO VISUALISATION WITH LITHOTRIPSY IN MIND B. ROSS -

Royal Hallamshire Hospital, Sheffield A major drawback to ultrasound lithotripsy is the poor access to the ureters from conventional ultrasound windows and hence the poor reputation of the piezo-electric ESWL in ureteric calculi. The author has explored alternative sites and positions for access and suggests that over 50% of calculi in the mid ureter can be both visualised by ultrasound and hence be accessible to ultrasounddirected lithotripsy. This access is a major advance as it avoids the necessity to use push-back or ureteroscopic techniques with the inevitable anaesthetic. Results in the visualisation using alternative sites are presented, as are various ancillary techniques which assist in the visualisation and eventual destruction. Results of the application of piezo-electric lithotripsy to ureteric calculi will be presented.

PERCUTANEOUS STONE AND STENT REMOVAL IN RENAL TRANSPLANTS W. M. W. G E D R O Y C , D. MacIVOR, M. L. J O Y C E and H. M. SAXTON

Guy's Hospital, London Techniques for the percutaneous removal of stones from normally sited kidneys are well described and accepted. A modified per-

cutaneous technique may be employed in calculus removal from renal transplants, and we describe four cases (two stones, one stent and one organised, infected blood clot) in which we have used this procedure effectively and safely in removing the above material from renal transplant collecting systems. We also describe the precise methods and their modifications which we have found useful for the successful application of radio-endourological procedures in renal transplant patients. ACQUIRED RENAL CYSTIC DISEASE: THE ROLE OF ULTRASOUND IN SCREENING R. A. MANNS, F. G. O. B U R R O W S , D. A D U and J. M. M I C H A E L

Queen Elizabeth Hospital, Birmingham Some patients with end-stage renal failure develop multiple cysts within their native kidneys. The importance of this so-called 'acquired cystic disease of the kidney' is because of several well described complications which may ensue. These include retroperitoneal haemorrhage, infection, calculi, painless haematuria and the development of solid tumours. Our study using ultrasonic examination was, initially, to document the incidence of acquired cystic disease in the renal unit at the Queen Elizabeth Hospital, Birmingham. Fifty-one patients were examined and twenty-four of these were found to have Cysts. As the period of renal replacement treatment (dialysis and renal transplantation) increased so there was a corresponding increase in acquired cystic disease. A n important group whose native kidneys could not be identified by ultrasound are also discussed. The second part of the study examined a particular subgroup of endstage renal failure patients who had been on dialysis (either haemo- or peritoneal dialysis) for over 3 years. From established literature and our own initial study, these patients should have a very high incidence of acquired cystic disease.

COMPUTED TOMOGRAPHY OF ACQUIRED CYSTIC KIDNEY DISEASE IN LONG TERM HAEMODIALYSIS PATIENTS G. T H O M A S and C. E V A N S

Cardiff Royal Infirmary, University Hospital of Wales, Cardiff End-stage kidneys in patients undergoing long term haemodialysis are known to undergo cystic change. There is also an increased incidence of adenocarcinoma, these complications being first described in the U K in pathological studies. The kidneys of dialysis patients are not routinely examined in this country unless there are clinical symptoms, whereas in the U S A routine screening by sonography or CT has been recommended and is being carried out in many centres. Regression of cystic disease has been demonstrated after successful transplantation. There have been no published clinical series in this country. We are in the process of carrying out renal CT in two patient groups. 1 Twenty-three patients who have been in haemodialysis for at least 5 years. 2 Twenty-one patients who were on haemodialysis for at least 5 years, but have subsequently had a successful renal transplantation for at least 5 years. The aim of the study is to demonstrate the prevalence of tumours and cysts, and to try and determine whether routine screening or long term dialysis patients is necessary.

ASSESSMENT OF ILEAL CONDUIT DIVERSIONS: IS INTRAVENOUS UROGRAPHY NECESSARY? K. K H A W and C. W. H E R O N

St George's Hospital, London Complications of ileal conduit diversions which may be detected radiologically include anastamotic leakage, stone formation, and recurrent tumour. These are rare and the most frequent long-term complication is hydronephrosis which is usually of obscure aetiology rather than obstructive. Intravenous urography (IVU) has been the primary investigation used to follow these patients. To date we have reviewed the IVUs of 30 patients with ileal conduits. In 25 patients surgery was performed for bladder carcinoma and the mean duration of follow-up was 34 months (range 6-84). Dilatation of the upper tracts was the only abnormality detected, occurring in three patients, none of whom had undergone an