ABSTRACTS 761

SEGMENTED K-SPACE ACQUISITION MAGNETIC RESONANCE ANGIOGRAPHY INCREASES PULSATILE FLOW SIGNAL. DOES IT IMPROVE THE QUALITY OF RENAL ARTERY IMAGING? (3. G, HARTNELL, B. BUFF, C. ZUO, J. MOORE and J. P. F INN Department of Radiological Sciences, Deaconess Hospital, Harvard, Medical School, Boston, MA, USA

Segmented k-space (SK) magnetic resonance angiography (MRA) is designed to optimise arterial flow signal by triggering acquisition to systolic flow. This should improve arterial imaging compared with conventional, time-of-flight (TOF) MRA.

We prospectively compared TOF to SK renal artery imaging to determine if SK improves signal and image quality.

Fourteen subjects were examined. Renal arteries were imaged in identical positions and orientations by TOF and SK. Contrast-to-noise ratios (CNR) and subjective image quality were assessed.

Signal intensity was higher with SK than TOF in all cases (SK: TOF = 1.68 : 1, SD + 0.31, p < 0.001). Mean CNR for SK was greater than TOF (SK : TOF1.4 : 1, SD + 0.48; p < 0.005). Subjective image quality with SK was superior to TOF, except when there was apparent respiratory motion. In 9 patients without respiratory motion the ratio of mean CNR -- 1.51 : 1 -4-0.5 (p < 0.001). In 5 patients with respira- tory motion the ratio was 1.25 : 1, SD • 0.25 (p < 0.025).

SK increases arterial flow signal, improves renal artery imaging and increases CNR compared to conventional TOF. SK is more susceptible to the effects of respiratory motion. In patients who can hold their breath segmented k-space MRA substantially improves renal artery imaging and may improve accuracy in detecting renal artery anomalies.

MRA OF FEMORO-POPLITEAL GRAFTS: CAN IT REPLACE DUPLEX ULTRASOUND IN THE FOLLOW-UP SURVEILLANCE OF GRAFTS? IS IT MORE ACCURATE THAN ANGIOGRAPHY IN DETECTING GRAFT STENOSES? P. MURPHY, S. WHITEHOUSE, A. JONES, Y. WILSON, D. PRESSDEE, P. LAMONT and R. N. BAIRD Bristol Royal Infirmary, Bristol

The development of stenosis in femoro-popliteal grafts particularly at the anastomotic end is well known and routine surveillance by duplex ultrasound is performed on all grafts in our hospital. Patients with velocities that may indicate a significant stenosis are referred for angiography. MRA, particularly the rephase/dephase sequence is useful in looking at peripheral vessels and we sought to establish its role in the surveillance of grafts and in its accuracy in detecting critical stenotic lesions.

We prospectively looked at 15 femoro-popliteal grafts which had been referred for angiography because of increasing velocities detected at duplex ultrasound. The patients had magnetic resonance angiogra- phy within a week of their angiogram. Both the 2D time of flight and rephase/dephase sequences were used, mainly the latter. The MRA images were reported prior to the angiogram.

MRA was found to have a higher sensitivity and specificity in detecting an anastomotic graft stenosis compared to angiography (MRA: sensitivity 90%, specificity 90%; angiography sensitivity; 85%, specficity 90%). This compares with an ultrasound sensitivity of 100% and a specificity of 90%.

MRA, particularly the rephase/dephase sequence is a sensitive method in detecting significant stenoses in femoro-popliteal grafts and may well challenge duplex ultrasound as the method of choice in follow-up screening, particularly as it is not operator dependent and has a high sensitivity and specificity for critical stenoses.

DOES PATENCY OF THE PROXIMAL SUPERFICIAL FEMORAL ARTERY AFFECT FEMORO-POPLITEAL GRAFT PATENCY? L. JONES, A. M. JONES, Y. WILSON and A. J. JONES Department of Clinical Radiology, Bristol Royal Infirmary, Bristol

Multiple factors predispose femoro-popliteal gifts to occlude. Early graft failure is usually due to technical problems and resolved surgi- cally. Thrombolysis is frequently used in later graft failure to gain secondary patency of thrombosed grafts. At this hospital there recently appeared to be a large number of patients requiring graft thrombolysis with persistence of a patent superficial femoral artery (SFA) for a variable distance from the origin of the graft. A hypothesis has been

suggested that the patent SFA in these patients may be causative rather than incidental perhaps resulting in a steal syndrome with sluggish graft flow and thus predisposing to thrombosis.

This study was designed to test this hypothesis. Pre operative arteriograms of 100 consecutive patients who had undergone femoral-popliteal or femoral-distal reconstruction were reviewed and the patency or otherwise of the SFA recorded. Complete one year followup data was available for seventy five patients.

Approximately one third overall of patients had occlusion of the SFA from its origin (or the origin of the graft). The distribution of graft failure was as follows:

SFA (graft) origin occluded patent

Early failure 9/33 11/56 (before discharge) Early or late failure 10/27 15/48

In total 25 patients (20 prior to discharge) required intervention to gain 2 ~ patency. Graft failure is thus rather more likely in those with a completely occluded SFA and this study therefore suggests the current policy at this hospital of leaving patent SFA's untied at femoral- popliteal or femoral-distal reconstruction is appropriate.

PERIPHERAL ARTERIAL DISEASE PROGRESSION -

I N C I D E N C E , PATTERN AND OUTCOME E. O 'GRADY, E. M. PARTRIDGE, P. C. ROWLANDS and R. D. EDWARDS Royal Liverpool University Hospital, Liverpool

Introduction: If limited resources result in a significant waiting time prior to angioplasty treatment of a lower limb arterial stenosis or occlusion an understanding of natural disease progression would be of benefit to rationalise the waiting list.

Design: A retrospective analysis of disease progression was per- formed in patients in whom an interval of more than a year had elapsed from initial arteriography to angioplasty appointment.

Subject and Methods: 26 patients (17 male: 9 female); age range 40-80 years were included in the study. Average waiting time for angioplasty appointment was 18 months. Repeated ateriography was performed prior to angioplasty.

Results: 9 out of 37 lesions (24%) initially judged suitable for angioplasty had progressed on the repeat arteriograms. 4 stenoses had progressed to occlusions. 8 of the 9 lesions that had progressed were still successfully treated by angioplasty. The remaining case required surgery. 40% disease progression rate was present in patients who continued to smoke. Analysis of type and site of lesion did not identify any specific factors which would determine disease progression.

Conclusion: 1. A delay of over a year prior to angioplasty results in a 24% lesion progression rate.

2. Although the technical success rate of angioplasty was not significantly affected by the delay, an adverse effect on primary patency should be expected in these patients progressing to occlusive disease.

OUTPATIENT ARTERIOGRAPHY USING 3 F CATHETERS - HAS IT REALLY ARRIVED? T. M. BUCKENHAM, A.-M. BELLI and S. A. RAY St George's Hospital, London

Arteriographic assessment of peripheral arteries in an invasive proce- dure usually necessitating inpatient admission. Digital subtraction imaging permits the use of 3 French gauge arterial catheters, leaving a 1 mm puncture and potentially facilitating earlier patient discharge.

Sixty-one patients underwent routine check arteriography 6 months after percutaneous balloon angioplasty. Only one patient required admission for a complication of the procedure this was a subintimal injection, which was treated conservatively with no sequelae. Four patients were admitted for social reasons, but the remaining 56 were discharged after a median of 4 hours (range 3-6 hours) following the procedure with none requiring readmission. Although all patients had a satisfactory arteriogram, the following technical problems severely limited the practicality of this technique.

(i) Catheter rupture (10-15%). (ii) Poor radio-opacity of catheter. (iii) Limited flow rates < 8 ml/sec. (iv) Inadequate stiffness of guide wire necessitating the use of multiple side hole catheters instead of pigtails - patients with scarred groins.