Introduction

Morphological and functional assessment of vessels without requirement of ionized radiation and nephrotoxic contrast agent are the most important advantages of magnetic resonance(MR). MR angiography is an accurate method used to depict significant stenoses and occlusions in lower extremity arteries(₁). MR angiography(MRA) is a feasible and minimally invasive alternative to DSA and provides angiograms of the aortoiliac region with high sensitivity, specificity, and diagnostic accuracy(₂). MRA is also an accurate method of evaluating patients for popliteal and infrapopliteal arterial occlusive disease and can be used for planning percutaneous interventions(₃). MRA's image quality was considered diagnostic in 99.3% of the arterial segments(₄).

A Few Case Examples

Diagnosis of Leriche syndrome or occlusive and/or severe stenotic lesions secondary to arteriosclerosis obliterans(ASO) at the segment between the abdominal aorta and popliteal artery and evaluating the MR angiographics to plan the revascularization operations were performed.

Our first case was a 57 years old Leriche patient and MR angio image was consistent with occlusive lesions of distal abdominal aorta,bilateral common iliac arteries and branches just from infrarenal level(Figure 1).

Figure 1

Figure 1: Our first patient's MRA image was consistent with occlusive lesions of distal abdominal aorta,bilateral common iliac arteries and branches.

Focal segmental lesions of femoral level,seen in next sequence,was consistent with atherosclerotic changes and didn't effect flow dynamics(Figure 2).

Figure 2

Figure 2: Focal segmental lesions of femoral level in our first patient's MRA.

In the same patient MRA of popliteal artery and distal part showed that popliteal arteries and anterior and posterior tibial arteries and peroneal arteries are in normal calibrations and all patent(Figure 3).

Figure 3

Figure 3: Our first patient's MRA showed popliteal artery and distal part .

All lower extremity arterial structures can be seen in one sequence (Figure 4).

Figure 4

Figure 4: Our first patient's MRA showed all lower extremity arterial structures in one sequence

We performed a successful aorta-bifemoral Y graft bypass operation with MR angio planning and postop 6th day he was discharged.All distal pulses were patent.

Our second case was a 55 years old ASO patient.He had an occlusive lesion at right common and external iliac artery and severe stenotic lesion at left external iliac artery in his MRA(Figure 5).

Figure 5

Figure 5: Our second patient's MRA image

We performed a successful aorta-bifemoral Y graft bypass operation for him also.

Our third patient was a 45 years old man. He had hypertension, which responsed partially to triple antihypertensives, claudication under 100 meters and occasionally rest pain at both feet. Further investigations were performed because of the negative pulses at femoral arteries and the ASO anamnesis. MRA showed Leriche syndrome beside the left renal artery duplication anomaly.At left accessory renal artery and main renal artery level, high-grade stenoses of osteal parts were found (Figure 6).

Figure 6

Figure 6: Our third patient's MRA image.

We performed a successful aorta-bifemoral Y graft bypass operation and aorto-left main renal artery bypass in same session for this third patient.

Discussion

Magnetic resonance angiography (MRA) has recently become instrumental in the diagnosis of arterial disease in various body districts and is gaining an increasingly important role in the study of peripheral vascularisation(₅). MRA has been claimed by many authors as a replacement of conventional angiography evaluating peripheral arterial occlusive disease. However, reliable detection of relevant stenoses (>70%) has to be provided for planning vascular interventions(₆).

The purpose of the study of Huegli et al is to prospectively evaluate the accuracy of intraarterial magnetic resonance (MR) angiography in the depiction of significant stenoses and occlusions, with intraarterial digital subtraction angiography (DSA) serving as the reference standard(₁). Moderate stenoses (luminal narrowing<or=50%), significant stenoses (luminal narrowing 51%-99%), and occlusions (luminal narrowing of 100%) were identified on MR angiograms, which were compared with intraarterial DSA images. Sensitivity, specificity, accuracy, and positive and negative predictive values of intraarterial MR angiography with intraarterial DSA were determined for characterization of significant stenoses (>50%) or vessel occlusions; 95% confidence intervals (CIs) were calculated for sensitivity and specificity. Sensitivity, specificity, and accuracy of intraarterial MR angiography in the characterization of significant stenoses or occlusions were 92% (95% CI: 72%, 99%), 94% (95% CI: 82%, 98%), and 93%, respectively, in femoropopliteal arteries and 93% (95% CI: 83%, 98%), 71% (95% CI: 51%, 86%), and 86%, respectively, in infrapopliteal arteries(₁).

The diagnostic accuracy of magnetic resonance angiography (MRA) in the infrapopliteal arterial segment is not well defined(₃). The study of Mell et al evaluated the clinical utility and diagnostic accuracy of time-resolved imaging of contrast kinetics (TRICKS) MRA compared with digital subtraction contrast angiography (DSA) in planning for percutaneous interventions of popliteal and infrapopliteal arterial occlusive disease(₃). Lesion morphology was classified according to the TransAtlantic Inter-Society Consensus (TASC). When evaluated by TASC classification, TRICKS MRA correlated with DSA in 83% of the popliteal and in 88% of the infrapopliteal segments. MRA correctly identified significant disease of the popliteal artery with a sensitivity of 94% and a specificity of 92%, and of the tibial arteries with a sensitivity of 100% and specificity of 84%. When used to evaluate for stenosis vs occlusion, MRA interpretation agreed with DSA 90% of the time. Disagreement occurred in 15 arterial segments, most commonly in distal tibioperoneal arteries. MRA misdiagnosed occlusion for stenosis in 11 of 15 segments,and stenosis for occlusion in four of 15 segments. Arterial access was accurately planned based on preprocedural MRA findings in 29 of 30 patients. MRA predicted technical success 83% of the time(₃).

The purpose of the study of Diehm et al is to prospectively determine the accuracy of 1.5 Tesla (T) and 3 T magnetic resonance angiography (MRA) versus digital subtraction angiography (DSA) in the depiction of infrageniculate arteries in patients with symptomatic peripheral arterial disease(₇). No significant difference in overall image quality, sufficiency for diagnosis, depiction of arterial anatomy, motion artifacts, and venous overlap was found comparing 1.5 T with 3 T MRA. Overall sensitivity of 1.5 and 3 T MRA for detection of significant arterial stenosis was 79% and 82%, and specificity was 87% and 87% for both modalities, respectively(₇).

The purpose of the study of Kreitner et al was to compare contrast-enhanced three-dimensional MR angiography with conventional digital subtraction angiography (DSA) for identifying and evaluating arteries of the distal calf and foot in diabetic patients with severe arterial occlusive disease who will undergo distal bypass surgery(₈). MRA was significantly better than DSA in revealing peripheral runoff vessels. In 38% of the patients, MRA showed patent pedal vessels suitable for distal bypass grafting that were not revealed by DSA. Because of the results of MR angiography, treatment plans changed in seven of the nine patients in whom patent vessels were subsequently used as target vessels for distal pedal bypass grafts. Contrast-enhanced three-dimensional MR angiography is superior to DSA in revealing patent vessel segments of the foot in diabetic patients with severe arterial occlusive disease(₈).

MRA is comparable to DSA for assessment of the pedal vasculature, and is able to delineate significantly more patent vessels without segmental occlusions and more metatarsal arteries than selective DSA(₉).

Fast MR angiography and conventional MR angiography do not differ significantly in terms of arterial stenosis grading or renal arterial variant detection(₁₀).

In conclusion; MRA is a noninvasive method and gives quantitative information about anatomy and flow dynamics to evaluate the peripheral occlusive arterial disease. For the patients with renal functions having risk to be effected by conventional angio and to increase the patient comfort,it is the method of choice. MRA allows a fast, safe, and accurate assessment of the arterial system in patients with arteriosclerosis and can be considered an alternative to DSA in the management of patients with steno-obstructive disease of the peripheral arteries(₅). MRA should be part of the diagnostic algorithm for patients in whom bypass grafting is a therapeutic option(₈).

Correspondence to

Doç. Dr. Ufuk YETK?N, 1379 Sok. No: 9,Burç Apt. D: 13 - 35220, Alsancak – ?ZM?R / TURKEY Tel: +90 505 3124906 , Fax: +90 232 2434848 e-mail: ufuk_yetkin@yahoo.fr