Use of magnetic resonance angiography for the preoperative evaluation of patients with infrainguinal arterial occlusive disease

Surveillance and Conservative Management of a Persistent Sciatic Artery Aneurysm

A persistent sciatic artery aneurysm is a rare congenital vascular anomaly. Surgical intervention is reserved for symptomatic cases. The authors report the case of a 72-year-old woman who presented with thromboembolic occlusion of an aneurysmal persistent sciatic artery. Although initially symptomatic, she was managed expectantly with the aid of serial duplex sonographic imaging. The persistent sciatic artery subsequently thrombosed as a result of hypotension secondary to a myocardial infarction. No surgical intervention was required. The current literature on this condition is reviewed.

Time-resolved contrast-enhanced magnetic resonance angiography in the investigation of suspected intracranial dural arteriovenous fistula

Cerebral angiography is widely regarded as the gold standard for the evaluation and diagnosis of neurovascular abnormalities. However, recent improvements in the spatial and temporal resolution of time-resolved magnetic resonance angiography (MRA) offer clinicians a non-invasive alternative to cerebral angiography. We explored the utility of this technique in an elderly female patient with a suspected intracranial dural arteriovenous fistula (dAVF). A product pulse sequence available from the scanner's manufacturer (time-resolved imaging of contrast kinetics, TRICKS; GE Healthcare, Milwaukee, WI, USA) was used with the following parameters: TR/TE 2.832/TE 1.072 ms, flip angle 25°, receiver bandwidth 31.25 kHz, 0.75 NEX, acceleration factor (ASSET) of 2, field of view 14 cm, matrix size 96 × 96, phase-encoding left-right. Twenty overlapping 8-mm-thick slices were acquired in an axial orientation, with a slice spacing of 4mm. Images were acquired at 48 time points, with a temporal resolution of 0.3s/image. We found that all intracranial venous structures enhanced synchronously. There was no evidence of arteriovenous shunting. Retrograde venous flow explained the signal abnormality seen on time-of-flight MRA. We concluded that time-resolved MRA is useful in the investigation of suspected intracranial dAVF.

Limitations of and Lessons Learned from Clinical Experience of 1,020 Duplex Arteriography

Objective: Due to the inherent risks, deficiencies and cost associated with contrast arteriography (CA), our group has been utitilizing duplex arteriography (DA) for evaluating the arteries of the lower extremity for patients undergoing lower extremity revascularization. In an effort to further explore the strengths and weaknesses of DA, we reviewed our evolving experience with DA from January 1, 1998, to January 1, 2005.

Patients and Methods: The arterial segments starting from mid-abdominal aorta to the pedal arteries were studied in cross-sectional and longitudinal planes using a variety of scanheads of 7–4, 10–5, 12–5, 5–2 and 3–2 MHz extended operative frequency range to obtain high-quality B-mode, color and power Doppler images as well as velocity spectra. In 906 patients, 1,020 duplex arteriograms were obtained. The ages ranged from 30–98 years old with a mean of 73±11 (SD) years. Fifty percent of the patients were diabetics. Indications for the examination included: tissue loss (409), rest pain (221), claudication (310), acute ischemia (74), popliteal aneurysm (45), SFA aneurysm (2), abdominal aortic aneurysms (AAA) (10) and failing bypass (55). Prior procedures had been performed in 262. DA was performed by six technologists (4 of whom are MDs). In all, 207 DA were performed intraoperatively and the remainder, preoperatively.

Results: The resultant procedures based upon DA included: bypass to the popliteal artery (262) and bypass to an infrapopliteal artery (325), endovascular procedures (363), thrombectomy (11), embolectomy (9), inflow bypass procedures to the femoral arteries (46), débridment (4), amputation (8) and no intervention (75). The areas not visualized well included: iliac (73), femoral (26), popliteal (17), and infrapopliteal (221). Additional imaging after DA was deemed necessary in 102 cases to obtain enough information to plan lower extremity revascularization. Factors associated with increased need to obtain CA included: DM ( p<.001), infrapopliteal calcification ( p<.001), older age ( p = .01) and limb threatening ischemia ( p<.001). Factors not associated with the need to obtain CA included: which technologist performed the exam, whether the technologist has a medical degree and whether the patient underwent prior revascularization.

Conclusions: In 90% of patients reviewed, DA is able to obtain the needed information to plan lower extremity revascularization. Severe tibial vessel calcification is the most common cause of an incomplete DA exam and determines when alternative imaging modalities need to be obtained.

Preprocedural imaging: new options to reduce need for contrast angiography

In vascular surgery, the gold standard for evaluation of the lower-extremity arterial tree has long been contrast arteriography (CA). Associated risks of CA are well-documented and include severe allergic reactions, arterial injury and/or hemorrhage, and contrast-induced nephropathy. Increasingly, less-invasive techniques, with fewer inherent risks for complication, are being explored as diagnostic alternatives. Magnetic resonance angiography, computed tomography angiography, and duplex arteriography, each offer distinct advantages, though are not without limitation. This review explores the indications, advantages, and disadvantages of these newer technologies and provides a comparison to CA as a means for defining the anatomic features of patients undergoing lower-extremity revascularization. This data suggests that noninvasive imaging technologies may, in the future, play an increasingly important role in the surgical evaluation of the patient with lower-extremity ischemia.

Limb-salvage angioplasty in vascular surgery practice

OBJECTIVE

To assess outcomes of percutaneous infrainguinal arterial angioplasty for treatment of chronic limb-threatening ischemia (CLI) in poor surgical candidates.

METHODS

A retrospective clinical analysis of 67 consecutively treated patients (76 limbs) with CLI over a 33-month period was performed. Patients were considered poor surgical candidates because of absent distal target vessels (31 limbs), severe comorbid conditions (36 limbs), or lack of an autologous vein for distal bypass (9 limbs). Limb salvage was defined as preservation of a functional foot without the need for a prosthesis. Technical success was defined as the ability to percutaneously recanalize the arterial segment with less than 30% residual stenosis. Clinical success was healing of ulcers or minor amputation sites, resolving rest pain, or avoiding a major amputation. Successful technical and clinical outcomes were correlated with patient demographics, clinical presentation, and TransAtlantic Inter-Society Consensus arterial lesion characteristics by using the Fisher exact test.

RESULTS

Seventy-six limbs were treated for rest pain (n = 12), gangrene (n = 22), or nonhealing ulcers (n = 42). There were 40 men and 27 women. The mean age was 70 years (range, 36-94 years). Lesions were located in tibial (n = 55), popliteal (n = 6), and superficial femoral (n = 15) arteries. Arterial recanalization and limb salvage was achieved in 64 (83.5%) limbs. Technical failure (n = 12) correlated with TransAtlantic Inter-Society Consensus D lesions ( P = .009) and the presence of occlusion ( P = .027). Clinical failure (major amputation, n = 12) correlated with the presence of gangrene ( P = .032) or the combination of diabetes, arterial occlusion, and gangrene ( P = .018). The single variables of age, sex, diabetes, and renal failure did not adversely affect outcomes. There was one mortality (myocardial infarction), and there were two major morbidities (femoral artery pseudoaneurysm and sepsis).

CONCLUSIONS

Peripheral arterial angioplasty should be considered as an alternative to primary amputation in selected patients with CLI who are poor candidates for traditional surgical bypass.

Magnetic resonance angiography versus duplex arteriography in patients undergoing lower extremity revascularization: which is the best replacement for contrast arteriography?

OBJECTIVE

In an effort to explore alternatives to contrast material-enhanced arteriography, we compared magnetic resonance angiography (MRA) and duplex arteriography (DA) with contrast arteriography (CA) for defining anatomic features in patients undergoing lower extremity revascularization.

METHODS

From August 1, 2001, to August 1, 2002, 61 consecutive inpatients (64 limbs) with chronic lower extremity ischemia underwent CA, MRA, and DA before undergoing lower extremity revascularization procedures. The reports of these tests and images were compared prospectively, and the differences in the iliac, femoropopliteal, and infrapopliteal segments were noted. The vessels were classified as mildly diseased (<50%), moderately diseased (50%-70%), severely diseased (71%-99%), or occluded. The studies and treatment plans based on these data were compared.

RESULTS

Mean patient age was 76 +/- 10 years (SD). Indications for the procedures included gangrene (43%), ischemic ulcer (28%), rest pain (19%), severe claudication (9%), and failing bypass (1%). During this period 35 patients were ineligible for the protocol, because they could not undergo MRA (n=27) or angiography (n=8). Of the total 192 segments in the 64 patients (iliac, femoropopliteal, tibial), 17% were not able to be fully assessed with DA, and 7% with MRA. Disagreements with CA and DA were found in the iliac, femoropopliteal, and tibial segments in 0%, 7%, and 14% of cases, respectively, and between CA and MRA in 10%, 26%, and 42% of cases, respectively. Two of 9 differences (22%) between DA and CA were thought to be clinically significant, and 28 of 45 differences (62%) between MRA and CA were thought to be clinically significant.

CONCLUSIONS

A review of the data obtained in this series indicates that MRA does not yet seem to yield adequate data, at least in this highly selected population at our institution. When severe calcification is identified, CA may be necessary in patients undergoing DA.

From the RSNA Refresher Courses

Acquired diseases of the aorta and peripheral arteries are common. Owing to technical advances, magnetic resonance (MR) angiography has become the primary imaging modality for assessment of aortic and peripheral arterial disease. Contrast material-enhanced MR angiography is a rapid and robust technique that has emerged as the principal MR angiographic technique for evaluation of vascular disease. Two-dimensional time-of-flight MR angiography still has some well-validated applications, especially in distal peripheral vascular disease. Phase-contrast flow imaging is an important technique for quantification of blood flow. Black-blood imaging is a valuable tool for evaluation of the vessel wall. Understanding the principles of the main MR angiographic techniques is essential for consistent acquisition of diagnostic images. In addition, tailoring the acquisition parameters and the imaging protocol to the vessel being imaged and the clinical question is mandatory for optimal results. Future technical developments that will lead to faster image acquisition and better contrast agents promise to further improve image quality.

Peripheral MR angiography

Peripheral arterial occlusive disease is a chronic and progressive disease with a reported incidence rate from 4.5% to 8.8% in men over 55 years of age. The diagnosis is usually made clinically, but for treatment planning and control, imaging of the peripheral arteries is required. Since its introduction in 1994, contrast-enhanced MR angiography has demonstrated a high diagnostic confidence and has replaced the invasive intra-arterial DSA, which is still the current gold standard for many different indications. For the peripheral arteries, clinical use of MR angiography was hampered for some years by the unsolved problem of the large imaging volume and the small diameter of the distal arteries. However, since the availability of ultra-fast high-gradient sequences and the possibility of moving-bed imaging, contrast-enhanced MR angiography, over the last few years, has shown its enormous potential and high accuracy in the diagnosis and follow-up of patients suffering from peripheral arterial occlusive disease. Exciting innovations in hardware and software allows very fast, very accurate, and very robust noninvasive imaging of the peripheral arteries, and both treatment planning as well as follow-up can be performed using contrast-enhanced MR angiography. The following review introduces the basic concepts of peripheral MR angiography--focusing on contrast enhanced imaging--and presents the different techniques as well as some potential limitations and how they could be solved. Finally, this article provides a look into the already-begun future of peripheral contrast-enhanced MR angiography with hybrid and combination techniques.

Magnetic resonance angiography unmasks reliable target vessels for pedal bypass grafting in patients with diabetes mellitus

OBJECTIVE

The purpose of this study was to evaluate the performance of pedal bypass grafts to foot vessels detected by magnetic resonance angiography (MRA) that were occult in conventional angiography in patients with diabetes mellitus and severe arterial occlusive disease.

METHODS

Vascular surgery and radiology registries were reviewed for patients with pedal bypass grafts to arteries that were not detected with digital subtraction angiography but unmasked with MRA. From December 1997 to March 1999, 15 patients (mean age, 73 +/- 8 years) were identified and analyzed retrospectively. All the patients were diabetic, with 60% being insulin-dependent. Advanced tissue loss was the operative indication in all the cases. Distal anastomosis was performed to the dorsalis pedis artery in 10 cases and to the plantar artery in five cases, with ipsilateral greater saphenous vein as graft material in all the cases.

RESULTS

The perioperative mortality rate was 7% (1 of 15 cases). One graft occlusion resulted in a secondary patency rate of 93.1%. During a mean follow-up examination period of 22 months, no graft occlusions and one major amputation were noted, which resulted in a secondary patency rate of 93.1% and a limb salvage rate of 89.5% at 36 months.

CONCLUSION

Foot vessels that were occult in conventional angiography but could be detected with MRA were shown to be suitable target vessels for pedal bypass grafting with promising results.

Contrast enhanced MR angiography in the assessment of relevant stenoses in occlusive disease of the pelvic and lower limb arteries: diagnostic value of a two-step examination protocol in comparison to conventional DSA

INTRODUCTION/OBJECTIVES

Contrast-enhanced MRA (ce-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. Only few data in the literature focuses on this crucial problem. The purpose of this study was to evaluate this topic using a two-step body-coil-based MRA protocol.

METHODS AND PATIENTS

Forty three patients presenting with 82 stenoses >/=50% and 61 stenoses >70% on conventional catheter angiogram received fast Gadolinium-DTPA-enhanced high resolution 3D MR angiography at 1.5 T covering the pelvic and peripheral vascular tree in two examination steps using the body-coil. The data were evaluated double-blinded by three readers distinguishing moderate (50-70%) from severe stenoses (>70%).

RESULTS

Overall sensitivity/specificity/accuracy was 84/60/70% evaluating 143 segments. Specificity was rather poor in the iliac (58%) and crural (50%) region and moderate in the femoral and popliteal level (73%). The negative predictive value ranged between 78 and 91%. The grade of stenosis tend to be overestimated rather than underestimated in all levels with positive predictive values between 55 and 78%.

DISCUSSIONS AND CONCLUSIONS

Body-coil-based contrast-enhanced MRA has limited potential in distinguishing moderate from severe stenoses in peripheral occlusive disease. Overestimations are more common than underestimations. Both occur mainly in small-sized crural arteries but also in larger iliac arteries where vessel course in partition direction may cause inadequacy between voxel size and lumen diameter in severe stenosis.

Peripheral vascular surgery and magnetic resonance arteriography--a review

OBJECTIVES

to review the current status of lower limb MRA.

DESIGN

a literature review based predominantly on a MEDLINE database search of English-language publications from January 1991 to October 2000.

MATERIALS AND METHODS

twenty-eight articles, concerning non-enhanced MRA (13), gadolinium-enhanced MRA (14) or both (1), met the predefined requirement for quality. Results gadolinium-enhanced MRA (CE-MRA) seems to be more accurate, quicker and associated with fewer problems than non-enhanced (TOF) MRA. TOF-MRA has a sensitivity and specificity of 93% (range 64-100%) and 88% (range 57-100%) respectively, and CE-MRA presents values of 96% (range 71-100%) and 96% (63-100%), respectively, using conventional arteriography as the gold standard. Some articles report a substantial incidence of runoff vessels suitable for distal bypass visible on MRA but invisible on conventional arteriography. Gadolinium contrast is given intravenously and is generally well tolerated and has no known nephrotoxicity.

CONCLUSION

CE-MRA is accurate compared to conventional arteriography, has the potential to increase the limb salvage rate for selected patients, is non-invasive and well tolerated.

Has arteriography gotten a bad name? Current accuracy and morbidity of diagnostic contrast arteriography for aortoiliac and lower extremity arterial disease

Recently, contrast arteriography has been challenged as the diagnostic test of choice for lower extremity arterial disease because of its associated morbidity and questionable accuracy in identifying suitable distal outflow arteries. The purpose of this report was to analyze our experience to determine if these concerns were justified. We reviewed 500 consecutive contrast arteriograms performed at our hospital for aortoiliac and lower extremity arterial disease between November 1994 and November 1998. Arteriograms performed in conjunction with therapeutic procedures such as balloon angioplasty, stent placement, and thrombolysis were excluded, leaving 244 diagnostic cases for analysis. Forty-six percent (112) of patients had diabetes mellitus, 14% (34) had an elevated baseline serum creatinine (> or =1.5 mg/dL), and an additional 7% (17) were dialysis dependent. Radiologists limited contrast volume by imaging only the symptomatic extremity when appropriate and using digital subtraction techniques as indicated. Our results showed that diagnostic contrast arteriography is associated with an acceptably low morbidity, has an accuracy that is unlikely to be surpassed by other modalities, and remains the diagnostic test of choice for lower extremity arterial disease.

Peripheral arterial disease: meta-analysis of the diagnostic performance of MR angiography

PURPOSE

To summarize the overall diagnostic performance of magnetic resonance (MR) angiography in the evaluation of peripheral arteriosclerotic occlusive disease and to identify the most important sources of variation in diagnostic accuracy between studies.

MATERIALS AND METHODS

A search strategy in MEDLINE and citation tracking were used to identify relevant English-language articles published since 1991. Each article was critically appraised for examination, patient, and study design characteristics. The accuracy data from different studies were analyzed by constructing summary receiver operating characteristic curves; multiple linear regression was used to examine the variation between study results.

RESULTS

Twenty-three studies were included. There was much heterogeneity in the study results, which could not be explained as differences in the threshold for a positive result. About half of the variation was due to the type of MR angiographic examination and the extent of image evaluation. The relative diagnostic odds ratio (DOR) for three-dimensional (3D) gadolinium-enhanced MR angiography compared with two-dimensional (2D) time-of-flight MR angiography was 7.46 (95% CI: 2.48, 22.20). The relative DOR for review of transverse source images or multiplanar reformations in addition to maximum intensity projections (MIPs) compared with the use of only MIPs for image evaluation was 4.53 (95% CI: 1.46, 13.87).

CONCLUSION

The diagnostic accuracy of 3D gadolinium-enhanced MR angiography is superior to that of 2D time-of-flight MR angiography. Also, the review of transverse source images or use of additional postprocessing techniques, such as multiplanar reformation, results in significantly better diagnostic performance.

Percutaneous vascular intervention based on gadolinium-enhanced MR angiography

PURPOSE

To determine if gadolinium-enhanced magnetic resonance angiography (Gd-MRA) could be used to reliably plan percutaneous vascular procedures.

PATIENTS AND METHODS

Over the course of 13 months, 31 patients underwent attempted percutaneous intervention solely on the basis of a preceding Gd-MRA study. A total of 49 arterial segments were targeted (28 extremities, 21 visceral). Five segments in four patients were not treated (less impressive disease severity on conventional catheter angiography [CA] in four segments, diffuse intrarenal atherosclerosis in one segment). Interventions attempted were percutaneous transluminal angioplasty (n = 10), angioplasty with stent placement (n = 29), and thrombolysis (n = 3). Interventions were successful in all segments, except two because of the inability to cross an occlusion.

RESULTS

Good to strong correlation was noted between Gd-MRA and CA regarding stenosis severity and length and the presence of poststenotic dilatation. MRA underestimated the complexity of stenosis. Subjective quality and preintervention confidence were excellent in the majority of MRA studies and satisfactory in the rest. The overall value in "procedural planning" was judged high in 40 segments, satisfactory in five segments, and poor in four segments. The procedural planning and positive predictive values of MRA were significantly lower for visceral arteries compared to iliac and peripheral arteries.

CONCLUSION

In most cases, Gd-MRA reliably yielded the anatomic and diagnostic information necessary to plan percutaneous vascular interventions noninvasively and without iodinated contrast. In the authors' practice, Gd-MRA is becoming a key imaging modality in the workup of patients in whom percutaneous intervention is anticipated.

Time-of-flight MR angiography with Gd-DTPA hexamethylene diamine co-polymer blood pool contrast agent: comparison of enhanced MRA and conventional angiography for arterial stenosis induced in rabbits

Vascular stenoses were induced in the external iliac arteries of New Zealand white rabbits by a combination of hypercholesterolemic diet and repeat balloon injury. Two-dimensional (2D) and three-dimensional (3D) time-of-flight (TOF) magnetic resonance angiography (MRA) was performed with a specifically designed phased array coil in a 1.5 T system. Enhancement with gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) hexamethylene diamine co-polymer (Nycomed: NC 22181), a blood pool MR contrast agent, was measured after contrast administration and compared with pre-contrast images at the same levels. Vessel diameter measurements were obtained at multiple levels and compared with comparable levels on conventional angiograms of the same animals. Stable enhancement, averaging 227% above baseline, was observed with the 3D TOF MRA over the 40 minutes of this study. Enhancement was not observed with the 2D TOF technique. Measurement of the smallest vessels in this study with 3D TOF MRA was slightly improved following contrast enhancement, although both pre- and post-contrast diameter measurements tended to underestimate the assumed true vessel diameter. Thus, Gd-DTPA hexamethylene diamine co-polymer (Nycomed: NC 22181), a blood pool MR contrast agent, produces significant, stable enhancement with the 3D TOF technique and may improve MRA measurement of small vessels.

MR angiography in the evaluation of atherosclerotic peripheral vascular disease

Magnetic resonance (MR) angiography of lower extremity occlusive vascular disease has evolved into a feasible diagnostic imaging option. The previous emphasis on time-of-flight techniques was associated with lengthy acquisition times and artifactual signal losses. Those limitations presented an obstacle to widespread clinical implementation. However, the emergence of rapid imaging sequences combined with gadolinium chelate enhancement offers time-efficient alternatives that can yield a truer representation of the vascular anatomic structure. The technology is now poised to serve as a routine screening study, provided that radiologists understand all factors needed to generate clinically relevant MR angiograms. This article is intended to provide a useful resource directed toward achieving that understanding.

Automated bolus chase peripheral MR angiography: initial practical experiences and future directions of this work-in-progress

Bolus chase 3-dimensional MR angiography (3D MRA) is a recent development that extends the effective field of view for arterial imaging from the typical single 40-50 cm to over 100 cm. This technique is well suited for imaging long vascular territories such as the lower extremity. Bolus chase peripheral 3D MRA is achieved with overlapping 3D gradient-echo scans during the arterial transit of a single intravenous injection of gadolinium-chelate contrast media. This technique can depict the arteries from the infrarenal aorta to the ankles in less than 2 minutes. The initial experiences with bolus chase peripheral MRA using an automated algorithm that controls both table translation and 3D data acquisition are described. Suggestions for future refinements to the technique are also discussed.

Comparison of treatment plans for lower extremity arterial occlusive disease made with electrocardiography-triggered two-dimensional time-of-flight magnetic resonance angiography and digital subtraction angiography

BACKGROUND

The purpose of the study was to determine whether preoperative treatment plans for patients with lower extremity ischemia can be made with electrocardiography (EKG)-triggered two-dimensional (2D) time-of-flight (TOF) magnetic resonance angiography (MRA) as accurately as digital subtraction angiography (DSA).

METHODS

Forty patients were prospectively evaluated with the combination of EKG-triggered 2D TOF MRA, DSA, and pulse volume recordings. Blinded reviewers graded arterial segments for disease severity. Accuracy of separate MRA- and DSA-based treatment plans was compared with the procedures performed based on all available information.

RESULTS

There was an 86% exact match between MRA- and DSA-based plans (92% MRA and 94% DSA accuracy). The MRA-based plan accurately predicted 90% of suprainguinal and 95% of infrainguinal procedures, whereas the DSA-based plan accurately predicted 100% of suprainguinal and 85% of infrainguinal procedures. Two-year primary patency was 83% for all procedures. Radiologists' review of disease severity resulted in a mean exact correlation between studies of 81% (kappa = 0.64). The agreement between radiologists interpreting the MRA was 84% (kappa = 0.7) compared with 82% (kappa = 0.66) for the DSA.

CONCLUSIONS

MRA- and DSA-based preoperative management plans were of comparable efficacy. Significant interobserver variability was seen with the interpretations of both preoperative studies. EKG-triggered 2D TOF MRA can be used to plan arterial reconstructions; however, all patients require arterial pressure measurements prior to suprainguinal repair and confirmatory intraoperative angiography during infrainguinal revascularization.

Contrast-enhanced subtraction MR angiography in occlusive disease of the pelvic and lower limb arteries: results of a prospective intraindividual comparative study with digital subtraction angiography in 76 patients

PURPOSE

The purpose of this work was to evaluate the feasibility and clinical use of MR angiography (MRA) for examining the pelvic and lower limb arteries in patients with arterial occlusive disease.

METHOD

Seventy-six patients with clinical signs of peripheral arterial occlusive disease were included in the study. MRA was performed using a fast contrast-enhanced high-resolution 3D technique that covered the area from the distal abdominal aorta to the distal lower limbs in two examination steps.

RESULTS

In all patients, diagnostic images comparable with those of conventional intraarterial digital subtraction angiography (DSA) could be obtained. No false-negative findings were seen in the iliac, femoral, or popliteal arteries. Ten to 16% of the mild stenoses and 6-14% of the severe stenoses, mainly in the crural vessels, were overgraded compared with intraarterial DSA. Particularly in patients with proximal severe obstructions or occlusions, the crural segments could be depicted more clearly due to decreased arterial runoff in conventional angiography.

CONCLUSION

The consistency of the excellent depiction of the vascular territories of the distal aorta and the pelvic and lower limb arteries in a standardized setting suggests great potential for the use of MRA in the primary diagnosis of peripheral arterial occlusive disease.

Vascular surgery without arteriography: use of Duplex ultrasound

Although contrast arteriography has served as the historical 'gold standard' for diagnosis of arterial disease, recent improvements in noninvasive diagnostic methods have made it possible to plan surgical treatment without subjecting patients to this invasive procedure. This approach avoids both the risks and costs associated with arteriography. Duplex scanning has become the standard noninvasive test for extracranial carotid artery disease, and it can also be used to directly evaluate the lower extremity arteries. In addition to the standard duplex criteria for classification of carotid stenosis, new criteria are available that reflect the stenosis thresholds identified in randomized clinical trials. Clinical experience has clearly shown that carotid endarterectomy can be performed safely based on the duplex scan alone in the majority of patients: however, arteriography is still indicated in selected cases. The evaluation of lower extremity arterial disease requires examination of multiple arterial segments, and most vascular surgeons still rely on the anatomic detail provided by arteriography for preoperative planning. Still, it may be possible to avoid formal preoperative arteriography in selected patients by using a combination of lower extremity duplex scanning and intraoperative arteriography. Further developments in noninvasive testing will continue to reduce the need for diagnostic arteriography prior to direct arterial surgery.

Alternative imaging techniques in vascular surgery

Progress in vascular surgery has led to the need for more sophisticated methods of imaging the vascular system. Although conventional contrast angiography is still the primary method of visualizing the vascular system, it has problems and limitations that occasionally render it unsafe or inadequate. When conventional angiography cannot provide the needed information, 3 newer imaging methods--3-dimensional (3-D) spiral computed tomographic scanning, computed tomographic angiography, and magnetic resonance angiography--are being used more widely to supplement or replace contrast angiography. The advantages, disadvantages, and clinical application of each method will be described. These methods have fundamentally changed the practice of vascular surgery and a thorough knowledge of them is essential.

Comparison of two-dimensional MR digital subtraction angiography of the lower extremity with x-ray angiography

PURPOSE

To perform a preliminary evaluation of the diagnostic accuracy of contrast-enhanced, two-dimensional (2D) magnetic resonance (MR) digital subtraction angiography (DSA) of the lower extremity by comparison with x-ray angiography (XRA).

MATERIALS AND METHODS

Forty lower extremities in 22 patients were imaged at multiple levels with both XRA and 2D MR DSA. Images were retrospectively analyzed by three radiologists in a randomized blinded manner. Seventeen vascular segments were graded as an insignificant lesion, a significant lesion, or as an occlusion. With the use of segments well depicted with XRA as the gold standard, the sensitivity, specificity, and accuracy of 2D MR DSA, as compared with XRA, were evaluated. The McNemar-Stuart-Maxwell test was performed to determine the significance of any differences found.

RESULTS

Three hundred eighty-three arterial segments were evaluated with both techniques. Three hundred one segments were well depicted with XRA. There was no significant difference between 2D MR DSA and XRA for assessing the degree of occlusive disease in these 301 segments (.25 < P < .5). The sensitivity, specificity, and diagnostic accuracy of 2D MR DSA were found to be 90%, 98%, and 93%, respectively.

CONCLUSION

Two-dimensional MR DSA is an accurate method for assessing arterial lesions in the lower extremity.

The role of infrapopliteal MR angiography in patients undergoing optimal contrast angiography for chronic limb-threatening ischemia

PURPOSE

To determine the benefit of infrapopliteal magnetic resonance angiography (MRA) in patients with chronic limb-threatening ischemia who have undergone optimal contrast angiography (CA).

PATIENTS AND METHODS

Thirty-four patients (37 limbs) with limb-threatening chronic lower extremity ischemia underwent MRA and CA of the symptomatic extremity. Selective, vasodilator-enhanced digital subtraction angiography of the infrapopliteal vessels was possible for 34 limbs. Two vascular surgeons retrospectively formulated treatment plans based on CA. They then formulated treatment plans based on CA and MRA together.

RESULTS

CA clearly visualized 495 of 888 vascular segments as patent, while MRA clearly visualized 412 of 888 segments. Treatment plans differed for at least one of two surgeons in eight limbs, but MRA would possibly have improved clinical outcome in only one. The amount of inflow disease did not appear to influence segment visualization or treatment planning. In eight of 11 limbs that eventually required below- or above-knee amputation, CA clearly visualized more vascular segments than MRA. One patient developed renal insufficiency after CA.

CONCLUSION

Most patients undergoing optimal CA for chronic limb-threatening ischemia will not benefit from the addition of MRA. However, MRA should be considered when CA is suboptimal and when it is necessary to conserve contrast material.

A phase contrast (PC) rephase/dephase sequence of magnetic resonance angiography (MRA): a new technique for imaging distal run-off in the pre-operative evaluation of peripheral vascular disease

OBJECTIVE

To prospectively compare a 3-D phase contrast (PC) magnetic resonance angiography (MRA) sequence (rephase/dephase) with digital subtraction angiography (DSA) in pre-operative evaluation for femoropopliteal grafting in peripheral vascular disease. Assessment of distal run-off vessels and suggested siting of distal graft anastomosis to the above or below knee segment of the popliteal artery was made.

METHODS

Twenty-two lower extremities booked for infra-inguinal vascular reconstruction were imaged pre-operatively using MRA and DSA. A PC rephase/dephase sequence which includes gradient motion refocusing (Siemens 1.0 T Magnetom Impact TR 50 ms, TE 14/14 ms and 15 degree flip angle) and 3-D MIP algorithm reconstruction was used to obtain the MR images. Standard techniques were used to obtain the DSA images, and the mean and median time between imaging modalities was one month. Blinded review by a consultant vascular radiologist scored nine vessel segments for each limb and assessed which popliteal arterial segment would be most suitable for distal anastomosis.

RESULTS

The score from DSA and MRA agreed for 155/198 vessel segments (kappa 0.57) and the suggested siting for distal anastomosis agreed for 19/22 limbs (kappa 0.72). Eighteen limbs had surgery as planned (distal anastomosis to the above knee popliteal eight limbs, below knee popliteal 10 limbs). For three limbs the siting of the distal anastomosis suggested by DSA and MRA disagreed. The more accurate modality was proved for one of three limbs and showed MRA to be superior to DSA.

CONCLUSION

Three-dimensional PC rephase/dephase MRA is a promising technique which compared well with DSA in the pre-operative assessment of distal run-off for femoropopliteal grafting.

Assessment of complicated arterial bypass grafts: value of contrast-enhanced subtraction magnetic resonance angiography

PURPOSE

To evaluate complicated aortoiliac and lower extremity arterial bypass grafts with contrast-enhanced subtraction magnetic resonance angiography (MRA).

METHODS

Twenty-three patients with 40 vascular grafts with either clinical symptoms or abnormal duplex findings were selected. They were examined using a fast T1-weighted gradient-echo sequence. Twelve to 19 coronal sections of 5 to 8 mm were acquired before and after an intravenous bolus injection of gadolinium (0.1 mmol/kg) in 25 to 40 seconds. Final images were created by subtracting each precontrast section from its corresponding postcontrast section. The MRA was obtained after subtraction and maximum intensity projection.

RESULTS

MRA detected 38 grafts (95%) with 28 abnormalities. Two stenoses were overestimated. MRA had a sensitivity of 91% and a specificity of 92% for diagnosis of graft stenoses and occlusions. MRA brought out more information in five cases by demonstrating four nonthrombotic ectasias that were unseen by duplex sonography and one thrombotic ectasia that was unseen by x-ray angiography.

CONCLUSIONS

MRA seems to compare favorably with x-ray angiography for the diagnosis of arterial bypass graft complications. A multicenter trial will be necessary to validate these preliminary results and to assess the exact role of MRA compared with the other established techniques.

Utility of magnetic resonance arteriography for distal lower extremity revascularization

PURPOSE

Magnetic resonance arteriography (MRA) of the lower extremities affords several possible advantages over conventional contrast arteriography (CA). We hypothesized that MRA of the infrageniculate vessels was sufficiently accurate to replace CA before revascularization procedures in patients with limb-threatening ischemia.

METHODS

Fifty-three extremities in 49 patients were prospectively evaluated before attempted infrageniculate revascularization procedures with preoperative infrageniculate time-of-flight MRA (cost, $170/study) and standard contrast arteriography (cost, $1310/study) of the aortoiliac and runoff vessels. Independent operative plans were formulated based on the MRA and CA results before the revascularization procedure. Intraoperative, prebypass arteriograms (IOA; cost, $46/study) were obtained in all patients to confirm the adequacy of the distal runoff. The preoperative plans formulated by the results of MRA and CA were compared with the actual procedure performed based on the IOA. All arteriograms (CA, MRA, IOA) were reviewed after the operation by two independent reviewers, and the number of patent vessel segments and those with < 50% stenosis was determined.

RESULTS

Revascularization procedures were performed in 44 of 53 extremities (83%), and amputation was performed in nine extremities (17%) because of an absence of a suitable bypass target. The CA and MRA were equally effective in predicting the optimal operative plans as determined from IOA (CA, 42 of 53 [77%] vs MRA, 40 of 53 [75%]; p = 0.79). More patent vessel segments were seen on CA than MRA (reviewer A, 229 vs 174, kappa = 0.32; reviewer B, 321 vs 314, kappa = 0.46); however, a comparable number of segments were seen if the vessels of the foot were excluded. The accuracy (reviewer A, 78% vs 68%, p = 0.003; reviewer B, 75% vs 67%, p = 0.003) and sensitivity (reviewer A, 69% vs 51%, p = 0.001; reviewer B, 68% vs 46%, p = 0.0001) of CA relative to IOA were superior to those of MRA, although the specificity was comparable (reviewer A, 86% vs 90%, p = 0.31; reviewer B, 82% vs 87%, p = 0.52). The combination of MRA and IOA would have resulted in the optimal operative plan in 51 of the 53 cases (96%) and was comparable with CA and IOA (53 of 53; 100%; p = 0.50). Substitution of MRA and IOA for CA and IOA could potentially have saved an estimated $60,420.

CONCLUSIONS

The combination of MRA and IOA provides an accurate, cost-efficient strategy for visualization of the infrageniculate vessels before revascularization procedures.