Magnetic resonance angiography in the management of lower extremity arterial occlusive disease: a prospective study

ACR Appropriateness Criteria® Sudden Onset of Cold, Painful Leg: 2023 Update

Acute onset of a cold, painful leg, also known as acute limb ischemia, describes the sudden loss of perfusion to the lower extremity and carries significant risk of morbidity and mortality. Acute limb ischemia requires rapid identification and the management of suspected vascular compromise and is inherently driven by clinical considerations. The objectives of initial imaging include confirmation of diagnosis, identifying the location and extent of vascular occlusion, and preprocedural/presurgical planning. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

ACR Appropriateness Criteria® Lower Extremity Arterial Claudication-Imaging Assessment for Revascularization: 2022 Update

Arterial claudication is a common manifestation of peripheral artery disease. This document focuses on necessary imaging before revascularization for claudication. Appropriate use of ultrasound, invasive arteriography, MR angiography, and CT angiography are discussed. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Diagnosis and Risk Assessment of Lower Extremity Peripheral Arterial Disease

Managing patients with peripheral arterial disease (PAD) requires an accurate assessment of the severity of the condition and the risk factors likely to predict disease progression. The spectrum of patient presentation ranges from asymptomatic to critical limb ischemia. Because about half of patients with PAD have coronary or cerebrovascular disease, the examination of presenting patients should be directed toward the entire cardiovascular system. The main diagnostic goal is to establish whether the symptoms are predominantly caused by PAD and to what degree the presenting problem is compounded by other comorbidities, such as diabetic neuropathy, arthritis, or venous disorders. The diagnostic process includes history taking, physical examination, noninvasive diagnostic testing, differential diagnosis, laboratory studies, and the use of the various imaging modalities, which in general are reserved for those PAD cases in which the clinician has already decided to intervene.

Role of induced hypothermia in thoracoabdominal aortic aneurysm surgery

For more than 50 years, hypothermia has been used in aortic surgery as a tool for neuroprotection. Hypothermia has been introduced into thoracoabdominal aortic aneurysm (TAAA) surgery by many cardiovascular centers to protect the body's organs, including the spinal cord. Numerous publications have shown that hypothermia can prevent immediate and delayed motor dysfunction after aortic cross-clamping. Here, we reviewed the historical application of hypothermia in aortic surgery, role of hypothermia in preclinical studies, cellular and molecular mechanisms by which hypothermia confers neuroprotection, and the role of systemic and regional hypothermia in clinical protocols to reduce and/or eliminate the devastating consequences of ischemic spinal cord injury after TAAA repair.

HPMA-RGD hydrogels seeded with mesenchymal stem cells improve functional outcome in chronic spinal cord injury

Chronic spinal cord injury (SCI) is characterized by tissue loss and a stable functional deficit. While several experimental therapies have proven to be partly successful for the treatment of acute SCI, treatment of chronic SCI is still challenging. We studied whether we can bridge a chronic spinal cord lesion by implantation of our newly developed hydrogel based on 2-hydroxypropyl methacrylamide, either alone or seeded with mesenchymal stem cells (MSCs), and whether this treatment leads to functional improvement. A balloon-induced compression lesion was performed in adult 2-month-old male Wistar rats. Five weeks after injury, HPMA-RGD hydrogels [N-(2-hydroxypropyl)-methacrylamide with attached amino acid sequences--Arg-Gly-Asp] were implanted into the lesion, either with or without seeded MSCs. Animals with chronic SCI served as controls. The animals were behaviorally tested using the Basso–Beattie-Breshnahan (BBB) (motor) and plantar (sensory) tests once a week for 6 months. Behavioral analysis showed a statistically significant improvement in rats with combined treatment, hydrogel and MSCs, compared with the control group (P < 0.05). Although a tendency toward improvement was found in rats treated with hydrogel only, this was not significant. Subsequently, the animals were sacrificed 6 months after SCI, and the spinal cord lesions evaluated histologically. The combined therapy (hydrogel with MSCs) prevented tissue atrophy (P < 0.05), and the hydrogels were infiltrated with axons myelinated with Schwann cells. Blood vessels and astrocytes also grew inside the implant. MSCs were present in the hydrogels even 5 months after implantation. We conclude that 5 weeks after injury, HPMA-RGD hydrogels seeded with MSCs can successfully bridge a spinal cord cavity and provide a scaffold for tissue regeneration. This treatment leads to functional improvement even in chronic SCI.

Decision making in the dysvascular lower extremity

Given the aging population, the number of patients at risk for peripheral arterial disease and critical limb ischemia will increase in the upcoming decade. Using a focused history and physical examination, along with a combination of noninvasive physiologic testing and noninvasive and invasive imaging modalities, one can accurately assess the location and physiologic effect of peripheral arterial disease. This assessment then allows the selection of the most appropriate treatment option for each patient. Treatment options may include exercise and risk-factor modification, amputation, and endovascular or surgical revascularization or a combination of both.

Clinical study of peroneal artery perforators with computed tomographic angiography: implications for fibular flap harvest

PURPOSE

Previous studies of cutaneous perforators of the peroneal artery have shown great variability, and attest to the significant anatomical variability in this region. Furthermore, the vascular anatomy of the region has been considered unreliable in the prediction of ideal perforator topography. Preoperative imaging has been suggested as a means for improving preoperative awareness, with Doppler ultrasound and eco-colour (duplex) ultrasound as useful tools. Multi-detector row computed tomographic angiography (CTA or angio CT), has emerged as a significant improvement, providing non-invasive operator-independent details of the vascular anatomy. We utilised this tool to perform an in vivo, anatomical study of the peroneal artery perforators, and demonstrating the usefulness of CTA in planning the osteocutaneous free fibula flap.

METHODS

Forty-one consecutive patients (82 limbs) underwent CTA of the lower limb vasculature, with the anatomical details of the peroneal artery cutaneous perforators assessed.

RESULTS

CTA was able to demonstrate the size, course and penetration pattern of all perforators over 0.3 mm in diameter, with measurements for perforators over 0.8 mm diameter recorded for analysis. Of 171 such perforators, accurate identification of the size (mean diameter 1.91 mm), course (59.6% septocutaneous, 29.2% musculocutaneous and 11.1% septomusculocutaneous) and location was achieved.

CONCLUSION

The vascular anatomy of peroneal artery perforators is highly variable, and thus there is a role for preoperative imaging. CTA can demonstrate cases where there is aberrant or non-preferred anatomy, or select the limb of choice for harvest.

Medical and endovascular management of critical limb ischemia

Critical limb ischemia (CLI) is the term used to designate the condition in which peripheral artery disease has resulted in resting leg or foot pain or in a breakdown of the skin of the leg or foot, causing ulcers or tissue loss. If not revascularized, CLI patients are at risk for limb loss and for potentially fatal complications from the progression of gangrene and the development of sepsis. The management of CLI requires a multidisciplinary team of experts in different areas of vascular disease, from atherosclerotic risk factor management to imaging, from intervention to wound care and physical therapy. In the past decade, the most significant change in the treatment of CLI has been the increasing tendency to shift from bypass surgery to less invasive endovascular procedures as first-choice revascularization techniques, with bypass surgery then reserved as backup if appropriate. The goals of intervention for CLI include the restoration of pulsatile, inline flow to the foot to assist wound healing, the relief of rest pain, the avoidance of major amputation, preservation of mobility, and improvement of patient function and quality of life. The evaluating physician should be fully aware of all revascularization options in order to select the most appropriate intervention or combination of interventions, while taking into consideration the goals of therapy, risk-benefit ratios, patient comorbidities, and life expectancy. We discuss the incidence, risk factors, and prognosis of CLI and the clinical presentation, diagnosis, available imaging modalities, and medical management (including pain and ulcer care, pharmaceutical options, and molecular therapies targeting angiogenesis). The endovascular approaches that we review include percutaneous transluminal angioplasty (with or without adjunctive stenting); subintimal angioplasty; primary femoropopliteal and infrapopliteal deployment of bare nitinol, covered, drug-eluting, or bioabsorbable stents; cryoplasty; excimer laser-assisted angioplasty; excisional atherectomy; and cutting balloon angioplasty.

Low Concentration of Isoflurane Promotes the Development of Neurogenic Pulmonary Edema in Spinal Cord Injured Rats

Anesthetics can either promote or inhibit the development of neurogenic pulmonary edema (NPE) after central nervous system (CNS) injury. The influence of isoflurane was examined in male Wistar rats using 1.5%, 2%, 2.5%, 3%, 4%, or 5% isoflurane in air. Epidural balloon compression of the thoracic spinal cord was performed. The development of NPE was examined in vivo and on histologic sections of lung tissue. Animals anesthetized with 1.5% or 3% isoflurane were behaviorally monitored using the BBB and plantar tests for 7 weeks post-injury. The spinal cord was examined using MRI and morphometry of the spared white and gray matter. All animals from the 1.5% and 2% groups developed NPE. Almost 42% of the animals in the 1.5% group died of severe pulmonary hemorrhage and suffocation; x-rays, the pulmonary index, and the histological picture revealed a massive NPE. More than 71% of the animals from the 2.5% and 3% groups did not develop any signs of NPE. Blood pressure after spinal cord compression rose more in the 1.5% group than in the 3% one. In the 1.5% group, the sympathetic ganglionic blockade prevented the neurogenic pulmonary edema development. Animals from the 3% group recovered behaviorally more rapidly than did the animals from the 1.5% group; morphometry and MRI of the lesions showed no differences. Thus, low levels of isoflurane anesthesia promote NPE in rats with a compressed spinal cord and significantly complicates their recovery. The optimal concentration of anesthesia for performing a spinal cord compression lesion is 2.5-3% isoflurane in air.

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.

Diagnosis and risk assessment of lower extremity peripheral arterial disease

Managing patients with peripheral arterial disease (PAD) requires an accurate assessment of the severity of the condition and the risk factors likely to predict disease progression. The spectrum of patient presentation ranges from asymptomatic to critical limb ischemia. Because about half of patients with PAD have coronary or cerebrovascular disease, the examination of presenting patients should be directed toward the entire cardiovascular system. The main diagnostic goal is to establish whether the symptoms are predominantly caused by PAD and to what degree the presenting problem is compounded by other comorbidities, such as diabetic neuropathy, arthritis, or venous disorders. The diagnostic process includes history taking, physical examination, noninvasive diagnostic testing, differential diagnosis, laboratory studies, and the use of the various imaging modalities, which in general are reserved for those PAD cases in which the clinician has already decided to intervene.

Natural history of stenosis in the iliac arteries in patients with intermittent claudication undergoing clinical treatment

PURPOSE

Inspite of the long experience with the treatment of intermittent claudication, little is known about the natural history of stenotic lesions in the iliac segment. With the advent of endovascular treatment, this knowledge has become important.

METHODS

Fifty-two stenosis, diagnosed using arteriography, in 38 claudicant patients were analyzed. After a minimum time interval of 6 months, a magnetic resonance angiography was performed to determine whether there was arterial occlusion. The primary factors that could influence the progression of a stenosis were analyzed, such as risk factors (smoking, hypertension, diabetes, sex, and age), compliance with clinical treatment, initial degree of stenosis, site of the stenosis, and length of follow-up.

RESULTS

The average length of follow-up was 39 months. From the 52 lesions analyzed, 13 (25%) evolved to occlusion. When occlusion occurred, there was clinical deterioration in 63.2% of cases. This association was statistically significant (P = .002). There was no statistically significant association of the progression of the lesion with the degree or site of stenosis, compliance with treatment, or length of follow-up. Patients who evolved to occlusion were younger (P = .02). The logistic regression model showed that the determinant factors for clinical deterioration were arterial occlusion and noncompliance with clinical treatment.

CONCLUSIONS

The progression of a stenosis to occlusion, which occurred in 25% of the cases, caused clinical deterioration. Clinical treatment was important, but it did not forestall the arterial occlusion. Prevention of occlusion could be achieved by early endovascular intervention or with the development of drugs that might stabilize the atherosclerotic plaque.

La perspective d’une étude dynamique des artères des membres inférieurs en IRM grâce à la séquence ECTRICKS

PURPOSE

This article presents a new MR angiography technique, Elliptic Centric Time Resolved Imaging on Contrast KineticS (ECTRICKS), which allows dynamic evaluation of the lower limb arteries opacification when venous return prevents adequate diagnostic evaluation of calf arteries.

PATIENTS AND METHODS

Comparative examinations could be compared. Additional arteries in 59 patients using a standard MRA technique and the ECTRICKS technique.

RESULTS

A total of 33 examinations could be compared. Additional arteries could be evaluated in 10% of our patient population using the ECTRICKS technique, and in 20% for our diabetic population. Arterial evaluation was better with the ECTRICKS technique in patients with diabetes and venous insufficiency.

CONCLUSION

ECTRICKS is a good complementary sequence for evaluation the calf arteries in patients with diabetes or early venous return.

Advances in vascular imaging

The improvement of vascular imaging has allowed the acquisition of vascular images with higher resolution while minimizing the risks and discomfort to patients. As imaging developments continue to progress, establishment of valid clinical-based evidence, before the application of each innovation, will assure maintenance of the current trend. Also, as the vascular surgeon adopts a more comprehensive approach in the care of vascular patients, a high-quality endovascular suite will provide an environment for integration of both traditional open and evolving endovascular procedures.

A Comparison of Magnetic Resonance Angiography, Contrast Arteriography, and Duplex Arteriography for Patients Undergoing Lower Extremity Revascularization

The objective of this study was to compare magnetic resonance angiography (MRA), contrast arteriography (CA), and duplex arteriography (DA) for defining anatomic features relevant to performing lower extremity revascularizations. From March 1, 2001 to August 1, 2001, 33 consecutive inpatients with chronic lower extremity ischemia underwent CA, MRA, and DA before undergoing lower extremity revascularization procedures. The reports of these tests were compared prospectively and the differences in the aortoiliac segment, femoral-popliteal, and infrapopliteal segments were noted. The vessels were classified as mild disease (<50%), moderate disease (50-70%), severe disease (71-99%), and occluded. These studies and treatment plans based on these data were compared. During this time period, 11 patients were not able to undergo MRA and therefore were excluded from the study. Thirty-three patients were included in this study. These patients underwent 35 procedures, as 2 patients underwent bilateral procedures. The mean age of the 33 patients was 76+/-10 years (SD). Indications for the procedures included gangrene (20), ischemic ulcer (8), rest pain (4), and severe claudication (1). Patients' medical history included diabetes mellitus (25), hypertension (20), and end-stage renal disease (5). No differences were noted between intraoperative findings and CA in this series. Two of the three differences between DA and CA were felt to be clinically significant whereas 9 of the 12 differences between MRA and CA were felt to be clinically significant. On the basis of these data in this series, MRA does not yet seem to be able to obtain adequate data on infrapopliteal segments, at least not for this highly selected population. When severe tibial calcification or very low flow states are identified, CA may be necessary for patients undergoing DA.

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.

Gadolinium-enhanced MR Angiography as First-Line Preoperative Imaging in High-Risk Patients with Lower Limb Ischemia

PURPOSE

To assess the clinical relevance of gadolinium-enhanced MR angiography (Gd-MRA) as the first-line angiographic examination for planning lower limb revascularization in patients at high risk of complications after contrast arteriography (CA).

METHOD

Forty-five consecutive patients at high risk of post-CA complications because of chronic renal insufficiency, diabetes mellitus, advanced age, or the need for brachial artery catheterization or graft puncture had Gd-MRA as first-line angiography before a surgical or endovascular procedure for lower limb ischemia.

RESULTS

After Gd-MRA, 59 procedures were performed, including 38 surgical reconstructions, 17 endovascular procedures, and four amputations. Complementary CA was only required in seven patients for whom a below-knee bypass was planned. Cumulative patency rates at 1 and 24 months were, respectively, 91% and 91% for suprainguinal bypasses, 100% and 92% for infrainguinal above-knee bypasses, 80% and 57% for below-knee bypasses, and 92% and 76% for iliofemoral angioplasties. After 24 months of follow-up, limb salvage, amputation, and mortality rates were, respectively, 86%, 3.5%, and 7% for stage II ischemia and 48%, 11%, and 30% for stages III and IV.

CONCLUSION

Gd-MRA can be proposed for first-line preoperative imaging in the management of lower limb ischemia for patients at high risk and permits the selective use of CA as a second-line examination if a below-knee bypass is required.

Comparison of Magnetic Resonance Angiography (MRA) and Duplex Ultrasound Arterial Mapping (DUAM) prior to infrainguinal arterial reconstruction

OBJECTIVE

the purpose of this study is to compare Magnetic Resonance Angiography (MRA) to Duplex Ultrasound Arterial Mapping (DUAM) and intraoperative findings to determine the clinical, accuracy of MRA for planning lower extremity revascularization procedures.

METHODS

forty-two patients who underwent lower extremity revascularization procedures had both MRA and DUAM evaluations. These data were analyzed retrospectively and two distinct endpoints were considered. First, we compared the MRA and DUAM findings for aorto-iliac, femoral-popliteal and infra-popliteal segments to intraoperative findings and evaluated the degree to which they agreed. Second, if there was a disagreement between imaging modalities, it was established whether a change in operative procedure would have resulted.

RESULTS

MRA and DUAM findings agreed in 26 of 31 cases (83%) of aorto-iliac segments, in 25 of 31 cases (81%) of femoral-popliteal segments, and in 16 of 21 cases (76%) of infra-popliteal segments. In total, DUAM agreed with intraoperative findings in 98% of cases while MRA agreed in 82% (p<.001). Disagreement between intraoperative findings and DUAM lead to an alternate surgical procedure in only one case (2%) while disagreement with MRA lead to a different procedure in 38% of cases (p<.001).

CONCLUSIONS

these data show that MRA is not yet adequate to replace conventional angiography and is less accurate that DUAM. Further improvements are necessary before MRA can be used as the sole modality for formulation of a pre-operative plan for lower extremity revascularization.

Lower extremity stepping-table magnetic resonance angiography with multilevel contrast timing and segmented contrast infusion

OBJECTIVES

Standard lower extremity contrast-enhanced magnetic resonance angiography (LE-CEMRA) with single injection bolus-chase methods on the basis of a single pelvis timing run can be accurate for depicting most vascular occlusive lesions but may fall short of catheter-based angiography when imaging tibial and pedal vessels. Magnetic resonance angiography techniques with a second contrast timing bolus and separate acquisitions for the calves and the pelvis greatly improve reliability and reduce venous contamination to levels that may render conventional angiography obsolete.

METHODS

From July to December 2001, 60 consecutive patients underwent LE-CEMRA of the calves with separate stepping-table acquisitions of the pelvis and thighs. Forty-five (75%) had complete or partial angiographic correlation during an endoluminal intervention or operative completion study. Lower extremity vessels were divided into anatomic segments (aortoiliac, femoropopliteal, tibial-pedal) for review. Three blinded observers assessed magnetic resonance source partitions, maximum-intensity projections, and volume-rendered images. Disease per segment was graded from insignificant (<20%) to occluded (100%) in 10% increments. Segments were also scored for venous contamination (scale, 0 to 3) and diagnostic quality (scale, 1 to 5). Digital subtraction angiograms were assessed similarly but separately.

RESULTS

The combination dual-timing/dual-injection technique had an overall sensitivity, specificity, and accuracy of 99%, 97%, and 98%. Venous contamination and artifact were virtually eliminated with combined technique LE-CEMRA. Diagnostic quality of calf and foot vessels was significantly superior to conventional bolus-chase magnetic resonance techniques (P <.01).

CONCLUSION

Hybrid dual-acquisition LE-CEMRA allows complete timing specification that consistently produces high-quality, artifact-free images of the calf and pedal vessels. These techniques may be accurate enough to replace conventional digital subtraction angiogram for evaluation of lower extremity vascular occlusive disease.

MR angiography for assessment of peripheral vascular disease

Contrast-enhanced 3D MRA is emerging as a powerful noninvasive imaging modality for the assessment of patients with PVD. Its clinical utility using current technology has already been well established, and the continuous development of hard- and software will likely result in significantly improved performance. Thus, Gd-enhanced MRA is likely to emerge as the dominant noninvasive imaging modality for PVD worldwide.

High-resolution multiphase contrast-enhanced three-dimensional MR angiography compared with two-dimensional time-of-flight MR angiography for the identification of pedal vessels

PURPOSE

The authors prospectively evaluated optimized multiphase high-resolution (HR) Gadolinium (Gd)-enhanced three-dimensional (3D) magnetic resonance (MR) angiography and standard two-dimensional (2D) time-of-flight (TOF) MR angiography for their ability to delineate distal calf and pedal vessels.

MATERIALS AND METHODS

Twelve patients (20 limbs) with limb-threatening peripheral arterial occlusive disease underwent HR Gd-enhanced and 2D TOF MR angiography to identify targets for distal bypass. Imaging of the region of the ankle and foot was performed on a 1.5 T system with a head coil. A standard 2D TOF MR angiography sequence was performed first. The HR Gd-enhanced MR angiography sequence was then performed after injection of 0.01-0.2 mmol/kg of gadodiamide, allowing the acquisition of multiple consecutive coronal partitions, each in 18-25 seconds. Two experienced angiographers independently analyzed both studies. Comparison with intraoperative conventional angiography was available in 10 limbs.

RESULTS

HR Gd-enhanced MR angiography allowed significantly faster imaging time (P <.0001) and larger coverage area (P <.0001) than 2D TOF MR angiography. All segments seen on 2D TOF MR angiography were visualized on HR Gd MR angiography, and significantly more suitable targets were seen well on HR Gd-enhanced MR angiography than on 2D TOF MR angiography (mean targets per limb: 3.9 +/- 1.9 vs 2.6 +/- 1.5, respectively; P =.02). In addition, HR Gd-enhanced MR angiography allowed better visualization of the arcuate pedal branch than 2D TOF MR angiography (P <.0001). Excellent correlation was demonstrated between HR Gd-enhanced MR angiography and intraoperative angiography in 29 segments (binary similarity coefficient, 0.90). A significantly higher percentage of artifacts adversely affected image interpretation with 2D TOF MR angiography than with HR Gd-enhanced MR angiography (14 limbs vs five limbs, P <.001). Artifacts on HR Gd-enhanced MR angiography included suboptimal mask in two limbs, venous contamination in one patient (two limbs), and motion artifact in one limb, although the studies remained diagnostic in all cases.

CONCLUSION

HR Gd-enhanced MR angiography identified more distal target vessels with greater confidence than 2D TOF MR angiography. Optimized HR Gd-enhanced MR angiography may replace 2D TOF MR angiography as the gold standard examination for evaluation of distal runoff.

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.

Utilizing SENSE to achieve lower station sub-millimeter isotropic resolution and minimal venous enhancement in peripheral MR angiography

PURPOSE

To use the parallel imaging technique, sensitivity encoding (SENSE), to increase spatial resolution and decrease venous contamination in peripheral magnetic resonance angiography (MRA).

MATERIALS AND METHODS

Moving table, single-bolus peripheral contrast-enhanced (CE) -MRA was performed on nine patients. Manual table movement combined with SENSE in the upper station allowed for more rapid overall scan coverage such that acquisition of the lower station began 34 seconds after aortic contrast arrival. True sub- millimeter isotropic resolution was achieved in the lower station.

RESULTS

Diagnostic MR angiograms of all three stations were obtained in all nine patients. Venous enhancement did not confound interpretation in any case. Sub-millimeter lower station resolution provided excellent vascular detail.

CONCLUSION

Decreased delay time between upper and lower station acquisition in single bolus peripheral MR angiograms, now possible using parallel imaging techniques, combined with lower station sub-millimeter resolution may decrease venous contamination and increase overall interpretability, thus increasing clinical acceptance of peripheral MRA.

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.

Preoperative magnetic resonance angiography in fibular-free flap reconstruction of head and neck defects

BACKGROUND

Conventional angiography has been recommended for imaging of the leg prior to fibular-free flap harvest. Magnetic resonance angiography (MRA) offers a similar level of accuracy at no risk to the patient and at a lower cost.

METHODS

Thirty-two patients who were considered for fibular-free flap were retrospectively reviewed. Preoperative MRA of the lower extremities was performed on all patients and used to evaluate vessel patency. The decision of free flap donor site was based upon MRA findings.

RESULTS

The choice of side harvested was changed in four (12.5%) patients and the fibula was excluded as a donor site in three patients (9%). Flap design was altered in one patient found to have abnormally short peroneal arteries. The usual correlation between palpable distal pulses and proximal patent arteries was found to be unreliable. All 29 patients underwent successful free flap reconstruction with no ischemic complications.

CONCLUSIONS

Preoperative MRA is useful when choosing the side of fibular harvesting and in excluding patients from the fibula as a donor site. We feel that the cost of obtaining preoperative imaging is outweighed by avoiding potential ischemic complications and additional operating room time with no risk to the patient's health.

Clinical evaluation and options for infrainguinal atherosclerosis therapy: when to intervene?

Cardiologists have gained considerable experience and expertise in the diagnosis and management of coronary artery disease. Interventional therapy has now become a standard cornerstone of therapy for coronary artery disease, and endoluminal stents are being used in over 70% of all coronary interventions. Diagnosis and treatment of peripheral arterial disease (PAD) has recently gained momentum. In the past, vascular surgeons and interventional radiologists were the classic caregivers for PAD patients, with an interest in deciding between intervention or no intervention. In addition, the majority of PAD patients had few medical resources since many medical specialists did not view PAD as important for many reasons, such as: (1) few effective options for the management of patients with PAD, (2) PAD did not represent a significant health hazard to patients, (3) few patients actually suffered from PAD, and (4) patients did not view PAD as a significant limitation in their quality of life. Over the past decade, a new medical specialty, vascular medicine, had dedicated itself to the comprehensive management of these complex patients. Vascular medicine specialists are predominantly internists and cardiologists. These physicians not only view PAD as an important medical issue, they understand the increasing prevalence of PAD among the "baby-boomer" generation, the shortened life-expectancy of patients with PAD, and the marked reduction in the quality of life among PAD patients. Most importantly, vascular medicine physicians are now aware of several effective options for patients with PAD.

Peripheral magnetic resonance angiography

Peripheral vascular disease (PVD) is a common disorder in western society. Reflecting on the risks and costs of contrast arteriography, magnetic resonance angiography is a powerful noninvasive imaging modality for the diagnostic workup of patients with peripheral vascular disease. This article reviews the current state of the art of magnetic resonance angiography of the peripheral vasculature.

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: gadolinium-enhanced MR angiography versus color-guided duplex US--a meta-analysis

PURPOSE

To summarize and compare the published data on gadolinium-enhanced magnetic resonance (MR) angiography and color-guided duplex ultrasonography (US) for the work-up for peripheral arterial disease.

MATERIALS AND METHODS

Studies published between January 1984 and November 1998 were included if (a) gadolinium-enhanced MR angiography and/or color-guided duplex US were performed for evaluation of arterial stenoses and occlusions in the work-up for peripheral arterial disease of the lower extremities, (b) conventional angiography was the reference standard, and (c) absolute numbers of true-positive, false-negative, true-negative, and false-positive results were available or derivable.

RESULTS

With a random effects model, pooled sensitivity for MR angiography (97.5% [95% CI: 95.7%, 99.3%]) was higher than that for duplex US (87.6% [95% CI: 84.4%, 90.8%]). Pooled specificities were similar: 96.2% (95% CI: 94.4%, 97.9%) for MR angiography and 94.7% (95% CI: 93.2%, 96.2%) for duplex US. Summary receiver operating characteristic analysis demonstrated better discriminatory power for MR angiography than for duplex US. Regression coefficients for MR angiography versus US were 1.67 (95% CI: -0.23, 3.56) with adjustment for covariates, 2.11 (95% CI: 0.12, 4.09) without such adjustment, and 1.73 (95% CI: 0.44, 3.02) with a random effects model.

CONCLUSION

Gadolinium-enhanced MR angiography has better discriminatory power than does color-guided duplex US and is a highly sensitive and specific method, as compared with conventional angiography, for the work-up for peripheral arterial disease.

Hypothermia-induced ischemic tolerance

Delayed resistance to ischemic injury can be induced by a variety of conditioning stimuli. This phenomenon, known as delayed ischemic tolerance, is initiated over several hours or a day, and can persist for up to a week or more. The present paper describes recent experiments in which transient hypothermia was used as a conditioning stimulus to induce ischemic tolerance. A brief period of hypothermia administered 6 to 48 hours prior to focal ischemia reduces subsequent cerebral infarction. Hypothermia-induced ischemic tolerance is reversed by 7 days postconditioning, and is blocked by the protein synthesis inhibitor anisomycin. Electrophysiological studies utilizing in vitro brain slices demonstrate that hypoxic damage to synaptic responses is reduced in slices prepared from hypothermia-preconditioned animals. Taken together, these findings indicate that transient hypothermia induces tolerance in the brain parenchyma, and that increased expression of one or more gene products contributes to this phenomenon. Inasmuch as hypothermia is already an approved clinical procedure for intraischemic and postischemic therapy, it is possible that hypothermia could provide a clinically useful conditioning stimulus for limiting injury elicited by anticipated periods of ischemia.

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.