Femoral MR angiography versus conventional angiography: preliminary results

Is Duplex Ultrasonography an Effective Single Modality for the Preoperative Evaluation of Peripheral Vascular Disease?

The purpose of this study was to determine whether duplex ultrasonography can be used as an effective modality for the preoperative evaluation of lower-extremity arterial occlusive disease. The records of all patients undergoing both color flow duplex scanning and contrast arteriography of the lower extremities during a 13-month period were reviewed. Comparisons between the two modalities were made at the femoral, popliteal, and tibial artery levels. Sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy were calculated for duplex scanning using angiography as the gold standard. Three hundred fifteen arterial segments were evaluated. Color flow imaging overestimated the degree of stenosis in seven vessels and underestimated the degree of stenosis in four vessels. Overall duplex ultrasonography accurately determined lower-extremity arterial anatomy as defined by contrast arteriography with a sensitivity of 96.9 per cent, a specificity of 96.2 per cent, a positive predictive value of 94.6 per cent, a negative predictive value of 97.8 per cent, and an overall accuracy of 96 per cent The accuracy of duplex ultrasonography must be determined in each individual vascular laboratory. Once this is satisfactorily accomplished color flow scanning may be used as the single imaging modality for lower-extremity arterial occlusive disease in selected patients deemed to be at high risk for contrast angiography.

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.

Abdomen, pelvis, and extremities: diagnostic accuracy of dynamic contrast-enhanced turbo MR angiography compared with conventional angiography-initial experience

To determine the value of contrast material-enhanced three-dimensional turbo magnetic resonance (MR) angiography compared with conventional cut-film or digital subtraction angiography for evaluating arterial stenosis in the abdomen, pelvis, and extremities. For detection of significant stenosis, MR angiography had 91% sensitivity and 89% specificity. This technique is highly sensitive in lesion detection, but stenosis tended to be overestimated.

Imaging in blood stasis. The role of imaging techniques in defining the causes, presence, and effects of blood stasis

There have been considerable developments in the ability to image blood vessels and blood flow using ultrasound, CT, and MR imaging. The effects of vascular pathology in causing changes in the blood leading to thrombus formation now can be seen clearly because of these developments. In particular, new ultrasound MR imaging techniques allow more precise assessment of vessel walls and flow than has ever been possible before using conventional techniques, such as angiography. MR imaging has a unique potential for noninvasively demonstrating the natural history of developing vascular disease and the effects of this on blood flow and progression to thrombosis.

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.

Magnetic resonance angiography of nonferromagnetic iliac artery stents and stent-grafts: A comparative study in sheep

PURPOSE

To compare nonferromagnetic iliac artery prostheses in their suitability for patency monitoring with magnetic resonance angiography (MRA) using conventional angiography as a reference.

METHODS

In experiment 1, three Memotherm stents were inserted into the iliac arteries of each of six sheep: two "tandem" stents on one side and a single stent on the other side. In experiment 2, four prostheses (normal and low-porosity Corvita stent-grafts, Memotherm, ZA-stent) were inserted in each of 11 sheep. Patency was monitored before and 1, 3, and 6 months after insertion with 3D phase-contrast and two 2D time-of-flight sequences (TOF-1: TR/TE = 18/6.9, TOF-2: 13/2.5) with and without contrast at 1.5 T. On 206 coronal MIP images (72 pre-, 134 post-stenting), three readers analyzed 824 iliac segments (206 x 4) for patency and artifacts.

RESULTS

There was no difference in the number of artifacts between tandem and single iliac Memotherm stents. The ZA-stent induced significantly fewer artifacts than the other prostheses (p < 0.00001). With MRA, patency of the ZA-stent was correctly diagnosed in 88% of cases, which was almost comparable to nonstented iliac segments (95%), patency of the Memotherm stent in 59%, and of the Corvita stent-grafts in 57% and 55%. The TOF-2 sequence with contrast yielded the best images.

CONCLUSION

MRA compatibility of nonferromagnetic prostheses depends strongly on the design of the device. MRA may be used to monitor the patency of iliac ZA-stents, whereas iliac Memotherm stents and Corvita stent-grafts appear to be less suited for follow-up with MRA.

Iliofemoral arterial occlusive disease: contrast-enhanced MR angiography for preinterventional evaluation and follow-up after stent placement

PURPOSE

To evaluate the efficacy of contrast material-enhanced magnetic resonance (MR) angiography for the diagnosis of peripheral arterial occlusion and follow-up after stent placement.

MATERIALS AND METHODS

Sixty-seven patients (21 women, 46 men; mean age, 64.6 years) were examined. Digital subtraction angiography and contrast-enhanced MR angiography were performed in 28 patients for preinterventional evaluation of iliofemoral arterial occlusion and in 39 patients for follow-up after stent placement in the iliac or femoral arteries, which had been performed several months before.

RESULTS

All 24 occlusions were correctly diagnosed with contrast-enhanced MR angiography. Of the 59 stenoses, 36 were greater than 50% and 23 were 50% or less. Sensitivity and specificity for the detection of stenoses greater than 50% were 100% and 83%, respectively. Patency of the different stents was determined correctly with contrast-enhanced MR angiography. Some stents caused signal intensity dropout, which made MR evaluation of stents difficult. Generally, these signal intensity artifacts were most severe in stainless steel stents and mild in some nitinol stents.

CONCLUSION

Contrast-enhanced MR angiography is comparable to digital subtraction angiography for the detection of stenosis greater than 50% and occlusion in the iliofemoral arteries. Stent patency can be determined, but contrast-enhanced MR angiography is not suitable for stent evaluation owing to signal intensity dropout; however, it provides information about the vascular anatomic areas proximal and distal to the stent.

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.

Electrocardiograph-triggered two-dimensional time-of-flight versus optimized contrast-enhanced three-dimensional MR angiography of the peripheral arteries

We determined whether the accuracy of magnetic resonance angiography (MRA) in the peripheral run-off vessels can be improved by using contrast-enhanced (CE) three-dimensional (3D) technique in comparison to electrocardiograph (ECG)-triggered two-dimensional (2D) time-of-flight (TOF) technique. In a prospective study 20 patients with occlusions of the pelvic and/or femoral arteries underwent a CE 3D MRA (repetition time (TR): 5 ms, (TE) echo time: 2 ms, flip angle (FA): 30 degrees ) and an ECG-triggered 2D time-of-flight (TOF) technique (TR: 408 resp. 608 ms, TE: 7 ms, FA: 70 degrees) of the run-off vessels on a 1.5 T MR system. Each patient received a contrast material volume of 0.15 mmol/kg of body weight of gadolinium (Gd)/DTPA using an automatic injector. The tube system to the patient was flushed by 50 mL of a saline solution applied with the same injection rate as the contrast material administration. The start of the 3D MR sequence was tailored individually to the applied contrast material after determination of circulation times by a prior bolus. All patients underwent each conventional or digital arteriography for comparison, as well. The visualization of the run-off vessels was ranked on a scale of 0-3 (0 = poor, 1 = fair, 2 = good, 3 = excellent) by three blinded reviewers. They also graded the vascular segments as either occluded or significantly altered (>50% reduction in diameter) or free of significant stenosis. CE 3D MRA was significantly faster in imaging the run-off vessels in comparison to the ECG-triggered 2D TOF technique. All 160 vascular segments were visualized with the 3D method, whereas only 142/160 segments were seen with 2D technique. The resulting image quality ranking of all vascular segments was significantly higher (p < 0.05) using CE 3D MRA (2.8) than with the 2D TOF technique (2.4). The detection of the stenoses was possible with both techniques. The grading of seven of seven stenoses was correct with 3D method and in five of seven cases with the 2D TOF technique. All vessel occlusions were detected by using both techniques. Small collaterals were visualized in more detail with the CE 3D MR angiography. These data demonstrate an improvement in image quality and accuracy of MRA of the peripheral arteries using a CE 3D technique in comparison to an ECG-triggered 2D TOF sequence.

Three-dimensional high-resolution dynamic contrast-enhanced MR angiography of the pelvis and lower extremities with use of a phased array coil and subtraction: diagnostic accuracy

In this study, our purpose was to compare the high-resolution contrast-material-enhanced three-dimensional subtraction MR angiography with conventional angiography for occlusive disease in the pelvic and lower extremity arteries. A three-dimensional fast-imaging with steady precession (FISP) sequence with a 256 x 512 matrix was obtained on 1.5T MR unit using a phased array coil. Twenty patients with arteriosclerotic obstructive disease underwent subtraction dynamic contrast-enhanced MR angiography. In 15 patients, three regions (pelvis, upper knee, and lower knee) were sequentially obtained after repeated injection of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). In the other five patients, one region was imaged (total of 50 examinations); a maximum-intensity projection (MIP) algorithm was used for subtracted images. All patients also underwent conventional angiography. Angiographic images were divided into several anatomical segments. Three blinded radiologists independently graded a total of 50 anatomic segments with stenotic or obstructive diseases and 90 segments without disease. Subtracted images allowed resolution of small branch vessels in all examinations, although misregistration was seen in eight examinations of five patients. All arteries larger than 1 mm in diameter were visualized on subtracted images. For detection of significant stenosis (>50%), MR angiography had 96% sensitivity and 83% specificity. The correlation coefficient of degree of agreement between MR angiography and conventional angiography was .92. Stenotic vessels tended to be overestimated. We conclude that high-resolution dynamic contrast-enhanced three-dimensional MR angiography is capable of depicting small vessel anatomy of the pelvis and lower extremities. Sequential MR angiography of different regions was feasible by repeated injection of Gd-DTPA and subtraction. This technique is highly sensitive in detecting lesions, but stenosis tended to be overestimated.

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.

Three-dimensional flow-independent peripheral angiography

A magnetization-prepared sequence, T2-Prep-IR, exploits T1, T2, and chemical shift differences to suppress background tissues relative to arterial blood. The resulting flow-independent angiograms depict vessels with any orientation and flow velocity. No extrinsic contrast agent is required. Muscle is the dominant source of background signal in normal volunteers. However, long-T2 deep venous blood and nonvascular fluids such as edema also contribute background signal in some patients. Three sets of imaging parameters are described to address patient-specific contrast requirements. A rapid, spiral-based, three-dimensional readout is utilized to generate high-resolution angiograms of the lower extremities. Comparisons with x-ray angiography and two-dimensional time-of-flight angiography indicate that this flow-independent technique has unique capabilities to accurately depict stenoses and to visualize slow flow and in-plane vessels.

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

PURPOSE

We conducted a prospective study to clarify the clinical utility of magnetic resonance angiography (MRA) in the treatment of patients with lower extremity arterial occlusive disease.

METHODS

During the interval of September 1993 through March 1995, 79 patients (43% claudicants, 57% limb-threatening ischemia) were studied with both MRA and contrast arteriography (ANGIO) and underwent intervention with either balloon angioplasty (9%), surgical inflow (28%), or outflow (63%) procedures. MRA and ANGIO were interpreted by separate blinded vascular radiologists, and arterial segments from the pelvis to the foot were graded as normal or with increasing degrees of mild (25% to 50%), moderate (51% to 75%), or severe (75% to 99%) stenosis or occlusion. Treatment plans were formulated by the attending surgeon and were based initially on hemodynamic, clinical, and MRA data and thereafter with ANGIO. Additional study surgeons formulated independent and specific treatment plans based on MRA or ANGIO alone. Indexes of agreement (beyond chance) for arterial segments depicted by MRA and ANGIO were assessed (kappa value), and treatment plans formulated were compared (chi-square).

RESULTS

Precise agreement (%) and the percent of major discrepancies (segment classified as normal/mild stenosis on one study and severe stenosis/occlusion on the other) between MRA and ANGIO for respective arterial segments was as follows: common and external iliacs (n = 256) 77/3.5; superficial femoral and above-knee popliteal (n = 255) 73/6.7; below-knee popliteal (n = 131) 84/3.8; infrapopliteal runoff vessels (n = 864) 74/12.4; pedal vessels (n = 111) 69/19.8 Kappa values indicated moderate agreement (between MRA and ANGIO) beyond chance for all arterial segments. Treatment plans formulated by the attending surgeon, the MRA surgeon, and the ANGIO surgeon agreed in more than 85% of cases. Inability of MRA to assess the significance of inflow disease and inadequate detail of tibial/pedal vessels were the principal deficiencies of MRA in those cases where it was considered an inadequate examination.

CONCLUSION

These findings suggest MRA and ANGIO are nearly equivalent examinations in the demonstration of infrainguinal vascular anatomy. MRA is an adequate preoperative imaging study (and may replace ANGIO), particularly in those circumstances when the risk of ANGIO is increased or when clinical and hemodynamic evaluation predict the likelihood of straightforward aortofemoral or femoral-popliteal reconstruction.

Evaluation of the iliac arteries: comparison of two-dimensional time of flight magnetic resonance angiography with cardiac compensated fast gradient recalled echo and contrast-enhanced three-dimensional time of flight magnetic resonance angiography

We compared dynamic contrast-enhanced three-dimensional time of flight (3DTOF) magnetic resonance angiography (MRA) with two-dimensional time of flight (2DTOF) MRA with cardiac compensated fast gradient recalled echo (C-MON) and conventional angiography (CA) when it was available. C-MON re-orders the normal data acquisition to minimize ghosting artifacts generated by pulsatile flow. The initial phase of the study involved optimization of parameters and comparison C-MON with no C = MON in eight patients and volunteers. The final phase of the study involved 53 patients who were imaged with contrast-enhanced 3DTOF MRA and 2DTOF MRA with C-MON. Thirty of these patients also had CA. In the initial phase, 2DTOF MRA with C-MON was found to be equal (n = 3) or superior (n = 5) to 2DTOF without C-MON. In the final phase, the agreement among all imaging modalities varied from substantial to almost perfect (Cohen's kappa = .6-.83). The lowest agreement was using 2DTOF to evaluate the external iliac segments. The among suggested treatments varied from substantial to almost perfect for all imaging modalities (Cohen's kappa = .73-93). The diagnostic efficacies of 2DTOF with C-MON and contrast-enhanced 3DTOF were high overall, with the lowest value being a specificity of 63% for one reader in the evaluation of an external iliac segment using 2DTOF. In summary, 2DTOF with C-MON helped to eliminate artifacts due to pulsatility in the iliac arterial segments. In our experience, both dynamic contrast-enhanced 3DTOF MRA and 2DTOF MRA with C-MON performed well in the evaluation of the iliac arteries. Both studies have high interobeserver agreement and high diagnostic efficacy. Contrast-enhanced 3DTOF MRA should be reserved for situations in which the iliac vessels are extremely tortuous or occluded or the external iliac segments are poorly seen.

MR angiography of the peripheral vasculature

MR angiography (MRA) for the evaluation of peripheral arterial occlusive disease is a rapidly evolving technique. Recent prospective clinical trials have indicated that MRA may play an important role in the evaluation of patients with peripheral arterial disease. This article discusses the pertinent technical aspects and limitations of peripheral MRA as well as some of the clinical data available.

MR angiography of abdominal and peripheral arteries. Techniques and clinical applications

This review article deals with MR angiography (MRA) of abdominal and peripheral arteries. Pulsatile flow, respiratory motion and peristalsis impose difficulties in imaging the vascular structures in the abdomen and the lower extremities. Development of new techniques, such as segmentation of the data acquisition, using specific acquisition windows in relation to a cardiac trigger, magnetization preparation of the tissue and phase-encoding re-ordering or sorting, have reduced the artifacts associated with abdominal and peripheral MRA. Clinical MR investigations of the arteries branching from the abdominal aorta such as the renal and mesenteric arteries and arteries in the lower extremities have revealed that severe stenoses or occlusions can be diagnosed accurately while the grading of less severe stenosis is more difficult. The phase-contrast method has been used to quantify blood flow and study the hemodynamics in abdominal and peripheral vessels. Quantitative flow information can be used to diagnose vascular disease and provides important physiological information. More prospective clinical studies, in which recently developed MRA techniques are compared with conventional angiography, are necessary before conclusive decisions can be made as to whether MRA may replace these methods.

Magnetic resonance angiography of intravascular endoprostheses: investigation of three devices

PURPOSE

To assess the value of magnetic resonance angiography (MRA) in the evaluation of vascular patency after intravascular endoprosthesis placement.

METHODS

Three different metallic stents (Wallstent, Strecker, Palmaz) were studied in vitro, and in vivo in six patients with spin-echo (SE) and gradient-echo (GRE) MR imaging. Time-of-flight, two-dimensional (2D) gadolinium-enhanced MRA was performed with GRE and flow-compensation technique, and reconstructed with a maximum-intensity projection (MIP) algorithm. MRA was compared to digital angiograms.

RESULTS

In vitro studies demonstrated that the signal intensity (SI) within the stent differed according to the device employed, the lowest SI being observed within the Palmaz stent (p = .001). There was no difference in SI or apparent diameter of the stent according to the sequence (SE vs GRE) or length of echo time (TE). In patients, the endoprostheses recorded as a well-defined area of signal void or drop-out (p = 0.004), whereas vessels above and below the stent displayed high signal intensities.

CONCLUSION

MRA does not seem as yet to be well suited for evaluating vascular patency after endoprosthesis placement, even if the Strecker and Wallstent endoprostheses provide fewer artifacts than the Palmaz stent.

Tumor angiography using high-resolution, three-dimensional magnetic resonance imaging: comparison of gadopentetate dimeglumine and a macromolecular blood-pool contrast agent

RATIONALE AND OBJECTIVES

We compared the peritumoral vascular definition in rats using either a paramagnetic extracellular or a macromolecular contrast medium in combination with high-resolution magnetic resonance (MR) imaging.

METHODS

High-resolution, three-dimensional spoiled gradient-refocused acquisition in a steady state (SPGR) images were acquired from tumor-bearing Fischer-344 rats before, immediately after, and again 40 min after administration of gadopentetate dimeglumine (0.1 mmol Gd/kg; n = 10) and albumin-(Gd-DTPA)30 (0.05 mmol Gd/kg; n = 5). Small peritumoral vessels were analyzed semiquantitatively on maximum intensity projection angiograms using a 4-point scoring system; quantitative analyses included signal-to-background ratios (SBRs) and signal-to-noise ratios.

RESULTS

Gadopentetate dimeglumine caused a transient and low-scoring (0.2 +/- 0.1, SBR = 1.9 +/- 0.2) vessel definition but strong rim enhancement (score = 1.4 +/- 0.2). Albumin-(Gd-DTPA)30 produced persistent, high-quality angiograms (score = 2.6 +/- 0.2, SBR = 7.4 +/- 0.2) but minimal rim enhancement (score = 0.3 +/- 0.2).

CONCLUSION

Albumin-(Gd-DTPA)30 combined with high-resolution MR imaging produces time-persistent, detailed angiographic definition of peritumoral vessels. Vascular maps obtained with gadopentetate dimeglumine enhancement are not time persistent or of equal quality.

MR and spiral/helical CT imaging of lower extremity occlusive disease

Magnetic resonance (MR) angiography and spiral CT angiography are promising new imaging modalities for evaluating patients with lower extremity arterial occlusive disease. Both techniques are less invasive than conventional angiography, and MR angiography has the additional advantages of not requiring iodinated contrast media or ionizing radiation. The basic principles of MR angiography and spiral CT angiography are reviewed with an emphasis on three-dimensional display techniques. This is followed by a discussion of their clinical applicability toward the diagnosis and treatment planning of lower extremity arterial occlusive disease.

Interpretations and treatment decisions based on MR angiography versus conventional arteriography in symptomatic lower extremity ischemia

PURPOSE

To determine the frequency with which treatment plans based on findings at magnetic resonance angiography (MRA) match those based on findings at conventional x-ray arteriography (XRA) in the evaluation of symptomatic lower extremity ischemia.

PATIENTS AND METHODS

Two-dimensional time-of-flight (TOF) MRA was performed in 42 patients undergoing XRA for evaluation of symptomatic lower extremity ischemia. The blind interpretations and treatment plans based on MRA findings were compared with those based on XRA findings, with use of XRA as the standard of reference.

RESULTS

For identification of hemodynamically significant stenosis or occlusion, the sensitivity and specificity of MRA was 100% and 23% for iliac segments, 100% and 82% for common femoral segments, 89% and 67% for superficial femoral segments, 100% and 88% for popliteal segments, and 92% and 91% for tibioperoneal segments, respectively. The treatment plan based on MRA findings matched that based on XRA findings in 41% of patients.

CONCLUSION

For evaluation of symptomatic lower extremity ischemia, two-dimensional TOF MRA cannot be considered a reliable substitute for XRA in patients who lack contraindications to XRA.

Accuracy of DSA in the evaluation of patency of infrapopliteal vessels

PURPOSE

To evaluate the accuracy of intraarterial digital subtraction angiography (DSA) in the demonstration of patent infrapopliteal vessels.

PATIENTS AND METHODS

One-hundred sixty-five arteriograms were obtained in 153 consecutive patients prospectively enrolled to evaluate lower extremity ischemia. In 86 cases a follow-up angiogram of the infrapopliteal vessels was obtained during surgery or after endovascular intervention (n = 57). Twenty-nine arteriograms were followed by surgical exploration of the infrapopliteal vessels. Standard angiographic technique was performed with intraarterial DSA of the most symptomatic foot. Visualization of distal vessels was compared with intraoperative or postintervention imaging or with the results of surgical exploration.

RESULTS

Of the 57 procedures after which either intraoperative or post-endovascular intervention angiography was performed, DSA results were equivalent in 47 (82%) and worse in five (9%). When individual vessels were evaluated, the sensitivity of DSA in the identification of patent named vessels was 95%, and the specificity was 92%. Among 29 cases with a surgical standard of reference, 28 patients underwent bypass to a vessel correctly identified as patent at DSA; one patient was incorrectly identified as having no patent named vessels.

CONCLUSION

Intraarterial DSA is accurate and reliable in the assessment of patency in infrapopliteal vessels before surgery or endovascular intervention in patients with infrainguinal atherosclerotic disease.