Accuracy Of Magnetic Resonance Angiography Research Articles

Clinical utility of time-resolved imaging of contrast kinetics (TRICKS) magnetic resonance angiography for infrageniculate arterial occlusive disease

The diagnostic accuracy of magnetic resonance angiography (MRA) in the infrapopliteal arterial segment is not well defined. This study evaluated the clinical utility and diagnostic accuracy of time-resolved imaging of contrast kinetics (TRICKS) MRA compared with digital subtraction contrast angiography (DSA) in planning for percutaneous interventions of popliteal and infrapopliteal arterial occlusive disease. Patients who underwent percutaneous lower extremity interventions for popliteal or tibial occlusive disease were identified for this study. Preprocedural TRICKS MRA was performed with 1.5 Tesla (GE Healthcare, Waukesha, Wis) magnetic resonance imaging scanners with a flexible peripheral vascular coil, using the TRICKS technique with gadodiamide injection. DSA was performed using standard techniques in angiography suite with a 15-inch image intensifier. DSA was considered the gold standard. The MRA and DSA were then evaluated in a blinded fashion by a radiologist and a vascular surgeon. The popliteal artery and tibioperoneal trunk were evaluated separately, and the tibial arteries were divided into proximal, mid, and distal segments. Each segment was interpreted as normal (0% to 49% stenosis), stenotic (50% to 99% stenosis), or occluded (100%). Lesion morphology was classified according to the TransAtlantic Inter-Society Consensus (TASC). We calculated concordance between the imaging studies and the sensitivity and specificity of MRA. The clinical utility of MRA was also assessed in terms of identifying arterial access site as well as predicting technical success of the percutaneous treatment. Comparisons were done on 150 arterial segments in 30 limbs of 27 patients. When evaluated by TASC classification, TRICKS MRA correlated with DSA in 83% of the popliteal and in 88% of the infrapopliteal segments. MRA correctly identified significant disease of the popliteal artery with a sensitivity of 94% and a specificity of 92%, and of the tibial arteries with a sensitivity of 100% and specificity of 84%. When used to evaluate for stenosis vs occlusion, MRA interpretation agreed with DSA 90% of the time. Disagreement occurred in 15 arterial segments, most commonly in distal tibioperoneal arteries. MRA misdiagnosed occlusion for stenosis in 11 of 15 segments, and stenosis for occlusion in four of 15 segments. Arterial access was accurately planned based on preprocedural MRA findings in 29 of 30 patients. MRA predicted technical success 83% of the time. Five technical failures were due to inability to cross arterial occlusions, all accurately identified by MRA. TRICKS MRA is an accurate method of evaluating patients for popliteal and infrapopliteal arterial occlusive disease and can be used for planning percutaneous interventions.

Contrast-enhanced magnetic resonance angiography of persistent fifth aortic arch in children

Cine angiography and echocardiography have been utilized to diagnose congenital aortic arch anomalies. However, the visualization of great vessels by echocardiography is limited, while cine angiography requires cardiac catheterization with ionizing radiation. Contrast-enhanced magnetic resonance angiography (MRA) is a noninvasive modality suitable for visualization of congenital aortic arch anomalies. To evaluate the utility of contrast-enhanced MRA in the diagnosis of persistent fifth aortic arch, a rare congenital aortic arch anomaly, and to compare the diagnostic accuracy of MRA with that of echocardiography and cine angiography. In four pediatric patients, contrast-enhanced MRA studies were performed for diagnosing persistent fifth aortic arch. The findings of MRA were compared with echocardiographic findings and confirmed by cine angiography and operation. Transthoracic surface echocardiography noted an aberrant vessel arising from the ascending aorta in two of four patients; the etiology of this vessel was uncertain. In the other two patients a diagnosis of coarctation was made. Of the four patients, only one was diagnosed with interruption of the aortic arch. Contrast-enhanced MRA clarified uncertain echocardiographic findings, enabling the correct diagnosis of persistent fifth aortic arch with fourth aortic arch interruption in all four patients. Contrast-enhanced MRA is a safe, accurate, and fast imaging technique for the evaluation of persistent fifth aortic arch and may obviate the need for conventional cine angiography. Cardiac catheterization may be reserved for some types of complicated congenital heart disease and for obtaining hemodynamic information.

Detection of Coronary Artery Stenosis With Whole-Heart Coronary Magnetic Resonance Angiography

We sought to determine the diagnostic performance of whole-heart coronary magnetic resonance (MR) angiography for detecting significant coronary artery disease. The accuracy of whole-heart coronary MR angiography has not been determined in a large number of patients. Three-dimensional coronary MR angiograms covering the entire heart were obtained during free breathing in 131 patients. Images were acquired during a patient-specific time window in the cardiac cycle with minimal motion of the coronary artery. Significant coronary artery disease was defined on X-ray coronary angiography as a diameter reduction of > or =50% in coronary arteries with a reference diameter of > or =2 mm. The acquisition of MR angiography was completed in 113 (86%) of 131 patients, with an imaging time averaged at 12.9 +/- 4.3 min. On a patient-based analysis, the sensitivity, specificity, positive and negative predictive value, and accuracy of MR angiography were 82% (95% confidence interval [CI] 69% to 91%), 90% (95% CI 79% to 96%), 88% (95% CI 74% to 95%), 86% (95% CI 75% to 93%), and 87% (95% CI 79% to 92%), respectively. These values in the individual segments were 78% (95% CI 68% to 85%), 96% (95% CI 95% to 97%), 69% (95% CI 60% to 77%), 98% (95% CI 96% to 98%), and 94% (95% CI 96% to 96%). Whole-heart coronary MR angiography allows for noninvasive detection of significant narrowing in coronary arterial segments with a diameter of > or =2 mm with moderate sensitivity and high specificity.

The Comparative Study of Magnetic Resonance Angiography Diagnosis and Pathology of Blunt Vertebral Artery Injury

Observational and comparative study of the vertebral artery injury detected by 2-dimensional (2-D) time-of-flight magnetic resonance angiography (MRA) for admitting patients. Construct a strike-induced flexion injury model of cervical spine with blunt vertebral artery injury in dogs. To evaluate the value of MRA for diagnosing vertebral artery injury in cervical spinal trauma patients, and conduct a comparative study of MRA image and pathology of blunt vertebral artery injury in an animal experiment. The 2-D time-of-flight MRA is the most important method for diagnosing vertebral artery injury. However, there is still controversy over MRA's accuracy in detecting vertebral artery injury of varying degrees. In addition, to our knowledge, no animal studies regarding this subject have been found in the literature so far. In a clinical study, 319 patients with close cervical spinal trauma underwent 2-D time-of-flight MRA prospective examination. The 2-D time-of-flight MRA detected vertebral artery injury in 52 of the 319 subjects. Of the 52 patients, 51 had unilateral vertebral artery injuries, including 22 injuries on the left vertebral artery and 29 on the right vertebral artery. One case involved bilateral vertebral artery injury. In an animal experiment, the strike-induced flexion injury model of cervical spine was constructed based on an animal experiment with 26 adult dogs. A radiograph was taken immediately after injury, and 2-D time-of-flight MRA was taken in 24-36 hours. The vertebral artery sample was then harvested for pathologic examination. In the animal experiment, cervical facet dislocation occurred in 14 of the 26 dogs. Of the 26 dogs, 7 had unilateral vertebral artery injury as detected by MRA. There were 2 dogs that had incomplete blood flow imaging on one side of the vertebral artery, which MRA diagnosed as suspect positive. There were no vertebral artery injuries in the other 17 dogs. The vertebral artery sample of all 26 dogs underwent the pathologic study. Of the 7 dogs with positive MRA, 4 had disruption of the intima and media, and 3 had disruption of the intima. Of the 2 dogs with suspicious positive MRA diagnosis, 1 had no intima injury, while the other had intima disruption and late mural thrombus. There was no intima injury in the 17 dogs with negative MRA findings. The 2-D time-of-flight MRA is an effective diagnostic method for blunt vertebral artery injury. It may have difficulties differentiating spasm, small disruption of the intima from others under certain conditions.

Diagnostic Value of Gadolinium-Enhanced 3D Magnetic Resonance Angiography in Patients With Suspected Hepatic Arterial Complications After Liver Transplantation

To evaluate the accuracy and clinical role of gadolinium-enhanced 3D magnetic resonance angiography (MRA) in patients with suspected hepatic arterial complications after liver transplantation. Thirty-six consecutive MRA studies were performed in 33 liver transplant recipients after transplantation. MRA image quality was assessed subjectively. Thirty-two MRA studies were retrospectively reviewed and correlated with surgery (n = 2), conventional angiography (n = 18), or clinical follow-up (n = 12). MRA findings were also correlated with those of Doppler sonography in 30 of the cases. In 20 cases, concordance between MRA and surgery or conventional angiography was evaluated for each grade of hepatic artery stenosis (normal, mild [<50%], moderate [50-75%], severe [>75%], or occluded). MRA image quality was degraded 13 of 36 cases (36.1%) studies. The sensitivity, specificity, and accuracy of MRA by consensus reading for more than 50% of hepatic artery stenosis or occlusion were 67%, 90%, and 81.3%, respectively. Of the 19 cases in which Doppler sonography was abnormal, MRA correctly characterized hepatic artery stenosis in 16 (84.2%). MRA also correctly identified all 5 occurrences of celiac artery stenosis. However, MRA overestimated the severity of hepatic arterial stenosis in 3 (15%) of 20 cases and underestimated 5 (25%) of 20 cases. MRA complements Doppler ultrasound to exclude significant hepatic artery stenosis. However, a substantial number of MRA studies were technically inadequate, and MRA demonstrated limited efficacy for correctly grading the severity of hepatic artery stenosis.

Pre-donation Assessment of Kidneys by Magnetic Resonance Angiography and Venography: Accuracy and Impact on Outcomes

Reports on the accuracy of magnetic resonance angiography (MRA) and magnetic resonance venography (MRV) in evaluating living donor renovasculature employ few patients or omit the consequences of inaccurate scans. We retrospectively compared intraoperative findings to MRA/MRV scans in 146 donor-recipient pairs. For detecting accessory arteries and early branching, MRA sensitivity was 57.6%, specificity 96.5%, false positive rate 3.5%, false negative rate 42.4%, positive predictive value 82.6%, negative predictive value 88.6% and overall accuracy 87.7%. By excluding clinically inconsequential accessory arteries, MRA sensitivity rose to 73.1%, specificity to 96.7% and overall accuracy to 92.5%. For MRVs, sensitivity was 56.2%, specificity 99%, false positive rate 1%, false negative rate 43.8%, positive predictive value 90%, negative predictive value 94.8% and accuracy 94.5%. Inaccurate scans were associated with prolonged donor and recipient operations and more frequently reconstructed arteries, but did not affect clinical outcomes. Because most missed accessory arteries are inconsequential, MRA is a useful, less invasive method for defining donor renovascular anatomy.

Diagnosis of moyamoya disease with transcranial Doppler sonography: correlation study with magnetic resonance angiography.

Although the diagnosis of moyamoya disease may be confirmed by digital subtraction angiography, recent studies have shown the accuracy of magnetic resonance angiography. Characteristics of transcranial Doppler, a noninvasive and cost-effective method, and specific transcranial Doppler parameters reflecting distinct vascular status in moyamoya disease are explored. Consecutive patients (> 15 years of age) diagnosed with moyamoya disease by a typical clinical history and digital sub traction angiography or magnetic resonance angiography were included. The statuses of the anterior, middle, and posterior cerebral arteries were graded as stage 1, stage 2, and stage 3 by magnetic resonance angiography. Mean flow velocity and pulsatility index were compared between these groups, and the receiver operating characteristic analysis was used to define transcranial Doppler criteria for distinct vascular status. Forty-five patients were included (37 women; mean age, 34.9 +/- 11.4 years). Mean flow velocity was higher and pulsatility index was lower in stage 2 (P < .01), while mean flow velocity was lower and pulsatility index was higher in stage 3 than in stage 1 (P < .01). Cutoff values reflecting stenosis or occlusion with substantial sensitivity and specificity were as follows: mean flow velocity > 85 cm/s or pulsatility index < 0.60 for stage 2, and mean flow velocity < 50 cm/s for stage 3 of middle cerebral artery; mean flow velocity > 80 cm/s or pulsatility index < 0.60 for stage 2 of anterior cerebral artery; and mean flow velocity > 60 cm/s or pulsatility index < 0.60 for stage 2 of posterior cerebral artery. Transcranial Doppler may help to refine magnetic resonance angiography findings and thus help clinicians differentiate severity or stages of moyamoya disease.

Noninvasive Carotid Imaging

The management of carotid stenosis has been based on major prospective trials that have used arteriography. However, noninvasive methods of evaluation have been sought because angiography has a significant risk of major complications and a high cost. Availability, low cost, and high diagnostic accuracy make duplex ultrasound the first line of investigation when carotid disease is suspected. Duplex ultrasound is limited by operator and machine variability. Magnetic resonance angiography in coordination with duplex ultrasound has increased accuracy and should be done after an equivocal or inadequate duplex ultrasound exam. Magnetic resonance angiography accuracy has improved with the use of contrast and three-dimensional time-of-flight techniques over a two-dimensional time-of-flight method. Computed tomographic angiography can also validate the duplex ultrasound exam and give additional information for the arch and intracranial vessels. Axial reconstruction has shown the greatest accuracy. Future studies defining the prognosis of area stenosis, plaque volume, and composition will further improve treatment that is based on noninvasive imaging.

Gadofosveset

Gadofosveset

Magnetic Resonance Angiography for the Diagnosis of Renal Artery Stenosis: A Meta-analysis

AIM: To review the published literature comparing the diagnostic accuracy of magnetic resonance angiography (MRA) with and without gadolinium in diagnosing renal artery stenosis, using catheter angiography as reference. MATERIALS AND METHODS: A meta-analysis was performed of English language articles identified by computer search using PubMed/MEDLINE, followed by extensive bibliography review from 1985 to May 2001. Inclusion criteria were: (1) blinded comparison with catheter angiography; (2)indication for MRA stated; (3) clear descriptions of imaging techniques; and (4) interval between MRA and catheter angiography<3 months and only the largest of all studies from one centre was selected in the analysis. RESULTS: A total of 39 studies were identified, of which 25 met the inclusion criteria. The number of patients included in the meta-analysis was 998: 499 with non-enhanced MRA and 499 with gadolinium-enhanced MRA. The sensitivity and specificity of non-enhanced MRA were 94% (95% CI: 90–97%) and 85% (95% CI: 82–87%), respectively. For gadolinium-enhanced MRA sensitivity was 97% (95% CI: 93–98%) and specificity was 93% (95% CI: 91–95%). Thus, specificity and positive predictive value were significantly better for gadolinium-enhanced MRA (P<0.001). Accessory renal arteries were depicted better by gadolinium-enhanced MRA (82%; 95% CI: 75–87%) than non-gadolinium MRA (49%; 95% CI: 42–60%) (P<0.001). CONCLUSIONS: Gadolinium-enhanced MRA may replace arteriography in most patients with suspected renal artery stenosis, and has major advantages in that it is non-invasive, avoids ionizing radiation and uses a non-nephrotoxic contrast agent. Tan, K.T. et al. (2002) Clinical Radiology57, 617--624.

Comparison of contrast-enhanced magnetic resonance angiography and conventional pulmonary angiography for the diagnosis of pulmonary embolism: a prospective study

Diagnostic strategies for pulmonary embolism are complex and consist of non-invasive diagnostic tests done to avoid conventional pulmonary angiography as much as possible. We aimed to assess the diagnostic accuracy of magnetic resonance angiography (MRA) for the diagnosis of pulmonary embolism, using conventional pulmonary angiography as a reference method. In a prospective study, we enrolled 141 patients with suspected pulmonary embolism and an abnormal perfusion scan. Patients underwent MRA before conventional pulmonary angiography. Two reviewers, masked with respect to the results of conventional pulmonary angiography, assessed MRA images independently. Statistical analyses used chi(2) and 95% CI. MRA was contraindicated in 13 patients (9%), and images were not interpretable in eight (6%). MRA was done in two patients in whom conventional pulmonary angiography was contraindicated. Thus, MRA and conventional pulmonary angiography results were available in 118 patients (84%). Prevalence of pulmonary embolism was 30%. Images were read independently in 115 patients, and agreement obtained in 105 (91%), kappa=0.75. MRA identified 27 of 35 patients with proven pulmonary embolism (sensitivity 77%, 95% CI 61-90). Sensitivity of MRA for isolated subsegmental, segmental, and central or lobar pulmonary embolism was 40%, 84%, and 100%, respectively (p<0.01 for isolated subsegmental vs segmental or larger pulmonary embolism). However, subgroups contained small numbers. MRA identified pulmonary embolism in two patients with normal angiogram (98%, 92-100). MRA is sensitive and specific for segmental or larger pulmonary embolism. Results are similar to those obtained with helical computed tomography, but MRA has safer contrast agents and does not involve ionising radiation. MRA could become part of the diagnostic strategy for pulmonary embolism.

How does the degree of carotid stenosis affect the accuracy and interobserver variability of magnetic resonance angiography?

OBJECTIVESThe accuracy of magnetic resonance angiography (MRA) was determined in patients with recently symptomatic tight (80%–99%) carotid stenosis (on Doppler ultrasound), and the effect of stenosis severity on the accuracy...

Magnetic resonance angiography is an accurate imaging adjunct to duplex ultrasound scan in patient selection for carotid endarterectomy

Purpose: The purpose of this study was to evaluate the accuracy of magnetic resonance angiography (MRA) for categorizing the severity of carotid disease relative to duplex ultrasound scan and cerebral contrast arteriography (CA) to determine if MRA imaging could replace the need for cerebral angiography in cases of indeterminate or inadequate duplex scan imaging. Methods: Seventy-four carotid bifurcations in 40 patients undergoing 45 carotid endarterectomies from 1996 to 1998 were imaged with duplex ultrasound scan; MRA (two-dimensional neck and three-dimensional intracranial, time-of-flight technique); and biplanar, digital subtraction cerebral arteriography. Studies were blindly reviewed by one reader who used established threshold velocity criteria for the duplex scan and the North American Symptomatic Carotid Endarterectomy Trial method for MRA and CA to determine the percentage of diameter reduction of the internal carotid artery (ICA). Disease severity was grouped into four categories (< 50%, 50%-74%, 75%-99% stenosis and occlusion), and the results of MRA and duplex ultrasound scan were compared with CA. Results: Sensitivity, specificity, positive predictive value, and negative predictive value for detection of > 50% ICA stenosis were 100%, 96%, 98%, and 100% for MRA and 100%, 72%, 88%, and 100% for duplex ultrasound scan, respectively; similarly, for detection of > 75% ICA stenosis values were 100%, 77%, 76%, and 100% for MRA and 90%, 74%, 72%, and 91% for duplex ultrasound scan, respectively. Both MRA and duplex ultrasound scan accurately differentiated all cases of > 95% stenosis (n = 7) from occlusion (n = 4). Short length ICA flow gaps were present on MRA in all cases of 75% to 99% stenosis and one half of cases of CA-defined 50% to 74% stenosis. In patients with 50% to 74% stenosis, the mean angiographic stenosis was significantly greater when a flow gap was present on MRA (64% ± 6%) versus no flow gap (57% ± 7%) (P =.04). There was overall agreement among duplex ultrasound scan, MRA, and CA in 73% of carotids imaged. Of the 24% discordant results between MRA and duplex ultrasound scan, MRA correctly predicted disease severity in all cases, and inaccurate duplex ultrasound scan results were due to overestimation in 83% of cases. The operative plan was altered by CA findings in only one patient (2%) after duplex ultrasound scan and MRA. Conclusions: MRA can accurately categorize the severity of carotid occlusive disease. Duplex ultrasound scan facilitates patient selection for carotid endarterectomy in most cases, but adjunct use of MRA improves diagnostic accuracy for > 75% stenoses and may obviate the need for cerebral arteriography when duplex scan results are inconclusive or demonstrate borderline disease severity. (J Vasc Surg 2000;32:429-40.)

Pediatric extracranial applications of mr angiography

Extracranial magnetic resonance angiography (MRA) was performed in 20 children to evaluate for various arterial and venous conditions. Time-of-flight and phase-contrast angiograms were constructed using a maximal-intensity-projection algorithm. The accuracy of MRA was comparable to Doppler ultrasound ( n = 12) and conventional angiography ( n = 3). MRA could provide an excellent mapping of patent (including collaterals) versus thrombosed vessels at sites not evaluated or inaccessible by sonography. Limitations included assessment of small and/or tortuous vessels, severely stenotic lesions, and very slow flow.

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°) and an ECG-triggered 2D time-of-flight (TOF) technique (TR: 408 resp. 608 ms, TE: 7 ms, FA: 70°) 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.

The Accuracy of Magnetic Resonance Angiography in the Assessment of Extracranial Carotid Artery Occlusive Disease

The accuracy of two-dimensional time-of-flight magnetic resonance angiography (MRA) in judging diameter narrowing of the extracranial carotid artery was studied using digital subtraction angiography (DSA) as the gold standard. Particular attention was paid to the specificity of the technique for 70–90% diameter stenoses. MRA and DSA examinations of 90 cervical carotid arteries were graded independently by 2 blinded readers. The examinations were compared in the categories 0–29, 30–69, 70–99 and 100% diameter narrowing (NASCET measurements). Overestimation of the degree of stenosis measured angiographically resulted in MRA sensitivity estimates of 77.8% for 0–29% angiographic stenosis and 31% for 30–69% angiographic stenosis. In the 70–99% stenosis group a false-positive rate of 21.9% resulted in 22 of 42 arteries being inappropriately placed in the high-grade stenosis group. In cases of 100% occlusion there was a false-negative rate of 35.7% (5 of 14 cases). MRA is reliable as a screening test for extracranial carotid occlusive disease. Limited ability of the technique to distinguish between ''surgical'' and ''non-surgical'' disease with inappropriate inclusion of some patients as potential surgical candidates limits its application as a single definitive pre-operative test.

Pediatric MR Angiography of the central nervous system

MRI has now become the initial procedure of investigation for the pediatric patients with stroke. Magnetic resonance angiography (MRA) is an important adjunct in the diagnostic evaluation of these patients who may be affected by vascular abnormalities. During the past year-and-a-half MRA has been utilized with an increasing frequency and has replaced in many cases the need for conventional angiography. The clinical management of the young patients can be planned on the basis of MRA, that can be performed as an intrinsic part of the initial MRI study. At present, the diagnostic accuracy of MRA is sufficient that conventional angiography can be circumvente or performed at a time when the patients clinical conditions have stabilized and just prior to the operative procedures, if surgery is requested.