Diagnosis of pulmonary embolism: comparison of CT angiography and MR angiography in canines

PURPOSE: To compare the sensitivity and specificity of helical computed tomographic angiography (CTA), CTA with multiplanar reconstructions (MPR)/three-dimensional-shaded surface display (3D-SSD), and gadolinium-enhanced magnetic resonance angiography (MRA) for pulmonary embolism (PE) detection. MATERIALS AND METHODS: Gelatin sponge emboli were introduced into the femoral veins of seven dogs and conventional digital subtraction angiography (CA), CTA, and MRA performed. Images from CTA, CTA with MPR/3D-SSD, and MRA were reviewed for the presence of PE in lobar and segmental arteries, and subsegmental zones. Postmortem angiography and CA were the gold standard. RESULTS: There were 50 emboli in the 294 vessels/zones analyzed. The sensitivity of CTA for the two readers was 76% (95% confidence interval [CI]; 64%-88%) and 64% (95% CI; 50%-78%), and for the two MRA readers was 52% (95% CI; 38%-66%) and 48% (95% CI; 34%-62%). CTA was more sensitive than MRA when PE were subdivided by vessel caliber. Specificity was high for CTA and MRA among all readers (98.8%-99.6%). MPR/3D-SSD did not improve results of axial CT. MRA perfusion defects were 46% and 47% sensitive and 100% specific. Interobserver agreement was high for CTA and MRA (kappa 0.92 and 0.93, respectively). The average diameter of vessels with emboli was 3.7 mm +/- 1.06. CONCLUSION: Helical CTA is more sensitive than three-dimensional gadolinium-enhanced MRA for the detection of PE. Both CTA and MRA are highly specific for PE detection and demonstrate high interobserver agreement. MPR/3D-SSD did not increase CTA performance over axial images alone.     

CT angiography in the assessment of carotid artery atherosclerosis

Objective: The aim of the study was to evaluate the ability of CT angiography (CTA) to detect atherosclerosis of the carotid arteries in comparison with 3D time-of-flight MR angiography (3D TOF MRA), using contrast angiography and intravascular ultrasound (IVUS) as a reference.Material and Methods: Contrast angiography and CTA were performed in 31 patients (mean age 65 years, range 45-79). The image quality was evaluated, atherosclerotic lesions were registered, and diameter stenosis degree was visually estimated from axial source images of CTA and 3D TOF MRA (21 patients), and results of interpretations were compared. The comparison of quantitative measurements was performed using IVUS as a reference.Results: Contrast angiography detected 51 lesions (mean diameter stenosis 50%, range 10-100%), and CTA detected all same lesions. CTA provided better image quality and consistency of image interpretation than 3D TOF MRA. IVUS verified 29 atherosclerotic lesions with a mean diameter stenosis of 35%, (range 4-40%). CTA yielded a sensitivity of 96% to 100% (≤10% or ≤20% diameter stenosis regarded as normal) for the detection of lesions with reference to IVUS.Conclusion: CTA seems feasible and accurate for the detection of atherosclerosis in carotid arteries.     

Pulmonary embolism: comparison of gadolinium-enhanced MR angiography with contrast-enhanced spiral CT in a porcine model

RATIONALE AND OBJECTIVES: The purpose of this study was to compare gadolinium-enhanced magnetic resonance (MR) angiography with contrast material-enhanced computed tomography (CT) for the detection of small (4-5-mm) pulmonary emboli (PE), with a methacrylate cast of the porcine pulmonary vasculature used as the diagnostic standard. MATERIALS AND METHODS: In 15 anesthetized juvenile pigs, colored methacrylate beads (5.2 and 3.8 mm diameter-the size of segmental and subsegmental emboli in humans) were injected via the left external jugular vein. After embolization, MR angiographic and CT images were obtained. The pigs were killed, and the pulmonary arterial tree was cast in clear methacrylate, allowing direct visualization of emboli. Three readers reviewed CT and MR angiographic images independently and in random order. RESULTS: Forty-nine separate embolic sites were included in the statistical analysis. The mean sensitivity (and 95% confidence intervals) for CT and MR angiography, respectively, were 76% (68%-82%) and 82% (75%-88%) (P > .05); the mean positive predictive values, 92% (85%-96%) and 94% (88%-97%) (P > .05). In this porcine model, PE were usually seen as parenchymal perfusion defects (98%) with MR angiography and as occlusive emboli (100%) with CT. CONCLUSION: MR angiography is as sensitive as CT for the detection of small PE in a porcine model.     

Value of contrast-enhanced MR angiography and helical CT angiography in chronic thromboembolic pulmonary hypertension

The aim of this study was to evaluate the diagnostic value of contrast-enhanced MR angiography (ce MRA) and helical CT angiography (CTA) of the pulmonary arteries in the preoperative workup of patients with chronic thromboembolic pulmonary hypertension (CTEPH). The ce MRA and CTA studies of 32 patients were included in this retrospective evaluation. Image quality was scored by two independent blinded observers. Data sets were assessed for number of patent segmental, subsegmental arteries, and number of vascular segments with thrombotic wall thickening, intraluminal webs, and abnormal proximal to distal tapering. Image quality for MRA/CTA was scored excellent in 16 of 16, good in 11 of 14, moderate in 2 of 5, and poor in no examinations. The MRA/CTA showed 357 of 366 patent segmental and 627 of 834 patent subsegmental arteries. CTA was superior to MRA in visualization of thrombotic wall thickening (339 vs 164) and of intraluminal webs (257 vs 162). Abnormal proximal to distal tapering was better assessed by MRA than CTA (189 vs 16). In joint assessment of direct and indirect signs, MRA and CTA were equally effective (353 vs 355). MRA and CTA are equally effective in the detection of segmental occlusions of the pulmonary arteries in CTEPH. CTA is superior for the depiction of patent subsegmental arteries, of intraluminal webs, and for the direct demonstration of thrombotic wall thickening.     

Intracranial vascular stenosis and occlusive disease: evaluation with CT angiography, MR angiography, and digital subtraction angiography

BACKGROUND AND PURPOSE: Although digital subtraction angiography (DSA) provides excellent visualization of the intracranial vasculature, it has several limitations. Our purpose was to evaluate the ability of helical CT angiography (CTA) to help detect and quantify intracranial stenosis and occlusion compared with DSA and MR angiography (MRA). METHODS: Twenty-eight patients underwent CTA, DSA, and 3D time-of-flight (TOF) MRA for suspected cerebrovascular lesions. All three studies were performed within a 30-day period. Two readers blinded to prior estimated or calculated stenoses, patient history and clinical information examined 672 vessel segments. Lesions were categorized as normal (0-9%), mild (10-29%), moderate (30-69%), severe (70-99%), or occluded (no flow detected). DSA was the reference standard. Unblinded consensus readings were obtained for all discrepancies. RESULTS: A total of 115 diseased vessel segments were identified. After consensus interpretation, CTA revealed higher sensitivity than that of MRA for intracranial stenosis (98% versus 70%, P < .001) and occlusion (100% versus 87%, P = .02). CTA had a higher positive predictive value than that of MRA for both stenosis (93% versus 65%, P < .001) and occlusion (100% versus 59%, P < .001). CTA had a high interoperator reliability. In 6 of 28 patients (21%), all 6 with low-flow states in the posterior circulation, CTA was superior to DSA in detection of vessel patency. CONCLUSION: CTA has a higher sensitivity and positive predictive value than MRA and is recommended over TOF MRA for detection of intracranial stenosis and occlusion. CTA has a high interoperator reliability. CTA is superior to DSA in the evaluation of posterior circulation steno-occlusive disease when slow flow is present. CTA results had a significant effect on patient clinical management.     

Noncontrast 3D steady-state free-precession magnetic resonance angiography of the whole chest using nonselective radiofrequency excitation over a large field of view: comparison with single-phase 3D contrast-enhanced magnetic resonance angiography

OBJECTIVES: To evaluate the feasibility of three-dimensional (3D) steady-state free-precession (SSFP) magnetic resonance angiography (MRA) using nonselective radiofrequency excitation in the assessment of cardiac morphology, thoracic aorta, main pulmonary, and proximal coronary arteries. MATERIAL AND METHODS: Thirty consecutive patients (19 males; 11 females; age range, 20-74) with various cardiac and thoracic vascular diseases underwent free-breathing respiratory navigator-gated electrocardiogram-triggered noncontrast SSFP MRA and conventional high-resolution 3D contrast-enhanced MRA (CE-MRA) of the thorax at 1.5 T. Two readers evaluated both datasets for findings, vascular delineation and sharpness (from 0, not visualized to 3, excellent definition), artifacts, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in 14 vascular segments including aorta, supra-aortic, pulmonary, and coronary arteries, and in cardiac chambers. Statistical analysis was performed using Wilcoxon test for vessel delineation, and [kappa] coefficient for interobserver variability. RESULTS: 3D SSFP and CE-MRA were successfully performed in all patients. Scan time for SSFP MRA ranged from 5 to 10 minutes (mean +/- standard deviation, 7 +/- 2 minutes). On SSFP MRA, readers 1 and 2 graded 233 (97.1%) and 234 (97.5%) coronary arterial segments and cardiac chambers, and 275 (91.7%) and 278 (92.7%) noncoronary arterial segments with diagnostic definition (grades 2 and 3) (k = 0.86). On conventional CE-MRA, readers 1 and 2 graded 10 (4.2%) and 12 (5%) coronary arterial segments and cardiac chambers, and 272 (90.7%) and 270 (90%) noncoronary arterial segments with diagnostic definition (grades 2 and 3) (k = 0.89). Segmental visibility was higher for aortic root, pulmonary trunk, proximal coronary arteries, and heart chambers (P < 0.001), and lower for supra-aortic arteries (P < 0.001) on SSFP MRA for each reader. SNR and CNR values were higher for aortic root and aorta on SSFP MRA (P < 0.001 for both). No significant difference existed between SNR and CNR values for the other vascular segments and cardiac chambers on SSFP and CE-MRA (P > 0.05 for all). The 2 readers demonstrated vascular stenosis and dilatation/aneurysm in 7 and 35 segments on both datasets, respectively. CONCLUSION: Noncontrast 3D SSFP MRA with nonselective radiofrequency excitation provides high image quality and sufficient SNR and CNR for confident assessment of cardiac and thoracic vascular diseases including congenital heart diseases. Our results suggest that noncontrast SSFP MRA outperforms CE-MRA in visualization of cardiac chambers, proximal coronary arteries, pulmonary trunk, and aortic root.     

Efficacy of MR angiography in the detection and characterization of occlusive disease in the vertebrobasilar system

PURPOSE: The purpose of this work was to determine the efficacy of MR angiography (MRA) in the detection and characterization of occlusive disease in the vertebrobasilar system. METHOD: We retrospectively reviewed the posterior circulation registry of our institution to select 42 consecutive patients with posterior circulation ischemic symptoms who underwent both MRA and angiography. The extracranial vertebral arteries (ECVAs) were examined by two-dimensional time-of-flight MRA above the C6 level, and the intracranial vertebral arteries (ICVAs) and basilar arteries (BAs) were examined by three-dimensional time-of-flight MRA. Sixty-two ECVAs, 63 ICVAs, and 39 BAs were examined by the readers. RESULTS: Occlusive disease was seen on angiography in 22 of the 42 patients. The sensitivity and specificity values for detection of lesions in 12 ECVA, 19 ICVA, and 12 BA abnormalities were as follows: ECVA, 92 and 96% for Reader A and 100 and 90% for Reader B; ICVA, 84 and 93% for Reader A and 74 and 82% for Reader B; and BA, 100 and 88% for Reader A and 100 and 78% for Reader B. For ICVA, the sensitivity of MRA was less than that of angiography because of lesions missed by the readers at the junctional area of the extra-and intracranial MRA. MRA accurately characterized 9 of the 12 (75%) ECVA, 10 of the 19 (43%) ICVA, and 11 of the 12 (92%) BA lesions. CONCLUSION: MRA is an effective method for detection of occlusive lesions in the ECVAs and BAs. Clinically important lesions can be missed by MRA in the ICVA. MRA is more accurate in characterization of occlusive lesions in BAs than in ECVAs or ICVAs.     

Diagnostic performance of helical CT angiography in trauma to large arteries of the extremities

PURPOSE: The purpose of this work was to assess the performance of helical CT angiography (CTA) in the diagnosis of injuries to large arteries of the extremities. METHOD: We performed helical CTA on 45 consecutive patients referred for conventional angiography for evaluation of suspected arterial injuries after sustaining trauma to the extremities (13 upper, 32 lower). Two radiologists interpreted the helical CTA studies independently. Diagnostic performance parameters evaluated included sensitivity, specificity, receiver operating characteristic (ROC) curves, and interobserver agreement (kappa statistics). Conventional angiography was used as the standard of reference for determination of final diagnoses. RESULTS: Forty-three of 45 patients (96%) had diagnostic helical CTA examinations. Final diagnoses in these 43 patients were arterial occlusion (n = 7), partial obstruction (n = 3), pseudoaneurysm (n = 5), arteriovenous fistula (n = 1), pseudoaneurysm and arteriovenous fistula (n = 3), and normal findings (n = 24). Sensitivity and specificity were 90% [95% confidence interval (CI), 80-99] and 100% (95% CI, 99-100), respectively, for Reader 1 and 100% (95% CI, 99-100) and 100% (95% CI, 99-100), respectively, for Reader 2. ROC curve analysis revealed high diagnostic performance, with areas under the curve of >0.9 for both readers. Interobserver agreement was 0.9. CONCLUSION: The diagnostic performance of helical CTA for detection of major injuries of large arteries of the extremities is high.     

Pulmonary MRA: Differentiation of pulmonary embolism from truncation artefact

Purpose

Truncation artefact (Gibbs ringing) causes central signal drop within vessels in pulmonary magnetic resonance angiography (MRA) that can be mistaken for emboli, reducing diagnostic accuracy for pulmonary embolism (PE). We propose a quantitative approach to differentiate truncation artefact from PE.

Methods

Twenty-eight patients who underwent pulmonary computed tomography angiography (CTA) for suspected PE were recruited for pulmonary MRA. Signal intensity drops within pulmonary arteries that persisted on both arterial-phase and delayed-phase MRA were identified. The percent signal loss between the vessel lumen and central drop was measured. CTA served as the reference standard for presence of pulmonary emboli.

Results

A total of 65 signal intensity drops were identified on MRA. Of these, 48 (74 %) were artefacts and 17 (26 %) were PE, as confirmed by CTA. Truncation artefacts had a significantly lower median signal drop than PE on both arterial-phase (26 % [range 12–58 %] vs. 85 % [range 53–91 %]) and delayed-phase MRA (26 % [range 11–55 %] vs. 77 % [range 47–89 %]), p?<?0.0001 for both. Receiver operating characteristic (ROC) analyses revealed a threshold value of 51 % (arterial phase) and 47 % signal drop (delayed phase) to differentiate between truncation artefact and PE with 100 % sensitivity and greater than 90 % specificity.

Conclusion

Quantitative signal drop is an objective tool to help differentiate truncation artefact and pulmonary embolism in pulmonary MRA.

Key points

? Inexperienced readers may mistake truncation artefacts for emboli on pulmonary MRA ? Pulmonary emboli have non-uniform signal drop ? 51 % (arterial phase) and 47 % (delayed phase) cut-off differentiates truncation artefact from PE ? Quantitative signal drop measurement enables more accurate pulmonary embolism diagnosis with MRA     

The non-invasive detection of intracranial aneurysms: are neuroradiologists any better than other observers?

Can non-neuroradiologists detect intracranial aneurysms as well as neuroradiologists, using CT and MR angiography? Sixty patients undergoing intra-arterial digital subtraction angiography (IADSA) to detect aneurysms also underwent computed tomographic angiography (CTA) and time-of-flight magnetic resonance angiography (MRA). Consensus review of IADSA by two neuroradiologists was the reference standard. Two neuroradiologists, a neurosurgeon, a neuroradiographer and a general radiologist blinded to IADSA, plain CT and clinical data, independently reviewed hard-copy base and reconstructed maximum intensity projection images of the CTA and MRA studies. Thirty patients had a total of 63 aneurysms, 71.4% were 相似文献   

Comparative assessment of helical CT-angiography, 2D TOF MR-angiography and 3D gadolinium enhanced MRA in aorto-iliac occlusive disease

PURPOSE: To compare helical CT-angiography (CTA) and two techniques of MR angiography (MRA) to conventional angiography in aorto-iliac occlusive disease. MATERIALS AND METHODS: The abdominal aorta and iliac arteries in 22 patients (4 for preoperative assessment of abdominal aortic aneurysm and 18 for peripheral vascular disease) were imaged using four techniques: digital subtraction angiography ("gold standard"), 2D TOF MR angiography, 3D Gd-enhanced MR angiography and helical CT angiography. Source (CTA and 2D TOF MRA) and MIPed images (after subtraction measures before and after gadolinium injection for 3D Gd-MRA) were reviewed. RESULTS: Sensitivity, specificity and accuracy for the detection of significant (>50%) stenosis and occlusion of aorto-iliac arteries were respectively: 38%, 89%, 77% for 2D TOF MRA; 75%, 71%, 72% for 3D Gd-MRA and 95%, 90%, 92% for CTA. Excluding the internal iliac arteries, results were 54%, 96%, 88% for 2D TOF MRA; 96%, 80%, 83% for 3D Gd-MRA and 92%, 93%, 95% for CTA. CONCLUSION: 3D Gd-MRA, a technique with potential for further improvement, is superior to 2D TOF MRA for detecting significant stenosis and occlusion of aorto-iliac arteries. Results at Gd-MRA are nearly similar to those at CTA (after excluding internal iliac arteries). Results at Gd-MRA are not affected by calcified plaque.     

颅内动脉CTA的前瞻性研究

目的：评价和研讨CTA对脑动脉的显示能力及扫描技术。材料和方法：脑MIP—CTA检查正常的患者50例。将CTA对颅内主要动脉的显示率与柳氏测得的MRA的类似数据进行比较。结果：对较粗大的动脉分支，CTA和MRA均显示良好。CTA对细小动脉分支的显示不及粗大动脉，差别较大。对前交通动脉的显示率，CTA明显高于MRA。CTA最佳延迟扫描时间的个体差异较大。结论：CTA能高质量地显示脑动脉，是评价脑血管状况，对脑血管疾病进行诊断和筛选的好方法。选择恰当的扫描参数很重要。CTA前有必要行小剂量试验。     

CT perfusion image of the lung: value in the detection of pulmonary embolism in a porcine model

RATIONALE AND OBJECTIVES: We assess the value of computed tomography perfusion image (CTPI) obtained by postprocessing the CT data in the diagnosis of pulmonary embolism. METHODS: An experimental pulmonary embolism model was made in 6 pigs by injecting 2 types of emboli into the pulmonary arteries. For each pig, 5 type-A (diameter 3.5 x 8 mm) and 5 type-B (diameter 2.5 x 6 mm) emboli were injected through a catheter with the distal tip located in the inflow tract of the right atrium. After obtaining precontrast and postcontrast CT data during a single breath-hold using a 4-slice multidetector CT, perfusion images were generated by data subtraction. Approximately 150 to 180 mL of contrast material was injected at an injection rate of 6 mL/s to obtain postcontrast CT. Three independent observers twice analyzed CT images for the presence of emboli: once with postcontrast CT scans (CT angiography: CTA) alone and again with both CTA and CTPI. The locations of the emboli in the pulmonary arteries were confirmed by examining the killed porcine lungs. RESULTS: The sensitivity and positive predictive value in the detection of pulmonary emboli with CTA alone were 59% (106/180) and 87% (106/122), respectively. The sensitivity and positive predictive value with both CTA and CTPI were 87% (156/180) and 85% (156/184), respectively. For type-A emboli, the sensitivity with both CTA and CTPI (76/90, 85%) was better than that with CTA alone (63/90, 70%) (P < 0.001). For type-B emboli, the sensitivity with both CTA and CTPI (80/90, 89%) was also better than that of CTA alone (43/90, 48%) (P < 0.001). CONCLUSIONS: CTPI could be obtained using digital subtraction of the CT data. It appeared to be an adjunct in enhancing the diagnostic accuracy of pulmonary embolism, particularly when detecting small pulmonary emboli.     

Preoperative evaluation of the hepatic vascular anatomy in living liver donors: comparison of CT angiography and MR angiography

PURPOSE: To compare the diagnostic performance of CT angiography (CTA) and MR angiography (MRA) for preoperative hepatic vascular evaluation in living liver donors. MATERIALS AND METHODS: Twenty-eight living donor candidates underwent preoperative CTA and MRA. Two blinded radiologists evaluated the anatomic types of the hepatic artery (HA) and portal vein (PV), and the number of aberrant hepatic veins (HVs) on both CTA and MRA, independently. Four grades of confidence levels were used to indicate the clarity of depiction of the HA and PV. Surgical findings were used as a standard of reference. RESULTS: For determining the anatomic types of the HA and PV, and the number of aberrant HVs, CTA and MRA did not significantly differ in terms of accuracy ([89%, 96%, and 68% on CTA] vs. [86%, 93%, and 68% on MRA] for reader 1, P>0.05; and [93%, 100%, and 86% on CTA] vs. [89%, 93%, and 79% on MRA] for reader 2, P>0.05). Confidence for the depiction of major branches of HA and PV did not differ between CTA and MRA, except for a better depiction of the left HA (LHA) on CTA (P<0.05) CONCLUSION: In living donor candidates, both CTA and MRA can provide a complete evaluation of the hepatic vascular anatomy.     

Gadomer-17-enhanced 3D navigator-echo MR angiography of the pulmonary arteries in pigs

The goal of this study was visualisation and quality assessment of the pulmonary arteries in pigs with modified navigator-echo magnetic resonance angiography using an intravascular contrast agent. Five sedated pigs were examined in a clinical 1.5-T system with modified three-dimensional navigator-echo magnetic resonance angiography (slice thickness 3 mm, pixel size 2.4x1.8 mm2) to evaluate the pulmonary arteries. Using a phased-array four-element thorax coil the entire thorax was scanned before and after intravenous infusion of a gadolinium-based intravascular contrast agent. Assessment of image quality, enhancement-related contrast-to-noise ratio (CNR) measurements and improvement of visibility of peripheral pulmonary vessels was performed. Improvement of quality using Gadomer-17 was found for smaller vessels; pulmonary trunks and the main pulmonary arteries were sufficiently imaged without enhancement. Mean rise of CNR measured in the pulmonary trunks was 28.64% ( P=0.0002), mean rise of CNR in the main pulmonary arteries and the segmental arteries were 79.6% and 148.2%, respectively. Mean distance between the visible peripheral end of 60 sub-segmental arteries and the inner thoracic wall was 12.2 +/- 0.4 mm, and was significantly ( P=0.00002) reduced after contrast infusion to 8.0 +/- 0.4 mm. The combination of inherent flow sensitivity of navigator-echo angiography and Gadomer-17 proved effective for imaging of the pulmonary arteries. In contrast to standard contrast-enhanced pulmonary MRA studies, breath holding is not required. Further studies and the evaluation of findings of patients suffering from pulmonary embolism are needed to evaluate the possible benefits of a higher spatial resolution which is achievable using navigator-echo techniques in contrast to the higher temporal resolution of ultra-fast pulmonary MRA.     

Gadolinium-enhanced pulmonary magnetic resonance angiography in the diagnosis of acute pulmonary embolism: a prospective study on 48 patients

OBJECTIVE: Gadolinium-enhanced pulmonary magnetic resonance angiography (MRA) can be an option in patients with a history of previous adverse reaction to iodinated contrast material and renal insufficiency. Radiation is also avoided. The aim of this study is to prospectively compare the diagnostic value of MRA with that of a diagnostic strategy, taking into account catheter angiography, computed tomography angiography (CTA), and lung scintigraphy [ventilation-perfusion (VQ)]. MATERIAL AND METHODS: Magnetic resonance angiography was done in 48 patients with clinically suspected pulmonary embolism (PE) using fast gradient echo coronal acquisition with gadolinium. Interpretation was done with native coronal images and multiplanar maximum intensity projection reconstructions. Results were compared to catheter angiography (n=15), CTA (n=34), VQ (n=45), as well as 6-12 months clinical follow-ups, according to a sequenced reference tree. RESULTS: The final diagnosis of PE was retained in 11 patients (23%). There were two false negatives and no false positive results with MRA. Computed tomography angiography resulted in no false negatives or false positives. Magnetic resonance angiography had a sensitivity of 82% and a specificity of 100%. CONCLUSION: In our study, pulmonary MRA had a sensitivity of 82% and a specificity of 100% for the diagnosis of PE, with slightly less sensitivity than CTA. In the diagnostic algorithm of PE, pulmonary MRA should be considered as an alternative to CTA when iodine contrast injection or radiation is a significant matter.     

Comparison of digital subtraction angiography with gadolinium-enhanced magnetic resonance angiography in the diagnosis of renal artery stenosis

Renal artery stenosis (RAS) is a treatable cause of hypertension and renal failure for which no ideal screening technique is currently available. We evaluated the use of dynamic gadolinium-enhanced magnetic resonance angiography (MRA) for the diagnosis of RAS. Sixty-two patients with secondary hypertension were enrolled in the study. All patients had conventional renal angiography and gadolinium enhanced MRA. The sequence used was a 3D FMP SPGR sequence with the following parameters (TR: 26 ms, TE: 6.9 ms, flip angle 40 °, field of view 36 × 36 cm, matrix 246 × 256, 1 excitation). Gadolinium 0.3 mmol/kg was administered and 60 1.5-mm-thick partitions were obtained over a duration of 3.5 min. The MRA images were then compared with conventional digital subtraction angiography (DSA) images. Conventional DSA demonstrated 138 renal arteries, whereas gadolinium-enhanced MRA demonstrated 129 (93 %). Twenty-one renal artery stenoses and four occluded arteries were seen at conventional DSA. Gadolinium-enhanced MRA had a sensitivity of 88 %, specificity of 98 %, accuracy of 96 %, positive predictive value of 92 % and negative predictive value of 97 % when compared with conventional DSA. Gadolinium-enhanced MRA is an accurate technique for identifying patients with RAS. It is less sensitive in picking up accessory renal arteries. Received: 17 March 1998; Revision received: 30 June 1998; Accepted: 28 August 1998     

Multiphase magnetic resonance angiography of the abdominal and pelvic arteries: results of a bicenter multireader analysis.

RATIONALE AND OBJECTIVES: The objective is to assess the diagnostic accuracy and interobserver variability of multiphase 3D gadolinium-enhanced magnetic resonance angiography (3D-Gd-MRA) for assessment of abdominal and pelvic vascular disease. METHODS: In 41 patients from two different institutions multiphase 3D-Gd-MRA of the aorta and pelvis was performed using an identical scanning protocol. In a single breath-hold three to four consecutive phases were acquired. Stenoses in the renal arteries, and aorta and pelvic arteries were independently evaluated by three readers and compared with digital subtraction angiography. Interobserver variability was compared by means of a kappa statistic. RESULTS: Accuracy for stenosis grading consistently ranged between 80% and 90% for all three readers in all vessel segments studied. Good interobserver agreement was found with kappa values exceeding 0.75. Vessel segments with delayed fill-in could be reliably detected on the multiple successive MRA phases. Overall, MRA was rated slightly superior to Digital Subtraction Angiography in terms of interobserver variability, diagnostic confidence and image quality. CONCLUSIONS: Multiphase MRA is a highly robust technique with reproducible accuracy for different observers and different institutions. It can therefore be recommended for screening of atherosclerotic abdominal and pelvic disease.     

3 T contrast-enhanced magnetic resonance angiography for evaluation of the intracranial arteries: comparison with time-of-flight magnetic resonance angiography and multislice computed tomography angiography

PURPOSE: We sought to prospectively evaluate the image quality and visualization of the intracranial arteries using high spatial resolution contrast-enhanced magnetic resonance angiography (CE-MRA) at 3 T and to perform intraindividual comparison with time-of-flight (TOF) MRA and multislice CT angiography (CTA). MATERIALS AND METHODS: Twelve patients (5 men, 7 women, 37-71 years of age) with suspected cerebrovascular disease prospectively underwent MRA and CTA. MRA was performed on a 3 T MR system, including both 3-dimensional (3D) TOF (Voxel dimension: 0.6 x 0.5 x 0.9 mm in 5 minutes and 40 seconds) and 3D CE-MRA (voxel dimension: 0.7 x 0.7 x 0.8 mm in 20 seconds, using parallel acquisition with an acceleration factor of 4). CTA images were acquired on a 16-slice CT scanner (voxel dimension: 0.35 x 0.35 x 0.8 mm in 17 seconds). The image quality and visualization of up to 26 intracranial arterial segments in each study was evaluated by 2 experienced radiologists. The arterial diameter for selective intracranial arteries was measured independently on each of the 3 studies, and statistical analysis and comparative correlation was performed. RESULTS: A total of 312 arterial segments were examined by CE-MRA, TOF-MRA, and CTA. The majority of intracranial arteries (87%) were visualized with diagnostic image quality on CE-MRA with a significant correlation to TOF (R values = 0.84; 95% confidence interval 0.79-0.86, P < 0.0001), and to CTA (R values = 0.74; 95% confidence interavl 0.68-0.78, P < 0.001). The image quality for small intracranial arteries, including the anterior-inferior cerebellar artery, the posterior communicating artery, and the M3 branch of the middle cerebral artery, was significantly lower on CE-MRA compared with TOF and CTA (P < 0.03). There was a significant correlation for the dimensional measurements of arterial diameters at CE-MRA with TOF (r = 0.88, 95% confidence interval 0.81-0.93), and CTA (r = 0.83, 95% confidence interval 0.73-0.90). CONCLUSION: The described 3 T CE-MRA protocol, spanning from the cervical to the intracranial vessels, visualized and characterized the majority of intracranial arteries with image quality comparable with that obtained using TOF-MRA and CTA. Further clinical studies are required to establish the accuracy of the technique in a broader clinical setting.     

Contrast-enhanced MR angiography of the carotid and vertebrobasilar circulations

BACKGROUND AND PURPOSE: Contrast-enhanced MR angiography (CE MRA) is a proven diagnostic tool in evaluation of the carotid arteries; however, few studies have addressed its accuracy in the vertebrobasilar system. The purpose of this study was to assess the sensitivity and specificity of CE MRA compared with digital subtraction angiography (DSA) for detection of vertebrobasilar disease. METHODS: Forty patients with suspected atherosclerotic disease of the carotid and vertebrobasilar circulations underwent CE MRA on a 1.5 T MR imaging scanner by use of a coronal 3D gradient-echo pulse sequence after intravenous injection of gadolinium diethylene triamine penta-acetic acid. All patients had correlative DSA within a 1-month period. CE MRA images were randomized and then independently assessed by 2 observers who were blinded to the DSA results. DSA examinations were analyzed in a similar manner. Each observer was asked to report the presence or absence of clinically significant stenosis (>50%), occlusion, fistula, aneurysm, and dissection. The MRA findings were then correlated with DSA. RESULTS: The sensitivity and specificity of MRA for detection of disease in the entire carotid and vertebrobasilar systems were 90% and 97%, respectively; for the carotid system alone, the sensitivity and specificity were 94% and 97%, respectively; and for the vertebrobasilar system they were 88% and 98% respectively. The overall interobserver reliability was 98% (kappa = 0.92). CONCLUSION: CE MRA is accurate at detecting disease not only in the carotid vessels, but also in the vertebrobasilar circulation, and has the potential to provide a comprehensive and noninvasive evaluation of the head and neck arteries in a single study.