T2 dark blood MRA for renal artery stenosis detection: preliminary observations.

OBJECTIVE: This study evaluated the ability of a fast spin echo T2 weighted dark blood sequence to characterize significant (>50%) renal artery stenosis compared to conventional angiography. METHODS: Sixteen patients underwent conventional catheter angiography for either renal artery stenosis evaluation or as potential renal donors. Each patient then had an MR study of the renal arteries and kidneys with fast spin echo T2 weighted MR (TR 4000, TE 102, 8 echo train length) on a Superconducting 1.5T Magnet. Results were compared with angiography and inter and intra observer statistics were calculated. RESULTS: A total of 36 renal arteries were imaged in 32 kidneys with 12 stenoses >50%. Fast spin echo T2 weighted MR is 94% accurate (95%CI: 87-100%) in detection of significant renal artery stenosis. Dark blood MRA (DBMRA) is 96% sensitive (95%CI: 89-100), 92% specific, with a predictive value positive of 96% for classifying real arteries as normal or significantly stenosed. Inter and intra observer statistics demonstrate good to excellent agreement in renal artery classification (kappa>0.60). CONCLUSION: DBMRA may be a useful adjunct to renal MR evaluation in hypertension. SUMMARY: A total of 36 renal arteries were imaged in 32 kidneys with 12 stenoses >50%. Fast spin echo T2 weighted MR is 94% accurate (95%CI: 87-100%) in detection of significant renal artery stenosis.     

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     

High-spatial-resolution 3D balanced turbo field-echo technique for MR angiography of the renal arteries: initial experience

PURPOSE: To compare a multislab balanced turbo field-echo magnetic resonance (MR) angiographic technique, without the use of a contrast agent, with digital subtraction angiography (DSA) for imaging of the renal arteries. MATERIALS AND METHODS: Twenty-five randomly selected patients (eight women and 17 men; age range, 27-88 years; mean age, 72 years) suspected of having renal artery stenosis underwent both DSA and balanced turbo field-echo MR angiography. A consensus result was obtained among three radiologists in evaluation of main renal arteries on balanced turbo field-echo images and DSA images. Sensitivity, specificity, and negative and positive predictive values of the balanced turbo field-echo technique were calculated, and receiver operating characteristic analysis was performed for depiction of hemodynamically significant stenosis. Cohen kappa analysis was used to assess agreement between the two imaging methods in grading of stenoses and depiction of significant stenosis. Accessory renal arteries also were evaluated. RESULTS: Fifty main renal arteries and 11 accessory arteries were fully depicted with DSA. DSA depicted 11 stenotic lesions in the main renal arteries. In comparison, balanced turbo field-echo MR angiography enabled visualization of 46 of 50 main renal arteries to their first branching points and depicted 10 of 11 accessory arteries. Sensitivity, specificity, negative predictive value, and positive predictive value of this technique for depiction of significant stenosis were 100% (four of four), 98% (41 of 42), 100% (41 of 41), and 80% (four of five), respectively. The area under the receiver operating characteristic curve was 0.988. kappa was 0.782 for grading of stenoses and 0.877 for depiction of significant stenosis. CONCLUSION: Multislab balanced turbo field-echo imaging has potential as an MR angiography technique for depiction of normal and diseased renal arteries.     

Using gadolinium-enhanced three-dimensional MR angiography to assess arterial inflow stenosis after kidney transplantation

OBJECTIVE: Our objective was to evaluate use of gadolinium-enhanced three-dimensional (3D) MR angiography in the assessment of suspected arterial inflow stenosis after kidney transplantation. SUBJECTS AND METHODS: Twenty-eight consecutive patients receiving kidney transplants (26 single-kidney transplants and two en block transplants) with suspected arterial inflow stenosis were examined with two MR angiography sequences: gadolinium-enhanced 3D fast spoiled gradient-recalled (SPGR) imaging and 3D phase-contrast imaging. Twenty-four of these patients then were examined using the gold standards: either digital subtraction angiography (DSA) (n = 23) or surgery (n = 1). MR angiography and DSA studies were independently and prospectively analyzed for the presence of arterial stenoses (mild [<50%], severe [50-90%], or critical [>90%]) in the iliac, anastomotic, and renal artery segments. Two independent observers retrospectively evaluated the MR angiography sequences for ability to detect or exclude significant (> or = 50%) arterial stenoses. RESULTS: In 22 single-kidney transplants, DSA showed eight significant stenoses in 66 arterial segments. MR angiograms adequately showed 66 of 66 segments (prospective observers) and 64 of 66 segments (each retrospective observer), which were subsequently evaluated. The sensitivity and specificity of MR angiography in revealing significant stenoses were 100% and 98% (prospective analysis), 88% and 98% (retrospective observer 1), and 86% and 100% (retrospective observer 2). Concordance between observers showed kappa values exceeding .85 for all comparisons except the analysis of phase-contrast series (kappa = .62). In one en block transplant, DSA showed that stenosis was greater than 90%, although it had been graded at less than 50% with MR angiography. CONCLUSION: Gadolinium-enhanced 3D MR angiography accurately evaluated arterial inflow in single-kidney transplants.     

Renal arterial stenosis: prospective comparison of color Doppler US and breath-hold, three-dimensional, dynamic, gadolinium-enhanced MR angiography

PURPOSE: To compare color Doppler ultrasonography (US) with fast, breath-hold, three-dimensional, gadolinium-enhanced magnetic resonance (MR) angiography in detecting renal arterial stenosis. MATERIALS AND METHODS: Forty-five patients with clinical suspicion of renovascular disease were prospectively examined with intra- and extrarenal color Doppler US and breath-hold, gadolinium-enhanced MR angiography. Digital subtraction arteriography (DSA) was the standard of reference in all patients for the number of renal arteries and degree of stenosis. RESULTS: DSA depicted 103 arteries and 52 stenoses. Color Doppler US was nondiagnostic in two examinations. Significantly more of 13 accessory renal arteries were detected with MR angiography (n = 12) than with color Doppler US (n = 3; P <.05). For assessing all stenoses, the sensitivity and accuracy were 94% and 91%, respectively, for MR angiography and 71% and 76%, respectively, for US (P <.05). The sensitivity was higher for MR angiography (100%) than for US (79%; P <.05) in diagnosing stenoses with at least 50% narrowing. The specificity, accuracy, and negative predictive value in diagnosing stenoses of at least 50% narrowing were 93%, 95%, and 100% for MR angiography and 93%, 89%, and 90% for US. CONCLUSION: Breath-hold, gadolinium-enhanced MR angiography is superior to color Doppler US in accessory renal artery detection. Although the specificity of MR angiography is similar to that of color Doppler US, MR angiography has a better sensitivity and negative predictive value in depicting renal arterial stenoses.     

肾动脉狭窄的三维增强磁共振血管成像诊断

目的:评价高分辨力三维增强磁共振血管成像术(3DCEMRA)对肾动脉狭窄的显示准确性。方法:对30例临床诊断或怀疑肾动脉狭窄患者进行高分辨力肾动脉3DCEMRA检查,分析所有患者的肾动脉和副肾动脉显示质量和病变显示情况,并与DSA做对照。结果:3DCEMRA显示了30例患者总共59支肾动脉主干(1例为单支移植肾动脉),显示率为100%。3DCEMRA显示4支副肾动脉,显示率100%。肾动脉段级分支的显示率为49%。所有病例在动脉显示区域内静脉均未显影或显影淡,对诊断不构成影响。DSA共显示59支肾动脉主干和4支副肾动脉(以63支计算),59支主干中2支闭塞,8支重度狭窄,11支中度狭窄,10支轻度狭窄,28支肾动脉主干和4支副肾动脉都正常。3DCEMRA除把2支轻度狭窄估为中度狭窄,1支中度狭窄估为重度狭窄外,其它结果都同DSA一致,故3DCEMRA显示肾动脉主干和副肾动脉狭窄程度超过50%的有血液动力学意义的明显狭窄的敏感性和特异性分别为100%和95%,阳性预测值为91%,阴性预测值为100%。结论:高分辨力肾动脉3DCEMRA能准确检出肾动脉主干和副肾动脉狭窄,并能较好判断其狭窄程度。     

Time-of-flight MR angiography of kidney transplants

The aim of the study was to apply time-of-flight MR angiography to renal transplant arteries with comparison of two- and three-dimensional (2D and 3D) sequences and to correlate the findings with colour flow sonography (CFS) and digital subtraction angiography (DSA). A total of 102 MR studies were performed in 101 patients: 87 with the 2D-FLASH sequence (18 repeated after Gd-DOTA administration), 49 with the 3D-FISP (both in 34). All patients were also studied with CFS and 15 with intra-arterial DSA. The 3D sequence produced good-quality MR angiograms in 94% of cases (82% in 2D). Gd-DOTA infusion improved the quality of the 2D angiograms in 7 of 18 cases. Only these patients were included in the remainder of the evaluation (90 patients with 103 arteries). CFS showed 72 normal and 10 abnormal arteries. In this group, the 2D sequence led to 7 (12%) false positives of stenosis and the 3D sequence yielded 1 (3%). Correlation between MR angiography and DSA was obtained for 21 arteries (15 patients) with suspicion of arterial complications. The 2D-FLASH (n = 13) and the 3D-FISP (n = 12) MR sequences allowed the correct diagnosis of all main artery complications (14 stenoses and 4 thromboses) without any false negatives and without discordance when both sequences were performed (n = 4). In the 3 other cases with a normal main artery, 2 segmental thromboses were correctly identified by both sequences and 1 stenosis of a segmental branch was correctly identified by the 2D sequence only but misdiagnosed as a thrombosis with the 3D sequence. Grading of the severity of stenoses was inaccurate with both sequences. It is concluded that the 3D time-of-flight MR sequence provides better MR angiograms than the 2D, with fewer false positives for stenosis. No false-negative arterial complications were noted. Correspondence to: N. Grenier     

Contrast-enhanced 3D MR angiography of the carotid artery: comparison with conventional digital subtraction angiography

BACKGROUND AND PURPOSE: Since 1996, several preliminary studies have shown the usefulness of contrast material-enhanced MR angiography for imaging supraaortic vessels. The aim of this study was to compare the accuracy of contrast-enhanced 3D MR angiography with that of digital subtraction angiography (DSA) in the evaluation of carotid artery stenosis. METHODS: A blinded comparison of first-pass contrast-enhanced MR angiography with conventional DSA was performed in 120 patients (240 arteries). MR angiography was performed with a 1.5-T magnet with gradient overdrive equipment, by using a coronal radiofrequency-spoiled 3D fast low-angle-shot sequence after the intravenous injection of gadodiamide. The guidelines of the North American Symptomatic Carotid Endarterectomy Trial for measuring stenosis of the internal carotid artery were applied on maximum intensity projection (MIP) images and conventional catheter angiograms. RESULTS: Grading of stenoses on MR angiograms agreed with grading of stenoses on DSA images in 89% of arteries. In the severe stenosis group (70-99%), agreement was 93%. All internal carotid occlusions (n = 28) and seven of nine pseudo-occlusions were accurately detected with contrast-enhanced MR angiography. The correlation between MR angiography and DSA for determination of minimal, moderate, and severe stenoses and occlusion was statistically significant (r = 0.91, P<.001). CONCLUSIONS: This investigation with a large number of patients confirms that contrast-enhanced MR angiography could become a diagnostic alternative to DSA in the treatment of patients with carotid artery disease.     

Gadolinium-enhanced 3D MR angiography of renal artery stenosis: a pilot comparison of maximum intensity projection, multiplanar reformatting, and 3D volume-rendering postprocessing algorithms

RATIONALE AND OBJECTIVES: The authors compared diagnostic accuracy of maximum intensity projection (MIP), multiplanar reformatting (MPR), and three-dimensional (3D) volume rendering (VR) in the evaluation of gadolinium-enhanced 3D magnetic resonance (MR) angiography of the renal arteries. They hypothesized that VR is as accurate as or more accurate than MIP and MPR at depicting renal artery stenosis. MATERIALS AND METHODS: The study group comprised 28 consecutive patients who underwent gadolinium-enhanced 3D MR angiography of the renal arteries. Studies were postprocessed to display images in MIP, MPR, and VR formats. Digital subtraction angiography (DSA), when performed (nine of 28 patients), was the standard for comparison. For each main renal artery, an estimate of percentage stenosis was made for any stenoses detected by three independent radiologists. For calculation of sensitivity, specificity, and accuracy, MR angiographic stenosis estimates were categorized as mild (0%-39%), moderate (40%-69%), or severe (> or = 70%). DSA stenosis estimates of 70% or greater were considered hemodynamically significant. RESULTS: Analysis of variance demonstrated MIP estimates of stenosis were statistically greater than VR estimates in two readers and greater than MPR estimates in all readers for all patients. MIP images also showed the largest mean difference from DSA stenosis estimates for all three readers. For both VR and MPR, mean differences between MR angiographic stenoses estimates and DSA estimates reached significance for only one reader, whereas, for MIP versus DSA, mean differences reached significance for all three readers. Although not statistically significant compared with DSA, accuracies of VR (87%) and MPR (89%) were greater than that of MIP (81%). CONCLUSION: In this pilot study, MIP was the least accurate of the three image display algorithms tested. VR and MPR yielded similar values for each method of comparison.     

Accuracy of normal-dose contrast-enhanced MR angiography in assessing renal artery stenosis and accessory renal arteries

OBJECTIVE: The purpose of this study was to evaluate the accuracy of breath-hold contrast-enhanced MR angiography in the assessment of renal artery stenosis and accessory renal arteries using a standard dose of gadolinium. SUBJECTS AND METHODS: Thirty-eight patients suspected of having renal artery stenosis underwent MR angiography and intraarterial digital subtraction angiography, which was the method of reference. Three-dimensional gradient-echo MR subtraction angiography (TR/TE, 5.8/1.8 msec) was performed on a 1.5-T imager using a phased array body coil. Before imaging, a separate timing bolus sequence was used, administering 1.0 ml of contrast agent. Gadopentetate dimeglumine (15 ml) was injected using an MR power injector. Two observers, who were unaware of each other's interpretation and of MR findings, assessed digital subtraction angiography. Likewise, two other observers assessed MR angiography. RESULTS: Digital subtraction angiography depicted 75 main and 17 accessory renal arteries (n = 92). All main renal arteries and 13 accessory renal arteries were identified on MR angiography. Compared with digital subtraction angiography, MR imaging correctly classified 57 of 66 arteries without a hemodynamically significant stenosis (0-49%), 22 of 22 arteries as significantly stenotic (50-99%), and four of four occluded arteries; five stenoses were overestimated. There was one false-positive finding of an accessory renal artery on MR angiography that was identified retrospectively on digital subtraction angiography. Interobserver agreement was high. Sensitivity and specificity for grading significant stenosis were 100% and 85%, respectively. CONCLUSION: Contrast-enhanced MR angiography, using +/-0.1 mmol/kg of gadolinium, is an accurate method in the assessment of renal artery stenosis and accessory renal arteries.     

Proximal great vessels of aortic arch: comparison of three-dimensional gadolinium-enhanced MR angiography and digital subtraction angiography

PURPOSE: To prospectively compare dynamic three-dimensional (3D) gadolinium-enhanced magnetic resonance (MR) angiography and digital subtraction angiography (DSA) for the detection of ostial stenosis of the craniocervical vessels. MATERIALS AND METHODS: Thirty-three patients with carotid stenosis of more than 50% at sonography prospectively underwent both MR angiography and DSA. The overall quality of each DSA and MR angiographic study was analyzed. For each craniocervical vessel (brachiocephalic, common carotid, subclavian, and vertebral arteries) (n = 231), ostial stenosis was graded as follows: normal, mild (<50%), moderate to severe (>50%), or occlusion. MR angiographic and DSA results were compared by means of the Spearman rank correlation coefficient (Rs). RESULTS: The overall diagnostic quality of MR angiography was excellent or adequate. Three studies were inadequate because of a poor signal-to-noise ratio (13 of 231 arteries) or a coverage error (five of 231 arteries). Findings at MR angiography and DSA agreed on the degree of stenosis (Rs = 0.82, P <.001). No cases of stenosis of more than 50% were missed at MR angiography. However, some discrepancies were noted between vertebral arteries and the other craniocervical vessels. The sensitivity and specificity for stenosis of more than 50% in other craniocervical vessels were 100% and 98%, respectively. The sensitivity and specificity for stenosis of more than 50% in the vertebral arteries were 100% and 85%, respectively. Findings at MR angiography tended to result in overestimation of the degree of ostial stenosis, especially in vertebral arteries (10 [15%] of 66 arteries). CONCLUSION: MR angiography is useful to rule out ostial stenosis of the craniocervical vessels. MR angiography is an adequate diagnostic tool for ostial stenosis, except in the vertebral artery.     

Renal artery stenosis: evaluation with conventional angiography versus gadolinium-enhanced MR angiography

PURPOSE: To evaluate the interobserver and intermodality variability of conventional angiography and gadolinium-enhanced magnetic resonance (MR) angiography in the assessment of renal artery stenosis. MATERIALS AND METHODS: Fifty-four patients underwent conventional angiography and gadolinium-enhanced three-dimensional gradient-echo MR angiography. Three angiographers blinded to each other's interpretations and the MR angiographic findings assessed the conventional angiograms for renal artery stenosis. Similarly, three blinded MR imagers evaluated the MR angiograms. RESULTS: Interobserver variability for the degree of renal artery stenosis in the 107 kidneys evaluated was not significantly different between the two modalities. The mean SD of the degree of stenosis was 6.9% at MR angiography versus 7.5% at conventional angiography (alpha < or = .05, P > .05). In 70 kidneys (65%), the average degree of stenosis reported by the readers for the two modalities differed by 10% or less. In 22 cases (21%), the degree of stenosis was overestimated with MR angiography by more than 10% relative to the results of conventional angiography. In 15 cases (14%), the degree of stenosis was underestimated with MR angiography by more than 10%. CONCLUSION: Gadolinium-enhanced MR angiography permits evaluation of renal artery stenosis with an interobserver variability comparable with that of conventional angiography.     

Preoperative evaluation of carotid artery stenosis: comparison of contrast-enhanced MR angiography and duplex sonography with digital subtraction angiography

BACKGROUND AND PURPOSE: Contrast-enhanced MR angiography and extracranial color-coded duplex sonography are noninvasive, preoperative imaging modalities for evaluation of carotid artery stenosis. Innovative techniques and improvements in image quality require frequent reassessment of accuracy, reliability, and diagnostic value compared with those of digital subtraction angiography (DSA). We evaluated contrast-enhanced MR angiography and duplex sonography compared with DSA for detection of high-grade carotid artery stenoses. METHODS: Four readers, blinded to clinical symptoms and the outcome of other studies, independently evaluated stenoses on contrast-enhanced MR angiograms in 71 vessels of 39 symptomatic patients. Duplex sonography was also performed in all vessels. The severity of stenosis was defined according to North American Symptomatic Carotid Endarterectomy Trial criteria (0-29%, 30-69%, 70-99%, 100%). Results of both modalities were compared with the corresponding DSA findings. RESULTS: Contrast-enhanced MR angiography had a sensitivity and specificity of 94.9% and 79.1%, respectively, for the identification of carotid artery stenoses of 70% or greater. Sensitivity and specificity of duplex sonography were 92.9% and 81.9%, respectively. Combining data from both tests revealed a sensitivity and specificity of 100% and 81.4%, respectively, for concordant results (80% of vessels). CONCLUSION: Concordant results of contrast-enhanced MR angiography and duplex sonography increase the diagnostic sensitivity to 100%. The reliability of MR angiography is comparable to that of DSA. The combination of contrast-enhanced MR angiography and duplex sonography might be preferable over DSA for preoperative evaluation in most patients, thus reducing the risk of perioperative morbidity and improving the overall outcome.     

Renal MR angiography at 1.0 T: three-dimensional (3D) phase-contrast techniques versus gadolinium-enhanced 3D fast low-angle shot breath-hold imaging.

OBJECTIVE: The purpose of this study was to evaluate the diagnostic usefulness of three different MR angiographic techniques at 1.0 T. SUBJECTS AND METHODS: In 22 patients with renal artery stenosis confirmed at intraarterial catheter angiography, we also performed unenhanced and gadolinium-enhanced three-dimensional phase-contrast MR angiography and gadolinium-enhanced single breath-hold three-dimensional fast low-angle shot MR angiography. We determined circulation time to optimize signal acquisition in gadolinium-enhanced breath-hold MR angiography after bolus injection of contrast material. RESULTS: Sensitivity, defined as the detection of a hemodynamically significant stenosis (>50% luminal narrowing), was 85% for enhanced phase-contrast MR angiography, 91% for gadolinium-enhanced MR angiography, and 95% for unenhanced phase-contrast MR angiography. The combination of unenhanced phase-contrast MR angiography and gadolinium-enhanced MR angiography yielded 100% sensitivity for hilar artery stenoses. There were 13 false-positive findings with unenhanced phase-contrast MR angiography, 10 with enhanced phase-contrast MR angiography, and four with gadolinium-enhanced MR angiography (specificity: 38%, 52%, and 79%, respectively). Accessory renal arteries were not seen on unenhanced or enhanced phase-contrast MR angiography (0/8 patients) but were detected with gadolinium-enhanced MR angiography in five of the eight patients. Interobserver agreement (kappa = .62) was best with gadolinium-enhanced MR angiography. The quality of the images was unsatisfactory for adequate evaluation of segmental renal arteries with all three MR angiographic techniques. CONCLUSION: A combination of unenhanced phase-contrast MR angiography and gadolinium-enhanced MR angiography at 1.0 T proved useful as a screening protocol for renal artery stenosis.     

3D MR angiography of renal arteries: comparison of volume rendering and maximum intensity projection algorithms

PURPOSE: To compare volume rendering (VR) and maximum intensity projection (MIP) as postprocessing techniques of magnetic resonance (MR) angiography for detection and quantification of renal artery stenosis. MATERIALS AND METHODS: Twenty-seven patients underwent three-dimensional contrast material-enhanced MR angiography of the renal arteries with a 1.5-T imager. For each renal artery, targeted MIP and VR images were reconstructed in oblique coronal and transverse orientations. For each modality, image generation and evaluation were performed interactively by two independent radiologists blinded to angiographic results. In comparison with digital subtraction angiography (DSA) findings, stenosis quantification and detection by using MIP and VR were evaluated with the use of 50% and 70% cutoff points by using linear regression analysis and 2 x 2 tables. Overall image quality and vascular delineation on MIP and VR images were also compared. RESULTS: All main and accessory renal arteries depicted at DSA were also demonstrated on MIP and VR images. VR performed slightly better than MIP for quantification of stenoses greater than 50% (VR: r(2) = 0.84, P <.001; MIP: r(2) = 0.38, P =.001) and significantly better for severe stenoses (VR: r(2) = 0.83, P <.001; MIP: r(2) = 0.21, P =.1). For detection of stenosis, VR yielded a substantial improvement in positive predictive value (VR: 95% and 90%; MIP: 86% and 68% for stenoses greater than 50% and 70%, respectively). Image quality obtained with VR was not significantly better than that with MIP; however, vascular delineation on VR images was significantly better. CONCLUSION: The VR technique of renal MR angiography enabled more accurate detection and quantification of renal artery stenosis than did MIP, with significantly improved vascular delineation.     

Prospective evaluation of suspected stenoocclusive disease of the intracranial artery: combined MR angiography and CT angiography compared with digital subtraction angiography

BACKGROUND AND PURPOSE: MR angiography is primarily and increasingly used to assess intracranial arterial stenoocclusion. However, MR angiography can cause overestimation of stenosis. Although CT angiography is accurate, it has limitations. Our purpose was to determine whether the accuracy of combined MR angiography and CT angiography is equal to that of digital subtraction angiography (DSA) in measuring stenosis and detecting major intracranial arterial occlusion. METHODS: CT angiography and intraarterial DSA were prospectively performed in 18 patients with suspected intracranial stenoocclusive disease, as revealed with MR angiography. Before DSA, two reviewers independently assessed MR intracranial angiograms. Subsequently, they assessed CT angiograms with MR angiograms. Results were compared with DSA results. The degree of stenoocclusion was categorized; stenosis of 50% or more indicated stenoocclusive disease. After the blinded study, two radiologists retrospectively reviewed the angiographic findings. RESULTS: Stenoocclusive disease was identified in 18 of 198 intracranial arteries at DSA. MR angiography had a sensitivity of 92%, a specificity of 91%, and an accuracy of 91% for the identification of stenosis of 50% or more; the addition of CT angiography yielded values of 100%, 99%, and 99%, respectively. Stenotic grades with combined CT angiography and MR angiography agreed with those of DSA in 98% of cases. In the retrospective study, CT angiography did not always correctly delineate arterial lumina with circumferential calcification and cavernous portions of the internal carotid artery. CONCLUSION: In this investigation, the evaluation of suspected stenoocclusive diseases in major intracranial arteries, the accuracy of combined MR angiography and CT angiography is equal to that of DSA in most cases.     

Intraarterial MR angiography and DSA in patients with peripheral arterial occlusive disease: prospective comparison

PURPOSE: To prospectively evaluate the accuracy of intraarterial magnetic resonance (MR) angiography in the depiction of significant stenoses and occlusions, with intraarterial digital subtraction angiography (DSA) serving as the reference standard. MATERIALS AND METHODS: Approval of the local ethics committee and informed consent were obtained. Twenty patients (11 men; nine women; age range, 48-86 years; mean age, 69.5 years+/-11.2 [standard deviation]) with symptomatic peripheral arterial occlusive disease (PAOD) were prospectively enrolled. After percutaneous transluminal angioplasty (PTA), intraarterial MR angiography was performed in the thigh and the calf with a 1.5-T MR imager in two consecutive runs. Intraarterial MR angiography was performed with a low-dose injection protocol (ie, two 20-mL injections of a 50-mmol gadolinium-based contrast agent). Moderate stenoses (luminal narrowing50%) or vessel occlusions; 95% confidence intervals (CIs) were calculated for sensitivity and specificity. RESULTS: Intraarterial DSA revealed 78 moderate stenoses, 57 significant stenoses, and 28 occlusions. Sensitivity, specificity, and accuracy of intraarterial MR angiography in the characterization of significant stenoses or occlusions were 92% (95% CI: 72%, 99%), 94% (95% CI: 82%, 98%), and 93%, respectively, in femoropopliteal arteries and 93% (95% CI: 83%, 98%), 71% (95% CI: 51%, 86%), and 86%, respectively, in infrapopliteal arteries. The main artifact observed with intraarterial MR angiography was venous contamination (12%). CONCLUSION: Intraarterial MR angiography is an accurate method used to depict significant stenoses and occlusions in lower extremity arteries with a low-dose injection protocol.     

Prospective evaluation of carotid artery stenosis: elliptic centric contrast-enhanced MR angiography and spiral CT angiography compared with digital subtraction angiography

BACKGROUND AND PURPOSE: Although digital subtraction angiography (DSA) is the reference standard for assessing carotid arteries, it is uncomfortable for patients and has a small risk of disabling stroke and death. These problems have fueled the use of spiral CT angiography and MR angiography. We prospectively compared elliptic centric contrast-enhanced MR angiography and spiral CT angiography with conventional DSA for detecting carotid artery stenosis. METHODS: Eighty carotid arteries (in 40 symptomatic patients) were assessed. Elliptic centric MR and spiral CT angiographic data were reconstructed with maximum intensity projection and multiplanar reconstruction techniques. All patients had been referred for DSA evaluation on the basis of findings at Doppler sonography, which served as a screening method (degree of stenosis > or = 70% or inconclusive results). Degree of carotid stenosis estimated by using the three modalities was compared. RESULTS: Significant correlation with DSA was found for stenosis degree for both elliptic centric MR and spiral CT angiography; however, the correlation coefficient was higher for MR than for CT angiography (r = 0.98 vs r = 0.86). Underestimation of stenoses of 70-99% occurred in one case with elliptic centric MR angiography (a 70% stenosis was underestimated as 65%) and in nine cases with spiral CT angiography, in comparison to DSA findings. Overestimation occurred in two cases with MR angiography (stenoses of 65-67% were overestimated as 70-75%). With CT, overestimation occurred in seven cases; a stenosis of 60% in one case was overestimated as 70%. Both techniques confirmed the three cases of carotid occlusion. With elliptic centric MR angiography, carotid stenoses of 70% or greater were detected with high sensitivity, 97.1%; specificity, 95.2%; likelihood ratio (LR) for a positive test result, 20.4; and ratio of LR(+) to LR(-), -0.3. With spiral CT angiography, sensitivity, specificity, LR(+), and LR(+):LR(-) were 74.3%, 97.6%, 31.2, and 0.3, respectively. CONCLUSION: Elliptic centric contrast-enhanced MR angiography is more accurate than spiral CT angiography to adequately evaluate carotid stenosis. Furthermore, elliptic centric contrast-enhanced MR angiography appears to be adequate to replace conventional DSA in most patients examined.     

Supraaortic arteries: contrast-enhanced MR angiography at 3.0 T--highly accelerated parallel acquisition for improved spatial resolution over an extended field of view

PURPOSE: To prospectively use 3.0-T breath-hold high-spatial-resolution contrast material-enhanced magnetic resonance (MR) angiography with highly accelerated parallel acquisition to image the supraaortic arteries of patients suspected of having arterial occlusive disease. MATERIALS AND METHODS: Institutional review board approval and written informed consent were obtained for this HIPAA-compliant study. Eighty patients (44 men, 36 women; age range, 44-90 years) underwent contrast-enhanced MR angiography of the head and neck at 3.0 T with an eight-channel neurovascular array coil. By applying a generalized autocalibrating partially parallel acquisition algorithm with an acceleration factor of four, high-spatial-resolution (0.7 x 0.7 x 0.9 mm = 0.44-mm(3) voxels) three-dimensional contrast-enhanced MR angiography was performed during a 20-second breath hold. Two neuroradiologists evaluated vascular image quality and arterial stenoses. Interobserver variability was tested with the kappa coefficient. Quantitation of stenosis at MR angiography was compared with that at digital subtraction angiography (DSA) (n = 13) and computed tomographic (CT) angiography (n = 12) with Spearman rank correlation coefficient (R(s)). RESULTS: Arterial stenoses were detected with contrast-enhanced MR angiography in 208 (reader 1) and 218 (reader 2) segments, with excellent interobserver agreement (kappa = 0.80). There was a significant correlation between contrast-enhanced MR angiography and CT angiography (R(s) = 0.95, reader 1; R(s) = 0.87, reader 2) and between contrast-enhanced MR angiography and DSA (R(s) = 0.94, reader 1; R(s) = 0.92, reader 2) for the degree of stenosis. Sensitivity and specificity of contrast-enhanced MR angiography for detection of arterial stenoses greater than 50% were 94% and 98% for reader 1 and 100% and 98% for reader 2, with DSA as the standard of reference. Vascular image quality was sufficient for diagnosis or excellent for 97% of arterial segments evaluated. CONCLUSION: By using highly accelerated parallel acquisition, the described 3.0-T contrast-enhanced MR angiographic protocol enabled visualization and characterization of the majority of supraaortic arteries, with diagnostic or excellent image quality (97% of arterial segments) and diagnostic values comparable with those obtained by using CT angiography and DSA for detection of arterial stenoses.     

Contrast-enhanced MR angiography of the supra-aortic vessels in 24 seconds: a feasibility study

A contrast-enhanced, gradient-echo 3D pulse sequence providing angiographic information in 24 s was tested in five healthy subjects and used prospectively in 21 patients for the investigation of the cervical arteries. Indications included suspected stenosis of the carotid (in 13), or vertebral arteries (in 1), carotid dissection (3), variants of the branches of the aortic arch (2) and extracranial carotid aneurysms (2). The results in all patients were compared with those of intra-arterial digital subtraction angiography (DSA). In patients with carotid stenosis, they were also compared with high-resolution 3D time-of-flight (TOF) MR angiography (MRA). Good quality MR angiograms of the neck vessels were obtained with the fast 3D sequence in 20 of the 21 patients. One claustrophobic patient was unable to co-operate. The degree of internal carotid artery (ICA) stenosis was graded correctly (compared to DSA) in 21 of 24 cases (87.5 %). Two mild stenoses were overestimated as moderate using the fast MR sequence and one high-grade stenosis was misdiagnosed as a complete occlusion. Carotid dissection was confirmed in one case and correctly excluded in two. Four extracranial ICA aneurysms in two patients, arterial variants and stenosis of the origin of the vertebral artery were correctly diagnosed using the contrast-enhanced MR angiogram. Three-dimensional TOF MRA was unsuccessful due to motion artefacts in half of the cases of ICA stenosis. Received: 6 August 1998 Accepted: 21 December 1998