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.     

Three-dimensional noninvasive contrast-enhanced electron beam tomography angiography of the kidneys: adjunctive use in medical and surgical management

OBJECTIVE: To indicate the use of 3D electron beam computerized tomography angiography (EBCTA) for renal artery lesions, vascular variants that are crucial to detect before surgery, especially partial nephrectomy and extension of the intravascular tumor. METHODS: Forty patients (30 men, 10 women, age range 13-82, mean age 54.2) underwent EBCT (GE-Imatron, C 150 ultrafast CT scanner) of the renal arteries. It is essential to review the axial images for all necessary information before the 3D technique is performed. RESULTS: Maximum intensity projection (MIP) and volume rendering (VR) images were excellent in demonstrating stenosis of the renal arteries. Accessory and main renal arteries were easily depicted, and stenosis has been shown. In our study, among 40 renal angiography patients, 21 had stenosis of the renal arteries with different percentages. A total of 12 accessory renal arteries (five left, seven right) were detected. EBCT, with its 3D techniques, was found to be accurate and useful for renal vascular anatomy as a noninvasive test to delineate renal tumors and renal anatomy prior to nephron sparing surgery because it is known to conserve normal renal parenchyma adjacent to tumor. CONCLUSION: EBCT, with its noninvasive VR and MIP techniques, is easy to apply and is functional and accurate for neoplasms, renal vascular anatomy and renal artery stenosis.     

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.     

Internal carotid arterial stenosis: CT angiography with volume rendering

PURPOSE: To determine the reliability of helical computed tomography (CT) with volume rendering for evaluation of internal carotid arterial stenosis. MATERIALS AND METHODS: In 22 patients, 44 carotid arteries were evaluated with helical CT and selective conventional angiography. CT data were displayed on volume-rendered and maximum intensity projection (MIP) images. Stenoses were measured separately on axial, volume-rendered, and MIP images and on conventional angiograms. Each artery was then graded as having no stenosis, mild (< 30%) stenosis, moderate (30%-70%) stenosis, severe (> 70%) stenosis, near occlusion, or occlusion. RESULTS: One case of stenosis was not assessable at axial CT because of an inappropriate scanning plane; four cases were not assessable at MIP CT because of mural calcifications. All carotid arteries were assessable on volume-rendered images despite no depiction of the residual lumen at the site of narrowing in three cases of near occlusion. Correlations between angiography and helical CT were good. Axial, volume-rendered, and MIP images enabled correct classification of stenosis in 88%, 89%, and 90% of arteries, respectively. CT with volume rendering was slightly more sensitive for determining candidates for endarterectomy (i.e., those with > 70% stenosis and near occlusion); sensitivity was 100% and specificity, 92%. CONCLUSION: CT angiography with volume rendering enabled accurate evaluation of carotid disease, even when dense calcifications were present. However, no definite advantage over currently available techniques for CT measurement of stenosis severity was found.     

64层螺旋CT血管成像对下肢动脉系统疾病的应用价值

目的:探讨64层螺旋CT血管成像术在下肢动脉疾病中的应用价值及技术优势。方法:对21例疑有下肢动脉疾病患者行64层螺旋CT增强扫描,扫描范围从肾动脉水平达足底。薄层重建横断面图像传入Wizard工作站,进行血管三维重建。其中21例结合常规血管造影评价64层螺旋CT血管成像术(CTA)的准确性。结果:在441个动脉节段中,435个节段在CTA与DSA均可以显示,在DSA图像上,狭窄闭塞的节段共130个(轻度狭窄16段,中度狭窄12段,重度狭窄22段,闭塞80段),最大密度投影(MIP)显示中度以上狭窄的敏感性、特异性及准确性分别为:99.1%、99.7%、99.5%。结论:64层CT血管成像是一种高度准确、非侵袭性的成像技术,在评估下肢动脉疾病方面与常规血管造影结果无明显差别,是下肢动脉疾病较好的影像学检查手段。     

US, CT, and MR evaluation of accessory renal arteries and proximal renal arterial branches

RATIONALE AND OBJECTIVES: The purpose of this study was to compare color Doppler ultrasound (US), computed tomographic (CT) angiography, and magnetic resonance (MR) angiography for the evaluation of accessory renal arteries and proximal branches of the main renal artery. MATERIALS AND METHODS: Fifty-six subjects who had undergone conventional arteriography of the renal arteries participated in a prospective comparison of Doppler US (45 patients), CT angiography (52 patients), and nonenhanced MR angiography (28 patients). Conventional arteriography depicted 28 accessory renal arteries and 21 proximal branches of the main renal artery within 2 cm of the aorta. RESULTS: US depicted five of 24 accessory renal arteries seen at arteriography but no proximal arterial branches. CT angiography depicted 24 of 26 accessory renal arteries and 13 of 17 proximal arterial branches, as well as 15 additional accessory renal arteries not seen at conventional arteriography. MR demonstrated 11 of 15 accessory arteries, as well as four additional accessory arteries not seen at conventional arteriography. MR did not depict any of nine proximal arterial branches seen at conventional arteriography. CONCLUSION: When compared with US or nonenhanced MR angiography, CT is the preferred method for evaluation of accessory renal arteries and proximal branches of the renal artery.     

Evaluation of the hepatic artery in potential donors for living donor liver transplantation by computed tomography angiography using multidetector-row computed tomography: comparison of volume rendering and maximum intensity projection techniques

PURPOSE: To compare the volume rendering (VR) and maximum intensity projection (MIP) computed tomography angiography (CTA) techniques using multidetector-row CT for hepatic artery evaluation of potential donors for living donor liver transplantation (LDLT). METHOD: Over a 9-month period, CTA using multidetector-row CT and conventional angiography was performed in 62 consecutive potential donors for LDLT. Acquisition of arterial phase scans was initiated within 5 seconds after reaching enhancement of the descending aorta up to 70 HU as measured by a bolus-tracking technique (collimation = 1.25 mm, table speed = 7.5 mm, reconstruction interval = 0.625 mm). Postprocessing was performed on a commercially available workstation. Computed tomography angiography images of the hepatic artery were made using the VR and MIP techniques. A total of 10 to 30 images of various planes were generated to reveal the origins and branching patterns of hepatic arteries. With a 2-week interval, two reviewers separately evaluated CTA using VR and MIP techniques, specifically evaluating anatomic variations and hepatic arterial conspicuity. The results of conventional angiography were considered to represent the gold standard. The difference in postprocessing time between the two techniques was statistically analyzed by the Student t test, and the differences in arterial conspicuity and in the identified number of the hepatic artery to segment IV of the liver were analyzed by the chi2 test. RESULTS: Two CT examinations (3%) were technically inadequate for generating CTA because of respiratory motion artifact. The average times for postprocessing of VR and MIP images were 8.1 +/- 3.8 minutes and 5.0 +/- 0.7 minutes, respectively. Variations of hepatic arterial anatomy were present in 19 patients (32%) on conventional angiography. In 8 patients (13%), there was discrepancy in the variations of hepatic arterial anatomy between the two techniques: MIP was correct in 7 patients, and VR was correct in 1 patient. The dominant artery supplying segment IV was identified in 51 patients (85%) with MIP and in 39 patients (65%) with VR. There was no significant difference in conspicuity of the hepatic arteries using either the MIP or VR technique. CONCLUSION: In CTA techniques using multidetector-row CT, MIP is superior to VR for the hepatic arterial evaluation of potential LDLT donors in terms of depicting anatomic variations and postprocessing time.     

Hepatic arteries in potential donors for living related liver transplantation: evaluation with multi-detector row CT angiography

PURPOSE: To assess the accuracy of multi-detector row computed tomographic (CT) angiography in the evaluation of hepatic arterial anatomy in living related liver transplantation (LRLT) donors. MATERIALS AND METHODS: During a 10-month period, 62 potential LRLT donors were evaluated with CT and conventional angiography. Multi-detector row CT was performed after intravenous injection of 150 mL of contrast material at 3 mL/sec. CT angiograms of the hepatic arteries were generated by a radiologist who used volume rendering and maximum intensity projection techniques without knowledge of results of conventional angiography. Two reviewers reviewed CT and conventional angiograms retrospectively in consensus. The results of the two examinations were then compared. RESULTS: CT examinations were technically adequate in 56 (90%) donors. Respiratory motion artifact compromised detailed hepatic artery analysis in six donors (10%). Second-order branches of right hepatic arteries were visualized in 58 donors (94%), and second-order branches of left hepatic arteries were visualized in 51 (82%). A total of 27 hepatic arterial anatomic variations were detected in 22 donors at conventional angiography. CT angiography accurately depicted 25 (93%) anatomic variations in 20 donors (91%). CT angiography did not depict an accessory right hepatic artery in two donors. The number and origins of dominant arteries supplying segment IV were accurately identified at CT angiography in 51 donors (82%). Hepatic arterial anatomy depicted at CT angiography was identical to that at conventional angiography in 50 donors (81%). CONCLUSION: Multi-detector row CT angiography is useful but limited in its ability to depict the dominant artery supplying segment IV and small accessory hepatic arteries.     

Detection of Accessory Renal Arteries with Virtual Vascular Endoscopy of the Aorta

Purpose: To evaluate the diagnostic accuracy of virtual vascular endoscopy (VVE) in the detection of accessory renal arteries. Methods: We retrospectively reviewed the CT angiography data sets of 67 patients (29 male and 38 female; age range 17–72 years, mean age 53 years) imaged for the study of the renal arteries, and affected by renovascular hypertension. All patients also had intraarterial digital subtraction angiography (DSA). CT angiography data sets were processed to obtain maximum intensity projection (MIP) and surface-rendered VVE of the aorta. Axial images, MIP, and VVE were evaluated separately and in combination in the detection of accessory renal arteries. Their results in terms of sensitivity and specificity were then compared with DSA. Results: Axial images had a sensitivity of 88% and specificity of 94% for accessory renal artery detection, MIP had a sensitivity of 88% and specificity of 98%, and VVE had a sensitivity of 63% and a specificity of 88% (p < 0.05 vs DSA), but these increased to 88% and 98% respectively if endoscopic views were integrated with the other display techniques. Conclusion: VVE based on surface rendering does not add substantial benefits to CTY angiography; by contrast MIP is the most accurate display technique for the detection of accessory renal arteries.     

64层螺旋CT血管造影在腹部中小动脉粥样硬化诊断中的应用

目的 探讨64层CT血管造影在腹部中小动脉粥样硬化诊断中的应用.资料和方法 应用容积再现(VR)、最大密度投影(MIP)、血管探针技术(VP)对70例腹主动脉粥样硬化斑的患者进行腹部动脉血管重组,比较其显示情况.结果 VP共检出病灶59处,测得狭窄度<30%,30%～50%,>50%分别有11、17、5例.VR及MIP均无一例明确显示<30%的狭窄管腔,且不能明确显示软斑块.对单纯钙化斑的显示,MIP检出结果与VP相同,VR有1例显示不清.对钙化软斑块的显示方面, VR、MIP对3处较小钙化斑显示不清.结论 在诊断腹部中小血管粥样斑块、微小钙化灶、血管轻度狭窄等方面,血管探针技术的敏感性较VR及MIP高.     

电子束CT血管三维重建技术与冠状动脉成像

目的　分析电子束CT(EBT)三维血管重建技术对冠状动脉及其狭窄的最佳显示方法。方法　对 40例分别行EBT冠状动脉增强扫描及常规冠状动脉造影 (CAG)的病例图像行回顾性三维重建。重建方法主要是最大密度投影法 (MIP)、曲面重建法(CPR)、多平面重组法 (MPR)及容积再现法 (VR)。所有三维重建图像由 2名不知CAG结果的医师按左主干、前降支、回旋支及右冠4支血管进行分析 (分支血管未包括在内 ) ,狭窄程度以 >5 0 %为标准与CAG结果对照。结果　MIP及CPR成像清晰 ,对 48支正常冠状动脉的评价准确率达 91.7%和 93 .8% ,对 5 9支狭窄 >5 0 %血管的评价准确率分别为 83 .1%和 88.1%。VR法重建立体效果好 ,但图像易造成正常血管狭窄的假象 ,48支正常血管中有 2 9支显示狭窄改变。对有狭窄血管的程度也较CAG夸大了约 10 %～3 0 %。MPR重建图像粗糙 ,无法评价冠状动脉。结论　MIP与CPR是显示冠状动脉及其狭窄的最佳三维重建方法 ,诊断准确性高 ,VR可作为补充显示方法 ,MPR可不采用     

颈部MSCTA:8层螺旋CT扫描与重建方法探讨

目的：探讨多层螺旋CT颈部CTA扫描技术条件、图像重建方法，评价CTA对颈部血管狭窄性病变的诊断价值。方法：8层螺旋CT颈部CTA检查22例，其中14例做了颈部DSA检查，CTA检查后在工作站经最大密度投影（MIP）容积再现（VR）及高级血管分析(AVA)重建血管，分析不同重建方法对颈部血管显示的能力。结果：CTA显示正常血管43支，狭窄血管45支，其中14例与DSA对照，经统计学分析二者对颈部血管狭窄的显示差异无显著性意义，AVA软件能清晰显示血管狭窄及椎动脉和周围骨质的关系，准确显示狭窄段，自动计算狭窄程度。结论：多层螺旋CT的颈部CTA检查可做为颈部动脉狭窄性病变筛选的首选检查方法，AVA软件使CTA对迂曲、与骨质关系密切的血管狭窄的分析更准确。     

Carotid bifurcation CT angiography: assessment of interactive volume rendering.

PURPOSE: The purpose of this study was to compare the accuracy of CT angiography (CTA) for the assessment of carotid bifurcation stenosis, using interactive volume rendering (VR), maximum intensity projection (MIP), and 2D transverse CT technique (t-CT). METHOD: Nineteen consecutive patients were prospectively studied with CTA and selective digital subtraction angiography (DSA). There were 13 men and 6 women from 51 to 84 years old (mean 70 years). Results of DSA were compared with those of interactive VR, MIP, and conventional t-CT results, using North American Symptomatic Carotid Endarterectomy Trial criteria for stenosis grading. RESULTS: There were a total of 38 carotid bifurcations studied, with 9 mild, 10 moderate, and 15 severe stenoses and 4 occlusions. Overall agreement with DSA for VR was achieved in 76%. Eighty percent of the severe stenoses were correctly predicted by VR. The overall agreement between t-CT and DSA was 89%. MIP images, when analyzed independently, showed an overall agreement with angiography of only 71%. VR was not significantly different from MIP (p = 0.60). The difference between VR and t-CT had borderline significance (p = 0.09). MIP had significantly poorer agreement with angiography than t-CT (p = 0.02). CONCLUSION: CTA has a high degree of accuracy for the assessment of carotid artery disease compared with catheter angiography. Interactive VR increases the accuracy of diagnosing carotid stenosis and decreases the number of unsatisfactory studies as compared with MIP. Further advances in computation speeds and improvements in software may dramatically alter the future use of VR for the communication of results to clinicians; however, careful analysis of transverse sections is essential to accurate CT interpretation.     

Multislice CT angiography of the celiac and superior mesenteric arteries: comparison with arteriographic findings

PURPOSE: The aim of the present study is to evaluate the feasibility of multislice computed tomography (MSCT) angiography of the celiac and superior mesenteric arteries with a non tailored protocol. Sixteen patients underwent both MSCT of the upper abdomen and digital subtraction celiac and superior mesenteric angiography. CT examinations included unenhanced scanning and dual-phase (arterial and portal) scanning of the upper abdomen. Retrospective 2.5 mm thick slices with 50% overlap were used for CT angiography reformations with volume rendering (VR), high density maximum intensity projection (HD-MIP) and subvolume MIP technique; normal arterial anatomy, variants, stenoses and aneurysms were assessed and compared with findings of digital subtraction angiography. RESULTS: All VR and HD-MIP reconstructions were considered satisfactory, except in two cases because of inappropriate setting of scan parameters; subvolume MIP reformations were considered satisfactory in all cases, and superior in the depiction of small arteries. Aneurysms and stenoses were always detected, whereas a case of replaced right hepatic artery in a patient with complex vascular anatomy was misdiagnosed by MSCT angiography. The overall accuracy of VR, HD-MIP and MIP CT angiographic reconstructions was 71.9%, 81.8% and 94.6%, respectively. CONCLUSIONS: In our preliminary report, CT angiography with multidetector CT has proved effective in depicting splanchnic arterial anatomy, and can replace diagnostic invasive angiography in most cases. Good quality of axial images is necessary for reformations with VR and MIP techniques.     

Multidetector-row CT angiography diagnostic sensitivity in evaluation of renal artery stenosis: comparison between multiple reconstruction techniques

PURPOSE: The aim of this study was to assess the image quality and interobserver agreement of various multidetector-row computed tomographic angiography postprocessing techniques in the diagnosis of renal artery stenosis (RAS). MATERIALS AND METHODS: We studied 36 patients (21 men and 15 women; mean age, 49 years) who underwent computed tomography angiography to assess renal arteries for suspected RAS. Patients were analyzed by using a multidetector-row computed tomography. Computer tomographic scans were obtained after intravenous bolus administration of 110 to 140 mL of nonionic contrast material using a 4- to 6-mL/s flow rate. We assessed every patient by using axial scans, multiplanar reconstruction (MPR), maximum intensity projection (MIP), and volume rendering (VR) techniques. For each patient and for each reconstruction method, the image quality of the main renal artery was scored as 0 for bad-quality, 1 for poor-quality, 2 for good-quality, and 3 for excellent-quality images. Two radiologists reviewed computed tomographic images independently. We calculated interobserver agreement and kappa value. We correlated the stenosis degree observed by the 2 readers with the type of reconstruction used. RESULTS: Overall number of renal arteries studied was 72, and we detected 24 RAS. Quality images obtained an overall (averaged between the 2 observers) value of 133 of 216, 163 of 216, and 145 of 216 for MPR, MIP, and VR, respectively. Our data underlined a statistical difference between MPR images and VR images (P < 0.001). Moreover, we noticed that the images classified as excellent were obtained from a vessel with 350 Hounsfield units or higher. Kappa value was good in MIP and VR methods evaluation but poor with the use of MPR. CONCLUSIONS: Reformatting techniques usually provided a high visual impact, and in our study, MIP and VR showed the best diagnostic interobserver agreement in quality and reproducibility of stenosis degree.     

Spiral CT angiography of renal arteries: comparison with angiography

A prospective study was carried out to determine the accuracy of spiral CT angiography (CTA) in the detection of renal artery stenosis (RAS). Eighty-two patients with arterial hypertension underwent CTA and digital subtraction angiography (DSA) to exclude RAS. For CTA a contrast medium bolus of 100–150 ml (flow rate 3 ml/s) was injected. A 24 or 40 s CTA was started at the origin of the superior mesenteric artery after a delay time determined by test bolus injection (collimation = 2 mm, pitch = 1/1.5). For stenosis detection transverse images supported by maximum intensity projections (MIP) or multiplanar reconstruction projections were used. Of 197 renal arteries examined (including 33 accessory arteries), 34 RAS were visualized using DSA. With CTA, one hemodynamic RAS was missed and one additional hemodynamic RAS was found. Sensitivity/specificity was calculated to be 94 %/98 %. For hemodynamically relevant RAS (> 50 %) the sensitivity/specificity was 96 %/99 %. CTA additionally depicted five adrenal masses. The high accuracy rate of RAS detection thus allows the use of CTA as a screening method in patients with arterial hypertension to exclude a renovascular cause. Received: 23 June 1997; Revision received: 6 January 1998; Accepted: 29 April 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.     

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.     

Preoperative evaluation of living renal donors: value of contrast-enhanced 3D magnetic resonance angiography and comparison of three rendering algorithms

The aim of this study was to assess the value of contrast-enhanced three-dimensional MR angiography (CE 3D MRA) in the preoperative assessment of potential living renal donors, and to compare the accuracy for the depiction of the vascular anatomy using three different rendering algorithms. Twenty-three potential living renal donors were examined with CE 3D MRA (TE/TR=1.3 ms/3.7 ms, field of view 260–320×350 mm, 384–448×512 matrix, slab thickness 9.4 cm, 72 partitions, section thickness 1.3 mm, scan time 24 s, 0.1 mmol/kg body weight gadobenate dimeglumine). Magnetic resonance angiography data sets were processed with maximum intensity projection (MIP), volume rendering (VR), and shaded-surface display (SSD) algorithms. The image analysis was performed independently by three MR-experienced radiologists recording the number of renal arteries, the presence of early branching or vascular pathology. The combination of digital subtraction angiography (DSA) and intraoperative findings served as the gold standard for the image analysis. In total, 52 renal arteries were correspondingly observed in 23 patients at DSA and surgery. Other findings were 3 cases of early branching of the renal arteries, 4 cases of arterial stenosis and 1 case of bilateral fibromuscular dysplasia. With MRA source data all 52 renal arteries were correctly identified by all readers, compared with 51 (98.1%), 51–52 (98.1–100%) and 49–50 renal arteries (94.2–96.2%) with the MIP, VR and SSD projections, respectively. Similarly, the sensitivity, specificity and accuracy was highest with the MRA source data followed by MIP, VR and SSD. Time requirements were lowest for the MIP reconstructions and highest for the VR reconstructions. Contrast-enhanced 3D MRA is a reliable, non-invasive tool for the preoperative evaluation of potential living renal donors. Maximum intensity projection is favourable for the processing of 3D MRA data, as it has minimal time and computational requirements, while having similar or superior accuracy for the depiction of vessel anomalies or pathology compared with VR and SSD, respectively. Electronic Publication     

Pancreaticoduodenal arcades and dorsal pancreatic artery: comparison of CT angiography with three-dimensional volume rendering, maximum intensity projection, and shaded-surface display

OBJECTIVE: The objective of this study was to compare the ability of CT angiography to depict the pancreaticoduodenal arcades and the dorsal pancreatic artery using the techniques of three-dimensional (3D) volume rendering, maximum intensity projection (MIP), and shaded-surface display (SSD). SUBJECTS AND METHODS: Twenty-seven patients were selected at random from a group of 42 patients undergoing arterial-phase helical CT angiography before liver transplantation. CT angiograms were constructed from identical data sets using 3D volume rendering, MIP, and SSD. RESULTS: Seventy-two vessels were evaluated in 27 patients. Three-dimensional volume rendering depicted 24 anterior and 22 posterior arcades and 26 dorsal pancreatic arteries; combined MIP and SSD depicted 14 anterior and 13 posterior arcades and 19 dorsal pancreatic arteries. Thirty vessels with diameters of between 2 and 3 mm were well seen with 3D volume rendering but were incompletely depicted with MIP and SSD. Sixteen vessels with diameters of greater than 3 mm were well seen using all three techniques. Twenty-six vessels with diameters of less than 2 mm were faintly seen with 3D volume rendering but were unidentifiable with MIP and SSD. CONCLUSION: Three-dimensional volume rendering is superior to MIP and SSD in the depiction of pancreaticoduodenal arcades and dorsal pancreatic arteries. Unlike the other rendering techniques, 3D volume rendering can also show relationships between these vessels and pancreatic parenchyma and adjacent structures.