MR-guided angioplasty of renal artery stenosis in a pig model: a feasibility study

PURPOSE: To test the hypothesis that magnetic resonance (MR) imaging can guide the percutaneous treatment of renal artery stenosis in a pig model. MATERIALS AND METHODS: Ameroid constrictors were surgically placed around six renal arteries in four pigs. After 30-36 days, all stenoses were documented by conventional x-ray aortograms. MR-guided renal angioplasty was attempted for three stenoses. For these pigs, MR angiography was performed with use of contrast-enhanced three-dimensional (3D) techniques. The authors visualized catheters by filling them with dilute 4% gadolinium and imaging with two-dimensional (2D) and 3D MR fast spoiled gradient recalled echo techniques. Under MR guidance, the authors advanced a selective catheter into the affected renal artery and crossed the stenosis with a nitinol guide wire. Angioplasty was performed with a balloon catheter filled with dilute gadolinium. Stenosis and luminal diameter measurements were compared before and after angioplasty. RESULTS: After ameroid constrictor placement, four significant stenoses, one mild stenosis, and one occlusion developed. Under MR guidance, the authors achieved technical success in performing three of three (100%) attempted dilations. After MR-guided angioplasty, the mean reduction in stenosis was 35% and the mean increase in luminal diameter was 1.6 mm. CONCLUSION: Use of MR guidance for the angioplasty of renal artery stenosis in pigs is feasible.     

MR-guided balloon angioplasty of stenosed aorta: in vivo evaluation using near-standard instruments and a passive tracking technique

The purpose of this study was to assess the feasibility of magnetic resonance (MR)-guided balloon angioplasty of a stenosed aorta on an open low-field magnet using a passive tracking technique. Visualization of vessels and position of instruments were realized by using a fast low-angle shot (FLASH) sequence. Catheters and guidewire were prepared for susceptibility-based MR visualization. Standard balloon catheters were inflated with diluted gadolinium, and nitinol guidewires were modified by incorporation of iron oxide markers into their walls. After validation on a flow phantom, balloon angioplasty was performed on an in vivo model of arterial stenosis. Creation of abdominal aorta stenosis was realized in five piglets. MR-guided balloon angioplasty of the aorta was performed with success in all but one. In one of them, stent implantation was achieved in the descending aorta. Balloon angioplasty using a passive tracking technique is a simple concept that can be realized with near-standard instruments and any MR imaging system. This represents an advance toward MR-guided vascular interventions in the future.     

Image-guided and -monitored renal artery stenting using only MRI

PURPOSE: To demonstrate the ability of a unique interventional MR system to be used safely and effectively as the only imaging modality for all phases of MR-guided stent-supported angioplasty. MATERIALS AND METHODS: An experimental disease model of renal stenosis was created in six pigs. An interventional MR system, which employed previously reported tools for real-time catheter tracking with automated scan-plane positioning, adaptive image parameters, and radial true-FISP imaging with steady-state precession (True-FISP) imaging coupled with a high-speed reconstruction technique, was then used to guide all phases of the intervention, including: guidewire and catheter insertion, stent deployment, and confirmation of therapeutic success. Pre- and postprocedural X-ray imaging was used as a gold standard to validate the experimental results. RESULTS: All of the stent-supported angioplasty interventions were a technical success and were performed without complications. The average postoperative residual stenosis was 14.9%. The image guidance enabled the stents to be deployed with an accuracy of 0.98 +/- 0.69 mm. Additionally, using this interventional MRI system to guide renal artery stenting significantly reduces the procedure time, as compared to using X-ray fluoroscopy. CONCLUSION: This study has clearly demonstrated the first successful treatment of renal artery stenting in an experimental animal model solely under MRI guidance and monitoring.     

MR imaging-guided vascular procedures using CO2 as a contrast agent

OBJECTIVE: The purpose of this study was to test the use of CO(2) as a black blood contrast agent for MR imaging-guided vascular procedures in an animal model. MATERIALS AND METHODS: Repeated intraarterial CO(2) injections were performed through a catheter located in the aorta and the renal arteries of three fully anesthetized pigs. Real-time images were acquired using a steady-state free precession sequence. RESULTS: During the CO(2) injections, the bright blood in the aorta and the main renal artery was totally replaced, and this procedure resulted in an immediate, statistically significant signal loss in the vessel lumen. In more peripheral vessels, CO(2) improved the vessel conspicuity substantially. Confirmation of vessel patency distal to the catheter tip position was possible. CONCLUSION: The use of carbon dioxide in combination with a bright blood MR imaging sequence improves vessel conspicuity and provides immediate information about blood flow distal to the catheter. This technique may be used to facilitate MR imaging-guided intravascular procedures.     

High-spatial-resolution contrast-enhanced MR angiography of the renal arteries: a prospective comparison with digital subtraction angiography

PURPOSE: To evaluate a high-spatial-resolution three-dimensional (3D) contrast material-enhanced magnetic resonance (MR) angiographic technique for detecting proximal and distal renal arterial stenosis. MATERIALS AND METHODS: Twenty-five patients underwent high-spatial-resolution small-field-of-view (FOV) 3D contrast-enhanced MR angiography of the renal arteries, which was followed several minutes later by more standard, large-FOV 3D contrast-enhanced MR angiography that included the distal aorta and iliac arteries. For both acquisitions, MR fluoroscopic triggering and an elliptic centric view order were used. Two readers evaluated the MR angiograms for grade and hemodynamic significance of renal arterial stenosis, diagnostic quality, and presence of artifacts. MR imaging results for each patient were compared with those of digital subtraction angiograms. RESULTS: The high-spatial-resolution small-FOV technique provided high sensitivity (97%) and specificity (92%) for the detection of renal arterial stenosis, including all four distal stenoses encountered. The portrayal of the segmental renal arteries was adequate for diagnosis in 19 (76%) of 25 patients. In 12% of the patients, impaired depiction of the segmental arteries was linked to motion. CONCLUSION: The combined high-spatial-resolution small-FOV and large-FOV MR angiographic examination provides improved spatial resolution in the region of the renal arteries while maintaining coverage of the abdominal aorta and iliac arteries.     

MR image-guided endovascular procedures with the ultrasmall superparamagnetic iron oxide SH U 555 C as an intravascular contrast agent: study in pigs

PURPOSE: To evaluate the feasibility of using the ultrasmall superparamagnetic iron oxide (USPIO) SH U 555 C as an intravascular contrast agent for magnetic resonance (MR) image-guided vascular procedures with an open MR imaging system. MATERIALS AND METHODS: All experiments were performed with MR imaging at 0.2 T. MR image-guided interventions were performed in USPIO-enhanced vessels in four pigs. With near real-time MR image guidance (acquisition time, 0.64 second per section), the splenic and renal arteries were consecutively catheterized by using a susceptibility artifact-based catheter-guide wire combination. Angioplasty and stent implantation were performed four times in the renal artery and twice in the iliac artery. Intraaortal signal intensity (SI) was measured during the interventions. RESULTS: After administration of SH U 555 C (40 micromol of iron per kilogram of body weight), a three-dimensional MR angiographic sequence was performed that allowed visualization of the abdominal and pelvic vessels that were as small as 2 mm in diameter. Catheterization, angioplasty, and stent implantation were successfully guided in the USPIO-enhanced vasculature. Sixty minutes after contrast agent injection, the mean aortic SI was 70% of the maximum measured enhancement levels. CONCLUSION: One intravenous injection of SH U 555 C enabled long, continuous intravascular SI enhancement at MR angiography, and, in combination with susceptibility artifact-based device tracking, the injection allowed the performance of MR imaging-guided intravascular interventions in an open MR imaging system.     

Comparison of intraarterial MR angiography at 3.0 T with X-ray digital subtraction angiography for detection of renal artery stenosis in swine

PURPOSE: To compare the accuracy of catheter-directed intraarterial (IA) magnetic resonance (MR) angiography at 3.0 T with that of x-ray digital subtraction angiography (DSA) for the measurement of renal artery stenosis (RAS) in swine. MATERIALS AND METHODS: Unilateral hemodynamically significant RAS (>50%) was induced surgically in six pigs with use of reverse cable ties. One to two weeks after surgery, each pig underwent x-ray DSA and MR angiography before and after percutaneous transluminal balloon angioplasty (PTA). X-ray DSA was performed before and after PTA of RAS by injection of iodinated contrast agent through a 5-F multiple-side hole angiographic catheter placed in the abdominal aorta under fluoroscopic guidance. MR angiography of RAS was performed before and after PTA of RAS on a 3.0-T clinical MR imager with use of gadolinium-based contrast agent. MR angiography and DSA images were analyzed with the full width at half maximum method. Percent stenosis measurements between x-ray DSA and MR angiography were compared with a paired t test and were correlated with linear regression and Bland Altman analysis (alpha = 0.05). RESULTS: Six cases of RAS were induced and imaged successfully with DSA and MR angiography techniques before and after PTA. On x-ray DSA, median stenoses was 64% (95% CI 57%-80%) before PTA and 20% (95% CI 5%-32%) after PTA. Corresponding MR angiography median stenosis measurement was 69% (95% CI 58%-80%) before PTA and 26% (95% CI 16%-36%) after PTA. A paired t test comparison did not show a difference between DSA and MR angiography (P = .16). RAS measurements on MR angiography correlated closely (P < .01) with DSA measurements (r(2) = 0.92). CONCLUSION: In swine, the accuracy of catheter-directed IA MR angiography with use of a clinical 3.0-T MR imaging unit for the measurement of RAS was similar to that of conventional x-ray DSA.     

Renal artery velocity mapping with MR imaging

An MR phase imaging sequence with a very short echo time was used to assess blood velocity and flow at the renal artery bifurcation. Cardiac-gated MR imaging data were obtained in six healthy subjects in sagittal planes adjacent to the abdominal aorta and transverse planes above and below the renal artery bifurcation. Average renal artery flow rate was 23.8 ±9 mL/sec. A strong individual variability was found for the velocity profiles in the abdominal aorta during end-systolic regurgitation. Flow rate was also determined in three patients with reduced renal artery blood flow. Two patients received therapy with percutaneous transluminal angioplasty. The successful outcome was documented with MR imaging. A reliable assessment of renal artery flow with MR phase imaging is feasible. Measurement of the velocity profiles yields valuable insights in the complicated flow regime at the renal artery bifurcation.     

A polymer-based MR-compatible guidewire: a study to explore new prospects for interventional peripheral magnetic resonance angiography (ipMRA)

PURPOSE: To introduce a newly developed polymer-based and magnetic resonance (MR)-compatible guidewire and to explore its capabilities with respect to interventional peripheral magnetic resonance angiography (ipMRA) in a flow phantom. MATERIALS AND METHODS: The guidewire is based on a polyetheretherketone (PEEK) polymer core, and small iron particles are embedded in its coating. A passive device tracking technique was designed utilizing a susceptibility artifact induced by the wire in images acquired with a balanced steady-state free precession (b-SSFP) sequence using small flip angles. The position of the guidewire tip was determined from image intensity maxima and overlayed onto a roadmap in near real-time. Guidewire tracking and balloon angioplasty of an artificial stenosis were attempted in two configurations of a flow phantom. RESULTS: Successful passive guidewire tracking was performed for all phantom configurations. Robustness and accuracy of the tracking technique were sufficient for phantom studies. A balloon catheter was placed into the stenosis using the guidewire under complete MR guidance, and subsequent balloon angioplasty yielded improved flow conditions. CONCLUSION: The new guidewire is well-suited for clinical application due to an absence of the risk of core fracture and its atraumatic flexible tip. It opens novel prospects for the realization of ipMRA in humans that need to be explored in further studies.     

二氧化碳造影在移植肾动脉狭窄诊断和球囊扩张术中的应用

目的：评价用二氧化碳（CO2）作为对比剂行移植肾动脉狭窄诊断和成形术的可行性和有效性。资料与方法：对9例怀疑移植肾动脉狭窄者行CO2数字减影血管造影（CO2－DSA），并对狭窄病变在重叠透视定位下行球囊扩张。其中3例在扩张前后同时行非离子型碘对比剂造影。结果：CO2－DSA均清晰显示吻合口后移植肾动脉50％以上的狭窄，均一次性扩张成功。3例中CO2－DSA与碘对比剂造影结果相符。无血清肌酐显著上升和严重并发症。结论：为避免对比剂可能导致的肾毒性，CO2作为对比剂行移植肾动脉狭窄诊断和球囊扩张术后DSA是可行、有效的。     

Diagnosis of renal vascular disease with MR angiography.

Renal magnetic resonance (MR) angiography allows accurate evaluation of patients suspected to have renal artery stenosis without the risks associated with nephrotoxic contrast agents, ionizing radiation, or arterial catheterization. Other applications of renal MR angiography are mapping the vascular anatomy for planning renal revascularization, planning repair of abdominal aortic aneurysms, assessing renal bypass grafts and renal transplant anastomoses, and evaluating vascular involvement by renal tumors. A variety of pulse sequences provide complementary information about kidney morphology, arterial anatomy, blood flow, and renal function and excretion. Three-dimensional gadolinium-enhanced MR angiography can be combined with several other sequences to produce a comprehensive approach to renal MR angiography. This comprehensive approach is designed to allow hemodynamic characterization of renal artery stenosis with a single MR imaging examination that can be easily completed in 1 hour. Three-dimensional gadolinium-enhanced MR angiography demonstrates the renal arteries along with the abdominal aorta, iliac arteries, and mesenteric arteries in a 20-30-second acquisition that can be performed during breath holding. Numerous projections are reconstructed from a single three-dimensional volume of data acquired with a single injection of contrast material to obtain perpendicular and optimized views of each renal artery.     

Superior mesenteric artery angioplasty with the TEGwire: usefulness and technical difficulties.

The TEGwire percutaneous transluminal angioplasty balloon on a guide wire was used successfully for dilation of a proximal superior mesenteric arterial stenosis that was not well suited to dilation by conventional angioplasty catheters. After the stenosis was dilated, however, the balloon deflated only partially due to a kink in the TEGwire as it coursed over the acute angle between the aorta and the superior mesenteric artery. Several unsuccessful attempts to correct this problem were made; finally, the partially deflated balloon and the guide catheter had to be withdrawn. Although the TEGwire was used within the guidelines and recommendations of the product, this experience supports the manufacturer's recommendation that the TEGwire system should not be used with narrow-radius vascular curves such as that formed between the superior mesenteric artery and the aorta.     

血管内超声在1例颈内动脉闭塞患者介入治疗中的应用

目的 探讨血管内超声(IVUS)技术在颈内动脉闭塞经皮腔内血管成形术(PTA)中的应用价值.方法 1例患者CTA明确颈内动脉闭塞,脑灌注成像见低灌注区与缺血相关症状符合,在IVUS导引下接受PTA治疗.采用微导丝及微导管同轴技术通过闭塞段,IVUS确认位于真腔内,微导管造影确认闭塞远端血管通畅,调整后放置栓塞保护器;IVUS测评斑块及管腔情况,球囊预扩张后再次测评;血管内恢复正向血流后通过IVUS虚拟组织学序列分析斑块稳定性,斑块纤维帽稳定且管腔狭窄率＜40％仅作单纯球囊扩张治疗.结果 单纯球囊扩张治疗后闭塞血管再通,恢复正向血流.IVUS全程检测狭窄段斑块纤维帽稳定,管腔狭窄率＜40％,脑灌注成像显示低灌注状态明显改善.结论 IVUS技术在PTA治疗颈内动脉闭塞中起重要导引作用,可增加再通手术成功率,降低并发症发生率.     

Magnetic resonance-guided percutaneous angioplasty of femoral and popliteal artery stenoses using real-time imaging and intra-arterial contrast-enhanced magnetic resonance angiography

OBJECTIVE: The aim of this study was to demonstrate the possibility of performing magnetic resonance (MR)-guided interventional therapy for femoral and popliteal artery stenoses with commercially available materials supported by MR real-time imaging and intra-arterial MR angiography. MATERIALS AND METHODS: A total of 15 patients suffering from symptomatic arterial occlusive disease of the lower limbs with 19 stenoses were included. Interventional intra-arterial digital subtraction angiography was performed before and after angioplasty on each patient as standard of reference. MR images were acquired on a 1.5-T MR scanner. A fast-low-angle shot (FLASH) 3D sequence was applied for a contrast enhanced MR-angiography (ceMRA). A total of 5 mL of diluted gadodiamide was injected via the arterial access. Maximum intensity projections (MIPs) were used as roadmaps and localizers for the interactive positioning of a continuously running 2D-FLASH sequence with a temporal solution of 2 images/second. The lesion was crossed by a balloon-catheter, which was mounted on a guidewire. The visibility was provided by the radiopaque markers on the balloon and was improved by injection of 1 mL of gadolinium into the balloon. Postinterventional control was performed by intra-arterial MR angiography and catheter angiography. RESULTS: Stenoses were localized by intra-arterial MR angiography. The guidewire/balloon combination was visible, and the balloon was placed correctly to cover the entire stenoses. Balloon dilation reduced the degree of stenosis by approximately 57% on average. No complications were observed. CONCLUSION: MR-guided balloon dilation of femoral and popliteal artery stenoses supported by real-time MR imaging and intra-arterial MR angiography is feasible with commercially available materials.     

MR imaging- versus conventional X-ray fluoroscopy-guided renal angioplasty in swine: prospective randomized comparison

PURPOSE: To test the hypothesis that the technical success rates, complication rates, and procedural times for magnetic resonance (MR) imaging-guided percutaneous transluminal angioplasty (PTA) and conventional (x-ray) fluoroscopy-guided PTA for treatment of renal artery stenosis are similar. MATERIALS AND METHODS: The study was animal care and use committee approved. After surgically inducing bilateral renal artery stenosis in 11 swine, the authors performed baseline digital subtraction angiography. They transferred each animal to a 1.5-T MR imaging unit and randomly decided which artery would be treated with MR-guided PTA. With MR imaging guidance, angioplastic devices were tracked by using active and passive techniques. Vascular depiction was achieved by using catheter-directed MR angiography. Stenotic vessels were dilated by using 5-6-mm-diameter balloon catheters. PTA was then performed in the contralateral artery by using conventional fluoroscopy-guided techniques. With the intention to treat, the authors compared the technical success (residual stenosis < 50%) rates, complication rates, and procedural times for each guidance method. They compared technical successes and complications by using the McNemar test and procedural times by using a paired t test, with P < .05 indicating a significant difference. RESULTS: The authors successfully dilated nine (82%) of 11 renal arteries with MR guidance and all 11 arteries (100%) with conventional fluoroscopic guidance. The difference was not significant (P = .5). Complications occurred in three (27%) arteries with MR guidance and in one (9%) artery with fluoroscopic guidance, with no significant differences (P = .5). The mean MR-guided PTA procedural time was 46 minutes longer than the fluoroscopy-guided PTA procedural time; this difference was significant (P = .01). CONCLUSION: In a small cohort of swine, the authors did not observe a significant difference between MR imaging- and conventional fluoroscopy-guided renal artery PTA in terms of success and complication rates. However, no evidence of similarity between the techniques should be assumed. Procedural times differed significantly.     

Renal artery stenosis in swine: feasibility of MR assessment of renal function during percutaneous transluminal angioplasty

PURPOSE: To prospectively test--in a swine model of renal artery stenosis (RAS)--the hypothesis that magnetic resonance (MR) imaging can reveal changes in renal function at the time of percutaneous transluminal angioplasty (PTA). MATERIALS AND METHODS: In this animal care and use committee-approved study, high-grade unilateral RAS was surgically induced in six pigs. MR imaging at 3.0 T was used for intraprocedural assessment of the anatomic and physiologic changes induced by x-ray-guided PTA. With use of MR imaging, changes in single-kidney glomerular filtration rate, extraction fraction, and renal blood flow were assessed during PTA. The arterial diameter of stenosis before and after PTA was assessed by using conventional digital subtraction angiography. Mean changes in functional and anatomic parameters were compared by using the Wilcoxon signed rank test (alpha = .05). RESULTS: At digital subtraction angiography, the mean percentage of stenosis was 69% +/- 10 (standard deviation) before PTA and 26% +/- 10 after PTA (P<.03). Mean pre- and post-PTA extraction fraction values were 0.11 +/- 0.03 and 0.19 +/- 0.06, respectively (P<.03). The mean single-kidney glomerular filtration rate before PTA, 19 mL/min +/- 13, increased to 41 mL/min +/- 33 after PTA (P<.03). There was no significant change in mean renal blood flow after PTA (P=.44). CONCLUSION: In swine, MR imaging can reveal changes in renal function after x-ray-guided PTA for unilateral RAS.     

Feasibility of MR imaging-guided percutaneous drainage of pancreatic fluid collections

PURPOSE: To assess the feasibility and safety of magnetic resonance (MR) imaging-guided percutaneous drainage of pancreatic fluid collections in an open configuration low field MR imaging system. MATERIALS AND METHODS: Ten patients with pancreatic fluid collections were examined prospectively. Five of the fluid collections were symptomatic pseudocysts and five were pancreatic abscesses. All percutaneous drainages were performed solely under MR imaging guidance with a 0.23-T open configuration C-arm shaped MR imaging scanner with interventional optical tracking. Every step of the procedure was monitored using balanced fast field echo sequences. In each case, the drainage of the fluid collection was performed with a MR imaging-compatible drainage kit using the Seldinger technique. The kit included an 18-gauge needle, a 0.035-inch stiff guide wire, 6-F and 8-F dilators, and an 8-F pigtail drainage catheter. RESULTS: All drainage catheters could successfully be placed into the pancreatic fluid collections under MR imaging guidance. Visualization of the needle, dilator, and drainage catheter was excellent. However, visualization of the guide wire was suboptimal. The mean time needed for the MR-guided drainage procedure was 44 minutes. No immediate complications occurred. The clinical success rate of the percutaneous drainage was 70%; three patients were subsequently treated surgically. There were no deaths. The average duration of catheterization was 40 days. CONCLUSION: MR imaging-guided percutaneous drainage of pancreatic fluid collections is feasible and safe. The presented technique has limitations--lack of real-time imaging control and small selection of MR imaging-compatible devices--that necessitate further technical developments before the procedure can be recommended for routine clinical use.     

MR measurement of coronary blood flow.

The functional significance of coronary arterial stenosis can be evaluated by measuring the pharmacological flow reserve. Magnetic resonance (MR) imaging has a unique potential for noninvasive measurement of coronary blood flow and flow reserve in the native coronary artery and bypass graft. Restenosis after coronary balloon angioplasty and stenting in the left anterior descending artery can be detected noninvasively with serial MR measurements of the coronary flow reserve. Further refinement of the MR pulse sequences to improve spatial and temporal resolutions may permit accurate quantification of blood flow volume and flow reserve in all major coronary arterial branches. MR assessments of blood flow volume and flow pattern allow noninvasive detection of significant stenosis in the coronary artery bypass graft as well. By integrating MR blood flow measurement in the coronary sinus and cine MR assessment of left ventricular myocardial mass, altered myocardial micro-circulation in patients with diffuse myocardial diseases, such as hypertrophic cardiomyopathy and cardiac transplant, has been documented. J. Magn. Reson. Imaging 1999;10:728-733.     

Flow pattern analysis in the abdominal aorta with velocity-encoded cine MR imaging

The sites of deposition of atherosclerotic plaque on the aortic wall are considered to be influenced by secondary and retrograde flow patterns that cause regions of altered shear stress. To detect secondary flow patterns and areas of retrograde flow in the abdominal aorta, velocity-encoded cine (VEC) magnetic resonance (MR) imaging was performed at five different levels of the abdominal aorta in nine healthy volunteers. Net retrograde flow (expressed as a percentage of antegrade flow) increased from proximal to distal levels and was maximal (13.8% ± 11.8) just distal to the origin of the renal arteries. An increase in the duration of retrograde flow over the cardiac cycle was observed from proximal to distal levels. Whereas retrograde flow was present at end systole and early diastole in each volunteer at every level, the duration and amount of retrograde flow during diastole showed high interindividual variation. Such differences suggest the possibility of variable vascular geometric risk factors in the population for the development of atherosclerotic plaque. The location of retrograde flow in the abdominal aorta demonstrated in vivo with VEC MR imaging was close to that obtained with in vitro flow visualization studies in models of the abdominal aorta.     

Renal transplant evaluation with MR angiography and MR imaging.

Magnetic resonance (MR) angiography is a widely used, noninvasive tool for evaluating the aorta and its branches. It is particularly useful in renal transplant recipients because it provides anatomic detail of the transplant artery without nephrotoxic effects. Volume rendering is underutilized in MR angiography, but this technique affords high-quality three-dimensional MR angiograms, especially in cases of tortuous or complex vascular anatomy. An imaging protocol was developed that includes gadolinium-enhanced MR angiography of the transplant renal artery with volume rendering and multiplanar reformation postprocessing techniques. Axial T2-weighted and contrast material-enhanced T1-weighted MR images are also obtained to examine the renal parenchyma itself and to evaluate for hydronephrosis or peritransplant fluid collections. This imaging protocol allows rapid global assessment of the renal transplant arterial system, renal parenchyma, and peritransplant region. It can also help detect or exclude many of the various causes of renal transplant dysfunction (eg, stenosis or occlusion of a transplant vessel, peritransplant fluid collections, ureteral obstruction). Conventional angiography can thus be avoided in patients with normal findings and reserved for those with MR angiographic evidence of stenosis.