Pancreatic carcinoma: MR, MR angiography and dynamic helical CT in the evaluation of vascular invasion

OBJECTIVE: To assess the value of MR angiography in combination with contrast-enhanced MR imaging, and to compare MR imaging including MR angiography with dynamic contrast-enhanced dual phase helical CT in the preoperative assessment of vascular invasion in patients with suspected pancreatic carcinoma. METHODS AND MATERIAL: MR imaging only, MR imaging including MR angiography and dynamic contrast-enhanced dual phase helical CT images of 48 patients who were operated due to suspicion of pancreas cancer were correlated with the surgery results in terms of vascular invasion. Pathologic diagnosis were pancreatic adenocarcinoma in 31 patients of which nine had surgically confirmed vascular invasion. Sensitivity, specificity, predictive values (including 95% confidence intervals) and accuracy of MR imaging only, MR imaging including MR angiography and helical CT were calculated. RESULTS: Sensitivity, specificity, positive and negative predictive values and accuracy were 56, 100, 100, 85, 87%; 67, 100, 100, 88, 90% and 67, 100, 100, 88, 90%, respectively, for MR imaging only, MR imaging including MR angiography and helical CT in the adenocarcinoma group. The corresponding figures in the overall study group were 56, 97, 83, 90, 90%; 67, 97, 86, 93, 92% and 67, 97, 86, 93, 92%. Confidence intervals (95%) showed that the differences in the diagnostic efficacy of the techniques were not statistically significant in the overall study group, but the confidence intervals were undefined in the adenocarcinoma group due to the small sample size. CONCLUSION: Diagnostic efficacy of MR imaging when combined with MR angiography is equal to that of dynamic contrast-enhanced dual phase helical CT in the assessment of vascular invasion of pancreatic tumors.     

Time-resolved three-dimensional contrast-enhanced MR angiography of the peripheral vessels

PURPOSE: To compare the diagnostic accuracy of time-resolved three-dimensional contrast material-enhanced magnetic resonance (MR) angiography with that of conventional angiography for imaging the lower extremity vasculature. MATERIALS AND METHODS: Sixty-nine patients who were evaluated for possible surgical intervention underwent conventional angiography (ie, digital subtraction angiography [DSA]) and contrast-enhanced MR angiography (ie, time-resolved imaging of contrast kinetics [TRICKS]). Two independent, blinded readers evaluated vessel stenosis and occlusion at DSA and MR angiographic image readings. Sensitivity, specificity, positive and negative predictive values, and area under the receiver operating characteristic curve were analyzed with repeated-measures analysis of variance. The Cohen kappa test was performed to examine interreader variability. RESULTS: At pooled readings, contrast-enhanced MR angiography had a sensitivity of 78% and a specificity of 98% for detection of occlusion. For detection of significant stenosis (at least one > or = 50% stenosis), sensitivity and specificity were 77% and 91%, respectively. Interreader agreement was high for detection of both occlusion (kappa = 0.76) and significant stenosis (kappa = 0.68). Sensitivity increased as MR angiographic technical parameters were optimized. When improvements resulting from coil type and injection protocol were considered, the sensitivity and specificity of TRICKS MR angiography were 89% and 97%, respectively, for occlusion detection and 87% and 90%, respectively, for significant stenosis detection. CONCLUSION: Contrast-enhanced TRICKS MR angiography is a feasible and minimally invasive means of acquiring angiograms of the peripheral vasculature with high sensitivity and specificity.     

Comprehensive time-resolved MRI of peripheral vascular malformations

OBJECTIVE: The purpose of this study was to evaluate the usefulness of MRI and MR angiography for the assessment of peripheral vascular malformations compared with the usefulness of conventional duplex sonography, venography, and arteriography. SUBJECTS AND METHODS. Nineteen patients (age range, 8-64 years; 11 males and eight females) with clinically diagnosed or suspected angiodyplastic abnormalities of the extremities were examined on a 1.5-T whole-body MR scanner. Using parameters based on a fast localizer sequence, we acquired transverse or coronal T1-, T2-, short tau inversion recovery (STIR), and contrast-enhanced T1-weighted images. Dynamic contrast-enhanced three-dimensional (3D) gradient-echo MRIs were acquired to determine the extent and type of the arteriovenous malformation for each patient. MR data sets were evaluated for lesion depiction, determination of the extent of the malformation, involvement of neighboring structures, vascular detail, and treatment planning. Results were compared with findings from duplex sonography, venography, and intraarterial digital subtraction angiography. RESULTS: All MRIs were of diagnostic quality and revealed 12 venous vascular malformations, four arteriovenous malformations, and three hemangiomas. The STIR sequence was helpful for determining the extent of the vascular malformation, which was often underestimated using contrast-enhanced 3D MR angiography alone, whereas dynamic contrast-enhanced 3D MR angiography was required for classifying the type of the lesion. MR angiography was inferior to conventional angiography for revealing vascular detail and for planning intervention. CONCLUSION: MRI and MR angiography appear to be valuable for the assessment of vascular malformations of the extremities. The protocol for imaging such malformations should combine dynamic contrast-enhanced 3D gradient-echo MRI with STIR sequences. However, digital subtraction angiography and venography are still required for definitive treatment decisions.     

46例脑动静脉畸形的MRI和MRA分析

目的：探讨MRI和MRA检查在脑AVM临床诊断中的价值。方法：46例脑动静脉畸形作了常规MRI和MR血管造影,MRI采用SET1、T2加权成像,MRA采用三维时飞跃法。结果：MRI准确显示了46例AVM的瘤巢,11例可见亚急性出血灶,5例可见含铁血黄素沉积,23例病灶区组织软化或萎缩,4例有占位效应。3D-TOF RMA显示41例AVM供血动脉、23例引流静脉。5例加做增强3D-TOF及6例加做2D-TOF后,引流静脉显示明显改善。结论：MRI和MRA结合应用能对脑血管畸形作出较准确的诊断,为临床治疗提供所需的基本信息并对治疗效果作出客观的评价。     

Peripheral vascular occlusive disease: evaluation with contrast-enhanced moving-bed MR angiography versus digital subtraction angiography in 106 patients

OBJECTIVE: The purpose of our study was to compare contrast-enhanced moving-bed MR angiography and digital subtraction angiography in the evaluation of peripheral vascular occlusive disease. MATERIALS AND METHODS: This retrospective report includes 106 patients (45 women, 61 men) with known or suspected peripheral vascular occlusive disease who underwent MR angiography and intraarterial digital subtraction angiography of the peripheral arteries. MR angiography was performed on a 1.0-T unit using a moving-bed technique. Every leg was divided into 14 vascular segments, and severity of disease was scored in four categories. Digital subtraction angiography was the standard of reference. RESULTS: In the 106 patients, 2378 vessel segments were evaluated with both imaging modalities. In 2156 segments, MR angiography and digital subtraction angiography were concordant for stenosis classification, in 188 segments the two modalities differed in one category, and in 24 segments they differed in two categories. MR angiography achieved sensitivity and specificity of 96.7% and 95.8%, respectively, for differentiating nonsignificant from hemodynamically significant stenosis (kappa = 0.91). CONCLUSION: This study indicates that MR angiography is an accurate imaging modality in clinical practice. Our data support the concept that MR angiography can modify the diagnosis of suspected peripheral vascular occlusive disease.     

Spinal cord vascular disease: characterization with fast three-dimensional contrast-enhanced MR angiography

BACKGROUND AND PURPOSE: Noninvasive characterization of spinal vascular lesions is essential for guiding clinical management, and several MR angiographic techniques have been applied in the past with variable results. The purpose of our study was to assess the potential of a dynamic 3D contrast-enhanced MR angiographic sequence to characterize spinal vascular lesions and to identify their arterial feeders and venous drainage. METHODS: A contrast-enhanced gradient-echo 3D pulse sequence providing angiographic information within 24 seconds was applied prospectively in 12 consecutive patients with a presumed spinal vascular lesion. The images were evaluated for visibility of the arterial feeder, and the results were compared with those of conventional angiography performed the next day. RESULTS: The MR angiographic findings proved that the lesions were correctly characterized as spinal arteriovenous malformations (AVMs) (n = 6), spinal dural arteriovenous fistulas (AVFs) (n = 3), a hemangioblastoma (n = 1), a teratoma (n = 1), and a vertebral hemangioma (n = 1). The arterial feeder was visible in all six AVMs and in the hemangioblastoma, corresponding to conventional angiographic findings. In two of three spinal dural AVFs, an enlarged draining medullary vein was seen within the neural foramen, providing correct localization. The third fistula could not be seen owing to reduced image quality from motion artifacts. CONCLUSION: Fast 3D contrast-enhanced MR angiography is a noninvasive technique with high accuracy in the characterization of spinal vascular disease. Visibility of the arterial pedicles corresponds well with that of digital subtraction angiography, facilitating the management of these patients.     

Three-dimensional dynamic MR digital subtraction angiography using sensitivity encoding for the evaluation of intracranial arteriovenous malformations: a preliminary study

BACKGROUND AND PURPOSE: Our aim was to develop 3D dynamic MR digital subtraction angiography with high temporal resolution without sacrificing spatial resolution by using sensitivity encoding for the evaluation of cerebral arteriovenous malformations. METHODS: Nineteen patients with 19 angiographically proven arteriovenous malformations (16 supratentorial and 3 infratentorial) were assessed by conventional catheter angiography and 3D dynamic MR digital subtraction angiography. A 3D contrast-enhanced gradient-echo sequence with sensitivity encoding based on a parallel imaging technique was performed and acquired 20 dynamic images, repeated 18 times every 1.7 seconds. Three-dimensional dynamic MR digital subtraction angiograms were analyzed independently by two radiologists in a blinded fashion with regard to arteriovenous malformation nidus and venous drainage. Conventional catheter angiography was used as reference. RESULTS: All MR imaging examinations were assessable. Interobserver agreement was excellent for the detection of nidus and for the evaluation of nidus size (kappa = 1 and 0.875, respectively) but moderate for the visualization of the venous drainage (kappa = 0.56). All nidi detected on conventional catheter angiography were clearly depicted on 3D dynamic MR digital subtraction angiography. The evaluation of the size of the nidus by both techniques was similar. On 3D dynamic MR angiograms, veins were correctly analyzed in 17 of 19 arteriovenous malformations. CONCLUSION: Our preliminary study demonstrates that 3D dynamic MR digital subtraction angiography using sensitivity encoding with a high spatial resolution is appropriate for the assessment of arteriovenous malformations.     

Peripheral arterial disease: comparison of color duplex US and contrast-enhanced MR angiography for diagnosis

PURPOSE: To prospectively compare the diagnostic accuracies of color duplex ultrasonography (US) and contrast material-enhanced magnetic resonance (MR) angiography and to assess interobserver agreement regarding contrast-enhanced MR angiographic findings in patients suspected of having peripheral arterial disease (PAD). MATERIALS AND METHODS: The institutional review board approved the study, and all patients provided signed informed consent. Two hundred ninety-five patients referred for diagnostic and preinterventional work-up of PAD with duplex US also underwent gadolinium-enhanced MR angiography. Data sets were reviewed for presence or absence of 50% or greater luminal reduction, which indicated hemodynamically significant stenosis, and to determine interobserver agreement. At duplex US, a peak systolic velocity ratio of 2.5 or greater indicated significant stenosis. Primary outcome measures were differences between duplex US and contrast-enhanced MR angiography in sensitivity and specificity for detection of significant stenosis, as assessed with the McNemar test, and interobserver agreement between the two contrast-enhanced MR angiogram readings, expressed as quadratic weighted kappa values. Intraarterial digital subtraction angiography (DSA) was the reference standard. RESULTS: Two hundred forty-nine patients had at least one hemodynamically significant stenotic lesion at contrast-enhanced MR angiography, duplex US, or both examinations. One hundred fifty-two patients underwent intraarterial DSA. The quadratic weighted kappa for agreement regarding the presence of 50% or greater stenosis at contrast-enhanced MR angiography was 0.89 (95% confidence interval [CI]: 0.87, 0.91). Sensitivity of duplex US was 76% (95% CI: 69%, 82%); specificity, 93% (95% CI: 91%, 95%); and accuracy, 89%. Sensitivity and specificity of contrast-enhanced MR angiography were 84% (95% CI: 78%, 89%) and 97% (95% CI: 95%, 98%), respectively; accuracy was 94%. Sensitivity (P = .002) and specificity (P = .03) of contrast-enhanced MR angiography were significantly higher. CONCLUSION: Results of this prospective comparison between contrast-enhanced MR angiography and duplex US provide evidence that contrast-enhanced MR angiography is more sensitive and specific for diagnosis and preinterventional work-up of PAD.     

First-line investigation of acute intracerebral hemorrhage using dynamic magnetic resonance angiography

Purpose: To report the initial experience of magnetic resonance (MR) digital subtraction angiography (MR-DSA) in the dynamic assessment of the cerebral circulation in acute non-traumatic intracerebral hemorrhage (ICH).

Material and Methods: Twelve patients with acute ICH were investigated within 6 days of the ictus using a dynamic contrast-enhanced 2-D MR angiogram that produces subtracted images with a temporal resolution of 1-2 frame/s. The MR-DSA examinations were assessed for evidence of an intracranial vascular abnormality and were compared with (i) the routine MR sequences, (ii) non-dynamic time-of-flight MR angiography, and (iii) catheter angiogram performed during the same admission.

Results: All 12 MR-DSA examinations were considered to be technically satisfactory. MR-DSA detected an intracranial vascular abnormality in 7 patients (3 arteriovenous malformations, 2 aneurysms, 1 dural arteriovenous fistula, and 1 venous thrombosis). All abnormalities were confirmed by catheter angiography with the exception of one patient with venous sinus thrombosis found on MR imaging that did not undergo catheter angiography. All four arteriovenous shunts were detected by MR-DSA by virtue of early venous filling.

Conclusion: MR-DSA can be performed satisfactorily in the setting of acute ICH and provides an alternative method to catheter angiography for identifying shunting vascular abnormalities such as arteriovenous malformations and fistulae, as well as large aneurysms and venous occlusions. MR-DSA is a contrast-medium-based technique that does not suffer from the T1 shortening effects of acute hemorrhage that can obscure abnormalities on conventional flow-based non-dynamic techniques.     

Pelvic and lower extremity arterial imaging: diagnostic performance of three-dimensional contrast-enhanced MR angiography

OBJECTIVE: The diagnostic performance of a three-dimensional MR angiography-based strategy was assessed with regard to its ability to characterize the arterial vasculature from the aortic bifurcation to the lower extremity runoff vessels. A single-injection, two-station protocol in combination with a lower-extremity vascular coil was used. SUBJECTS AND METHODS: Both conventional digital subtraction angiography and three-dimensional contrast-enhanced MR angiography with a dedicated peripheral vascular coil were performed in 61 patients with suspected peripheral vascular disease. In a prospective analysis, one reviewer evaluated the digital subtraction angiographic images and a second reviewer evaluated the MR angiographic images; both were unaware of the results of the other imaging technique. Each vascular segment (29 segments per patient) was evaluated for the presence of occlusive vessel disease. The following grading system was applied: 0, normal; 1, vessel irregularity with a luminal reduction of less than 10%; 2, mild stenosis (lumen reduction, 10-49%); 3, severe stenosis (lumen reduction, 50-99%); and 4, occlusion (lumen reduction, 100%). In 11 patients surgical graft patency was assessed. RESULTS: MR angiography provided an image quality comparable with that of digital subtraction angiography. Overall sensitivity and specificity for MR angiography were 92% and 96.6%, respectively, for the detection of hemodynamically significant disease and 92.3% and 99.4%, respectively, for the detection of occlusions. CONCLUSION: Two-station contrast-enhanced three-dimensional MR angiography with a dedicated lower-extremity vascular coil proved effective enough to consider it as a noninvasive alternative to digital subtraction angiography in the assessment of the pelvic and lower extremity arterial vasculature.     

Intracranial dural arteriovenous fistulas: classification, imaging findings, and treatment

Intracranial DAVFs are pathologic dural-based shunts and account for 10%-15% of all intracranial arteriovenous malformations. These malformations derive their arterial supply primarily from meningeal vessels, and the venous drainage is either via dural venous sinuses or through the cortical veins. DAVFs have a reported association with dural sinus thrombosis, venous hypertension, previous craniotomy, and trauma, though many lesions are idiopathic. The diagnosis is dependent on a high level of clinical suspicion and high-resolution imaging. Cross-sectional imaging techniques by using CT and MR imaging aid in the diagnosis, but conventional angiography remains the most accurate method for complete characterization and classification of DAVFs. The pattern of venous drainage observed on dynamic vascular imaging determines the type of DAVF and correlates with the severity of symptoms and the risk of hemorrhage.     

Contrast-enhanced MR angiography of peripheral arteries including pedal vessels at 1.0 T: feasibility study with dedicated peripheral angiography coil

PURPOSE: To prospectively determine feasibility of contrast material-enhanced magnetic resonance (MR) angiography of the peripheral arteries from distal aorta to pedal arteries with a 1.0-T system and a dedicated phased-array coil. MATERIALS AND METHODS: Twenty-seven patients with peripheral arteriosclerotic occlusive disease underwent contrast-enhanced MR angiography with an automatic moving-table technique. In addition, lower-leg and pedal arteries were examined without table movement (hybrid technique). Two radiologists independently reviewed MR angiograms to assess image quality and grade stenosis in 13 segments per leg. Each was blinded to patients' clinical data. Twenty-five of the patients also underwent conventional angiography. Stenosis grade at conventional angiography was assessed by two radiologists in consensus. Interobserver variability for stenosis grade at MR angiography was calculated with Cohen kappa test. Specificity and sensitivity of MR angiography in detection of stenosis of more than 50% and occlusion were calculated for both observers. The study was approved by the local ethics committee. RESULTS: In 14 of the 27 patients, hybrid technique was superior to moving-table technique because there was less venous overlap (11 patients), fewer motion artifacts (one patient), or both (two patients). In nine patients, there was no difference between techniques; in four patients, moving-table technique was superior. Stenosis grade was analyzed in 698 segments with MR angiography and in 638 segments with both conventional and MR angiography. Kappa analysis of interobserver agreement with MR angiography yielded a score of 0.84. For the 638 segments evaluated with both conventional and MR angiography, observers 1 and 2 assigned same grade of stenosis with both modalities in 558 and 555 segments, respectively. Sensitivity for stenoses greater than 50% and occlusion was 94.4% and 91.1% for observers 1 and 2, respectively, and specificity was 90.6% and 91.3%. More distal runoff vessels were shown with MR angiography in seven cases and with conventional angiography in two cases. CONCLUSION: Contrast-enhanced MR angiography of the peripheral vessels with a 1.0-T system and dedicated peripheral angiography coil is feasible, and in some cases, it provides additional information compared with conventional angiography.     

MR angiography of run-off vessels

Magnetic resonance angiography has taken a huge step forward since the introduction of contrast-enhanced MR angiography using gadolinium chelates. The more conventional MR angiographic techniques, such as time-of-flight and phase-contrast MR angiography, have been ousted by contrast-enhanced MR angiography in most vascular areas. However, in imaging the lower extremities, the major obstacle is the length of the vascular tree. In order to cover the entire peripheral vasculature, at least two to three fields of view are required. Using contrast-enhanced MR angiography, the best results are obtained if the vessels of interest are imaged during passage of a bolus of contrast material. Vessel-to-background contrast in subsequent acquisitions using subsequent injections of contrast material is hampered by recirculation and leakage of previously injected gadolinium, enhancing both the venous system and surrounding tissue. To overcome this problem several research groups have come up with various solutions. The three main strategies employed can be classified as either bolus catch, bolus chase, or bolus track techniques. The purpose of this article is to explain working mechanisms of the three bolus imaging strategies for imaging both inflow and outflow vessels of the lower extremities, to show their advantages and disadvantages, and to review results described in the literature in imaging patients using these techniques.     

Head and neck paragangliomas: improved tumor detection using contrast-enhanced 3D time-of-flight MR angiography as compared with fat-suppressed MR imaging techniques

BACKGROUND AND PURPOSE: MR imaging techniques have proved their efficacy in imaging the head and neck region. In this study, we compared T1-weighted, dual T2-weighted, and fat-suppressed MR imaging and unenhanced and contrast-enhanced 3D time-of-flight MR angiography sequences for detection of head and neck paragangliomas. METHODS: Thirty-one patients with 70 paragangliomas were examined. Four combinations of MR images were reviewed by two neuroradiologists: T1-weighted and dual T2-weighted fast spin-echo images, T1- and T2-weighted fat-suppressed fast spin-echo images, T1-weighted and contrast-enhanced T1-weighted fat-suppressed spin-echo images, and unenhanced and contrast-enhanced 3D time-of-flight MR angiograms. The randomized examinations were independently evaluated for image quality, presence of tumor, tumor size, and intratumoral flow signal intensity. The standard of reference for presence of tumor was digital subtraction angiography. Data were analyzed by using the logistic regression method. RESULTS: Mean sensitivity, specificity, and negative predictive values, respectively, were assessed by the two observers to be as follows: for dual T2-weighted fast spin-echo, 74%/99%/86%; for T2-weighted fat-suppressed fast spin-echo, 70%/100%/85%; for contrast-enhanced T1-weighted fat-suppressed spin-echo, 73%/100%/86%; and for unenhanced and contrast-enhanced 3D time-of-flight MR angiography, 89%/99%/93%. Sensitivity was significantly better for unenhanced and contrast-enhanced 3D time-of-flight MR angiography (P =.000028). More intratumoral flow signal intensity was depicted with unenhanced and contrast-enhanced 3D time-of-flight MR angiography. CONCLUSION: A combination of unenhanced and contrast-enhanced 3D time-of-flight MR angiography is superior for detecting paragangliomas and should be added to a standard imaging protocol, especially for patients with familial paragangliomas because they are more susceptible to multicentric disease.     

Retrograde cortical and deep venous drainage in patients with intracranial dural arteriovenous fistulas: comparison of MR imaging and angiographic findings

BACKGROUND AND PURPOSE: We assessed MR imaging, specifically contrast-enhanced three-dimensional (3D) magnetization-prepared rapid gradient-echo (MP-RAGE), in evaluating retrograde venous drainage in patients with intracranial dural arteriovenous fistulas (dAVFs) that may result in catastrophic venous infarction or hemorrhage. METHODS: Twenty-one patients with angiographically proved dAVFs underwent nonenhanced spin-echo (SE) and fast SE imaging, 3D fast imaging with steady-state precession, and enhanced SE and 3D MP-RAGE imaging. Retrograde venous drainage was categorized as cerebral cortical, deep cerebral, posterior fossa medullary, ophthalmic, or spinal venous. We assessed retrograde venous drainage and graded its severity. MR imaging and angiographic severities were correlated. Sensitivity, specificity, and accuracy were calculated to evaluate the diagnostic utility of each technique compared with conventional angiography. We retrospectively correlated angiograms and MR images. RESULTS: Enhanced 3D MP-RAGE and T1-weighted SE images had higher diagnostic accuracy higher than nonenhanced images, especially when retrograde drainage involved cerebral cortical, posterior fossa, and spinal veins. Correlation of severity for enhanced MP-RAGE images and enhanced T1-weighted images with angiograms was good to excellent and better than that with nonenhanced images. All sequences had low diagnostic accuracy when drainage was via deep cerebral veins. On retrospective review, 3D MP-RAGE images showed two thrombotic inferior petrosal sinuses. CONCLUSION: Enhanced MR images were superior to nonenhanced images in assessing retrograde venous drainage in intracranial dAVFs. Enhanced 3D MP-RAGE is superior to enhanced T1-weighted SE imaging for determining the route and severity of venous reflux because of its increased spatial resolution and ability to contiguously delineate the venous system.     

3.0T磁共振高分辨磁敏感成像在血管畸形中的应用价值

目的:探讨高分辨磁敏感成像(HR-SWI)在脑部血管畸形中的应用价值。方法:对45例脑血管畸形的患者行常规MR序列和HRSWI扫描。其中8例同时行MRA检查,31例行增强检查。结果:45例患者均在HR-SWI上清晰显示畸形血管,其中海绵状血管瘤26例,动静脉畸形5例,静脉瘤11例,Sturge-Weber综合征3例。结论:SWI显示血管畸形更清晰,明显优于常规序列,可为临床提供更多有用的信息并有助于脑血管畸形的确诊。     

Evaluation of vascular complications of pancreas transplantation with high-spatial-resolution contrast-enhanced MR angiography

PURPOSE: To retrospectively evaluate high-spatial-resolution contrast material-enhanced three-dimensional (3D) magnetic resonance (MR) angiography for assessment of vascular complications of pancreas allografts. MATERIALS AND METHODS: The institutional review board approved the study and waived the requirement for informed patient consent owing to the retrospective nature of the study with use of an anonymous-subject database. The study was HIPAA compliant. The clinical and MR angiography findings in 11 patients (eight men, three women; mean age, 43 years; age range, 30-54 years) who had a history of pancreatic transplant dysfunction and underwent a total of 13 contrast-enhanced 3D MR angiography examinations were retrospectively reviewed. Comparison with conventional angiography findings was possible for four MR angiography examinations, comparison with surgical findings was possible for two examinations, and clinical follow-up was possible for all examinations. Two observers in consensus and blinded to the clinical results performed image analysis of the arterial and venous segments. Classification agreement was assessed with quadratic weighted kappa statistics. RESULTS: Ten MR angiography examinations revealed vascular complications or signs suggestive of rejection. Only three examinations were considered to have completely normal results. All major complications were detected and included complete or partial arterial graft occlusion, stenosis of the arterial Y-graft caused by a kink, complete venous thrombosis, and arteriovenous fistula with pseudoaneurysm formation. For 46 arterial segments and 15 venous segments with angiographic and/or surgical comparison, overall agreement with MR angiography findings was nearly perfect (mean kappa, 0.983; standard error of the mean, 0.128). CONCLUSION: High-spatial-resolution MR angiography of pancreas allografts enables assessment of the arterial and venous vascular anatomy and can be used to reliably identify clinically relevant vascular complications.     

MR angiography in children with cerebral neurovascular diseases: findings in 31 cases.

OBJECTIVE. We evaluated the suitability of MR angiography for routine use in children with suspected intracranial vascular disease. SUBJECTS AND METHODS. Thirty-one children, 6 months to 14 years old, with intracranial lesions or clinically suspected vascular malformations were studied prospectively with conventional MR imaging and time-of-flight MR angiography. In nine cases, MR angiographic findings were verified with digital subtraction angiography or conventional angiography. All MR studies were performed on a 1.5-T MR system using a circularly polarized head coil. RESULTS. Arterial MR angiography, performed in 24 cases, revealed congenital abnormalities of the arterial vessels in 20 cases. Vessel stenosis was observed in nine patients, and displacement of intracranial arteries due to tumors could be seen in 10 patients. Seven children had no abnormal findings. Venous MR angiography was performed in seven children, with depiction of sinus thrombosis in six cases. The comparative analysis of MR angiography and digital subtraction angiography showed equivalent results in nine patients; in one patient the degree of stenosis was overestimated with MR angiography. CONCLUSION. MR angiography, when combined with MR imaging, reveals information about soft-tissue and vascular structures in a single setting. At this point, MR angiography can replace invasive conventional angiography or digital subtraction angiography only in selected cases because of software and hardware limitations. Arterial or venous MR angiography can be helpful as an additional scan in MR examinations of children with suspected cerebral neurovascular diseases, and its noninvasive nature makes it well suited for routine use in children.     

Contrast-enhanced MR angiography in patients after kidney transplantation

The aim of this study was to investigate the value of a contrast-enhanced 3D MR angiography in detecting postoperative vascular complications after kidney transplantation in comparison with digital subtraction angiography (DSA). Forty-one patients who underwent a kidney transplantation were examined with MR angiography and DSA. Contrast-enhanced MR angiography was performed as a dynamic measurement with one precontrast and three postcontrast measurements. Maximum intensity projection reconstructions were performed for all postcontrast data sets after DSA. The results were evaluated by two independent observers who were unaware of the DSA results. Twenty-three hemodynamically significant arterial stenoses were identified with DSA in the iliac arteries ( n=7), the renal allograft arteries ( n=12), and in their first branches ( n=4). For a patient-based analysis the sensitivity and specificity, respectively, for observer 1 were 100 and 97%, and for observer 2, 100 and 93%. Respective data were 100 and 100% after a consensus evaluation by two observers. Complications involving the renal veins were detected in 2 cases and perfusion defects of the kidney parenchyma were detected in 4 cases. Contrast-enhanced MR angiography is a reliable method in identifying postoperative arterial stenoses after kidney transplantation. In addition, dynamic MR angiography can be helpful in detecting venous complications and perfusion defects in kidney allografts.     

Comparison of MS-325- and gadodiamide-enhanced MR venography of iliocaval veins

PURPOSE: To compare conventional extracellular and blood-pool magnetic resonance (MR) contrast agents in "indirect" contrast-enhanced three-dimensional (3D) MR venography of the iliocaval veins. MATERIALS AND METHODS: Twenty-nine gadodiamide-enhanced 3D MR (Gd-MR) angiography studies and 12 MS-325-enhanced 3D MR (MS-325-MR) angiography studies were reviewed retrospectively. Abnormalities of the inferior vena cava (IVC) or iliac veins were not suspected before MR imaging. The MR angiography studies were reviewed with and without subtraction. Diagnostic conspicuity and subjective contrast of the various iliocaval venous segments (suprarenal IVC, infrarenal IVC, and iliac veins) and the presence of artifacts were subjectively scored by two blinded observers. RESULTS: In the Gd-MR angiography group, the infrarenal IVC and iliac veins were visualized with good conspicuity in only 55% of segments compared to 92%-100% of segments in the MS-325-MR angiography group. Although subtraction improved subjective conspicuity and contrast relative to background in the Gd-MR angiography group, it resulted in increased artifacts and luminal blurring. Subtraction offered little diagnostic advantage in the MS-325-MR angiography group. CONCLUSION: Indirect contrast-enhanced 3D MR venography with use of MS-325 offered significantly improved diagnostic conspicuity and contrast in iliocaval venous opacification compared to gadodiamide-enhanced studies.