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Bile duct strictures in adults are secondary to a wide spectrum of benign and malignant pathologic conditions. Benign causes of bile duct strictures include iatrogenic causes, acute or chronic pancreatitis, choledocholithiasis, primary sclerosing cholangitis, IgG4-related sclerosing cholangitis, liver transplantation, recurrent pyogenic cholangitis, Mirizzi syndrome, acquired immunodeficiency syndrome cholangiopathy, and sphincter of Oddi dysfunction. Malignant causes include cholangiocarcinoma, pancreatic adenocarcinoma, and periampullary carcinomas. Rare causes include biliary inflammatory pseudotumor, gallbladder carcinoma, hepatocellular carcinoma, metastases to bile ducts, and extrinsic bile duct compression secondary to periportal or peripancreatic lymphadenopathy. Contrast material-enhanced magnetic resonance (MR) imaging with MR cholangiopancreatography is extremely helpful in the noninvasive evaluation of patients with obstructive jaundice, an obstructive pattern of liver function, or incidentally detected biliary duct dilatation. Some of these conditions may show characteristic findings at MR imaging-MR cholangiopancreatography that help in making a definitive diagnosis. Although endoscopic retrograde cholangiopancreatography with tissue biopsy or surgery is needed for the definitive diagnosis of many of these strictures, certain MR imaging characteristics of the narrowed segment (eg, thickened wall, long-segment involvement, asymmetry, indistinct outer margin, luminal irregularity, hyperenhancement relative to the liver parenchyma) may favor a malignant cause. Awareness of the various causes of bile duct strictures in adults and familiarity with their appearances at MR imaging-MR cholangiopancreatography are important for accurate diagnosis and optimal patient management., (RSNA, 2014)

The aim of this study was to prospectively assess the accuracy of three-dimensional magnetic resonance (MR) angiography for evaluation of stenosis in the peripheral arterial system with a continuous moving table technique, with conventional MR angiography as reference. This study was approved by the local institutional review board; informed consent was obtained. Five healthy male volunteers (mean age, 27 years; range, 24-35 years) and four men and one woman (mean age, 63 years; range, 46-78 years) with peripheral arterial occlusive disease were examined. Images obtained with both techniques showed excellent concordance (Cohen kappa = 0.75). Images obtained with a conventional protocol had higher quality compared with those obtained with the continuous technique (mean, 1.07 +/- 0.25 [standard deviation] vs 1.58 +/- 0.6; P < .05); small vessels appeared sharper on them. For detection of significant stenosis and occlusion, accuracy, sensitivity, and specificity of the continuous technique were 92.8%, 100%, and 89.2%, respectively.

Purpose: To prospectively determine the diagnostic performance of a combination of standard bolus-chase magnetic resonance (MR) angiography and MR angiography with time-resolved imaging of contrast kinetics (TRICKS) for depicting severity of peripheral vascular disease of the lower extremity, including the pedal arteries, in diabetic patients with digital subtraction angiography (DSA) as the reference standard., Materials and Methods: An ethical committee approved this study; written informed consent was obtained from patients. Standard three-station and TRICKS MR angiography of the calf and foot were performed in 31 consecutive diabetic patients (23 men, eight women; mean age, 67 years; range, 43-81 years). Two readers separately assessed images of arterial segments as diagnostic or nondiagnostic and graded stenosis. Results were compared with those at DSA when the corresponding arterial segments were considered diagnostic at DSA. Wilcoxon signed rank test was used to determine if a significant difference between imaging techniques existed, and kappa statistics were used to determine interobserver agreement., Results: The difference between standard MR angiography and DSA regarding the number of diagnostic segments in the thigh was not significant (P = .50). A significantly higher number of calf and foot segments was considered diagnostic at TRICKS MR angiography than at standard MR angiography (P < .025). Sixteen of 26 segments in the foot that were considered nondiagnostic at DSA were considered diagnostic at TRICKS MR angiography. Average sensitivity of standard MR angiography for depicting hemodynamically significant arterial stenosis was 84% (reader 1) and 83% (reader 2) in the thigh and 78% (reader 1) and 80% (reader 2) in the calf. For both readers, average specificity was 97% in the thigh and 90% in the calf. Sensitivity and specificity of TRICKS MR angiography in the calf and foot were improved compared with those at standard MR angiography., Conclusion: TRICKS MR angiography of the distal calf and pedal vessels is superior to standard MR angiography regarding the number of diagnostic segments and assessment of the degree of luminal narrowing., ((c) RSNA, 2007.)

Purpose: To prospectively evaluate the accuracy of intraarterial magnetic resonance (MR) angiography in the depiction of significant stenoses and occlusions, with intraarterial digital subtraction angiography (DSA) serving as the reference standard., Materials and Methods: Approval of the local ethics committee and informed consent were obtained. Twenty patients (11 men; nine women; age range, 48-86 years; mean age, 69.5 years+/-11.2 [standard deviation]) with symptomatic peripheral arterial occlusive disease (PAOD) were prospectively enrolled. After percutaneous transluminal angioplasty (PTA), intraarterial MR angiography was performed in the thigh and the calf with a 1.5-T MR imager in two consecutive runs. Intraarterial MR angiography was performed with a low-dose injection protocol (ie, two 20-mL injections of a 50-mmol gadolinium-based contrast agent). Moderate stenoses (luminal narrowing50%) or vessel occlusions; 95% confidence intervals (CIs) were calculated for sensitivity and specificity., Results: Intraarterial DSA revealed 78 moderate stenoses, 57 significant stenoses, and 28 occlusions. Sensitivity, specificity, and accuracy of intraarterial MR angiography in the characterization of significant stenoses or occlusions were 92% (95% CI: 72%, 99%), 94% (95% CI: 82%, 98%), and 93%, respectively, in femoropopliteal arteries and 93% (95% CI: 83%, 98%), 71% (95% CI: 51%, 86%), and 86%, respectively, in infrapopliteal arteries. The main artifact observed with intraarterial MR angiography was venous contamination (12%)., Conclusion: Intraarterial MR angiography is an accurate method used to depict significant stenoses and occlusions in lower extremity arteries with a low-dose injection protocol., (Copyright (c) RSNA, 2006.)

Purpose: To retrospectively evaluate criteria for differentiating extrahepatic bile duct cholangiocarcinoma from benign cause of stricture at magnetic resonance cholangiopancreatography (MRCP) and to compare diagnostic accuracy with this modality versus endoscopic retrograde cholangiopancreatography (ERCP)., Materials and Methods: MRCP and ERCP images in 50 patients (27 with cholangiocarcinoma [18 men, nine women; mean age, 58 years] and 23 with benign cause of stricture [13 men, 10 women; mean age, 60 years]) were retrospectively reviewed to assess the appearance of bile duct strictures. Final diagnosis was based on surgical or biopsy findings. Strictures were described according to their imaging appearance (irregular or smooth margins, asymmetric or symmetric narrowing, abrupt narrowing or gradual tapering, and presence or absence of double-duct sign). Sensitivity, specificity, and accuracy of MRCP and ERCP were calculated by using ratings of confidence in image-based diagnosis. Lengths of stricture were electronically measured and compared by using the Student t test., Results: Among cholangiographic criteria for malignant biliary stricture, irregular margins and asymmetric narrowing were more common in cholangiocarcinomas (24 [89%] of 27 patients) than in benign strictures (six [26%] and eight [35%] of 23 patients, respectively). Sensitivity, specificity, and accuracy of the two methods for differentiation of malignant from benign causes of biliary stricture were 81% (22 of 27), 70% (16 of 23), and 76% (38 of 50), respectively, for MRCP and 74% (20 of 27), 70% (16 of 23), and 72% (36 of 50), respectively, for ERCP. Mean length (+/- standard deviation) of cholangiocarcinomas was 30.0 mm +/- 8.5, and that of benign strictures was 13.6 mm +/- 9.1 (P <.001)., Conclusion: Accuracy of MRCP is comparable with that of ERCP. Regardless of modality, a lengthy segment of extrahepatic bile duct stricture with irregular margin and asymmetric narrowing suggests cholangiocarcinoma, and a short segment with regular margin and symmetric narrowing suggests benign cause., (Copyright RSNA, 2004)

Purpose: To compare the accuracy of contrast material-enhanced three-dimensional (3D) dedicated calf magnetic resonance (MR) angiography with that of bolus-chase MR angiography, with conventional angiography as the reference standard, in patients with symptomatic peripheral vascular disease (PVD)., Materials and Methods: Thirty men with symptomatic PVD were examined. MR angiography was performed at 1.5 T before conventional angiography. MR angiographic examination included 3D contrast-enhanced dedicated calf MR angiography and three-station bolus-chase MR angiography. Two radiologists blinded to conventional angiographic results evaluated the MR angiograms independently. Two angiographers evaluated the conventional angiograms in consensus. Calf artery segments were graded as having 50% or less stenosis, greater than 50% stenosis, or occlusion or as being nondiagnostic. Statistical analyses were performed with paired permutation testing., Results: Analyses of 472 calf segments and 420 pelvic and thigh segments were performed. Of the 472 calf segments, three and 75 segments (reader 1) and seven and 91 segments (reader 2) were graded as nondiagnostic at dedicated calf MR angiography and bolus-chase MR angiography, respectively. Differences in diagnostic grade between the two examinations were significant (P <.001), accounting for within-subject correlations, with a mean estimated difference of -17.1% (95% confidence interval [CI]: -25.8%, -8.4%). In the calf arteries, the dedicated and bolus-chase MR angiographic sequences had diagnostic accuracies, respectively, of 81.5% (reader 1) and 79.1% (reader 2) and of 67.8% (reader 1) and 63.4% (reader 2). The dedicated calf sequence was significantly more accurate than the bolus-chase sequence (P =.001). The point estimate of the difference was 14.7%, with estimated correct diagnosis rates of 80.3% and 65.6% for the dedicated calf and bolus-chase examinations, respectively (95% CI for difference: 4.0%, 25.4%). The diagnostic accuracy of bolus-chase MR angiography at the pelvis-thigh level was slightly higher when it was performed first: 81.9% (reader 1) and 83.8% (reader 2) versus 74.3% (reader 1) and 80.0% (reader 2) when it was performed last. The difference was not significant (P =.21)., Conclusion: Use of dedicated calf MR angiography led to significantly increased diagnostic accuracy in the calf arteries compared with standard bolus-chase MR angiography. Use of the dual-bolus technique did not jeopardize the diagnostic accuracy in the pelvic and thigh arteries., (Copyright RSNA, 2004)

Nonneoplastic diseases of the central airways are uncommon but can be categorized as either focal or diffuse, although there is some overlap. Focal diseases include postintubation stenosis, postinfectious stenosis, posttransplantation stenosis, and various systemic diseases that may involve the airways and lead to focal stenosis (eg, Crohn disease, sarcoidosis, Behçet syndrome). Diffuse diseases of the central airways include Wegener granulomatosis, relapsing polychondritis, tracheobronchopathia osteochondroplastica, amyloidosis, papillomatosis, and rhinoscleroma. Conventional radiography is often the first step in the evaluation of suspected central airway disease and may be adequate in itself to identify the abnormality. However, computed tomography (CT) improves both the detection and characterization of central airway disease. Bronchoscopy remains the primary procedure for the diagnostic work-up of these disease entities. Nevertheless, a thorough radiologic evaluation with radiography and CT may demonstrate specific imaging findings (eg, calcification) that can help narrow the differential diagnosis and aid in the planning of bronchoscopy or therapeutic intervention.

The software tools required for postprocessing of magnetic resonance (MR) angiograms include the following functions: data handling, image visualization, and vascular analysis. A custom postprocessing software called Magnetic Resonance Angiography Computer Assisted Analysis (MARACAS) has been developed. This software combines the most commonly used three-dimensional visualization techniques with image processing methods for analysis of vascular morphology on MR angiograms. The main contributions of MARACAS are (a) implementation of a fast method for stenosis quantification on three-dimensional MR angiograms, which is clinically applicable in a personal computer-based system; and (b) portability to the most widespread platforms. The quantification is performed in three steps: extraction of the vessel centerline, detection of vessel boundaries in planes locally orthogonal to the centerline, and calculation of stenosis parameters on the basis of the resulting contours. Qualitative results from application of the method to data from patients showed that the vessel centerline correctly tracked the vessel path and that contours were correctly estimated. Quantitative results obtained from images of phantoms showed that the computation of stenosis severity was accurate., (Copyright RSNA, 2002)

Purpose: To evaluate the accuracy of magnetic resonance (MR) sialography in detecting salivary glandular calculi and ductal stenoses., Materials and Methods: In a prospective study, 64 salivary glands in 61 consecutive patients with acute or recurrent parotid or submandibular glandular swelling were examined by using three-dimensional (3D) extended-phase conjugate-symmetry rapid spin-echo (EXPRESS) MR imaging. Transverse and sagittal-oblique source images and maximum intensity projection images were obtained. All MR images were analyzed independently by two radiologists, without knowledge of the final diagnosis. The reference standard was conventional sialography, ultrasonography (US), and sialendoscopy with or without surgery in 31 glands and was conventional sialography and US in 33 glands., Results: Final diagnoses included sialolithiasis (n = 23), sialolithiasis and stenosis (n = 9), stenosis without lithiasis (n = 11), early Sjögren syndrome without ductal stenosis (n = 2), ductal displacement (n = 3), and normal salivary glands (n = 16). The sensitivity, specificity, and positive and negative predictive values of MR sialography to detect calculi were 91%, 94%-97%, 93%-97%, and 91%, respectively. False-negative readings occurred due to calculi with a diameter of 2-3 mm in nondilated salivary ducts. Ductal stenosis was assessed, with a sensitivity of 100%, specificity of 93%-98%, positive predictive value of 87%-95%, and negative predictive value of 100%. Interobserver agreement was very good (kappa = 0.85-0.97)., Conclusion: MR sialography with 3D EXPRESS imaging enables reliable prediction of salivary gland calculi and stenoses.

Magnetic resonance cholangiopancreatography (MRCP) is a relatively new, noninvasive cholangiographic technique that is comparable with invasive endoscopic retrograde cholangiopancreatography (ERCP) in the detection and characterization of extrahepatic bile duct abnormalities. The role of MRCP in evaluation of the intrahepatic bile ducts, especially in patients with primary or secondary sclerosing cholangitis, is under investigation. The key cholangiographic features of primary sclerosing cholangitis are randomly distributed annular strictures out of proportion to upstream dilatation. As the fibrosing process worsens, strictures increase and the ducts become obliterated, and the peripheral ducts cannot be visualized to the periphery of the liver at ERCP. In addition, the acute angles formed with the central ducts become more obtuse. With further progression, strictures of the central ducts prevent peripheral ductal opacification at ERCP. Cholangiocarcinoma occurs in 10%-15% of patients with primary sclerosing cholangitis; cholangiographic features that suggest cholangiocarcinoma include irregular high-grade ductal narrowing with shouldered margins, rapid progression of strictures, marked ductal dilatation proximal to strictures, and polypoid lesions. Secondary sclerosing and nonsclerosing processes can mimic primary sclerosing cholangitis at cholangiography. These processes include ascending cholangitis, oriental cholangiohepatitis, acquired immunodeficiency syndrome-related cholangitis, chemotherapy-induced cholangitis, ischemic cholangitis after liver transplantation, eosinophilic cholangitis, and metastases.

Purpose: To assess the usefulness of half-Fourier rapid acquisition with relaxation enhancement (RARE) magnetic resonance cholangiopancreatography (MRCP) for evaluation of postoperative changes in the pancreaticobiliary ductal system., Materials and Methods: The study included 34 patients (20 men, 14 women; mean age, 65.5 years) who underwent surgery of the pancreaticobiliary ductal system. Half-Fourier RARE MRCP images were obtained after surgery. Qualitative evaluation included ratings by two observers for depiction of postoperative anatomy and for artifacts, as well as analysis of postoperative complications. Direct cholangiographic, computed tomographic, and ultrasonographic findings and 6-month follow-up results were the reference standard. Sensitivity, specificity, and accuracy were calculated for the evaluation of postsurgical complications seen at half-Fourier RARE MRCP., Results: The sensitivity, specificity, and accuracy of MRCP for the evaluation of postsurgical complications were each 100% for ductal dilatation; 100%, 87%, and 89%, respectively, for choledochoenteric anastomotic stricture; 100%, 86%, and 87%, respectively, for pancreaticoenteric anastomotic stricture; 100% each for intraductal stones and anastomotic leakage; and 80%, 100%, and 94%, respectively, for cholangitis., Conclusion: Half-Fourier RARE MRCP is a reliable imaging technique for the evaluation of anatomy and of complications associated with a surgically altered pancreaticobiliary ductal system.

Purpose: To develop and refine a pulse sequence and protocol for testing the feasibility of magnetic resonance (MR) hysterosalpingography in a phantom model., Materials and Methods: A phantom simulating the uterus, fallopian tubes, and surrounding pelvic cavity was constructed. T2-weighted acquisition strategies-breath-hold fast spin-echo, rapid acquisition with relaxation enhancement (RARE), and haff-Fourier RARE-were refined to acquire sequential 70-mm coronal imaging volumes. Contrast agent was injected into the introducing catheter entering the os of the simulated uterus. Interacquisition interval, type of contrast agent (eg, sterile saline solution or water), and quantity of contrast agent (eg, 1-5 mL per acquisition) were varied. Digital image subtraction was used to enhance image quality. Images were qualitatively analyzed and rated good, fair, or poor for temporal resolution, spatial resolution, fallopian tube conspicuity, and free spill conspicuity. Once the technique was refine, the phantom was reconfigured to simulate unilateral and bilateral hydrosalpinx., Results: The RARE sequence with an 8-second interacquisition interval and a 5-mL interacquisition of sterile water produced good images of the simulated fallopian tubes and free spill. Depiction of unilateral and bilateral hydrosalpinx was also reliably demonstrated., Conclusion: This study with a phantom model demonstrates the feasibility of MR hysterosalpingography to depict normal and diseased fallopian tubes.

Purpose: To assess the usefulness of magnetic resonance (MR) cholangiopancreatography (MRCP) in the evaluation of disease in patients with acute or chronic pancreatitis., Materials and Methods: MR imaging was performed at 1.5 T in 39 patients with chronic (n = 30) or acute (n = 9) pancreatitis. The patients underwent a pancreas MR imaging protocol that included an MRCP sequence. Comparison was made with findings at endoscopic retrograde cholangiopancreatography (ERCP), performed within 30 days. Three blinded readers used a scoring system to evaluate nine segments of the pancreatic and biliary ducts as depicted on the ERCP and MRCP images. MRCP image quality was also evaluated., Results: Of 196 segments analyzed, 17 were not seen at MRCP (sensitivity, 91%). Of the segments visualized at MRCP, 14 were incorrectly characterized (accuracy, 92%). At MRCP, segments not detected or mischaracterized were either normal, slightly dilated, or narrowed. At ERCP, 42 segments in 19 patients were not visualized. MRCP findings were considered useful in all those cases. MRCP image quality was not interpretable in two cases due to artifacts., Conclusion: Very good correlation between ERCP and MRCP findings was demonstrated. Both modalities failed to depict pathologic conditions depicted by the alternative method. MRCP may obviate ERCP, particularly in patients who cannot undergo ERCP or in whom ERCP has been unsuccessful.

Purpose: To compare subtracted and nonsubtracted gadolinium-enhanced magnetic resonance (MR) angiography and cardiac-synchronized time-of-flight MR angiography for help in detecting pelvic-region stenoses., Materials and Methods: Twenty-eight patients with intermittent claudication underwent MR angiography with a 1.5-T system; two-dimensional cardiac-synchronized time-of-flight MR angiograms and three-dimensional MR angiograms (without and with gadolinium enhancement) were obtained. Subtracted images were obtained by subtracting unenhanced data from enhanced data of identical volumes, and maximum intensity projection images were constructed, which two observers independently evaluated in blinded fashion, with conventional angiographic results as the reference standard., Results: Sensitivity and specificity for grading of hemodynamically significant stenoses (> or = 50% lumen reduction) on subtracted MR angiograms were 94% and 93%, respectively. Sensitivity of subtracted images was significantly higher compared with that of time-of-flight images (P < .05) but not with that of nonsubtracted images. Contrast-to-noise ratio on subtracted images was significantly higher compared with that on nonsubtracted images (P < .05) but not with that on time-of-flight images. There was good correlation between stenosis length measurements on gadolinium-enhanced MR angiograms and those on conventional angiograms., Conclusion: Subtracted MR angiography is superior to cardiac-synchronized time-of-flight MR angiography for imaging of iliac and upper femoral arteries and provides higher contrast-to-noise ratio, fewer artifacts, and easier image interpretability than nonsubtracted MR angiography.

Purpose: To compare findings with magnetic resonance (MR) cholangiography with rapid acquisition with relaxation enhancement (RARE) and half-Fourier acquisition with single-shot turbo spin-echo (hereafter, half Fourier RARE) snapshot imaging techniques to those with endoscopic retrograde cholangiography (ERC)., Materials and Methods: Heavily T2-weighted thick-section (RARE) and thin-section (half-Fourier RARE) MR cholangiography were performed prospectively, on a 1.5-T imager, in the biliary tree of 61 consecutive patients before ERC. Findings at ERC were considered the standard of reference. The radiologist and endoscopist were blinded to each other's report. On- and off-site MR cholangiographic readings were performed to detect stones (n = 24), biliary dilatation (n = 34), or stenosis (n = 36)., Results: The sensitivity and specificity of MR cholangiography, respectively, calculated on a lesion-by-lesion basis, were 92.3% and 95.8% for cholangiolithiasis, 94.1% and 92.6% for duct dilatation, and 88.8% and 84.0% for stenosis. With snapshot MR cholangiography, on a patient-by-patient basis, differentiation between normal (n = 15) and abnormal (n = 46) results yielded a sensitivity of 92.4%, a specificity of 83.4%, and a positive predictive value of 95.6%. Pitfalls were caused by flow artifacts, compression by vessels, and low contrast between calculi and surrounding parenchyma., Conclusion: Snapshot MR cholangiography allowed noninvasive, accurate detection of biliary stones, strictures, and dilatation similar to that with ERC. Discrepancies regarding low-grade dilatation and strictures had no clinical relevance at retrospective review.

Purpose: To evaluate a magnetic resonance (MR) angiographic technique for imaging of the peripheral arteries with gadolinium enhancement., Materials and Methods: Moving-bed infusion-tracking MR angiograms were obtained in 15 healthy volunteers and in 28 patients with intermittent claudication before and during slow infusion of contrast material. Lower- and upper-leg and pelvic regions were imaged. Unenhanced images were subtracted from gadolinium-enhanced images, and maximum intensity projection images were generated. Image quality was evaluated subjectively and objectively, and maximum intensity projection images were compared with conventional angiograms, which served as the standard of reference., Results: Moving-bed infusion-tracking MR angiography proved to be a robust technique, and image quality on maximum intensity projection images was comparable with that on conventional angiograms. Sensitivity and specificity for grading hemodynamically significant stenoses were 93% and 98%, respectively, with excellent interobserver agreement., Conclusion: Moving-bed infusion-tracking MR angiography can be used to image all peripheral arteries in 4 minutes by using a small amount of contrast material and a conventional 1.5-T MR imager.

Purpose: To assess the clinical and imaging findings in children with severe tracheal or bronchial compression caused by abnormal thoracic configuration., Materials and Methods: Clinical and imaging findings, care, and outcome were reviewed in six patients with airway compression caused by abnormal thoracic configuration. Radiographs and magnetic resonance (MR) images were available in all patients., Results: Mechanisms of airway compression included alteration of mediastinal anatomy and direct airway compression secondary to a narrow anteroposterior chest diameter. In three patients, the trachea was compressed at the level of the thoracic inlet. In the other three patients, the left main bronchus was compressed. Four patients underwent surgery for the thoracic deformity, with resolution of airway symptoms. In all four patients, the presence, location, and cause of airway obstruction determined at MR imaging were confirmed at surgery., Conclusion: Abnormal thoracic configuration, in addition to causing restrictive lung disease, can cause respiratory distress secondary to severe compression of the central airways.

Magnetic resonance (MR) angiography is a noninvasive means of assessing the portal venous system that has potential advantages over currently used modalities. Time-of-flight and phase-contrast MR angiography are useful techniques that differ fundamentally in their means of data acquisition but are comparable in their ability to demonstrate normal anatomy as well as abnormalities of the portal venous system. Occasionally, artifacts caused by respiratory motion, implanted metallic devices or surgical clips, in-plane saturation, or areas of complex flow are seen at MR angiography of the portal venous system. However, most artifacts can easily be identified as such and either remedied or ignored. In addition, the suppression of signal from surrounding soft tissues may result in poor detection of parenchymal lesions. The utility of standard projection angiograms and source images can be increased through the use of intravenously administered contrast material and postprocessing techniques such as partial-volume maximum intensity projection reconstructions and shaded surface renderings. In addition to providing information on portal venous anatomy and portosystemic collateral vessels, MR angiography of the portal vein has clinical application in portal venous thrombosis and stenosis, liver transplantation, and the evaluation and planning of surgical and transjugular intrahepatic portosystemic shunts.

Purpose: To study the association between petrous carotid canal (PCC) and internal carotid artery (ICA) stenoses in patients with malignant osteopetrosis., Materials and Methods: Mean and minimum PCC diameters obtained from cranial computed tomographic (CT) scans in 20 patients were compared with similar measurements in 52 control subjects. ICA caliber, evaluated with magnetic resonance (MR) arteriography, was correlated with age and PCC dimensions., Results: There was a statistically significant difference between patient and control PCC diameters. There was a strong positive correlation between age and PCC diameter in the control subjects, but only a weakly positive correlation in the patients. One or both ICAs were stenotic on all patient MR arteriograms. MR angiographic stenosis grade correlated positively with age but not with PCC diameters., Conclusion: PCC and ICA stenoses occur frequently in patients with malignant osteopetrosis. Bony overgrowth or a "persistent fetal state" may produce the PPC stenoses. The findings do not support progressive PCC narrowing in these patients.

Purpose: To determine the clinical feasibility of a contrast material--enhanced two-dimensional (2D) magnetic resonance (MR) angiographic sequence in lower extremity arteries., Materials and Methods: Four healthy volunteers and 12 patients underwent dynamic contrast-enhanced MR angiography; all patients also underwent conventional angiography. A 2D multisection gradient-echo sequence with image subtraction was used for all MR imaging examinations., Results: Oblique-coronal contrast-enhanced MR angiography was completed in less than 4 minutes, with a 256 x 512 matrix. The arterial contrast enhancement ratio was 2.0 +/- 0.8 (standard deviation), and the pre- and post-contrast contrast-to-noise ratios were 2.1 +/- 13.8 and 46.2 +/- 18.7, respectively. The sensitivity for MR angiography was 100% and specificity was 69% for distinction of vessels with greater than 50% stenoses from normal or mildly stenotic vessels., Conclusion: Dynamic contrast-enhanced 2D MR angiography is capable of increasing intraarterial signal intensity and depicting small vessel anatomy of the lower extremities over a large field of view in a short imaging time.

Purpose: To determine if a three-dimensional (3D) gadolinium-enhanced technique is useful for improving the accuracy of magnetic resonance (MR) angiography., Materials and Methods: Prospectively, two-dimensional (2D) time-of-flight (TOF) and 3D gadolinium-enhanced MR angiography was performed in 23 patients. Conventional arteriography, the reference standard, was performed in all but five patients. Images from each examination were interpreted blindly by two observers., Results: For common and external iliac arteries, interpretations of dynamic 3D gadolinium-enhanced MR angiograms matched those of conventional arteriograms in 12 of 18 patients (67%) for both observers. Interpretations of 2D TOF images matched those of conventional arteriograms in six (33%) and seven (39%) patients for the two observers respectively., Conclusion: Preliminary results suggest that iliac artery MR angiography can be improved by complementing standard 2D TOF acquisitions with 3D gadolinium-enhanced acquisitions.

Purpose: To determine if functional popliteal entrapment can occur in healthy subjects and to define the mechanism of vascular compression., Materials and Methods: The right lower extremities were examined in 13 subjects (nine men 27-34 years of age, mean age 31 years; four women 29-44 years of age, mean age 34 years) with no symptoms of popliteal artery entrapment. Magnetic resonance (MR) and Doppler ultrasound images were obtained while the subjects were at rest and while they performed plantar flexion against resistance., Results: Blood flow during plantar flexion ceased in nine of 13 subjects (69%) and was impaired in three of 13 (23%). MR images showed muscular compression of the popliteal artery at two levels: between the plantaris muscle and the medial head of the gastrocnemius muscle and between the plantaris and popliteus muscles., Conclusion: Functional impairment of popliteal arterial flow during plantar flexion occurs in subjects who have no symptoms of popliteal entrapment syndrome.

Purpose: This study compared gradient-recalled echo (GRE) magnetic resonance (MR) imaging with technetium-99m-methoxyisobutyl isonitrile (MIBI) single photon emission computed tomography (SPECT) during the same dobutamine stress for the localization of coronary artery stenoses., Materials and Methods: In 35 consecutive patients (28 men and seven women, aged 41-79 years) with angiographically documented coronary artery disease, corresponding GRE MR images and SPECT tomograms were acquired at rest and during dobutamine infusion and were evaluated for regional wall motion or perfusion abnormalities., Results: Images in both examinations could be analyzed in 32 of 35 (91%) patients. Wall motion or perfusion abnormalities were observed in 27 of 32 (84%) GRE MR imaging and in 28 of 32 (87%) SPECT examinations. Sensitivity and specificity of dobutamine GRE MR imaging and dobutamine SPECT for the localization of left anterior descending coronary artery stenoses were 74% and 100% versus 70% and 100% for the combined left circumflex and right coronary artery perfusion territories., Conclusion: GRE MR imaging and SPECT have a high concordance with respect to the detection of a dobutamine-induced ischemic response.

Purpose: To determine the reliability and efficacy of magnetic resonance (MR) cholangiography in demonstrating the site and extent of stricture., Materials and Methods: In 40 patients with obstructive jaundice, three-dimensional MR cholangiography was performed with a sequence of mirrored fast imaging with steady-state precession and was compared with conventional cholangiography in 39 cases. The level of obstruction was determined by examining all imaging data available., Results: Diagnostic MR cholangiograms were acquired in 39 patients; absence of obstruction was confirmed in three, and obstruction was seen in 36. The level of obstruction or absence of obstruction was accurately shown in 36 of 40 patients with MR cholangiography and in 37 of 39 patients with conventional cholangiography. The peripheral biliary tree was shown more completely with MR cholangiography than with endoscopic retrograde cholangiography in all 32 patients undergoing diagnostic studies with both modalities., Conclusion: Three-dimensional MR cholangiography shows particular promise for the assessment of complex strictures, in which conventional cholangiography carries a higher risk of sepsis, for planning optimal drainage before intervention.

Two hypotheses were tested: (a) that view-to-view variations in bulk phase and modulus of magnetization in vascular volume elements can indicate the presence of disordered blood flow, and (b) that a substantial loss of signal intensity on magnetic resonance (MR) angiograms of poststenotic regions is due to view-to-view changes in magnetization. To test these hypotheses, a technique was developed in which view-to-view variations in transverse magnetization were used to create angiographic projection images, which showed only disordered flow (disordered flow maps) in vitro and in vivo. In phantom studies, this technique recovered signal intensity downstream from stenoses. A combination of disordered flow maps with morphologic images improved visualization of stenotic regions and provided information on characteristics of local flow. These results show that view-to-view variations in transverse magnetization occur in regions of disordered flow and are an important cause of loss of signal intensity. This technique can provide information about dynamic blood flow and improve depiction of anatomic structures on MR angiograms.

This article explores the causes and manifestations of obstruction of the inferior vena cava (IVC) with a multiple-modality approach. Caval obstruction may be due to thrombus, extension of a tumor, extrinsic compression, or intrinsic caval disease. Evaluation of the IVC should be tailored to the individual circumstance; no single modality is best in all situations. Although magnetic resonance offers multiplanar imaging, vena cavography or ultrasound are often necessary to exclude intraluminal tumor extension. Computed tomography is sensitive for intracaval thrombus and compression but does not delineate the hepatic IVC well. Nuclear venography demonstrates well the resultant collateral pathways, which can be separated into the deep, intermediate, superficial, and portal systems. Despite the clear visualization of these pathways with this modality, congenital caval anomalies, such as caval interruption with azygos continuation, can be confused with acquired caval disease.

The authors compared the three-dimensional Fourier transform (3DFT) time-of-flight magnetic resonance (MR) angiograms in 38 patients initially studied with selective intraarterial digital subtraction angiography (DSA) for suspected arteriosclerotic disease of the carotid bifurcation. MR angiograms were successfully obtained in 65 of the 75 carotid arteries (87%) visualized with DSA. DSA and MR angiographic studies were assessed for percentage area stenosis by two independent observers on two occasions. Statistical tests indicated consistency in interpretation for each observer as well as between observers. No significant difference was found between the two modalities in ability to depict changes in percentage area stenosis. For the 32 right carotid arteries in the comparison, the median for the difference between MR angiography and intraarterial DSA was 1.83% (range, -22.38% to 55.60%); for the 33 visualized left carotid arteries, it was 0.00% (range, -20.55% to 49.95%). Receiver operating characteristic analysis indicated that technically adequate MR angiography may be a sensitive screening examination for stenoses.

Conventional angiography, two-dimensional inflow magnetic resonance (MR) angiography, and color duplex ultrasound (US) were performed on 12 patients in a blinded, prospective study. The ability to grade arterial lesions and plan revascularization interventions were compared. Arterial lesions were categorized as nonsignificant (0%-49% diameter reduction) or significant (50%-100% diameter reduction). Determination of nonsignificant and significant lesions with MR angiography was in agreement with that at conventional angiography in 100 of 140 lesions (71%). Agreement between results of conventional angiography and color duplex US occurred with 114 of 123 infrainguinal lesions (93%). Twenty-one vascular interventions were planned by using conventional angiography; there was agreement with color duplex US in 11 cases and MR angiography in five. Color duplex US performed well in the assessment of infrainguinal disease but was limited in the evaluation of iliac segments because of nonvisualization. The iliac region was visualized in more patients with MR angiography than with color duplex US, but image quality with MR angiography was inconsistent. Strategies to improve MR angiography of the peripheral vasculature merit further study.

For measurement of poststenotic jet velocities with magnetic resonance (MR) imaging, the authors reduced the echo time (TE) of the field even-echo rephasing (FEER) velocity mapping sequence from 14.0 to 3.6 msec, so minimizing the problem of MR signal loss from turbulent fluid. In vitro use of rotating disk and stenotic flow phantoms confirmed that the 3.6-msec TE sequence enables accurate measurement of jet velocities of up to 6.0 m/sec (r = .996). Peak jet velocity measurements were made with MR imaging in 36 patients with stenosis of native heart valves (n = 9), conduits (n = 19), or Fontan connections (n = 2) or with aortic coarctation (n = 6). Peak velocity measurements made with MR imaging agreed well with measurements made with Doppler ultrasound (US), which were available in 18 cases (standard deviation = 0.2 m/sec). Velocity mapping with fast-echo MR imaging is likely to have considerable importance as a noninvasive means of locating and evaluating stenoses, particularly at sites inaccessible to US, but care must be taken to prevent errors caused by malalignment, signal loss, phase wrap, or partial-volume effects.

Transcervical fallopian tube catheterization (TFTC) was performed in 22 infertile patients with bilateral fallopian tube obstruction and a mean duration of infertility of 3.3 years. A high prevalence of previous ectopic pregnancy (n = 8, 36%), tubal ligation and/or reconstruction (n = 5, 23%), spontaneous or therapeutic abortion (n = 6, 27%), and previous intrauterine device use (n = 14, 64%) was noted. The authors successfully catheterized 40 (98%) of 41 tubes without serious complication and visualized the distal tube in 36 (88%) of 41 tubes. Free spill in at least one tube was seen in 17 (77%) of 22 patients. Nineteen patients had a history of previous laparoscopy or laparotomy for tubal disease, in 16 of whom laparoscopic results were available for review. Retrospectively, in 15 (94%) of 16 patients all clinically relevant abnormalities would have been detected by means of TFTC alone. Five patients conceived, three with intrauterine and two with ectopic pregnancies. Patients with intrauterine pregnancies had normal-appearing tubes after TFTC, while those with ectopic pregnancies had residual tubal abnormalities after recanalization. TFTC is a safe, accurate diagnostic procedure that provides more information than hysterosalpingography and, in most cases, as much or more information about the fallopian tubes than laparoscopy.

Eleven patients who had lung tumors associated with obstructive pneumonitis and who failed to yield diagnostic material at conventional bronchoscopic biopsy underwent real-time ultrasonographic (US) studies and US-guided aspiration biopsy. Sonography of the consolidated lung showed a wedge-shaped hypoechoic lesion containing a fluid bronchogram. The presumed obstructing tumor was seen as a hypoechoic nodule near the hilum or as a well-defined hyperechoic mass inside the partially consolidated lung. Computed tomography (CT) was superior to US in demonstrating the bronchial obstruction (P less than .05). However, there were no significant differences between CT and US in demonstrating the obstructing tumor (P greater than .10). In all 11 patients the diagnosis was made by means of US-guided transthoracic aspiration biopsy and in eight patients also by means of Trucut biopsy. No complications were observed in the studies. It is concluded that US and US-guided aspiration biopsy are useful adjunct diagnostic techniques for lung tumor patients with obstructive pneumonitis.

Segmental intensity differences (SIDs) in hepatic parenchyma free of tumor were noted in six patients with hepatic masses (hepatocellular carcinoma in five and metastatic liver cancer in one). Areas of SID were homogeneous in intensity. The intensity of the affected region was high in all six patients on T2-weighted magnetic resonance (MR) images and low in two on T1-weighted images. Three of five patients examined with plain computed tomography (CT) had corresponding segmental areas of low attenuation. Angiograms obtained in five patients showed occlusion of the intrahepatic portal vein, segmental staining corresponding to the region of the SID, or both. Twelve of 82 patients examined with MR imaging and angiography had similar findings on angiograms, and ten of them had abnormal intensity of anatomic distribution around or beside the liver tumors on MR images. MR imaging may be more sensitive than plain CT in the detection of secondary changes caused by intrahepatic portal flow stoppage.

Duplex Doppler ultrasound (US) examination of the renal vasculature has proved valuable in assessing the kidney transplant. The normal renal allograft exhibits low-impedance arterial inflow similar to that seen in the normotopic kidney. The authors and others previously reported that a high vascular impedance, defined as either a pulsatility index (PI) greater than 1.8 or a resistive index greater than 0.9, indicates acute vascular rejection (AVR). Although AVR remains the most common cause of increased PI, the authors noted ten episodes among 180 serially followed-up transplants in which abnormal waveforms were clearly not due to rejection. Four other causes of increased vascular impedance are reported, including renal vein obstruction, severe acute tubular necrosis, pyelonephritis, and extrarenal compression of the graft. These new causes only slightly decrease the specificity of high vascular impedance for rejection. Furthermore, the cause can usually be recognized from the clinical history or other US findings.

Color Doppler flow imaging is a new technique providing simultaneous display of a gray-scale tissue and a color-flow vascular image. We demonstrate its ability to predict accurately occlusions of numerous vessels, including the internal carotid, external carotid, common carotid, subclavian and innominate arteries. Alterations in flow direction and changes in spectral wave form provide useful clues to the presence of these occlusions. The cases are correlated with angiographic findings and functional flow diagrams of the hemodynamic changes involved.

Severe stenosis of the cervical internal carotid artery was detected on magnetic resonance images in three patients from a series of eight with abnormality of flow. In contrast to complete loss of "flow void" in the horizontal carotid within the petrous bone seen in patients with complete occlusion, these three patients had partial flow void in which there was a central area of signal void in the artery, surrounded by circumferential increase in signal in the outer third of the artery. This was seen on axial views at right angles to the long axis of the artery below the petrous bone and on "in-plane" sections through the horizontal carotid canal. An animal model with 70% and 90% carotid stenosis and carotid occlusion was created. The model with 70% stenosis showed no significant change. The 90% stenosis model showed partial flow void in the center of the lumen with peripheral signal exactly as seen in the human patients.

Both carotid bifurcations were examined in 353 patients over a 20-month interval using a combination of real-time and pulsed Doppler ultrasound (duplex scanning). Angiographic correlation was available in 72 cases. Stenosis of the internal carotid was evaluated using a Doppler input frequency of 5 MHz and a scan angle of 60 degrees. A peak frequency shift of less than 3.5 kHz was found to be a sign of less than or equal to 30% stenosis; 3.5-4 kHz with moderate turbulence suggested 31-50% stenosis, 4-8 kHz 51-90% stenosis, and greater than 8 kHz greater than 90% stenosis. Subtotal stenosis (greater than 95%) was manifested by a frequency shift of less than 8 kHz, but the waveform was totally distorted. Overall accuracy improved from 77% for the first 6 months to 87% for the last 14 months. For stenosis greater than 50%, sensitivity improved from 82% to 97% during this period. Analysis of errors and suggestions for avoiding them are presented.

Sixteen patients with various lesions involving the brachiocephalic arteries were studied ultrasonographically. The examination was very useful in diagnosing aneurysms of the peripheral arteries and in differentiating an aneurysm from other causes of palpable pulsatile masses, such as a tortuous artery and tumor beneath an artery. The ultrasound technique used for evaluation of these lesions is described.

Intravascular signal from flowing blood is frequently observed on magnetic resonance (MR) images and may be indistinguishable from partial or complete vascular occlusion caused by thrombus or tumor. With a phase-display reconstruction method, qualitative assessment of large-vessel patency within the abdomen was undertaken in 15 healthy subjects and 12 patients with angiographically or surgically documented intravascular thrombus or tumor. Computed tomographic (CT) scans were available in all patients for correlation. MR studies were performed with a multisection spin-echo pulse sequence and two-dimensional Fourier transform spatial encoding. Data acquired from a single sequence was reconstituted in two ways to provide both routine anatomic images and a pictorial representation of large-vessel flow on a phase-sensitive image. With this method, reliable and easy differentiation of intraluminal thrombus and tumor from blood flow signal within large vessels was achieved. Information from these phase-display images compared favorably with findings from angiography and contrast-enhanced CT in the determination of luminal patency and obstruction.

In magnetic resonance (MR) imaging the distinction between vascular signal from flowing blood and thrombus of any nature is often difficult. Even though there are qualitative criteria to identify intravascular signal as coming from flowing blood, these can fail, and no definitive statement can be made on the nature of intravascular MR signal. In this study, the authors compared the effectiveness of T2 calculations with that of phase images in distinguishing thrombus from flow. In 13 patients with 21 regions of questionable flow or thrombus, T2 calculations were found to have a sensitivity of 69% and a specificity of 88%. Phase images correctly identified thrombus or flow in all but one case with thrombus. Whenever a thrombus is suspected on the basis of MR magnitude images, reconstruction of phase images is the method of choice. However, for the positive identification of flow, T2 value calculations are often sufficient.

To assess the utility of gradient echo (GRE) magnetic resonance (MR) imaging in documenting aqueductal patency, spin-echo (SE) and GRE axial images were obtained with a 1.5-T system in 26 patients with aqueductal or periaqueductal lesions and in 26 control subjects. All SE images with a long repetition time (TR) were obtained with first-order gradient moment nulling. GRE imaging was performed with the use of the sequential section acquisition technique called gradient recalled acquisition in the steady state (GRASS), with a TR of 150 msec, an echo time of 14-17 msec, and a flip angle of 50 degrees, so to depict stationary cerebrospinal fluid (CSF) as low intensity and flowing CSF as high intensity. All patent aqueducts were seen as high intensity on GRE images. In 18 of 20 obstructed aqueducts, low intensity was seen within the aqueducts on GRE images. SE images obtained with gradient moment nulling did not allow confident distinction between patent and obstructed aqueducts. It appears that GRE imaging is useful in rapidly assessing aqueductal patency.