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Objective: Segmental arterial mediolysis is a rare noninflammatory vascular disease of the abdominal splanchnic arteries. The purpose of our study was to retrospectively describe the CT angiography (CTA) findings of this disease and the evolution of those findings over time in five patients., Conclusion: Comparison of CTA and digital subtraction angiography suggests that CTA is useful to diagnose symptomatic segmental arterial mediolysis. Midterm CTA follow-up (median, 3 years) indicates that segmental arterial mediolysis lesions may resolve or remain unchanged.

Objective: Our aim was to assess the feasibility and image quality of dynamic cine-mode imaging of the mitral valve using retrospectively ECG-gated 16-MDCT., Subjects and Methods: Contrast-enhanced MDCT was performed in 37 patients who have a normal mitral valve, as shown on transesophageal echocardiography. Twenty CT data sets covering the valve apparatus were reconstructed every 5% step of the R-R interval. Multiplanar reconstructions were performed in the parallel short axis and perpendicular long axis of the left ventricle. Two independent blinded reviewers evaluated the image quality for dynamic cine-mode visualization of the valve components in systole and diastole and during the transitional phases in between., Results: Interobserver agreement for image quality ratings of valve components in all cardiac cycle phases ranged from good to excellent. Image quality for the visualization of valve leaflets, apposition zone, commissures, and mitral annulus (ranging from adequate to excellent) was significantly superior on perpendicular plane images than on parallel plane images for all cardiac phases (p < 0.05). Tendinous cords were visualized on both perpendicular and parallel planes with bad to adequate quality, whereas visualization of the papillary muscles was adequate to excellent on both imaging planes. Visualization of each valve component was superior in systole and diastole in both imaging planes as compared with the transitional phases (p <0.001)., Conclusion: Noninvasive cine-mode imaging of the mitral valve using retrospectively ECG-gated MDCT is feasible and allows accurate visualization of the moving valve. Perpendicular long-axis reconstructions yield images of superior quality when compared with the short-axis reconstructions and enable a determination of its functional morphology.

Objective: Our goal was to determine the impact of ECG gating and different postprocessing techniques on 3D imaging of the bronchial tree. SUBJECTS AND METHODS. Retrospective ECG-gated MDCT and non-ECG-gated MDCT of the chest were performed in 25 patients. ECG-gated MDCT data were reconstructed mid diastole using a fixed interval of -400 msec in 25 patients and then additionally at -200, -300, and -500 msec in 10 of those patients. Shaded surface display and volume rendering of the bronchial tree combined with virtual bronchoscopy were performed using all data sets. The extent of bronchial tree visualization in shaded surface display-virtual bronchoscopy and volume rendering-virtual bronchoscopy and the presence of artifacts in volume-rendered images were scored by three blinded reviewers. The effective radiation doses of the ECG-gated and nongated acquisitions were compared., Results: The summary scores of all bronchial segments for gated shaded surface display-virtual bronchoscopy and gated volume rendering-virtual bronchoscopy did not differ significantly. The summary scores for nongated shaded surface display-virtual bronchoscopy and nongated volume rendering-virtual bronchoscopy were not significantly different. Non-gated acquisition yielded significantly better visualization of the bronchial tree for both post-processing techniques, regardless of the time interval used for reconstruction of the ECG-gated series. Artifact scores in volume-rendered images were significantly higher for ECG-gated MDCT compared with nongated MDCT. Effective radiation dose was significantly higher for the ECG-gated acquisition., Conclusion: Given the advantage of volume rendering for representing the entire data set and given the lower radiation dose and better 3D image quality of nongated acquisition, volume rendering performed on nongated MDCT data is the method of choice for 3D visualization of the bronchial tree.

Objective: The purpose of this study was to evaluate physiologic changes of the cross-sectional area of the spinal canal and neural foramina in young asymptomatic volunteers., Subjects and Methods: Twelve asymptomatic volunteers were examined in a 0.5-T open-configuration MR system. T2-weighted fast spin-echo sequences were obtained in upright neutral, upright flexed, upright extended, and supine extended positions. The cross-sectional area of the spinal canal and the thickness of the ligamentum flavum were measured on angled axial images at the L4-L5 level. The anteroposterior diameter of the spinal canal and cross-sectional areas of the neural foramina were measured on sagittal images from L1 to S1., Results: At disk level, the cross-sectional area of the spinal canal varied significantly between body positions, most notably between the upright flexed (mean, 268 mm2) and the upright extended (mean, 224 mm2) positions (p < .0001). The maximum thickness of the ligamenta flava increased in the extended positions (p < .0001). The cross-sectional area of the neural foramina underwent position-dependent variations of as much as 44.4%. The smallest cross-sectional areas were found in the extended positions., Conclusion: In asymptomatic volunteers, MR imaging is able to show position-dependent changes in the cross-sectional areas of the spinal canal and the intervertebral foramina. The extended positions best reveal important findings.

Objective: Release of a tourniquet on the thigh and termination of Valsalva's maneuver result in a transient increase in venous blood flow in the leg. The purpose of this study was to determine the value of time-of-flight echoplanar imaging performed with these flow-enhancing methods to image the veins of the calf., Subjects and Methods: Flow volumes in the femoral veins in eight volunteers were determined with a two-dimensional phase-contrast MR imaging technique before and immediately, 20, 40, and 60 sec after termination of Valsalva's maneuver and thigh vein occlusion. Subsequently, the calf veins of 11 healthy volunteers were imaged with a two-dimensional four-shot echoplanar MR imaging technique. Forty-one 5-mm-thick sections were obtained over 10 sec immediately after termination of venous occlusion. Visibility of the three venous bundles was analyzed in the proximal, middle, and distal portions of the calf on the basis of a four-point scale. Finally, the calf of a single patient with documented DVT was imaged by the same MR imaging technique., Results: Both Valsalva's maneuver and venous occlusion caused significant increases in venous flow (p < .05) only during the first 20 sec after termination of the maneuver and the occlusion. Venous occlusion had a significantly greater effect than did Valsalva's maneuver (p < .05). Flow augmentation by venous occlusion of the thigh improved calf vein visualization with time-of-flight echoplanar MR imaging (p < .0001). Of the 99 calf vein segments examined, 93 were clearly seen. Thrombi were seen in the patient study., Conclusion: Multishot time-of-flight echoplanar imaging can exploit the short-lived effect of mechanical flow-enhancing measures, resulting in good visualization of calf veins. The true diagnostic impact of this technique needs to be evaluated in a patient study.

Objective: This article reports on the preliminary evaluation of a new technique for guiding intravascular interventional procedures with MR imaging. Active real-time position monitoring of catheters with MR imaging is made possible by incorporating a small RF coil into the tip of the catheter. The purpose of this study was to evaluate the practicability and localizing precision of this MR catheter tracking technique in vitro and in vivo in comparison with fluoroscopy., Materials and Methods: Feed cables employing a 0.9-mm-diameter coaxial cable, a 0.5-mm-diameter partially shielded coaxial cable, and a twisted pair cable attaching RF coils at the catheter tip to a coaxial plug at the catheter base were assessed. Further, miniature copper loop RF coils of two, three, and four turns were tested. In vitro validation of MR tracking was achieved by using a phantom consisting of a water-filled harvested segment of human aorta and iliac arteries embedded in gel. Accuracy of catheter placement was compared with MR and fluoroscopy. Subsequently, the MR tracking technique was evaluated in a swine model using a prototype 5-French MR tracking catheter., Results: A fully shielded coaxial cable was found to be crucial for localizing the attached RF coil by means of the tracking technique. The number of coil turns had a lesser impact. Positions of the catheter tip measured with the MR technique and with fluoroscopy correlated well (r > .98), with a 6-mm 95% confidence interval of positional differences. Active real-time tracking of the coil-tipped catheters was achieved both in vitro and in vivo. The 5-French tracking catheter was successfully placed in the splenic and renal arteries of the swine., Conclusion: Robust in vivo tracking and accurate placement of catheters equipped with miniature RF coils are possible with MR imaging.