High-speed black blood imaging of vessel stenosis in the presence of pulsatile flow.

Stenosis phantoms were created to study the ability of "black blood" methods to image a vessel stenosis in the presence of pulsatile flow. Black blood images were acquired with a modified TurboFLASH (fast low-angle shot) method that eliminates flow signal by applying a set of prepulses before segmented data acquisition. With this high-speed approach, imaging can be completed within 16 seconds. This technique was compared with conventional spin-echo black blood, gradient-echo black blood, and gradient-echo bright blood methods. Loss of flow signal, which extended beyond the site of the stenosis, was seen on the gradient-echo bright blood images. The pattern of signal loss varied with the type of stenosis. Flow voids were achieved with spin-echo black blood imaging; however, substantial ghosting artifacts were seen. With gradient-echo black blood imaging, it was difficult to eliminate all flow signal, particularly for in-plane flow. The modified TurboFLASH method produced high-quality black blood images in a fraction of the time needed for spin-echo imaging. It showed no ghosting artifacts even in the presence of pulsatile flow.     

Evaluation of adrenal masses with gadolinium enhancement and fat-suppressed MR imaging

A study was undertaken to determine the ability to characterize benign and malignant masses with unenhanced and contrast material-enhanced fast lowangle shot and fat-suppressed spin-echo magnetic resonance (MR) imaging. Thirty patients with adrenal masses detected at computed tomography (CT) underwent MR imaging within 14 days after CT. CT and MR images were interpreted in a prospective, blinded fashion. Sixteen patients had 20 benign adrenal masses, and 14 patients had 18 malignant masses. Quantitative measurements included percentage of contrast enhancement on immediate postcontrast dynamic images and periphery - center signal-to-noise ratio (S/N) on gadolinium-enhanced fat-suppressed images. Qualitative evaluation included determination of the regularity of lesion margins, homogeneity of signal intensity, and local extension. MR imaging depicted all adrenal masses discovered at CT examinations. Lesions ranged in diameter from 1 to 15 (mean, 4.4) cm. No significant difference was observed in percentage of contrast enhancement between benign (90.5% ± 59.0 [standard deviation]) and malignant (110.5% ± 116.4) masses. A difference was observed between periphery - center S/N for benign (?.05 ± 1.5) and malignant (7.7 ± 9.8) masses; overlap between the two, however, occurred. Qualitative evaluation allowed correct characterization of 32 of 38 masses, comparing favorably with CT, which allowed characterization of 30 lesions.