Purpose:To improve the accuracy of dynamic susceptibility contrast (DSC) measurements of cerebral blood flow (CBF) and volume (CBV). Materials and Methods:In eight volunteers, steady-state CBV (CBV SS ) was measured using TrueFISP readout of inversion recovery (IR) before and after injection of a bolus of contrast. A standard DSC (STD) perfusion measurement was performed by echo-planar imaging (EPI) during passage of the bolus and subsequently used to calculate the CBF (CBF DSC ) and CBV (CBV DSC ). The ratio of CBV SS to CBV DSC was used to calibrate measurements of CBV and CBF on a subject-by-subject basis. Results:Agreement of values of CBV (1.77 Ϯ 0.27 mL/100 g in white matter (WM), 3.65 Ϯ 1.04 mL/100 g in gray matter (GM)), and CBF (23.6 Ϯ 2.4 mL/(100 g min) in WM, 57.3 Ϯ 18.2 mL/(100 g min) in GM) with published goldstandard values shows improvement after calibration. An F-test comparison of the coefficients of variation of the CBV and CBF showed a significant reduction, with calibration, of the variability of CBV in WM (P Ͻ 0.001) and GM (P Ͻ 0.03), and of CBF in WM (P Ͻ 0.0001). Conclusion:The addition of a CBV SS measurement to an STD measurement of cerebral perfusion improves the accuracy of CBV and CBF measurements. The method may prove useful for assessing patients suffering from acute stroke.

In living liver donation, a fatty liver poses risks for both recipient and donor. Currently, liver biopsy is the standard for assessing the presence and extent of steatosis. The goals of this study were to correlate a steatosis index derived from magnetic resonance imaging (MRI) to the histologic grade on biopsy as well as to determine the topographic distribution of steatosis within the liver. We examined the ability of dual-echo, chemical shift gradientecho MRI to predict the degree of steatosis on liver biopsy. A total of 22 subjects received both a liver biopsy and detailed MRI evaluation. These individuals included 15 potential living donors and 7 patients with nonalcoholic fatty liver disease. MRI steatosis index was then compared with histologic grade on liver biopsy. The topographic distribution of hepatic steatosis was determined from those subjects in whom MRI detected hepatic steatosis.

Comprehensive aortic magnetic resonance (MR) examinations currently include multiple nonenhanced and contrast material-enhanced sequences. The authors hypothesized that the nonenhanced true fast imaging with steady-state precession (FISP) portion alone of their comprehensive imaging protocol would be adequate to confidently confirm or exclude dissection or aneurysm of the aorta. In a retrospective review of 29 comprehensive thoracic aortic MR examinations, nonenhanced true FISP MR imaging alone was 100% accurate for determining the presence or absence of dissection or aneurysm.

The purpose of the study was to implement a three-dimensional (3D) magnetic resonance (MR) angiographic technique with acquisition times on the order of 800 msec with use of a spoiled gradient-echo pulse sequence (repetition time, 1.60 msec; echo time, 0.65 msec) and bolus intravenous injection of contrast material doses as small as 6 mL. High-spatial-resolution conventional MR angiography performed with 30 mL of gadopentetate dimeglumine was the reference standard. As implemented, subsecond 3D MR angiography allowed temporal sampling that was rapid enough to depict short-lived processes, as illustrated in patients with shunts and dissections. With small contrast material doses and subsecond frame rates, it is also possible to measure pulmonary arteriovenous circulation times with this 3D MR angiographic technique.

No abstract