Black blood MR angiography using multislab three-dimensional TI-weighted turbo spin-echo technique: imaging of intracranial circulation.

Abstract

A number of black blood MR angiography techniques have been described I I . 2 . These techniques are based oti intentional suppression of signal intensity froni flowing blood and simultaneous max inlization of signal intensity from stationary tissues. Black blood MR angiography techniques show pronlise in their ability to overcome 5(.)!Tle of the shortcon ings of the white blood MR angiography techniques currently in use. Specifically. flow void artifacts due to intravoxel phase dispersion. which plague white blood MR angiography techniques. actually help suppress intravascular signal intensity in black blood techniques 13. 4). Black blood MR angiography methods that have been implemented 11r efiective suppres5i011 of signal intensity from flowing blood indude spatial presaturation outside the imaging volume and TI nulling ofhlood before entering the imaging volume using a spatially selective spin preinversion pulse I I . 2 I. In both methods. spatial coverage is restricted by intravascular signal recovery as a function ofTI relaxation of blxxl protons. More recently. a black blood MR angiography technique based on turbo spin echo. which does not rely oti inflow effects, has been described (Jara H et al., presented at the Society tbr Magnetic Resonance meeting. May 1995). This nonreliance on inflow effects provides a significant advantage over time-of-flight MR angiography techniques with regard to in-plane and intravolume flow saturation. In this technique. the effectiveness of signal attenuation from straight vessels depends on the direction of flow relative to the frequency-encoding direction (maximum signal attenuation versus phase-encoding and slice-select directions (incomplete signal attenuation). Sonic investigators have suggested that in curvilinear vessels (i.e.. intracranial circulation) and in regions of nonunifomi flow. effective attenuation of intravascular signal intensity is achieved as long as a compolient of the flow is in the frequency-encoding direction (Jara H. unpublished data). Further. this technique shows sensitivity to a wide range of velocities. with effective intravascular suppression of signal intensity for all velocities greater than 7 x 10-2 ni/sec (Jara H. unpublished data). We describe our initial clinical experience with a three-diniensional T I -weighted turbo spin-echo black blood MR angiography technique for imaging intracranial circulation. We also describe three-dimensional time-of-flight MR angiography matched for spatial resolution as a comparative imaging technique.