Targeted-HASTE imaging with automated device tracking for MR-guided needle interventions in closed-bore MR systems.

Percutaneous MR-guided interventions with needles require fast pulse sequences to image the needle trajectory with minimal susceptibility artifacts. Spin-echo pulse sequences are well suited for reducing artifact size; however, even with single-shot turbo spin-echo techniques, such as rapid acquisition with relaxation enhancement (RARE) or half-Fourier acquisition single-shot turbo spin-echo (HASTE), fast imaging remains challenging. In this work we present a HASTE pulse sequence that is combined with inner-volume excitation to reduce the scan time and limit the imaging field of view (FOV) to a small strip close to the needle trajectory (targeted-HASTE). To compensate for signal saturation from fast repeated acquisitions, a magnetization restore pulse (driven equilibrium Fourier transform (DEFT)) is used. The sequence is combined with dedicated active marker coils to measure the position and orientation of the needle so that the targeted-HASTE image slice is automatically repositioned. In an animal experiment the coils were attached to an MR-compatible robotic assistance system for MR-guided interventions. Needle insertion and infusion via the needle could be visualized with a temporal resolution of 1 s, and the needle tip could be localized even in the presence of a stainless steel mandrel. Copyright (c) 2006 Wiley-Liss, Inc.