Parallel and nonparallel simultaneous multislice black‐blood double inversion recovery techniques for vessel wall imaging

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Abstract
Purpose To reduce long examination times of black-blood vessel wall imaging by acquiring multiple slices simultaneously and by using parallel acquisition techniques. Materials and Methods DIR-rapid acquisition with relaxation enhancement (;RARE) techniques imaging up to 10 simultaneous slices per acquisition with single and multiple 180°-reinversion pulses were developed. A slab-selective reinversion multislice DIR-RARE sequence incorporating generalized autocalibrating partially parallel acquisitions (GRAPPA) imaging was implemented. Four-channel and eight-channel carotid coils were built to test these sequences. A total of 11 subjects were studied. Contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) efficiency factor (SEF, SNR/unit time/slice) were measured from aortic images of three healthy subjects to determine optimal MR parameters. The DIR–RARE-GRAPPA sequence was run on aortas and carotid arteries of the five remaining healthy subjects and three atherosclerotic patients with optimal parameters (acquisition times 12–21 seconds). Results SEFs of slab-selective protocols were significantly higher than those of slice-selective protocols, and SEFs of DIR-RARE-GRAPPA protocols were significantly higher than corresponding non-GRAPPA protocols (P < 0.05). CNR was not significantly different for all imaging protocols. The DIR-RARE-GRAPPA multislice sequence showed 8.35-fold time improvement vs. single–slice DIR-2RARE sequence. Conclusion Future MRI atherosclerotic plaque studies can be performed in substantially shorter times using these methods. J. Magn. Reson. Imaging 2004;19:459–467.