An amplitude optimized single-shot hybrid QUEST technique.

Rapid MR imaging techniques either deposit high amounts of radio frequency power or require powerful gradient systems with high slew rates, which might not be available on conventional scanners. QUEST provides a fast imaging method with scan times of the order of hundreds of milliseconds and avoids these problems at the cost of low signal-to-noise ratios (SNR). In this work, QUEST was optimized with regard to image quality and measuring time. With the use of a Hybrid QUEST technique, that refocuses the image echoes several times, a spatial resolution of 1.9 mm x 1.6 mm x 5 mm was achieved. By acquiring both the necessary correction data and the image information in a single echo train, the Hybrid QUEST technique was implemented as a true single-shot measurement with a total scan time of 190 ms. Optimization of the excitation flip angles and the amplitude and phase correction methods for image reconstruction resulted in an improved SNR of 53.7 in the white matter of the human head for a 10 mm slice thickness at 1.5 T. In contrast to echo planar imaging techniques, no image distortions were observed with Hybrid QUEST in anatomic regions with many tissue interfaces.