Highly Accelerated T1-Weighted Abdominal Imaging Using 2-Dimensional Controlled Aliasing in Parallel Imaging Results in Higher Acceleration

Abstract

The purpose of this study was to evaluate the feasibility and technical quality of an abdominal 3-dimensional interpolated breath-hold (volumetric interpolated breath-hold examination [VIBE]) magnetic resonance examination using the new parallel acquisition technique, controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA). In this institutional review board-approved study, 15 volunteers underwent an abdominal magnetic resonance imaging examination including axial unenhanced 3-dimensional VIBE sequences with the conventional parallel acquisition technique, generalized autocalibrating partially parallel acquisitions parallel imaging (GRAPPA), with an acceleration factor (R) of 2, 3, 4, and 2 × 2 in comparison with a CAIPIRINHA-VIBE sequence with an acceleration factor of 2 × 2. Images were evaluated regarding the overall image quality, liver edge sharpness, and parallel imaging artifacts. Signal-to-noise ratio was evaluated using 2 different methods. In a second study population, 17 patients were examined with our new routine protocol for abdominal imaging that now comprises VIBE sequences with CAIPIRINHA with R = 2 × 2. In the volunteer population, the overall image quality of CAIPIRINHA with R = 2 × 2 was significantly higher compared with GRAPPA with R = 3, 4, and 2 × 2 (P < 0.05). There were significantly less parallel imaging artifacts with CAIPIRINHA with R = 2 × 2 (P < 0.05). Acquisition time varied between 21.1 (GRAPPA with R = 2, 320 matrix) and 6.9 seconds (CAIPIRINHA with R = 2 × 2, 256 matrix). Signal-to-noise ratio performance of CAIPIRINHA with R = 2 × 2 was superior to GRAPPA with R = 3, 4, and 2 × 2. In the patient population, VIBE sequences with CAIPIRINHA with R = 2 × 2 showed consistently good image quality, minimal motion artifacts, and minimal parallel imaging artifacts. The CAIPRINHA-VIBE with an acceleration factor of R = 2 × 2 is feasible in a clinical setting and is characterized by fast and robust imaging with an image quality comparable with a 2-fold acceleration with GRAPPA.