Combo acquisitions: balancing scan time reduction and image quality

Abstract

Recently a new technique for the combined acquisition of multicontrast images, termed "combo acquisition," was introduced. In combo acquisitions, the three concepts of 1) variable acquisition parameters, 2) k-space data sharing, and 3) multicontrast imaging are systematically integrated to reduce MRI scan time and improve data utilization in a clinical setting. In this study, two-contrast and three-contrast spin-echo (SE) and turbo spin-echo (TSE) combo acquisition protocols that were designed and optimized in simulation experiments were implemented on a 1.5 T clinical scanner. Phantom and human brain data from volunteers and patients were acquired. Scan time reductions of 25-52% were achieved compared to standard acquisitions, largely confirming the simulation results. We evaluated the resulting images by quantitatively analyzing the preservation of contrast and the signal-to-noise ratio (SNR). In addition, data sets for 10 clinical cases obtained with TSE combo and corresponding standard acquisitions were graded by two experienced neuroradiologists in terms of the level of artifacts and image quality for comparison. Only minor image degradation with the combo scans was observed, indicating an inherent trade-off between scan time reduction and image quality. The specific aspects of combo acquisitions with respect to motion, flow, and k-space data weighting are discussed.