Simultaneous Multi-Slice And Partially Parallel Acquisition Based Accelerated MR Myocardial Viability Imaging

Assessment of myocardial viability,which can be used for detecting diseases including myocardial infarction,has a great practical value for the clinical diagnosis and treatment.Using the late enhancement effort of infarcted myocardium,MR myocardial viability imaging can reveal the infarcted areas through an inversion recovery scan at 10–20 minutes after contrast agent administration.To eliminate the sensitivity to the selection of inversion time,phase-sensitive inversion recovery（PSIR）was widely used to assess the myocardial viability.ECG gating and breath-hold are required in MR myocardial viability imaging.The conventional PSIR may bring heavy burdens to patients due to the long acquisition time and too many breath-holds.The application of MR myocardial viability imaging can be even limited when patients have difficulty in holding breath.To achieve the acceleration of myocardial viability imaging and extend its clinical application,we proposed a method to integrate simultaneous multi-slice（SMS）and partially parallel acquisition（PPA）into PSIR sequence.In T₁-weighted inversion recovery imaging part,multi slices were excited simultaneously with inter-slice shift by using an excitation pulse after appropriate phase modulation and fusion.Additionally,PPA was also introduced into this framework to achieve acceleration in two orientations and further improve the acquisition efficiency.The sampling pattern for reference image was revised to only acquire the central part of the K-space with fewer phase encoding steps and the spatial resolution correspondingly became lower.As for reconstruction,reference images were utilized to evaluate the coil sensitivity along both slice and phase encoding directions as well as the background phase information,which can realize the un-aliasing and phase sensitive reconstruction without performing extra calibration scan.To validate our proposed method,phantom and in-vivo experiments were performed on a 3T United-Imaging MR scanner.In phantom experiments,similar results were found in both structure and T₁ contrast using traditional and our proposed method,thus confirmed the feasibility of multiplexing reference images.In in-vivo experiments,there was no significant difference between scores for different studies among 18subjects.Counting the interval between breath-holds,the acquisition time of two short-axis slices was reduced from 56 seconds to about 18 seconds and 10 seconds under two and four times acceleration.The quantitative measurement of enhanced area was also consistent for each study.These demonstrated that our proposed method was feasible for clinical diagnosis.It can obtain accurate results with significantly reduced acquisition time.