Diffusion Weighted Imaging Based On Single-shot Center-out Echo Planar Imaging Technology

Diffusion magnetic resonance imaging(MRI)is widely used in clinic,as a useful non-invasive imaging technique for evaluating early cerebrovascular diseases and distinguishing benign and malignant tumors.For better analyzing the change of the magnetic resonance signals due to the effect of the molecular diffusion,a bipolar gradient with long duration and strong gradient strength is applied in diffusion-weighted imaging(DWI).However,the bipolar gradient may lead to the decay of signal,result in degradation of image quality and lower signal-to-noise ratio(SNR).Furthermore,the bipolar gradient will prolong the sequence echo time(TE).As a consequence,the application of DWI in the tissue with short T2 value is limited.In order to reduce the signal decay when diffusion gradients for high b-value are applied,a new DWI sequence is proposed.A center-out DWI technique based on single-shot center-out echo-planar imaging(COEPI)is proposed to reduce T2 effect and increase SNR by further shortening the TE.The acquisition trajectory is modified,and the first phase encoding(PE)line is acquired at Ky=0.Experiments were performed on a 3.0T United-Imaging MRI system to evaluate the proposed method.In phantom experiments,COEPI-DWI is demonstrated to provide higher SNR than that in conventional DWI.Additionally,the measured apparent diffusion coefficient(ADC)in COEPI-DWI is closer to the referenced value compared with conventional DWI.The advantages of COEPI-DWI in improving SNR were further demonstrated in the white matter with selected regions of interest(ROIs)of human volunteers.