Improvement of renal diffusion-weighted magnetic resonance imaging with readout-segmented echo-planar imaging at 3T

To assess the feasibility of a respiratory-gated implementation of readout-segmented SE-EPI (RESOLVE) for renal diffusion-weighted imaging (DWI) by comparison with single-shot SE-EPI (ss-EPI) in a phantom, healthy volunteers and chronic kidney disease (CKD) patients.

A fluid-filled phantom, 20 healthy volunteers and 10 CKD patients were scanned with the same parameters and coils on a 3T MR system with 3 DW sequences (b-values=0, 300, 500, 900s/mm(2)): a standard ss-EPI (Reference EPI), a ss-EPI with higher resolution, bandwidth and acceleration factor (HR-EPI) and RESOLVE with the same spatial resolution as HR-EPI but a segmentation of the readout into 5 shots. Geometric distortions, image blurring using a 'Canny' edge detection based measure, cortico-medullary differentiation measured on b0 images and ADC quantification were compared between the 3 sequences using one-way analysis of variance (ANOVA) with post-hoc Bonferroni (p<0.05 was taken as statistically significant).

RESOLVE reduced significantly geometric distortions and blurring and improved, in the volunteers and patients, the sharpness score by 56% on average in comparison to ss-EPI (p=0.02). In healthy volunteers, the cortico-medullary differentiation with RESOLVE was also possible on a wider range of b-values (p<0.02) with ADC values (in 10(-6)mm(2)/s) of 1994±246 in the cortex and 1762±238 in the medulla (p<0.001). In CKD patients, ADC values (in 10(-6)mm(2)/s) from the RESOLVE sequence were not different between the cortex (1755±145) and the medulla (1799±163, p=0.49).

Despite a longer scan time, RESOLVE enhanced significantly the quality of renal diffusion-weighted images by improving the difference in SI and ADC between the renal cortex and medulla in healthy volunteers. In CKD patients, RESOLVE showed a disappearance of this cortico-medullary ADC difference. These improvements justify further clinical studies.