Diffusion-weighted imaging of the kidney: comparison between simultaneous multi-slice and integrated slice-by-slice shimming echo planar sequence

Abstract

To compare the simultaneous multi-slice (SMS) and integrated slice-by-slice shimming (iShim) single-shot echo planar imaging (ssEPI) for diffusion-weighted imaging (DWI) of the kidneys. In this prospective study, six healthy volunteers and 22 patients with renal diseases underwent SMS and iShim DWI of the kidney with five b-values (0, 80, 400, 800, 1,600 s/mm2) at 3 T. The subjective image quality, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and ADC values were evaluated. The subjective image quality scores, SNR, CNR, ADC values and scan time of SMS and iShim DWI were compared. Scan time of SMS DWI (1 minute 38 seconds) was significantly reduced compared to iShim ssEPI (3 minutes 33 seconds). No statistically significant differences in the SNR or subjective image quality were observed on the b=0 images, but the SNR and overall image quality scores were significantly higher on the other four b-value images at SMS DWI. Image distortions were also comparable, but there were fewer artefacts on the b=80 and b=800 images in SMS DWI. CNR was significantly higher on the b=0 and b=1,600 images in SMS DWI. SNR and subjective image-quality scores of ADC maps were significantly higher in SMS DWI, whereas CNR showed no significant difference. The ADC value of renal parenchyma was similar in SMS and iShim DWI (1.54±0.11 × 10-3 versus 1.52±0.16×10-3 mm2/s, p=0.343). SMS can substantially reduce imaging time of kidney DWI with slightly improved image quality and comparable ADC values of renal parenchyma compared to iShim ss-EPI sequence.