Comparison of readout-segmented and conventional single-shot for echo-planar diffusion-weighted imaging in the assessment of kidney interstitial fibrosis

Purpose: To compare readout-segmented echo-planar imaging (EPI) (RESOLVE) to single-shot EPI (ss-EPI) diffusion-weighted imaging (DWI) for the assessment of renal interstitial fibrosis.

Materials and methods: A phantom, eight healthy volunteers (under 30 years to avoid age-fibrosis related) and 27 chronic kidney disease (CKD) patients (scheduled for kidney biopsy) were scanned (at 3T) with ss-EPI and 5-shot RESOLVE DWI (resolution: 2 × 2 × 5 mm³ , 10 b-values). The cortico-medullary difference for each DW parameter from a monoexponential fit (ΔADC) or, segmented biexponential fit (ΔD, ΔD*, ΔF_p ) were compared between both sequences. A fibrosis threshold of 40% was defined to separate all 35 subjects into low and high fibrosis groups. The linear relationship between DW parameters and percentage fibrosis (up to 80%) from Masson trichrome was assessed with the Pearson product-moment correlation coefficient. Fisher Z-transform was used for R² correlation comparison.

Results: A coefficient of variation between ADCs of 3% was measured between both sequences in the phantom. In healthy volunteers, no significant difference was measured for all DW parameters. Both sequences separated low to high level of fibrosis with a significant decrease of ΔADC (RESOLVE P = 3.1 × 10^-6 , ss-EPI P = 0.003) and ΔD (RESOLVE P = 8.2 × 10^-5 , ss-EPI P = 0.02) in the high level of fibrosis. However, RESOLVE ΔADC had a stronger negative correlation (P = 0.04 for R² comparison) with fibrosis than ss-EPI ΔADC (RESOLVE R² = 0.65, P = 5.9 × 10^-9 , ss-EPI R² = 0.29, P = 8.9 × 10^-4 ). ΔD (RESOLVE) was correlated (moderately) with fibrosis (R² = 0.29, P = 9.2 × 10^-4 ); however, ΔD* and ΔF_p did not show, in our population, a significant correlation with interstitial fibrosis (0.01 < R² < 0.08).

Conclusion: ΔADC derived from both sequences correlated with fibrosis. ΔADC from RESOLVE showed better correlation with fibrosis than ΔADC from ss-EPI and therefore has potential to monitor CKD.

Level of evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1631-1640.