Reproducibility and Repeatability of Intravoxel Incoherent Motion MRI Acquisition Methods in Liver

Background: Intravoxel incoherent motion (IVIM) diffusion weighted MRI (DWI) has potential for evaluating hepatic fibrosis but image acquisition technique influence on diffusion parameter estimation bears investigation.

Purpose: To minimize variability and maximize repeatably in abdominal DWI in terms of IVIM parameter estimates.

Study type: Prospective test-retest and image quality comparison.

Subjects: Healthy volunteers (3F/7M, 29.9 ± 12.9 years) and Family Study subjects (18F/12M, 51.7 ± 16.7 years), without and with liver steatosis.

Field strength/sequence: Abdominal single-shot echo-planar imaging (EPI) and simultaneous multi-slice (SMS) DWI sequences with respiratory triggering (RT), breath-holding (BH), and navigator echo (NE) at 3 Tesla.

Assessment: SMS-BH, EPI-NE, and SMS-RT data from twice-scanned healthy volunteers were analyzed using 6 × b-values (0-800 s⋅mm^-2) and lower (LO) and higher (HI) b-value ranges. Family Study subjects were scanned using SMS and standard EPI sequences. The biexponential IVIM model was used to estimate fast-diffusion coefficient (D_f), fraction of fast diffusion (f), and slow-diffusion coefficient (D_s). Scan time, estimated signal-to-noise ratio (eSNR), eSNR per acquisition, and distortion ratio were compared.

Statistical tests: Coefficients of variation (CoV) and Bland Altman analyses were performed for test-retest repeatability. Interclass correlation coefficient (ICC) assessed interobserver agreement with P < 0.05 deemed significant.

Results: Within-subject CoVs among volunteers (N = 10) for f and D_s were lowest in EPI-NE-LO (11.6%) and SMS-RT-HI (11.1%). Inter-observer ICCs for f and D_s were highest for EPI-NE-LO (0.63) and SMS-RT-LO (0.76). D_f could not be estimated for most subjects. Estimated eSNR (EPI = 21.9, SMS = 4.7) and eSNR time (EPI = 6.7, SMS = 16.6) were greater for SMS, with less distortion in the liver region (DR-PE: EPI = 23.6, SMS = 13.1).

Data conclusion: Simultaneous multislice acquisitions had significantly less variability and higher ICCs of D_s, higher eSNR, less distortion, and reduced scan time compared to EPI.

Evidence level: 2 TECHNICAL EFFICACY: Stage 1.