In vivo assessment of optimal b-value range for perfusion-insensitive apparent diffusion coefficient imaging

Purpose: To assess the optimalb-values range for perfusion-insensitive apparent diffusion coefficient (ADC) imaging of abdominal organs using short-duration DW-MRI acquisitions with currently available ADC estimation methods. Methods: DW-MRI data of 15 subjects were acquired with eightb-values in the range of 5–800 s/mm2. The reference-standard, a perfusion insensitive, ADC value (ADCIVIM), was computed using an intravoxel incoherent motion (IVIM) model with all acquired diffusion-weighted images. Simulated DW-MRI data was generated using an IVIM model with b-values in the range of 0–1200 s/mm2. Monoexponential ADC estimates were calculated using: (1) Two-point estimator (ADC2); (2) least squares three-point (ADC3) estimator and; (3) Rician noise model estimator (ADCR). The authors found the optimal b-values for perfusion-insensitive ADC calculations by minimizing the relative root mean square error (RRMS) between the ADCIVIM and the monoexponential ADC values for each estimation method and organ. Results: Lowb-value = 300 s/mm2 and high b-value = 1200 s/mm2 minimized the RRMS between the estimated ADC and the reference-standard ADCIVIM to less than 5% using the ADC3 estimator. By considering only the in vivo DW-MRI data, the combination of low b-value = 270 s/mm2 and high b-value of 800 s/mm2 minimized the RRMS between the estimated ADC and the reference-standard ADCIVIM to