Diffusion-Weighted and Dynamic Contrast-Enhanced MRI Derived Imaging Metrics for Stereotactic Body Radiotherapy of Pancreatic Ductal Adenocarcinoma: Preliminary Findings.

We aimed to assess longitudinal changes in quantitative imaging metric values obtained from diffusion-weighted (DW-) and dynamic contrast-enhanced magnetic resonance imaging (DCE)-MRI at pre-treatment (TX[0]), immediately after the first fraction of stereotactic body radiotherapy (D1-TX[1]), and 6 weeks post-TX (Post-TX[2]) in patients with pancreatic ductal adenocarcinoma. Ten enrolled patients (n = 10) underwent DW- and DCE-MRI examinations on a 3.0 T scanner. The apparent diffusion coefficient, ADC (mm/s), was derived from DW imaging data using a monoexponential model. The tissue relaxation rate, , time-course data were fitted with a shutter-speed model, which provides estimates of the volume transfer constant, (min), extravascular extracellular volume fraction, , and mean lifetime of intracellular water protons, τ (seconds). Wilcoxon rank-sum test compared the mean values, standard deviation, skewness, kurtosis, and relative percentage (r, %) changes (Δ) in ADC, , , and τ values between the magnetic resonance examinations. rADC values were significantly greater than rADC values ( = .009). r values were significantly lower than r values ( = .048). r and rv values were significantly different ( = .016). rτ values were significantly lower than rτ values ( = .008). For group comparison, the pre-TX mean and kurtosis of ADC ( = .18 and = .14), skewness and kurtosis of values ( = .14 for both) showed a leaning toward significant difference between patients who experienced local control (n = 2) and failed early (n = 4). DW- and DCE-MRI-derived quantitative metrics could be useful biomarkers to evaluate longitudinal changes to stereotactic body radiotherapy in patients with pancreatic ductal adenocarcinoma.