Characterization and correction of cardiovascular motion artifacts in diffusion--weighted imaging of the pancreas

Purpose: To assess the effects of cardiovascular-induced motion on conventional DWI of the pancreas and to evaluate motion-robust DWI methods in a motion phantom and healthy volunteers. Methods: 3T DWI was acquired using standard monopolar and motion-compensated gradient waveforms, including in an anatomically accurate pancreas phantom with controllable compressive motion and healthy volunteers (n = 8, 10). In volunteers, highly controlled single-slice DWI using breath-holding and cardiac gating and whole-pancreas respiratory-triggered DWI were acquired. For each acquisition, the ADC variability across volunteers, as well as ADC differences across parts of the pancreas were evaluated. Results: In motion phantom scans, conventional DWI led to biased ADC, whereas motion-compensated waveforms produced consistent ADC. In the breath-held, cardiac-triggered study, conventional DWI led to heterogeneous DW signals and highly variable ADC across the pancreas, whereas motion-compensated DWI avoided these artifacts. In the respiratory-triggered study, conventional DWI produced heterogeneous ADC across the pancreas (head: 1756 +/- 173 x 10(-6) mm(2)/s; body: 1530 +/- 338 x 10(-6) mm(2)/s; tail: 1388 +/- 267 x 10(-6) mm(2)/s), with ADCs in the head significantly higher than in the tail (P <.05). Motion-compensated ADC had lower variability across volunteers (head: 1277 +/- 102 x 10(-6) mm(2)/s; body: 1204 +/- 169 x 10(-6) mm(2)/s; tail: 1235 +/- 178 x 10(-6) mm(2)/s), with no significant difference (P >= .19) across the pancreas. Conclusion: Cardiovascular motion introduces artifacts and ADC bias in pancreas DWI, which are addressed by motion-robust DWI.