Improved repeatability of dynamic contrast‐enhanced MRI using the complex MRI signal to derive arterial input functions: a test‐retest study in prostate cancer patients

PURPOSE: The arterial input function (AIF) is a major source of uncertainty in tracer kinetic (TK) analysis of dynamic contrast‐enhanced (DCE)‐MRI data. The aim of this study was to investigate the repeatability of AIFs extracted from the complex signal and of the resulting TK parameters in prostate cancer patients. METHODS: Twenty‐two patients with biopsy‐proven prostate cancer underwent a 3T MRI exam twice. DCE‐MRI data were acquired with a 3D spoiled gradient echo sequence. AIFs were extracted from the magnitude of the signal (AIF(MAGN)), phase (AIF(PHASE)), and complex signal (AIF(COMPLEX)). The Tofts model was applied to extract K(trans), k(ep) and v(e). Repeatability of AIF curve characteristics and TK parameters was assessed with the within‐subject coefficient of variation (wCV). RESULTS: The wCV for peak height and full width at half maximum for AIF(COMPLEX )(7% and 8%) indicated an improved repeatability compared to AIF(MAGN) (12% and 12%) and AIF(PHASE) (12% and 7%). This translated in lower wCV values for K(trans) (11%) with AIF(COMPLEX )in comparison to AIF(MAGN) (24%) and AIF(PHASE )(15%). For k(ep), the wCV was 16% with AIF(MAGN), 13% with AIF(PHASE), and 13% with AIF(COMPLEX). CONCLUSION: Repeatability of AIF(PHASE) and AIF(COMPLEX) is higher than for AIF(MAGN), resulting in a better repeatability of TK parameters. Thus, use of either AIF(PHASE )or AIF(COMPLEX) improves the robustness of quantitative analysis of DCE‐MRI in prostate cancer.