Arterial Input Functions Determined From MR Signal Magnitude and Phase for Quantitative Dynamic Contrast-Enhanced MRI in the Human Pelvis

` Dynamic contrast-enhanced (DCE) MRI is often used to measure the transfer constant (K(trans)) and distribution volume (v(e)) in pelvic tumors. For optimal accuracy and reproducibility, one must quantify the arterial input function (AIF). Unfortunately, this is challenging due to inflow and signal saturation. A potential solution is to use MR signal phase (phi), which is relatively unaffected by these factors. We hypothesized that phase-derived AIFs (AIF(phi)) would provide more reproducible K(trans) and v(e) values than magnitude-derived AIFs (AIF(vertical bar S vertical bar)). We tested this in 27 prostate dynamic contrast-enhanced MRI studies (echo time = 2.56 ms, temporal resolution = 13.5 s), using muscle as a standard. AlF(phi), peak amplitude varied much less as a function of measurement location (inferior-superior) than AIF(vertical bar S vertical bar) (5.6 +/- 0.6 mM vs. 2.6 +/- 1.5 mM), likely as a result of phi inflow insensitivity. However, our main hypothesis was not confirmed. The best AlF(vertical bar S vertical bar) provided similar reproducibility versus AlF(phi) (interpatient muscle K(trans) = 0.039 +/- 0.021 min(-1) vs. 0.037 +/- 0.025 min(-1), v(e) = 0.090 +/- 0.041 vs. 0.062 +/- 0.022, respectively). Magn Reson Med 66:498-504, 2011. (C) 2011 Wiley-Liss, Inc.