Inflow correction of hepatic perfusion measurements using T1-weighted, fast gradient-echo, contrast-enhanced MRI

Inflow effects were studied for T(1)-weighted, fast gradient-echo, contrast-enhanced MRI. This was done on the basis of realistic simulations (e.g., taking slice profiles into account) for unsteady flow. The area under the point spread function (PSF) was used to estimate the flow-related enhancement. A simple analytical model that accurately describes the inflow effects was derived and validated. This model was used to correct the experimental perfusion calibration curves (signal intensity vs. relaxation rate) for inflow effects. Hepatic perfusion measurements, performed on patients, were analyzed in terms of a dual-input, first-order linear model. It was shown that inflow causes incorrect perfusion input functions. The resulting estimated perfusion parameters displayed a systematic error of typically 30-40%. By performing two extra time-resolved flow measurements during the examination, one can correct the input functions.