A functional form for a representative individual arterial input function measured from a population using high temporal resolution DCE MRI

Purpose: To measure the arterial input function (AIF), an essential component of tracer kinetic analysis, in a population of patients using an optimized dynamic contrast-enhanced imaging sequence and to estimate inter- and intra-patient variability. From these data to extract a representative AIF that may be used for realistic simulation studies.

Methods: Thirty-nine female patients were imaged on multiple visits before and during a course of neoadjuvant chemotherapy for breast cancer. A total of 97 T1-weighted dynamic contrast-enhanced studies were analyzed including bookend estimates of T1 and model-fitting to each individual AIF. Area under the curve and cardiac output were estimated from each first pass peak and these data were used to assess inter- and intra-patient variability of the AIF.

Results: Inter-patient variability exceeded intra-patient variability of the AIF. There was no change in cardiac output as a function of MR visit (mean value 5.6 ± 1.1 L/min) but baseline blood T1 increased significantly following the start of chemotherapy (which was accompanied by a decrease in hematocrit).

Conclusion: The AIF in an individual patient can be measured reproducibly but the variability of AIFs between patients suggests that use of a population AIF will decrease the precision of tracer kinetic analysis performed in cross-patient comparison studies. A representative AIF is presented that is typical of the population but retains the characteristics of an individually measured AIF.