MRI estimation of the arterial input function in mice1

Rational and Objectives. Dynamic contrast-enhanced (DCE) MRI offers the potential to provide quantitative maps of tumor perfusion parameters and is therefore expected to play an important role in the study of cancer in small animal models. Extraction of such information from DCE-MRI data requires a methodology for determination of the arterial input function (AIF) for the target tissues. An MRI based method for observation of the AIF in a mouse model is demonstrated in the present report. Materials and Methods. A series of short-axis cardiac images was acquired during the first pass of a bolus of Gadodiamide using a low-resolution, EEG-gated, saturation-recovery gradient echo imaging sequence. The AIF was then extracted from the observed signal intensity changes in the left ventricle (LV) blood pool. Results. The proposed technique provides sufficient temporal and spatial resolution to accurately characterize the AIF of Gadodiamide in mouse models. The AIF was observed in 4 mice and was found to be qualitatively similar to that previously observed in larger animals. However, significant inter-animal variability in the precise form of the AIF was evident. Conclusions. The proposed method for determination of AIF in mice has been shown to be effective and reliable. The inter-animal variability observed in the present study suggests that the AIF should be measured in each animal undergoing analysis by DCE-MRI.