Simultaneous dynamic T1 and T*2 measurement for AIF assessment combined with DCE MRI in a mouse tumor model

A double-delay SR-MGE-SNAP sequence allowing simultaneous T-1 and T-2(*) 2 measurement was developed for integrating arterial input function (AIF) measurement into DCE MRI. Implemented on a 4.7-T animal MR system, this technique was applied to mice with colorectal tumor xenografts. AIF, measured in the mouse heart, was modeled by a bi-exponential function, whereas tumor K-trans and v(e) parameter maps were obtained from analysis with a two-compartment model using an individually measured AIF. AIF analysis of T-2(*)-corrected data yielded A(1) = 9.2 +/- 4.3kg/ l, A(2) = 4.2 +/- 0.8kg/ l, m(1) = 2.3 +/- 1.1 min(-1), and m(2) = 0.05 +/- 0.02 min(-1). The mean initial plasma concentration Cp(t = 0) = 8.0 +/- 2.7mM was compatible with estimated 8.6mM. Without T (*)(2)-correction distribution phase parameters A1, m1, and Cp( t = 0) were underestimated. In tumors, neglect of T-2(*) effects yielded mean Ktrans values which were reduced by 14% ( P < 0.05), whereas ve showed only a slight non-significant reduction. Simultaneous measurement of Delta R-1 and Delta R-2(*) studied in highly and poorly vascularized and (pre-)necrotic tumor regions revealed complementary behavior of both parameters with respect to vascular properties. In conclusion, the presented measurement technique is a promising tool for dynamic MRI applications studied in animal models at high field strengths and/or with CA of high relaxivities, as it combines classical DCE MRI integrating AIF assessment with dynamic T-2(*) measurement.