The use of Gd-DOTA in magnetic resonance imaging of experimentally induced mammary tumors

Abstract Gd-DOTA contrast enhancement of MR images was evaluated on induced mammary tumors in female rats. A single intravenous injection of the carcinogenic N -nitrosourea ENU was administered to Wistar rats; this simple treatment led to a high percentage of mammary tumors without causing death. All the induced tumors were adenocarcinoma and their heterogeneousness depended on their size. The induced tumors did not have intra- or extravascular inflammatory spaces caused by heterotopic lesions, as is the case with implanted tumors. Before injection of Gd-DOTA, appearance of the patchy internal structure was clearly demonstrated on spin-echo images performed with long repetition times. Three doses of the paramagnetic contrast agent (0.1, 0.2, and 0.5 mmol/kg) were evaluated on two different T 1 -weighted MR sequences. Images were recorded before and repeatedly after intravenous injection of Gd-DOTA, and signal intensities and relaxation times were measured. On images acquired with the spin-echo 500 28 as well as the inversion-recovery 928/26/300 sequences, the results showed that 0.2 mmol/kg Gd-DOTA was the optimal dose for contrast enhancement and for clear visualization of the heterogeneousness of the mammary tumor.