T1(rho) imaging of murine brain tumors at 4 T

Rationale and Objectives. The goal of this study was to evaluate the utilit y of T1(p) weighting in magnetic resonance imaging of murine brain tumors. Materials and Methods. S91 Cloudman melanoma was implanted in mouse brains (n = 4). A T2-weighted spin-echo (SE) and a T1(p)-weighted fast SE-based se quence were performed on a 4-T clinical imager. T2 and T1(p) maps were comp uted. The tumor-to-normal-tissue contrast was compared between T2-weighted, T1(p)-weighted, proton-density-weighted, and pre- and postcontrast T1-weig hted SE images. Results. The tumor-tissue contrast of the T1(p)-weighted images was similar to that of the T2-weighted images but less than that of the postcontrast T 1-weighted images, The T1(p)-weighted images provided better definition of tumor boundaries than T2-weighted images. At spin-locking powers of 0.5 and 1.5 kHz, the T1(p) of the tumor was 64.0 msec +/- 0.46 and 68.65 msec +/- 0.59. respectively. There was no significant inter- or intra-animal variati on in Tip for tumor or normal brain cortex. Conclusion. T1(p)-weighted imaging performed at low spin-lock strengths qua litatively depicted tumor borders better than proton-density or T2-weighted imaging and could be useful in treatment planning when combined with other imaging sequences.