T1ρ imaging of murine brain tumors at 4 T

Rationale and Objectives. The goal of this study was to evaluate the utility 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 sequence were performed on a 4-T clinical imager. T2 and T1(p) maps were computed. The tumor-to-normal-tissue contrast was compared between T2-weighted, T1(p)-weighted, proton-density-weighted, and pre- and postcontrast T1-weighted 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 T1-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 variation in Tip for tumor or normal brain cortex. Conclusion. T1(p)-weighted imaging performed at low spin-lock strengths qualitatively depicted tumor borders better than proton-density or T2-weighted imaging and could be useful in treatment planning when combined with other imaging sequences.