Detection of T2 changes in an early mouse brain tumor

The aim of the study was to determine the effect of early tumor growth on T₂ relaxation times in an experimental glioma model. A 9.4-T magnetic resonance imaging (MRI) system was used for the investigations. An animal model (n=12) of glioma was established using an intracranial inoculation of U87MGdEGFRvIII cells. The imaging studies were performed from Day 10 through Day 13 following tumor inoculation. Tumor blood vessel density was determined using quantitative immunochemistry. Tumor volume was measured daily using MR images. T₂ values of the tumor were measured in five areas across the tumor and calculated using a single exponential fitting of the echo train. The measurements on Days 10 and 13 after tumor inoculation showed a 20% increase in T₂. The changes in T₂ correlated with the size of the tumor. Statistically significant differences in T₂ values were observed between the edge of the tumor and the brain tissue on Days 11, 12 and 13 (P=.014, .008, .001, respectively), but not on Day 10 (P=.364). The results show that T₂-weighted MRI may not detect glioma during an early phase of growth. T₂ increases in growing glioma and varies heterogenously across the tumor.