Statistical analysis was performed using OriginPro® 8 software (OriginLab, Wellesley Hills, MA, USA). Student’s paired t test was performed to determine statistical significance of the difference in signal between the tumor regions and corresponding contralateral brain or animals undergoing sham surgery. Statistics assessment was also used to determine the difference between different doses and time points. Linear regression was used to compare the size of the tumor and contralateral normal brain fluorescence. This information was reported as a Pearson correlation coefficient (r). Results were considered statistically significant at a P < 0.05.