Evaluation of tumour vascular distribution and function using immunohistochemistry and BOLD fMRI with carbogen inhalation.

Aim To evaluate oxygenation changes in rat subcutaneous C6 gliomas using blood-oxygen-level dependent (BOLD) functional magnetic resonance imaging (fMRI) combined with non-haemodynamic response function (non-HRF) analysis. Materials And Methods BOLD fMRI were performed during carbogen inhalation in 20 Wistar rats bearing gliomas. Statistical maps of spatial oxygenation changes were computed by a dedicated non-HRF analysis algorithm. Three types of regions of interest (ROIs) were defined: (1) maximum re-oxygenation zone (ROI max ), (2) re-oxygenation zones that were less than the maximum re-oxygenation (ROI non-max ), and (3) zones without significant re-oxygenation (ROI none ). The values of percent BOLD signal change (PSC), percent enhancement (ΔSI), and significant re-oxygenation (T) were extracted from each ROI. Tumours were sectioned for histology using the fMRI scan orientation and were stained with haematoxylin and eosin and CD105. The number of microvessels (MVN) in each ROI was counted. Differences and correlations among the values for T, PSC, ΔSI, and MVN were determined. Results After carbogen inhalation, the PSC significantly increased in the ROI max areas ( p none areas (20/20). Some changes occurred in a minority of the ROI non-max areas (3/60) corresponding to tumour necrosis. MVN and PSC ( R =0.59, p =0.01) were significantly correlated in the ROI max areas. In the ROI non-max areas, MVN was significantly correlated with PSC ( R =0.55, p =0.00) and ΔSI ( R =0.37, p =0.00). Conclusions Statistical maps obtained via BOLD fMRI with non-HRF analysis can assess the re-oxygenation of gliomas.