Topographic mapping of oxygen extraction and cerebral venous blood volume fraction in Brain tumors using quantitative BOLD: A case report

Abstract

Background: While oxygen extraction fraction (OEF) reflects the underlying variations in cerebral brain oxygen metabolism, tissue voxels having elevated volume fraction of blood vessel network with deoxygenated blood, will apparently contribute to higher cerebral venous blood volume fraction (CVBVF). This Case report examines the difference in intra and peri-tumoral topographical patterns of OEF and CVBVF in cases of a meningioma tumor (Case-I) and a low- grade glioma (Case-II). Methods: Using a “static dephasing regime” BOLD model, we use the BOLD signal model containing parameters representing OEF and CVBVF. For each voxel in the region of interest, the parameters are solved by non-linearly fitting the signal model using paired differences between logarithms of the measured echo signal after inhomogeneity correction. Results: OEF and CVBVF maps in Case-I reveals an interesting phenomenon in the peritumoral parenchyma showing reduced OEF and increased CVBVF levels. The uniformly low CVBVF and elevated OEF in Case-II indicates that even with less density of vasculature, the region extracts higher amount of oxygen. Conclusion: While topographic mapping using qBOLD revealed elevated levels of intra-tumoral OEF for both cases, the pattern of CVBVF variation was uniformly low in Case-II.