Blood-oxygenation-level-dependent (BOLD) MRI responses to CO2 and O2 inhalation in brain gliomas.

PURPOSE: Cerebrovascular abnormalities are intricately involved in gliomas. While static cerebrovascular properties such as cerebral blood flow, volume, and permeability have been extensively studied, dynamic vascular parameters have not been fully understood. This study aimed to characterize the vascular responses to CO2 and O2 inhalation in brain gliomas.

METHODS

In 15 glioma patients, concomitant CO2 and O2 inhalation was applied while BOLD MR images were continuously acquired for nine minutes, resulting in the measurement of O2-reactivity, CO2-reactivity, and bolus arrival time (BAT). Vascular parameters were compared between the tumor regions and contralateral healthy tissue using Student t-tests. The dependence of vascular parameters on glioma grade, glioma subtypes, and molecular biomarkers were assessed using a multiple linear regression.

RESULTS

Visual inspection suggested that reliable O2-reactivity, CO2-reactivity, and BAT maps could be obtained in every patient. Compared to the contralateral healthy tissue, glioma regions on average revealed a diminished O2-reactivity (p < 0.001) and CO2-reactivity (p < 0.001), but a lengthened BAT (p < 0.001). Intra-tumoral heterogeneity in the vascular parameters between core and periphery was also observed. Astrocytomas had a lower CO2-reactivity (p = 0.014) and a longer BAT (p = 0.012) relative to oligodendrogliomas. Glioma grade had no association with O2-reactivity, CO2-reactivity, or BAT. Patients who lost ATRX expression had a lower CO2- and O2-reactivity (p = 0.005 and p = 0.035) compared to patients who retained ATRX expression.

CONCLUSIONS

Gliomas are associated with abnormal CO2- and O2-reactivity measured with MRI. These dynamic parameters may provide new insights into the vascular pathophysiology in gliomas.