Quantification of CMRO2 and CBF Using Simultaneous NIRS and FMRI

Sungho Tak¹, Jong Chul Ye¹

This paper introduces an accurate technique to estimate the cerebral metabolic rate of oxygen (CMRO₂) and cerebral blood flow (CBF) using simultaneously measured near infrared spectroscopy (NIRS) and blood oxygenation level dependent (BOLD) fMRI signals. Owing to simultaneous acquisition of both fMRI and NIRS, separate hypercapnia condition or arterial spin labeling (ASL) acquisition are not necessary to quantify CMRO₂ and CBF, which greatly improves the accuracy of the proposed method. The dynamic coupling ratio of CBF changes to CMRO₂ changes has been also investigated. Experimental results using finger tapping task showed that the activation pattern of CBF calculated using NIRS-SPM software is more specific to the primary motor cortex than fMRI BOLD and NIRS-HbR signal. Furthermore, the dynamic couple ratio coincides with the existing results from the literature.