Measurement of physiological parameters during brain activation usingfMRI

The changes in cerebral metabolic rate of oxygen consumption (CMRO ₂), cerebral blood flow (CBF) and cerebral blood volume (CBV) are correlated with the changes in blood deoxyhemoglobin content that determine the blood oxygen level-dependent (BOLD) signal. Both CBF and CBV have been widely measured and well understood by previous studies, while CMRO₂ measurement is still in development. The central hypothesis of the proposed study is that those physiological parameters can be simulated by biophysical models with fixed parameters and measured directly. The goal of this proposal is to test the central hypothesis.; In summary, this dissertation focused on measurements of physiological parameters in two image modalities. Cerebral blood flow (CBF), cerebral blood volume (CBV), blood oxygenation level dependent (BOLD) signal, and cerebral metabolic rate of oxygen consumption (CMRO₂) were studied in chapters II to IV. It is going to help to understand human brain metabolism during neuronal activity. Chapter V compared two image modalities—MR and PET and furthermore determine β* in existing MR model for clinic use. This dissertation shows that the characteristics of BOLD signal can be examined by balloon model in both block-designed and event-related designed paradigm. The dynamic change of CMRO₂ and OER using event-related fMRI can be measured using existing biophysical model proposed by Kim and his coworker in 1999. Furthermore, PET experiment was used to determine the parameters contained in Kim's model. This dissertation verify the central hypothesis that we made early on and we expect CMRO₂ model with fixed parameters will bring a big impact in research and clinical use.