154 Chapter 6 Figure 2. Data analysis steps for the BOLD and ASL MRI data. 1. BOLD time series and PetCO2 traces were used to generate CVR and hemodynamic lag maps. 2. Quantitative AAT and CBF maps were generated based on Multi-delay ASL data 3. CSF and previously resected or irradiated brain metastases were excluded from all the maps. 4. Based on the CVR values, the brain was segmented into non-steal and steal regions of interest (ROI). Parameter maps were analyzed comparatively (shown in grey). For analysis A, the brain was divided into GM, WM, edema and brain metastases ROIs for each individual and the mean and standard deviation were calculated for each hemodynamic parameter map (CBF, AAT, CVR and hemodynamic lag) for each tissue-ROI. For analysis B, the AAT data were sorted and the AAT maps were divided into ROIs each containing 5% of the sorted data (‘5%-bins’ - visualized by the colored histogram) for each individual. For each bin-ROI the mean value of each hemodynamic parameter map (CBF, AAT, CVR and hemodynamic lag) was calculated and used in subsequent repeated-measures correlation analysis. Abbreviations: AAT, arterial arrival time; ASL, arterial spin labeling; BM, brain metastases; BOLD, blood oxygenation level-dependent; CBF, cerebral blood flow; CSF, cerebrospinal fluid; CVR, cerebrovascular reactivity; GM, grey matter; PetCO2, end-tidal CO2; ROI, region of interest; WM, white matter.
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