Oxygen Metabolic Mapping by MRI-BOLD technique

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Background : Evaluation of regional oxygen metabolism of the brain in acute ischemia provides useful information for salvage of penumbral area, but PET is the only available method for this purpose at present We carried out a preliminary study to develop a new approach by using MR imaging.Methods : We used the equations proposed by Davis et al.^1 :Δ BOLD = M{1-(rCMRO_2)^β(Δ CBF)}^<α-β>where M is dependent on tissue dHb content If CMRO_2 is not affected by acetazolamide administration, we can get rCMRO_2 value from the following equation :rCMRO_2=ΔCBF^<1-α/β>(1-ΔBOLD/M)^<1/β>α and β come from the following equations : CBV=CBF^α,1/T_2^*=C(1-Y) ^βCBV_v, where Y is venous blood oxygenation level and CBV_v is venous cerebral blood volume. Here, we set α=0.38 and β=1.5.Pairs of BOLD and CBF measurements were performed in five patients with large vessel occlusion. We used Ostargaad' s algorism ^2 for CBF measurements. We measured venous output function from the sagittal sinus to correct the partial volume effect of arterial input function(AIF). For verification of the results, the patients were also underwent PET study.Results : There was reasonable gray/white contrast in the rCMRO_2 map obtained by BOLD/perfusion methods in all patients. In a patient with left MCA occlusion, the area of lowered rCMRO_2 seemed to be in agreement with that of the PET(Figure).Conclusions : We showed that oxygen metabolism could be visualized on the map by the combination of CBF and BOLD measurements. Although careful verification is necessary, this technique has a potential for clinical use.