Oxygen Metabolic Mapping by MRI-BOLD technique

背景：急性脑缺血时局部氧代谢的评估为半影区的挽救提供了有用的信息，但正电子发射计算机断层扫描是目前唯一有效的方法。我们进行了初步的研究，以开发一种利用磁共振成像的新方法。方法：采用Davis等人提出的公式：ΔBOLD=M{1-(RCMRO_2)^β(ΔCbF)}^&lt；α-β&gt；其中M依赖于组织dHb的含量如果CMRO_2不受乙酰唑胺给药的影响，我们可以从以下公式中得到rCMRO_2的值：rCMRO_2=ΔCbF&lt；1-α/β&gt；(1-ΔBOLD/M)^&lt；1/β&gt；α和β来自以下公式：Cbv=Cbf^α，1/T_2^*=C(1-Y)βCbv_v，其中Y为静脉血氧分压水平，Cbv_v为静脉脑血容量。在此，我们设置α=0.38，β=1.5。对5例大血管闭塞患者进行了BOLD和CBF测量。我们使用Ostargaad的S算法^2来测量脑血流量。测量矢状窦的静脉输出功能，以校正动脉输入功能(AIF)的部分容量效应。结果：所有患者的BLOD/灌注法rCMRO2图均有合理的灰白对比。在1例左侧大脑中动脉闭塞患者中，rCMRO2降低的面积似乎与PET的面积一致(图)。结论：结合CBF和BOLD测量，我们可以在MAP上显示氧代谢。尽管有必要进行仔细的验证，但这项技术具有临床应用的潜力。

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.