Department of Radiology and Nuclear Medicine, Akita Research Institute of Brain and Blood Vessels, 6-10 Senshu-Kubota Machi, Akita, Japan.
J Cereb Blood Flow Metab. 2010 Jul;30(7):1296-305. doi: 10.1038/jcbfm.2010.13. Epub 2010 Feb 17.
Regional cerebral blood flow (CBF) and oxygen metabolism can be measured by positron emission tomography (PET) with (15)O-labeled compounds. Hemoglobin (Hb) concentration of blood, a primary determinant of arterial oxygen content (C(a)O(2)), influences cerebral circulation. We investigated interindividual variations of CBF, cerebral blood volume (CBV), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO(2)) in relation to Hb concentration in healthy human volunteers (n=17) and in patients with unilateral steno-occlusive disease (n=44). For the patients, data obtained only from the contralateral hemisphere (normal side) were analyzed. The CBF and OEF were inversely correlated with Hb concentration, but CMRO(2) was independent of Hb concentration. Oxygen delivery defined as a product of C(a)O(2) and CBF (C(a)O(2) CBF) increased with a rise of Hb concentration. The analysis with a simple oxygen model showed that oxygen diffusion parameter (L) was constant over the range of Hb concentration, indicating that a homeostatic mechanism controlling CBF is necessary to maintain CMRO(2). The current findings provide important knowledge to understand the control mechanism of cerebral circulation and to interpret the (15)O PET data in clinical practice.
区域脑血流（CBF）和氧代谢可以通过正电子发射断层扫描（PET）用（15）O 标记化合物来测量。血液的血红蛋白（Hb）浓度，是动脉氧含量（C(a)O(2)）的主要决定因素，影响脑循环。我们研究了健康人类志愿者（n=17）和单侧狭窄闭塞性疾病患者（n=44）的 CBF、脑血容量（CBV）、氧提取分数（OEF）和脑氧代谢率（CMRO(2)）与 Hb 浓度之间的个体间差异。对于患者，仅分析来自对侧半球（正常侧）的数据。CBF 和 OEF 与 Hb 浓度呈负相关，但 CMRO(2)与 Hb 浓度无关。氧输送定义为 C(a)O(2)和 CBF 的乘积（C(a)O(2) CBF）随着 Hb 浓度的升高而增加。用简单的氧模型进行的分析表明，氧扩散参数（L）在 Hb 浓度范围内保持恒定，表明控制 CBF 的自动平衡机制是维持 CMRO(2)所必需的。目前的研究结果为理解脑循环的控制机制以及在临床实践中解释（15）O PET 数据提供了重要知识。
