Iida H, Rhodes C G, Araujo L I, Yamamoto Y, de Silva R, Maseri A, Jones T
MRC Cyclotron Unit Hammersmith Hospital, London, UK.
Circulation. 1996 Aug 15;94(4):792-807. doi: 10.1161/01.cir.94.4.792.
A method has been developed to measure the regional myocardial metabolic rate of oxygen consumption (rMMRO2) and oxygen extraction fraction (rOEF) quantitatively and noninvasively in humans by use of 15O2 inhalation and positron emission tomography. This article describes the theory, an error analysis of the technique, and procedures of the method used in a human feasibility study.
Inhaled 15O2 is transported to peripheral tissues, where it is converted to 15O-labeled water of metabolism, which exchanges with the relatively large extravascular tissue space. Quantification of this buildup of radioactivity allows the calculation of rMMRO2 and rOEF. However, a correction for the spillover of the pulmonary gas radioactivity signal into myocardial regions is required and has been made by use of a gas volume distribution estimated from the transmission scan. This was validated by comparative measurements using the inert gas [11C]CH4 in four greyhounds. Spillover of the cardiac chamber radioactivity has been corrected for with an inhaled [13O]CO (blood volume) scan. The underestimation of myocardial radioactivity due to wall motion and thickness has been corrected for by use of values of tissue fraction obtained from the flow measurement [15OKCO2 scan). Values of rOEF were similar (within 4%) whether obtained from gas volume measurements determined from the transmission or [11C]CH4 scan data. 15O2 scan information from six healthy volunteers showed a clear distribution of myocardial radioactivity after the vascular and pulmonary gas 15O background was subtracted. Subsequent compartmental analysis resulted in values for rOEF and rMMRO2 of 0.60 +/- 0.11 and 0.10 +/- 0.03 mL.min-1.g-1 in the human myocardium at rest.
The results of this study are in good agreement with established values. This is the first known approach to allow the direct quantitative determination of rOEF and oxygen metabolism to be made noninvasively on a regional basis.
已开发出一种方法，通过吸入(^{15}O_2)和正电子发射断层扫描，在人体中定量且无创地测量局部心肌氧消耗代谢率（rMMRO2）和氧摄取分数（rOEF）。本文描述了该技术的理论、误差分析以及在人体可行性研究中使用的方法步骤。
吸入的(^{15}O_2)被输送到外周组织，在那里它被转化为代谢的(^{15}O)标记水，与相对较大的血管外组织间隙进行交换。对这种放射性积累的定量分析可计算出rMMRO2和rOEF。然而，需要对肺气体放射性信号溢出到心肌区域进行校正，已通过利用从透射扫描估计的气体体积分布来进行校正。这通过在四只灵缇犬中使用惰性气体([^{11}C]CH_4)的对比测量得到验证。已通过吸入([^{13}O]CO)（血容量）扫描对心腔放射性的溢出进行了校正。由于壁运动和厚度导致的心肌放射性低估已通过使用从流量测量([^{15}OKCO_2)扫描）获得的组织分数值进行了校正。无论从透射或([^{11}C]CH_4)扫描数据确定的气体体积测量中获得，rOEF值都相似（在4%以内）。来自六名健康志愿者的(^{15}O_2)扫描信息显示，在减去血管和肺气体(^{15}O)背景后，心肌放射性有明显分布。随后的房室分析得出，静息状态下人体心肌的rOEF和rMMRO2值分别为(0.60\pm0.11)和(0.10\pm0.03 mL·min^{-1}·g^{-1})。
本研究结果与既定值高度一致。这是已知的第一种能够在区域基础上无创地直接定量测定rOEF和氧代谢的方法。
