Evaluation of equivalence of upslope method-derived myocardial perfusion index and transfer constant based on two-compartment tracer kinetic model

T. Ichihara, R. George, J. Lima, Y. Ikeda, A. Lardo
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引用次数: 5

Abstract

The purpose of this study was to describe the upslope method-derived myocardial perfusion index using the parameters based on a tracer kinetic model of iodixanol contrast agent and to validate this theoretically derived relationship using an ischemic canine model. The established modified Kety model was used to describe the extravascular diffusion of iodixanol contrast agent, which undergoes no cellular uptake or metabolism. This model consists of two functional compartments, one describing the vascular compartment and the second representing all myocardial capillaries, interstitium, and cells. These compartments are connected by two rate constants, K1 and k2, which represent the first-order transfer constants from the left ventricular (LV) blood to myocardium and from myocardium to the vascular system, respectively. In the early phase after the arrival of contrast agent in the myocardium, the relationship between K1 and the concentrations of iodixanol contrast agent in the myocardium and arterial blood (LV blood) is described by K1 = {dCmyo(tpeak)/dt}/Ca(tpeak) (Eq. 1), where Cmyo(t) is the relative concentration of iodixanol contrast agent in the myocardium at time t, Ca(t) is the relative concentration of iodixanol contrast agent in the LV blood, and tpeak is the time at the peak of Ca(t) and maximum upslope of Cmyo(t). Six canine models of left anterior descending (LAD) artery stenosis were prepared and underwent first-pass contrast-enhanced mult-detector row computed tomography (MDCT) perfusion imaging during adenosine infusion (0.14–0.21 mg/kg/min) to study a wide range of flow rates. K1 was measured using the Patlak plot method and upslope method applied to time-attenuation curve data of the LV blood pool and myocardium. The results were compared against microsphere myocardial blood flow measurements. The Patlak plot-derived K1 and upslope method-derived K1 showed a good linear association. Regional K1 can be measured accurately using the upslope method-derived myocardial perfusion index based on a compartment model.
基于双室示踪动力学模型的上坡法心肌灌注指数和传递常数等效性评价
本研究的目的是利用基于碘二沙醇造影剂示踪动力学模型的参数来描述上坡法衍生的心肌灌注指数,并利用缺血犬模型验证这一理论推导的关系。采用所建立的改良Kety模型描述碘沙醇造影剂不经细胞摄取和代谢的血管外扩散。该模型由两个功能室组成,一个描述血管室,第二个代表所有心肌毛细血管、间质和细胞。这些室室由两个速率常数K1和k2连接,这两个速率常数分别代表从左心室(LV)血液到心肌和从心肌到血管系统的一级传递常数。在造影剂到达心肌后的早期,K1与心肌和动脉血(左室血)中碘二沙醇造影剂浓度的关系为K1 = {dCmyo(tpeak)/dt}/Ca(tpeak)(式1),其中Cmyo(t)为t时刻心肌中碘二沙醇造影剂的相对浓度,Ca(t)为左室血中碘二沙醇造影剂的相对浓度,tpeak为Ca(t)峰值和Cmyo(t)最大上坡时间。制备6只犬左前降支(LAD)狭窄模型,在腺苷输注(0.14 ~ 0.21 mg/kg/min)过程中进行第一遍对比增强多排计算机断层扫描(MDCT)灌注成像,研究大范围血流速率。采用Patlak图法和上斜率法测量左室血池和心肌时间衰减曲线数据。将结果与微球心肌血流量测量结果进行比较。Patlak图导出的K1和上坡法导出的K1表现出良好的线性相关性。基于室室模型的上斜法心肌灌注指数可以准确测量区域K1。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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