Consequences of using a simplified kinetic model for dynamic PET data.
Consequences of using a simplified kinetic model for dynamic PET data.
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发表时间：
1997-04
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通讯作者：
P. Coxson;R. H. Huesman;L. Borland
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作者：
P. Coxson;R. H. Huesman;L. Borland
我们比较了心肌中82Rb动力学的生理模型和两个降阶模型，以确定它们在从动态PET数据中评估生理参数的有效性。方法采用82Rb心肌三室模型模拟动态PET感兴趣区数据。模拟产生了8种不同的血流速度，反映了感兴趣的生理范围。用两种常用的降阶模型对模拟数据进行拟合，并将降阶模型的参数与生理参数进行比较。然后将这三个模型与添加了噪声的模拟数据进行了拟合。蒙特卡罗模拟被用来评估和比较降阶模型的诊断效用。使用描述长度标准来评估每个模型的拟合优度。最后，将模拟数据与实际动态PET数据的拟合结果进行了比较。结果降阶模型与三室模型的拟合无噪声模拟数据产生了模型误判现象，如流动参数偏差和非流动参数估计中的系统变化等。蒙特卡罗模拟表明，两室模型的一些参数估计在PET噪声水平下是高度可变的。与实际PET数据的拟合显示出类似的可变性。对于模拟数据和实际数据，对高、低流量下流动参数的单室模型估计值被几个S.D.S分开。在两室模型下，分离度约为一个标准差，因此很难在一次实验中区分高流量和低流量。固定非流动参数降低了两室模型中流动参数的变异性，而对单室模型中的变异性没有显著影响。拟合优度表明，在真实的噪声水平下，两个降阶模型都至少符合模拟数据以及产生数据的三室模型。结论82Rb动态PET数据的一室降阶模型可以有效地比较静息和负荷水平下的心肌血流速度。只有在对非流动参数使用先验值的情况下，两室模型才能区分流动。
UNLABELLED We compared a physiological model of 82Rb kinetics in the myocardium with two reduced-order models to determine their usefulness in assessing physiological parameters from dynamic PET data. METHODS A three-compartment model of 82Rb in the myocardium was used to simulate kinetic PET ROI data. Simulations were generated for eight different blood-flow rates reflecting the physiological range of interest. Two reduced-order models commonly used with myocardial PET studies were fit to the simulated data, and parameters of the reduced-order models were compared with the physiological parameters. Then all three models were fit to the simulated data with noise added. Monte Carlo simulations were used to evaluate and compare the diagnostic utility of the reduced-order models. A description length criterion was used to assess goodness of fit for each model. Finally, fits to simulated data were compared with fits to actual dynamic PET data. RESULTS Fits of the reduced-order models to the three-compartment model noise-free simulated data produced model misspecification artifacts, such as flow parameter bias and systematic variation with flow in estimates of nonflow parameters. Monte Carlo simulations showed some of the parameter estimates for the two-compartment model to be highly variable at PET noise levels. Fits to actual PET data showed similar variability. One-compartment model estimates of the flow parameter at high and low flow were separated by several s.d.s for both the simulated and the real data. With the two-compartment model, the separation was about one s.d., making it difficult to differentiate a high and a low flow in a single experiment. Fixing nonflow parameters reduced flow parameter variability in the two-compartment model and did not significantly affect variability in the one-compartment model. Goodness of fit indicated that, at realistic noise levels, both reduced-order models fit the simulated data at least as well as the three-compartment model that generated the data. CONCLUSION The one-compartment reduced-order model of 82Rb dynamic PET data can be used effectively to compare myocardial blood-flow rates at rest and stress levels. The two-compartment model can differentiate flow only if a priori values are used for nonflow parameters.