Herholz K
Stroke. 1985 Mar-Apr;16(2):301-6. doi: 10.1161/01.str.16.2.301.
Based on data from routine intravenous Xe133-rCBF studies in 50 patients, using Obrist's algorithm the effect of counting rate statistics and amount of recirculating activity on reproducibility of results was investigated at five simulated counting rate levels. Dependence of the standard deviation of compartmental and noncompartmental flow parameters on recirculation and counting rate was determined by multiple linear regression analysis. Those regression equations permit determination of the optimum accuracy that may be expected from individual flow measurements. Mainly due to a delay of the start-of-fit time an exponential increase in standard deviation of flow measurements was observed as recirculation increased. At constant start-of-fit, however, a linear increase in standard deviation of compartmental flow parameters only was found, while noncompartmental results remained constant. Therefore, and in regard to other studies of potential sources of error, an upper limit of 2.5 min for the start-of-fit time and usage of noncompartmental flow parameters for measurements affected by high recirculation are suggested.
基于50例患者常规静脉注射Xe133 - rCBF研究的数据，使用奥布里斯算法，在五个模拟计数率水平下，研究了计数率统计和再循环活度量对结果可重复性的影响。通过多元线性回归分析确定了房室和非房室血流参数标准差对再循环和计数率的依赖性。这些回归方程允许确定个体血流测量可能预期的最佳准确性。主要由于拟合开始时间的延迟，随着再循环增加，观察到血流测量标准差呈指数增加。然而，在恒定的拟合开始时间，仅发现房室血流参数标准差呈线性增加，而非房室结果保持不变。因此，结合其他潜在误差来源的研究，建议拟合开始时间上限为2.5分钟，并对受高再循环影响的测量使用非房室血流参数。
