Department of Electrical and Computer Engineering, University of Calgary, Calgary, Alberta, Canada.
J Magn Reson Imaging. 2010 Mar;31(3):753-6. doi: 10.1002/jmri.22052.
To investigate the impact of tracer recirculation on estimates of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT).
The theoretical model used to derive CBF, CBV, and MTT was examined. CBF and CBV estimates with and without tracer recirculation were compared in computer simulations to examine the effects of tracer recirculation.
The equations used to derive CBF, CBV, and MTT assume that the arterial input function and tissue tracer signals define the input and output signals, respectively, of a linear time-invariant system. As a result of the principle of superposition, these perfusion parameters are immune to tracer recirculation, which was confirmed by computer simulation. However, limited acquisition durations can lead to CBV and CBF errors of up to 50%.
Tracer recirculation does not impact estimation of CBF, CBV, or MTT. However, previous approaches used to remove recirculation effects may be beneficial when used to compensate for limited acquisition durations in which the passage of the bolus is not adequately captured.
探讨示踪剂再循环对脑血流量（CBF）、脑血容量（CBV）和平均通过时间（MTT）估计的影响。
检查了用于推导 CBF、CBV 和 MTT 的理论模型。通过计算机模拟比较了有无示踪剂再循环的 CBF 和 CBV 估计值，以检查示踪剂再循环的影响。
用于推导 CBF、CBV 和 MTT 的方程假设动脉输入函数和组织示踪剂信号分别定义了线性时不变系统的输入和输出信号。由于叠加原理，这些灌注参数不受示踪剂再循环的影响，这通过计算机模拟得到了证实。然而，有限的采集时间会导致 CBV 和 CBF 误差高达 50%。
示踪剂再循环不影响 CBF、CBV 或 MTT 的估计。然而，当用于补偿由于未能充分捕获团注通过而导致的采集时间有限的情况时，先前用于去除再循环效应的方法可能是有益的。
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