Jaggi J L, Noordergraaf A
Department of Neurology, University of Pennsylvania, Philadelphia.
J Cereb Blood Flow Metab. 1995 Mar;15(2):321-8. doi: 10.1038/jcbfm.1995.37.
Activation studies employing the noninvasive xenon-133 technique are widely used to investigate the cerebral circulation. Typical examples are the investigation of hemispheral specialization of higher cortical function with cognitive activation or the assessment of the hemodynamic reserve in occlusive cerebrovascular disease by CO2 inhalation. Traditionally, in studies using this technique, there is the requirement of a circulatory steady state during the measurement. Due to limitations in the duration of the stimulus or habituation to the stimulus, the basic assumption is often violated. In this study we investigated with the aid of a computer model to what extent blood flow measurement results are affected by non-steady-state blood flow. The findings indicate that cortical activation need not extend throughout the whole measurement to be detectable. Maintenance of activation for at least 5 min is sufficient for a successful measurement. In addition, the results show that the activation should be fully established when the measurement starts to achieve maximal sensitivity. Delay in activating the circulation will result in attenuated responses, especially if the stimulus is delayed beyond 2 min.
采用无创性氙 - 133技术的激活研究被广泛用于研究脑循环。典型的例子包括通过认知激活来研究高级皮质功能的半球特化，或通过吸入二氧化碳来评估闭塞性脑血管疾病中的血流动力学储备。传统上，在使用该技术的研究中，测量期间需要循环稳态。由于刺激持续时间的限制或对刺激的适应，这一基本假设常常被违反。在本研究中，我们借助计算机模型研究了非稳态血流在多大程度上影响血流测量结果。研究结果表明，皮质激活无需在整个测量过程中持续存在即可被检测到。激活至少维持5分钟足以成功测量。此外，结果表明，测量开始时激活应充分建立以实现最大灵敏度。循环激活延迟将导致反应减弱，特别是如果刺激延迟超过2分钟。
