von Oettingen G, Bergholt B, Ostergaard L, Jensen L C, Gyldensted C, Astrup J
Department of Neurosurgery, Aarhus University Hospital, Denmark.
Neuroradiology. 2000 Mar;42(3):168-73. doi: 10.1007/s002340050039.
The noninvasive xenon-enhanced CT (Xe CT) cerebral blood flow (CBF) method has been used in patients with severe traumatic brain injury (TBI) to identify the blood-flow thresholds for the development of irreversible ischaemia or infarction following severe TBI. Quantitative regional CBF (rCBF) estimates are based on the assumption of identity between the end-tidal xenon concentration curve, used as the input function, and the arterial xenon concentration curve, being the true input function to the brain. Accordingly, rCBF data addressing the issue of ischaemia should be viewed in relation to possible deviations between the end-tidal and arterial xenon concentration curves. To evaluate this possible source of error, we studied five patients with severe TBI (Glasgow coma score < or =7) who also had pulmonary trauma. CBF was studied with the Xe CT CBF method and flow rates were determined by fitting the Kety equation to each CT voxel using either the end-tidal or the arterial xenon curve as input function. In all patients rCBF estimates were lower using the end-tidal xenon curve than with the arterial xenon curve; the mean underestimation was 20.3% in gray metter and 17.3 % in white matter. The deviation between the end-tidal and arterial xenon concentration curves should be considered as a source of error when defining critical flow values according to the flow thresholds of tissue viability.
无创氙增强CT（Xe CT）脑血流量（CBF）测定方法已用于重度创伤性脑损伤（TBI）患者，以确定重度TBI后不可逆缺血或梗死发生时的血流阈值。定量局部脑血流量（rCBF）评估基于这样一个假设：用作输入函数的潮气末氙浓度曲线与作为大脑真正输入函数的动脉氙浓度曲线是一致的。因此，在考虑潮气末和动脉氙浓度曲线之间可能存在的偏差时，应审视针对缺血问题的rCBF数据。为评估这一可能的误差来源，我们研究了5例重度TBI（格拉斯哥昏迷评分≤7）且伴有肺损伤的患者。采用Xe CT CBF方法测定脑血流量，并通过将Kety方程拟合到每个CT体素，分别以潮气末或动脉氙曲线作为输入函数来确定血流速度。在所有患者中，使用潮气末氙曲线得出的rCBF估计值均低于使用动脉氙曲线得出的估计值；灰质平均低估20.3%，白质平均低估17.3%。根据组织存活的血流阈值定义临界血流值时，应将潮气末和动脉氙浓度曲线之间的偏差视为误差来源。
