Data from: Increase in extraction of I-123 iomazenil in patients with chronic cerebral ischemia

Background: Cerebral extraction of diffusively distributed substances like oxygen has been suggested to change according to the cerebral blood flow (CBF) and status of the microvasculature. The relationships between the cerebral extraction of diffusively distributed lipophilic tracers and the severity of cerebral ischemia has not yet been clarified. In the present study, we attempted to elucidate the association between the extraction fraction of the lipophilic tracer I-123 iomazenil (IMZ) (IMZ-EF) and the oxygen extraction fraction (OEF) derived from O-15 PET in patients with chronic steno-occlusive disease of internal carotid artery (ICA) or middle cerebral artery (MCA). Methods: Seven patients with unilateral chronic severe stenosis or occlusion of the middle cerebral/internal cerebral artery were prospectively recruited for this study. All the patients underwent both O-15 PET and quantitative I-123 IMZ SPECT. Parametric images derived from the PET and SPECT scans were anatomically normalized and evaluated by automated image analysis based on the volume-of-interest template. Results: The asymmetry index (AI) of IMZ-EF was shown to significantly correlated with the AI of OEF (r = 0.562, P < 0.001) in the internal carotid artery perfusion area. Strong and significant correlation between the AI of the influx rate constant K1 of IMZ and the AI of the cerebral metabolic rate of oxygen (r = 0.552, P = 0.001) was clarified. Conclusions: Our results suggested that the transportation efficiency of I-123 IMZ into the brain tissue was an indicator for evaluating severity of cerebral ischemia in patients with chronic steno-occlusive disease of ICA or MCA. Cerebral metabolic state can possibly be estimated by I-123 IMZ SPECT without cyclotron.背景：已有研究表明，氧气等弥散性分布物质的脑摄取量会随脑血流量（cerebral blood flow, CBF）及微血管状态发生变化。目前尚不清楚弥散性亲脂性示踪剂的脑摄取量与脑缺血严重程度之间的关联。本研究旨在明确亲脂性示踪剂碘-123-碘马唑仑（I-123 iomazenil, IMZ）的摄取分数（IMZ-EF），与慢性颈内动脉（internal carotid artery, ICA）或大脑中动脉（middle cerebral artery, MCA）狭窄闭塞性疾病患者中，由O-15正电子发射断层扫描（O-15 PET）得到的氧摄取分数（oxygen extraction fraction, OEF）之间的关联。 方法：本研究前瞻性纳入7例单侧慢性重度大脑中动脉/颈内动脉狭窄或闭塞患者。所有患者均接受O-15正电子发射断层扫描（O-15 PET）与定量碘-123-碘马唑仑单光子发射计算机断层扫描（single-photon emission computed tomography, SPECT）。将PET与SPECT扫描得到的参数图像进行解剖学归一化处理，并基于感兴趣体积模板通过自动化图像分析进行评估。 结果：在颈内动脉灌注区域内，碘-123-碘马唑仑摄取分数（IMZ-EF）的不对称指数（asymmetry index, AI）与氧摄取分数（OEF）的不对称指数呈显著相关（r=0.562，P<0.001）。同时明确，碘-123-碘马唑仑的摄取速率常数K1的不对称指数与脑氧代谢率的不对称指数呈强显著相关（r=0.552，P=0.001）。 结论：本研究结果表明，碘-123-碘马唑仑向脑组织的转运效率可作为评估慢性颈内动脉/大脑中动脉狭窄闭塞性疾病患者脑缺血严重程度的指标。无需回旋加速器即可通过碘-123-碘马唑仑SPECT估算脑代谢状态。