Kato Hiroki, Isohashi Kayako, Shimosegawa Eku, Hatazawa Jun
Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Department of Molecular Imaging of Medicine, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
PLoS One. 2018 Jan 11;13(1):e0190720. doi: 10.1371/journal.pone.0190720. eCollection 2018.
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).
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.
The asymmetry index (AI) of IMZ-EF was shown to be 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.
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.
有研究表明，像氧气这类扩散性分布物质的脑摄取量会根据脑血流量（CBF）和微血管状态而发生变化。扩散性分布的亲脂性示踪剂的脑摄取量与脑缺血严重程度之间的关系尚未阐明。在本研究中，我们试图阐明亲脂性示踪剂 I-123 碘美普尔（IMZ）的摄取分数（IMZ-EF）与来自 O-15 PET 的氧摄取分数（OEF）在颈内动脉（ICA）或大脑中动脉（MCA）慢性狭窄闭塞性疾病患者中的关联。
本研究前瞻性纳入了 7 例大脑中动脉/大脑内动脉单侧慢性重度狭窄或闭塞的患者。所有患者均接受了 O-15 PET 和定量 I-123 IMZ SPECT 检查。从 PET 和 SPECT 扫描获得的参数图像进行了解剖学归一化，并基于感兴趣体积模板通过自动图像分析进行评估。
在颈内动脉灌注区域，IMZ-EF 的不对称指数（AI）与 OEF 的 AI 显著相关（r = 0.562，P < 0.001）。明确了 IMZ 的流入速率常数 K1 的 AI 与脑氧代谢率的 AI 之间存在强且显著的相关性（r = 0.552，P = 0.001）。
我们的结果表明，I-123 IMZ 进入脑组织的转运效率是评估 ICA 或 MCA 慢性狭窄闭塞性疾病患者脑缺血严重程度的一个指标。无需回旋加速器，通过 I-123 IMZ SPECT 可能估计脑代谢状态。
