Heiss W-D, Sobesky J
Max Planck Institute for Neurological Research, Köln, Germany.
Keio J Med. 2008 Sep;57(3):125-31. doi: 10.2302/kjm.57.125.
The penumbra--tissue perfused below the flow threshold for functional disturbance but above that for maintenance of morphological integrity--is the target for therapy in acute ischemic stroke. Irreversible tissue damage and penumbra can be reliably identified by multitracer positron emission tomography (PET) which has severe limitations due to complexity, invasiveness and radiation exposure. Therefore other modalities served as surrogate markers, with diffusion/perfusion-weighted magnetic resonance imaging (DW/PW-MRI) and perfusion computed tomography (PCT) being applied widely in clinical routine. In order to evaluate the limitations of DW/PW-MRI a comparative study was performed in acute stroke patients in whom cerebral perfusion was assessed by perfusion-weighted magnetic resonance imaging (PW-MRI) and H2(15)O-PET, tissue damage was estimated by diffusion-weighted magnetic resonance imaging (DW-MRI) and 11C-flumazenil (FMZ) PET and DW/PW-MRI mismatch was related to the tissue with increased oxygen extraction fraction (OEF) as an indicator of penumbra. The lesions in DW-MRI and in FMZ-PET were reliable predictors of final infarct on late MRI, but DW-MRI showed a high false positive rate. PW-MRI was limited in estimating flow and yielded values comparable to H2(15)O-PET only in the range between 20 and 30 ml/100 g/min. The DW/PW-MRI mismatch overestimated the penumbra as determined by increased OEF. These limitations of DW/PW-MRI have to be considered if used for selection of patients for treatment and might have an impact on the outcome of clinical trials based on this surrogate marker.
半暗带——即灌注量低于功能障碍血流阈值但高于维持形态完整性血流阈值的组织——是急性缺血性卒中的治疗靶点。不可逆组织损伤和半暗带可通过多示踪剂正电子发射断层扫描（PET）可靠识别，但PET因复杂、有创及辐射暴露等问题存在严重局限性。因此，其他影像学方法作为替代标志物，其中弥散/灌注加权磁共振成像（DW/PW-MRI）和灌注计算机断层扫描（PCT）在临床实践中得到广泛应用。为评估DW/PW-MRI的局限性，对急性卒中患者进行了一项对比研究，通过灌注加权磁共振成像（PW-MRI）和H2(15)O-PET评估脑灌注，通过弥散加权磁共振成像（DW-MRI）和11C-氟马西尼（FMZ）PET评估组织损伤，并将DW/PW-MRI不匹配与氧摄取分数（OEF）增加的组织相关联，以此作为半暗带的指标。DW-MRI和FMZ-PET中的病变是晚期MRI上最终梗死灶的可靠预测指标，但DW-MRI显示出较高的假阳性率。PW-MRI在估计血流方面存在局限性，仅在20至30 ml/100 g/min范围内得出与H2(15)O-PET相当的值。DW/PW-MRI不匹配高估了由OEF增加所确定的半暗带。如果将DW/PW-MRI用于选择治疗患者，必须考虑这些局限性，并且这可能会对基于该替代标志物的临床试验结果产生影响。
