Identifying thresholds for penumbra and irreversible tissue damage
Identifying thresholds for penumbra and irreversible tissue damage
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DOI：
10.1161/01.str.0000143329.81997.8a
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发表时间：
2004-11-01
期刊：
影响因子：
8.3
通讯作者：
Hesselmann, V
中科院分区：
文献类型：
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作者：
Heiss, WD;Sobesky, J;Hesselmann, V
弥散加权MRI（DWI）结合灌注加权MRI（PWI）已成为一种广泛接受的模式，用于选择适合急性治疗的患者，如果这些程序之间的不匹配表明有活性的半影组织。然而，DWI以及PWI产生半定量的措施，限制了不可逆损伤和潜在的可行半影组织的定义。如果将个体患者的结果与正电子发射断层扫描（PET）获得的血流、氧代谢和苯二氮卓类受体结合的测量结果进行比较，则可以更好地理解PWI/DWI的这些局限性。在3组患者中进行PET和MRI的对比研究：（1）在12例急性卒中患者中，比较DWI（中位数，症状发作后6.5小时）和C-11-氟马西尼（FMZ）PET（中位数，DWI和PET之间85分钟）的结果与24至48小时后T2加权MRI上的梗死扩展。(2)在11例急性卒中患者中，将PWI（中位数，症状发作后8小时）的结果与[O-15]H2O PET（PWI和PET之间间隔60分钟）获得的脑血流量测量结果进行比较。(3)在10例急性（n=5）或慢性卒中（n=5）患者中，将PWI/DWI结果与脑血流和氧耗的PET结果进行比较，以检测不匹配或氧提取分数增加作为半暗带的替代标志物。结果如下：（1）计算DWI强度增加、表观扩散系数（ADC）降低和FMZ结合率降低的区域的最终梗死概率曲线，并确定95%预测限。这些限值预测了最终梗死体积的83.5%（FMZ）、84.7%（DWI）和70.9%（ADC）。然而，DWI变量的假阳性预测值要高得多（DWI和ADC分别为5.1和3.6 cm（3），而FMZ的中位数为0）。(2)由不同的达峰时间（TTP）阈值（PWI）和低灌注4秒产生的体积的比较并不可靠地对应于PET评估的半影区（氧提取分数> 150%）。10例不匹配的患者中只有6例有半暗带区域。在这些病例中，MRI高估了半暗带体积。DWI与FMZ结果相关，除了少数例外，DWI可以很好地估计急性组织损伤和最终梗死体积。PWI测量似乎不太可靠; TTP延长>4秒仅评估了83%的低灌注量
Diffusion-weighted MRI (DWI) in combination with perfusion-weighted MRI (PWI) has become a widely accepted modality for the selection of patients amenable for acute therapy, if a mismatch between these procedures suggests viable penumbral tissue. However, DWI as well as PWI yields semiquantitative measures limiting the definitions of irreversible damage and of potentially viable penumbral tissue. These limitations of PWI/DWI may be better understood if findings in individual patients are compared with the results from measurements of blood flow, oxygen metabolism, and benzodiazepine receptor binding obtained with positron emission tomography (PET). Comparative studies with PET and MRI were performed in 3 groups of patients: (1) In 12 acute stroke patients, results from DWI (median, 6.5 hours after symptom onset) and C-11-flumazenil (FMZ) PET (median, 85 minutes between DWI and PET) were compared with infarct extension 24 to 48 hours later on T2-weighted MRI. (2) In 11 acute stroke patients, results from PWI (median, 8 hours after symptom onset) were compared with cerebral blood flow measurements obtained with [O-15]H2O PET (interval, 60 minutes between PWI and PET). (3) In 10 patients with acute (n=5) or chronic stroke (n=5), results from PWI/DWI were compared with PET of cerebral blood flow and oxygen consumption to detect mismatch or increased oxygen extraction fraction as surrogate markers of penumbra. Results were: (1) from regions with increased DWI intensity, decreased apparent diffusion coefficient (ADC) and decreased FMZ binding probability curves were computed for eventual infarction, and 95% prediction limits were determined. These limits predicted 83.5% (FMZ), 84.7% (DWI), and 70.9% (ADC) of the final infarct volume. However, the false-positive predictions were much higher for the DWI variables (5.1 and 3.6 cm(3) for DWI and ADC versus a median of 0 for FMZ). (2) The comparison of volumes generated by different time to peak (TTP) thresholds (PWI) and hypoperfusion 4 seconds did not reliably correspond to the penumbra as assessed by PET (oxygen extraction fraction > 150%). Only 6 of 10 patients with a mismatch had areas of penumbra. In these cases, the penumbra volume was overestimated by MRI. DWI correlates with FMZ results and, with a few exceptions, yields a good estimate of acute tissue damage and final infarct volume. PWI measures seem to be less reliable; the TTP prolongation of >4 seconds assessed only 83% of the volume of hypoperfusion