Price S J, Jena R, Green H A L, Kirkby N F, Lynch A G, Coles C E, Pickard J D, Gillard J H, Burnet N G
Academic Neurosurgical Unit, Cambridge University and Addenbrooke's Hospital, Cambridge, UK.
Clin Oncol (R Coll Radiol). 2007 Oct;19(8):577-87. doi: 10.1016/j.clon.2007.04.010. Epub 2007 Jul 13.
To determine if magnetic resonance perfusion markers can be used as an analytical marker of subclinical normal brain injury after radiotherapy, by looking for a dose-effect relationship.
Four patients undergoing conformal radiotherapy to 54Gy in 30 fractions for low-grade gliomas were imaged with conventional T(2)-weighted and fluid attenuated inversion recovery imaging as well as dynamic contrast susceptibility perfusion imaging. Forty regions of interest were determined from the periventricular white matter. All conventional sequences were examined for evidence of radiation-induced changes. Patients were imaged before radiotherapy, after one fraction, at the end of treatment and then at 1 and 3 months from the end of radiotherapy. For each region the relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF) and mean transit time (MTT) expressed as a ratio of the baseline value, and radiotherapy dose were determined.
Of the 40 regions, seven occurred within the gross tumour volume and a further four occurred in regions later infiltrated by tumour, and were thus excluded. Regions within the 80% isodose showed a reduction in rCBV and rCBF over the 3 month period. There was no significant alteration in rCBV or rCBF in regions outside the 60% isodose (i.e. <32Gy). MTT did not alter in any region. There seemed to be a threshold effect at 132 days from the end of radiotherapy of 47% (standard error of the mean 11.5, about 25.4Gy) for rCBV and 59% (standard error of the mean 14.2, about 31.9Gy) for rCBF.
There was a dose-related reduction in rCBV and rCBF in normal brain after radiotherapy at higher dose levels. Although this study used a limited number of patients, it suggests that magnetic resonance perfusion imaging seems to act as a marker of subclinical response of normal brain and that there is an absence of an early hypersensitivity effect with small doses per fraction. Further studies are required with larger groups of patients to show that these results are statistically robust.
通过寻找剂量效应关系，确定磁共振灌注标记物是否可作为放疗后亚临床正常脑损伤的分析标记物。
对4例接受适形放疗、30次分割、总剂量54Gy治疗低级别胶质瘤的患者，进行常规T2加权成像、液体衰减反转恢复成像以及动态对比增强磁共振灌注成像检查。从脑室周围白质确定40个感兴趣区。检查所有常规序列，寻找放射性改变的证据。在放疗前、照射1次后、治疗结束时以及放疗结束后1个月和3个月对患者进行成像。对于每个区域，确定以基线值的比值表示的相对脑血容量（rCBV）、相对脑血流量（rCBF）和平均通过时间（MTT），以及放疗剂量。
40个区域中，7个位于肿瘤大体体积内，另外4个位于后来被肿瘤浸润的区域，因此将这些区域排除。80%等剂量线内的区域在3个月期间rCBV和rCBF降低。60%等剂量线外（即<32Gy）的区域rCBV或rCBF无显著改变。MTT在任何区域均未改变。放疗结束后132天，rCBV似乎存在阈值效应，为47%（平均标准误差11.5，约25.4Gy），rCBF为59%（平均标准误差14.2，约31.9Gy）。
在较高剂量水平放疗后，正常脑内rCBV和rCBF存在剂量相关的降低。尽管本研究使用的患者数量有限，但提示磁共振灌注成像似乎可作为正常脑亚临床反应的标记物，且每次小剂量照射不存在早期超敏效应。需要对更多患者进行进一步研究，以表明这些结果具有统计学稳健性。
