Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2, Canada.
Phys Med Biol. 2010 Mar 7;55(5):1381-93. doi: 10.1088/0031-9155/55/5/008. Epub 2010 Feb 11.
The purpose of this study is to investigate the response of transverse relaxation time (T2) and apparent diffusion coefficient (ADC) in human glioma tumor xenografts during and after fractionated radiotherapy. Tumor-bearing mice were divided into four treatment groups (n=6 per group) that received a total dose of 800 cGy of 200 kVp x-rays, given over two or three fractions, with a fraction spacing of either 24 or 72 h. A fifth treatment group received 800 cGy in a single fraction, and a sixth group of mice served as an untreated control. All mice were scanned pretreatment, before each fraction and at multiple points after treatment using a 9.4 T magnetic resonance imaging (MRI) system. Quantitative T2 and ADC maps were produced. All treated groups showed an increase in mean tumor ADC, though the time for this response to reach a maximum and return toward baseline was delayed in the fractionated groups. The highest ADC was measured 7 days after the final fraction of treatment for all groups. There were no significant differences in the maximum measured change in ADC between any of the treated groups, with the average measured maximum value being 20.5% above baseline. After treatment, all groups showed an increase in mean tumor T2, with the average measured maximum T2 being 4.7% above baseline. This increase was followed by a transition to mean T2 values below baseline values, with the average measured tumor T2 being 92.4% of the pretreatment value. The transition between elevated and depressed T2 values was delayed in the cases of fractionated therapies and occurred between 3.6 and 7.3 days after the last fraction of treatment. These results further the understanding of the temporal evolution of T2 and ADC during fractionated radiotherapy and support their potential use as time-sensitive biomarkers for tumor response.
本研究旨在探讨在分次放射治疗过程中和之后，人类脑胶质瘤肿瘤异种移植模型的横向弛豫时间（T2）和表观扩散系数（ADC）的变化。荷瘤小鼠分为四组（每组 6 只），接受 200 kVp X 射线的 800 cGy 总剂量，分 2 或 3 次给予，间隔 24 或 72 小时。第五组接受单次 800 cGy 剂量，第六组为未处理的对照组。所有小鼠在预处理前、每次分割前以及治疗后多个时间点使用 9.4 T 磁共振成像（MRI）系统进行扫描。生成定量 T2 和 ADC 图谱。所有治疗组的肿瘤平均 ADC 均增加，尽管在分次组中，这种反应达到最大值并恢复到基线的时间延迟。所有组在治疗的最后一次分割后 7 天测量到的 ADC 最高。在任何治疗组中，测量到的 ADC 最大变化值之间没有显著差异，平均测量的最大值比基线高 20.5%。治疗后，所有组的肿瘤平均 T2 均增加，平均测量的最大 T2 比基线高 4.7%。这种增加之后是平均 T2 值低于基线值的转变，平均测量的肿瘤 T2 为预处理值的 92.4%。在分次治疗的情况下，T2 值升高和降低之间的转变延迟，发生在最后一次分割治疗后 3.6 至 7.3 天之间。这些结果进一步了解了 T2 和 ADC 在分次放射治疗过程中的时间演变，并支持它们作为肿瘤反应的时间敏感生物标志物的潜在用途。
