Epel Boris, Maggio Matt, Pelizzari Charles, Halpern Howard J
Center for EPR Imaging In Vivo Physiology; Department of Radiation and Cellular Oncology, University of Chicago, Chicago, IL, USA.
Adv Exp Med Biol. 2017;977:287-296. doi: 10.1007/978-3-319-55231-6_39.
Modern standards for radiation treatment do not take into account tumor oxygenation for radiation treatment planning. Strong correlation between tumor oxygenation and radiation treatment success suggests that oxygen-guided radiation therapy (OGRT) may be a promising enhancement of cancer radiation treatment. We have developed an OGRT protocol for rodents. Electron paramagnetic resonance (EPR) imaging is used for recording oxygen maps with high spatial resolution and excellent accuracy better than 1 torr. Radiation is delivered with an animal intensity modulated radiation therapy (IMRT) XRAD225Cx micro-CT/ therapy system. The radiation plan is delivered in two steps. First, a uniform 15% tumor control dose (TCD) is delivered to the whole tumor. In the second step, an additional booster dose amounting to the difference between TCD and TCD is delivered to radio-resistant, hypoxic tumor regions. Delivery of the booster dose is performed using a multiport conformal beam protocol. For radiation beam shaping we used individual radiation blocks 3D-printed from tungsten infused ABS polymer. Calculation of beam geometry and the production of blocks is performed next to the EPR imager, immediately after oxygen imaging. Preliminary results demonstrate the sub-millimeter precision of the radiation delivery and high dose accuracy. The efficacy of the radiation treatment is currently being tested on syngeneic FSa fibrosarcoma tumors grown in the legs of C3H mice.
现代放射治疗标准在制定放射治疗计划时并未考虑肿瘤的氧合情况。肿瘤氧合与放射治疗成功率之间的强相关性表明，氧引导放射治疗（OGRT）可能是癌症放射治疗的一种有前景的改进方法。我们已经为啮齿动物开发了一种OGRT方案。电子顺磁共振（EPR）成像用于记录具有高空间分辨率且精度优于1托的氧分布图。使用动物调强放射治疗（IMRT）XRAD225Cx微型CT/治疗系统进行放射治疗。放射治疗计划分两步进行。首先，向整个肿瘤给予均匀的15%肿瘤控制剂量（TCD）。在第二步中，向放射抗拒的缺氧肿瘤区域给予额外的增强剂量，其剂量等于TCD与TCD之间的差值。使用多端口适形束方案进行增强剂量的输送。对于放射束整形，我们使用了由注入钨的ABS聚合物3D打印而成的单个放射挡块。在氧成像后，紧接着在EPR成像仪旁边进行束几何形状的计算和挡块的制作。初步结果证明了放射治疗的亚毫米精度和高剂量准确性。目前正在对生长于C3H小鼠腿部的同基因FSa纤维肉瘤肿瘤进行放射治疗效果测试。
