Lin R, Hug E B, Schaefer R A, Miller D W, Slater J M, Slater J D
Department of Radiation Medicine, Loma Linda University Medical Center, Loma Linda, CA, USA.
Int J Radiat Oncol Biol Phys. 2000 Nov 1;48(4):1219-26. doi: 10.1016/s0360-3016(00)00741-0.
Conventional radiation therapy for pediatric posterior fossa tumors can cause sequelae such as hearing loss and impairments in language and learning. Modern three-dimensional (3D) treatment techniques have improved dose conformity to the posterior fossa. This report compares the normal tissue dose-sparing capabilities of proton radiation therapy (PRT) with 3D conformal photon plans.
Nine children underwent previous PRT for primary CNS malignancies. Using original planning CT scans, the posterior fossa, inner and middle ear, and temporal lobes were delineated. Three-dimensional treatment plans were generated for protons and photons. Normal tissue exposures were calculated by averaging mean doses received and by analysis of dose-volume histogram.
The 95% isodose encompassed the posterior fossa in all plans. Normal structures received markedly less radiation from PRT plans than from 3D photon plans. The cochlea received an average mean of 25 +/- 4% of the prescribed dose from PRT, and 75 +/- 6% from photons. Forty percent of temporal lobe volume was completely excluded using protons; with photons 90% of the temporal lobe received 31% of the dose.
PRT resulted in increased dose sparing of normal structures analyzed. Posterior fossa conformity of 3D photons came at the expense of increasing amounts of normal tissue receiving low to moderate doses.
儿童后颅窝肿瘤的传统放射治疗可导致听力丧失以及语言和学习障碍等后遗症。现代三维（3D）治疗技术提高了后颅窝的剂量适形性。本报告比较了质子放射治疗（PRT）与3D适形光子计划对正常组织的剂量 sparing 能力。
9名儿童曾接受PRT治疗原发性中枢神经系统恶性肿瘤。使用原始计划CT扫描，勾勒出后颅窝、内耳和中耳以及颞叶。生成了质子和光子的三维治疗计划。通过平均接受的平均剂量并分析剂量体积直方图来计算正常组织的照射剂量。
所有计划中95%等剂量线均覆盖后颅窝。与3D光子计划相比，正常结构从PRT计划中接受的辐射明显更少。耳蜗从PRT接受的平均剂量为规定剂量的25±4%，从光子计划接受的为75±6%。使用质子时，40%的颞叶体积完全被排除；使用光子时，90%的颞叶接受了31%的剂量。
PRT导致所分析的正常结构的剂量 sparing 增加。3D光子的后颅窝适形性是以增加接受低至中等剂量的正常组织量为代价的。
