Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, TX 75390-8542, USA.
Radiother Oncol. 2013 Jan;106(1):101-5. doi: 10.1016/j.radonc.2012.08.007. Epub 2012 Sep 14.
This study was performed to test the hypothesis that spinal cord radiosensitivity is significantly modified by uniform versus laterally non-uniform dose distributions.
A uniform dose distribution was delivered to a 4.5-7.0 cm length of cervical spinal cord in 22 mature Yucatan minipigs for comparison with a companion study in which a laterally non-uniform dose was given [1]. Pigs were allocated into four dose groups with mean maximum spinal cord doses of 17.5 ± 0.1 Gy (n=7), 19.5 ± 0.2 Gy (n=6), 22.0 ± 0.1 Gy (n=5), and 24.1 ± 0.2 Gy (n=4). The study endpoint was motor neurologic deficit determined by a change in gait within one year. Spinal cord sections were stained with a Luxol fast blue/periodic acid Schiff combination.
Dose-response curves for uniform versus non-uniform spinal cord irradiation were nearly identical with ED(50)'s (95% confidence interval) of 20.2 Gy (19.1-25.8) and 20.0 Gy (18.3-21.7), respectively. No neurologic change was observed for either dose distribution when the maximum spinal cord dose was ≤ 17.8 Gy while all animals experienced deficits at doses ≥ 21.8 Gy.
No dose-volume effect was observed in pigs for the dose distributions studied and the endpoint of motor neurologic deficit; however, partial spinal cord irradiation resulted in less debilitating neurologic morbidity and histopathology.
本研究旨在验证以下假设，即脊髓放射敏感性会因均匀与非均匀侧向剂量分布而发生显著改变。
将均匀剂量分布应用于 22 只成熟的尤卡坦小型猪的 4.5-7.0 厘米长的颈段脊髓，与之前的一项研究进行对比，该研究采用了非均匀侧向剂量分布[1]。将猪分为 4 个剂量组，平均最大脊髓剂量分别为 17.5 ± 0.1 Gy（n=7）、19.5 ± 0.2 Gy（n=6）、22.0 ± 0.1 Gy（n=5）和 24.1 ± 0.2 Gy（n=4）。研究终点为一年内步态改变导致的运动神经功能缺损。用卢索快速蓝/过碘酸希夫组合染色脊髓切片。
均匀与非均匀脊髓照射的剂量反应曲线几乎相同，ED（50）值（95%置信区间）分别为 20.2 Gy（19.1-25.8）和 20.0 Gy（18.3-21.7）。当最大脊髓剂量≤17.8 Gy 时，两种剂量分布均未观察到神经变化，而当剂量≥21.8 Gy 时，所有动物均出现缺陷。
对于研究中所涉及的剂量分布和运动神经功能缺损终点，猪未观察到剂量-体积效应；然而，部分脊髓照射导致的神经发病率和组织病理学损伤程度较轻。
