Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
Int J Radiat Oncol Biol Phys. 2012 Nov 1;84(3):e441-6. doi: 10.1016/j.ijrobp.2012.04.041. Epub 2012 Jun 9.
To evaluate the temporal dose response of normal liver tissue for patients with liver metastases treated with stereotactic body radiation therapy (SBRT).
Ninety-nine noncontrast follow-up computed tomography (CT) scans of 34 patients who received SBRT between 2004 and 2011 were retrospectively analyzed at a median of 8 months post-SBRT (range, 0.7-36 months). SBRT-induced normal liver tissue density changes in follow-up CT scans were evaluated at 2, 6, 10, 15, and 27 months. The dose distributions from planning CTs were mapped to follow-up CTs to relate the mean Hounsfield unit change (ΔHU) to dose received over the range 0-55 Gy in 3-5 fractions. An absolute density change of 7 HU was considered a significant radiographic change in normal liver tissue.
Increasing radiation dose was linearly correlated with lower post-SBRT liver tissue density (slope, -0.65 ΔHU/5 Gy). The threshold for significant change (-7 ΔHU) was observed in the range of 30-35 Gy. This effect did not vary significantly over the time intervals evaluated.
SBRT induces a dose-dependent and relatively time-independent hypodense radiation reaction within normal liver tissue that is characterized by a decrease of >7 HU in liver density for doses >30-35 Gy.
评估立体定向体部放射治疗（SBRT）治疗肝转移患者的正常肝脏组织的时间剂量反应。
对 2004 年至 2011 年间接受 SBRT 的 34 例患者的 99 次非增强随访 CT 扫描进行回顾性分析，中位随访时间为 SBRT 后 8 个月（范围，0.7-36 个月）。在随访 CT 扫描中评估 SBRT 诱导的正常肝脏组织密度变化，时间点分别为 2、6、10、15 和 27 个月。将计划 CT 的剂量分布映射到随访 CT 上，以将平均亨氏单位变化（ΔHU）与 3-5 分次 0-55 Gy 范围内的剂量相关联。正常肝脏组织的绝对密度变化 7 HU 被认为是影像学上的显著变化。
随着辐射剂量的增加，SBRT 后肝脏组织密度呈线性降低（斜率为-0.65 ΔHU/5 Gy）。在 30-35 Gy 范围内观察到显著变化的阈值（-7 ΔHU）。这种效应在评估的时间间隔内没有显著变化。
SBRT 诱导正常肝脏组织中剂量依赖性且相对时间独立的低剂量辐射反应，其特征为肝脏密度下降>7 HU，剂量>30-35 Gy。
