Bornstein B A, Cheng C W, Rhodes L M, Rashid H, Stomper P C, Siddon R L, Harris J R
Department of Radiation Therapy, Dana-Farber Cancer Institute, Boston, MA.
Int J Radiat Oncol Biol Phys. 1990 Jan;18(1):181-7. doi: 10.1016/0360-3016(90)90282-o.
A simple method of estimating the amount of lung irradiated in patients with breast cancer would be of use in minimizing lung complications. To determine whether simple measurements taken at the time of simulation can be used to predict the lung volume in the radiation field, we performed CT scans as part of treatment planning in 40 cases undergoing radiotherapy for breast cancer. Parameters measured from simulator films included: (a) the perpendicular distance from the posterior tangential field edge to the posterior part of the anterior chest wall at the center of the field (CLD); (b) the maximum perpendicular distance from the posterior tangential field edge to the posterior part of the anterior chest wall (MLD); and (c) the length of lung (L) as measured at the posterior tangential field edge on the simulator film. CT scans of the chest were performed with the patient in the treatment position with 1 cm slice intervals, covering lung apex to base. The ipsilateral total lung area and the lung area included within the treatment port were calculated for each CT scan slice, multiplied by the slice thickness, and then integrated over all CT scan slices to give the volumes. The best predictor of the percent of ipsilateral lung volume treated by the tangential fields was the CLD. Employing linear regression analysis, a coefficient of determination r2 = 0.799 was calculated between CLD and percent treated ipsilateral lung volume on CT scan. In comparison, the coefficients for the other parameters were r2 = 0.784 for the MLD, r2 = 0.071 for L, and r2 = 0.690 for CLD x L. A CLD of 1.5 cm predicted that about 6% of the ipsilateral lung would be included in the tangential field, a CLD of 2.5 cm about 16%, and a CLD of 3.5 cm about 26% of the ipsilateral lung, with a mean 90% prediction interval of +/- 7.1% of ipsilateral lung volume. We conclude that the CLD measured at the time of simulation provides a reasonable estimate of the percent of the ipsilateral lung treated by the tangential fields. This information may be of value in evaluating the likelihood of pulmonary complications from such treatment and in minimizing toxicity.
一种估算乳腺癌患者肺部受照射剂量的简单方法，对于将肺部并发症降至最低会有帮助。为了确定在模拟时进行的简单测量是否可用于预测放射野内的肺体积，我们对40例接受乳腺癌放疗的患者进行了CT扫描，作为治疗计划的一部分。从模拟片测量的参数包括：(a) 从后切线野边缘到野中心处前胸壁后部的垂直距离（CLD）；(b) 从后切线野边缘到前胸壁后部的最大垂直距离（MLD）；以及(c) 在模拟片上后切线野边缘处测量的肺长度（L）。胸部CT扫描是在患者处于治疗体位时进行的，层厚为1 cm，覆盖肺尖至肺底。对每个CT扫描层面计算同侧全肺面积和治疗野内包含的肺面积，乘以层厚，然后在所有CT扫描层面上进行积分以得出体积。切线野治疗的同侧肺体积百分比的最佳预测指标是CLD。采用线性回归分析，计算出CLD与CT扫描上同侧肺治疗体积百分比之间的决定系数r2 = 0.799。相比之下，其他参数的系数分别为：MLD的r2 = 0.784，L的r2 = 0.071，CLD×L的r2 = 0.690。CLD为1.5 cm时预测约6%的同侧肺会被包括在切线野内，CLD为2.5 cm时约为16%，CLD为3.5 cm时约为26%的同侧肺，同侧肺体积的平均90%预测区间为±7.1%。我们得出结论，模拟时测量的CLD可合理估算切线野治疗的同侧肺百分比。该信息对于评估此类治疗引起肺部并发症的可能性以及将毒性降至最低可能有价值。
