同一射野角度不同优化方式对中央型肺癌调强适形放射治疗计划的影响

目的 探讨中央型肺癌调强适形放射治疗（IMRT）同一射野角度、不同优化方式对靶区和危及器官剂量分布的影响。 方法 回顾性分析2017年11月至2019年10月在广州市番禺区中心医院接受IMRT的6例中央型肺癌患者的临床资料，其中男性5例、女性1例，中位年龄64（53~73）岁。6例患者分别制定2种治疗计划：F-plan和B-plan。2种治疗计划均采用相同的射野方向，根据靶区边缘到皮肤表面的距离，遵循射野穿过肺部最小的原则对所给定的射野方向进行优化，其中，F-plan为部分射野进行锁铅门设计，B-plan为部分射野入射路径处添加虚拟的“Block”设计。评估2种治疗计划的患者的靶区覆盖情况、危及器官受照剂量和机器跳数，差异的比较采用配对t检验。 结果 2种治疗计划均能满足临床要求，计划临床靶体积和计划大体肿瘤体积（PGTV）的剂量分布基本一致，PGTV的适形度指数、均匀性指数以及2种计划下的机器跳数等各参数之间的差异均无统计学意义（t=−1.383~1.863，均P>0.05）。B-plan的双肺的肺平均剂量（MLD）（1572.13±148.08） cGy]、V5（62.58±5.91）%]、V25（24.33±1.83）%]、V30（20.14±2.43）%]、V40（13.38±2.78）%]（Vx指接受x Gy剂量照射的体积占总体积的百分比）和正常组织的平均剂量（Dmean）（1246.63±485.12） cGy]、V5（58.46±24.31）%]、V40（6.38±2.67）%]普遍高于F-plan的受照剂量 双肺的MLD：（1546.45±152.98） cGy、V5：（60.66±5.34）%、V25：（23.79±2.20）%、V30：（19.59±2.71）%、V40：（12.70±2.79）%；正常组织的Dmean：（1209.37±466.66） cGy、V5：（54.87±22.60）%、V40：（5.89±2.63）%]，且差异均有统计学意义（t=−6.370~−2.601，均P<0.05）；对于心脏和脊髓的受照剂量，2种治疗计划之间的差异均无统计学意义（t=−1.120~0.377，均P>0.05），但B-plan的心脏的V30（17.21±10.42）%]、V40（11.70±8.04）%]高于F-plan V30：（14.67±5.82）%、V40：（9.42±4.19）%]，而脊髓的最大剂量（4112.12±304.66） cCy]却略低于F-plan（4128.73±254.72） cCy]。 结论 2种治疗计划均能得到满意的靶区剂量学分布，在危及器官保护方面也各有优缺点，临床应用中可根据个体差异、靶区分布有选择性地使用或结合使用。

Effect of different optimization methods for the same beam angles on IMRT plan of central lung cancer

Objective To investigate the effect of different optimization methods in the same beam angles on the dose distribution of the target area and organ at risk (OAR) in intensity modulated radiotherapy (IMRT) for central lung cancer. Methods Six patients with central lung cancer and received IMRT in Panyu Central Hospital of Guangzhou from November 2017 to October 2019 were retrospectively analyzed, including 5 males and 1 female; the median age was 64 (53–73) years old. Six patients were treated with two plans, namely, F-plan and B-plan. Both plans adopted the same beam angles, and the given beam angle was optimized in accordance with the distance between the edge of the target area to the surface of the skin and the principle of the minimum penetration of field into lung. The F-plan was that part of the beam angles was designed to fix the jaw, and the B-plan was that part of the beam angles was designed to add a block in the incident path of the view. The target area coverage, OAR distribution, and monitor unit (MU) with two treatment plans were receptivity evaluated. Paired t-test was used to compare the differences. Results The two treatment plans could satisfy the clinical requirements, the dose distributions of the planning clinical target volume and the planning gross target volume (PGTV) were basically the same, and no significant difference was found between the parameters such as the conformal index and uniformity index of PGTV, machine MU under the two plans (t=−1.383−1.863, all P>0.05). The mean lung dose (MLD) ((1572.13±148.08) cGy)/V5 ((62.58±5.91)%)/V25 ((24.33±1.83)%)/V30 ((20.14±2.43)%) and V40 ((13.38±2.78)%) of the double lung (where Vx refers to the percentage of the volume exposed to x-Gy dose to the total volume) and the mean dose (Dmean) ((1246.63±485.12) cGy)/V5 ((58.46±24.31)%) and V40 ((6.38±2.67)%) of normal tissue (NT) in the B-plan were generally higher than in the F-plan (MLD ((1546.45±152.98) cGy)/V5 ((60.66±5.34)%)/V25 ((23.79±2.20)%)/V30 ((19.59±2.71)%) and V40 ((12.70±2.79)%) of the double lung and the Dmean ((1209.37±466.66) cGy)/V5 ((54.87±22.60)%) and V40 ((5.89±2.63)%) of NT). Their difference was statistically significant (t=−6.370 to −2.601, all P<0.05). For the heart and spinal cord, no significant differences were found between the two plans (t=−1.120−0.377, all P>0.05). However, B-plan cardiac V30 ((17.21±10.42)%) and V40 ((11.70±8.04)%) were higher than F-plan cardiac V30 ((14.67±5.82)%) and V40 ((9.42±4.19)%). In addition, spinal cord maximum dose (Dmax) ((4112.12±304.66) cGy) was slightly lower than F-plan spinal cord Dmax ((4128.73±254.72) cGy). Conclusions Both treatment plans can obtain satisfactory target dosimetric distribution, and each plan has its own advantages and disadvantages in the protection of OARs. In clinical application, they can be used selectively or in combination according to individual differences and target distribution.