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放疗是肺癌治疗的常见手段,其中,调强适形放射治疗(intensity modulated radiotherapy,IMRT)是目前常用的一种放疗技术,其采用一系列不同射野从不同方向照射靶区,通过调整射野内强度分布,使高剂量区适形于靶区,并在一定程度上避开靶区周围的正常组织。对于中央型肺癌,由于其主要发生在段支气管至主支气管[1],靶区趋近纵隔而使周围正常组织如脊髓、食管、心脏等不可避免地受到照射,进行IMRT计划设计时,需要选择合适的射野方向和射野数目,其中射野方向的选择是关键。目前,临床上普遍仍采用物理师根据经验给出的射野方向,射野大小也普遍采用铅门自动跟随适形于整个靶区。这样对部分中央型肺癌来说,可能某一个或某几个射野有部分位置需穿过较多的正常肺组织才能到达靶区,增加了正常肺组织的照射剂量。为了达到更好地保护正常肺组织的目的,我们在参考相关文献[2~5]的基础上,选取6例中央型肺癌患者,根据靶区分布情况和靶区边缘到皮肤表面的距离,遵循射野以最短路径到达靶区(即穿过肺部最小)的原则,采用锁铅门[2-3]和添加虚拟“Block”[4-5]的方法对所给定的射野方向进行一定的优化处理,探讨给定射野方向进一步优化对肿瘤靶区和危及器官剂量分布的影响。
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6例患者的PGTV和PCTV分别为(241.84±148.21) cm3和(581.79±233.47) cm3。图2、3为其中1例患者的靶区剂量分布图和DVH。结合图3和表1可知,2种治疗计划的靶区覆盖率基本符合临床要求(V95%均>99%,V100%均在95%左右),且均具有较好的靶区适形度和剂量均匀性(CI接近0.78,HI接近0.09)。由表1可知,2种治疗计划的PGTV和PCTV的各参数的差异均无统计学意义(均P>0.05),但B-plan的PGTV的高剂量区(D2、D50)略低于F-plan,低剂量区(D95、D98)略高于F-plan;另外,2种治疗计划的总的机器跳数相近,差异无统计学意义(P>0.05)。
图 2 中央型肺癌患者(男性,73岁)调强适形放射治疗的靶区剂量分布图
Figure 2. Target dose distribution graph of intensity modulated radiotherapy in patients with central lung cancer(male,73 years old)
图 3 中央型肺癌患者(男性,73岁)调强适形放射治疗的剂量-体积直方图
Figure 3. Dose-volume histogram of intensity modulated radiotherapy in patients with central lung cancer(male,73 years old)
评估参数 F-plan B-plan t值 P值 PGTV Dmean(cGy) 6245.55±27.55 6244.48±32.84 0.244 0.817 D2(cGy) 6464.21±46.10 6458.18±53.75 1.228 0.274 D50(cGy) 6258.60±28.25 6255.79±33.04 0.427 0.687 D95(cGy) 6023.78±21.96 6028.10±27.41 −0.738 0.494 D98(cGy) 5939.17±39.43 5944.32±43.07 −0.603 0.573 V95%(%) 99.84±0.23 99.78±0.42 0.745 0.490 V100%(%) 95.21±1.04 95.38±1.37 −0.503 0.636 V105%(%) 28.04±11.22 27.72±11.79 0.151 0.886 CI 0.780±0.045 0.778±0.048 0.237 0.822 HI 0.087±0.010 0.088±0.008 −1.000 0.363 PCTV Dmean(cGy) 5784.35±173.08 5784.60±171.99 −0.049 0.963 V95%(%) 99.35±0.33 99.29±0.30 0.626 0.559 V100%(%) 96.05±0.98 95.45±1.27 1.863 0.122 V105%(%) 78.46±14.42 78.62±12.83 −0.204 0.846 机器跳数 1106.67±111.28 1142.50±71.88 −1.383 0.225 注:F-plan为锁铅门设计;B-plan为添加虚拟的“Block”设计;PGTV为计划大体肿瘤体积;Dmean为平均剂量;Dx为x%的靶区体积所接受的照射剂量;Vx%为接受x%处方剂量照射的体积占总体积的百分比;CI为适形度指数;HI为均匀性指数;PCTV为计划临床靶体积 表 1 中央型肺癌调强适形放射治疗中2种治疗计划的靶区 覆盖结果的比较(n=6,
)$\bar x \pm s $ Table 1. Comparison of target coverage between the two plan types of intensity modulated radiotherapy in central lung cancer (n=6,
)$\bar x \pm s $ -
6例患者双肺的体积为(3374.70±990.20)cm3、脊髓在三维方向上距靶区的最近距离为(1.45±0.61)cm。由表2可知,2种治疗计划的危及器官受照剂量基本满足临床的限量要求,其中,B-plan的双肺的MLD、V5、V25、V30、V40和正常组织的Dmean、V5、V40普遍高于F-plan,且差异均有统计学意义(均P<0.05);对于心脏和脊髓的受照剂量,2种治疗计划的差异均无统计学意义(均P>0.05),但B-plan的心脏受照剂量(V30、V40)高于F-plan,脊髓的受照剂量(Dmax)却低于F-plan。
评估参数 F-plan B-plan t值 P值 双肺 MLD(cGy) 1546.45±152.98 1572.13±148.08 −5.951 0.002 V5(%) 60.66±5.34 62.58±5.91 −6.370 0.001 V10(%) 44.79±3.14 44.73±2.82 0.129 0.902 V13(%) 39.12±2.93 38.87±2.76 0.527 0.621 V15(%) 35.89±2.79 35.91±2.62 −0.069 0.948 V20(%) 29.12±2.15 29.46±1.76 −1.835 0.126 V25(%) 23.79±2.20 24.33±1.83 −2.601 0.048 V30(%) 19.59±2.71 20.14±2.43 −2.912 0.033 V40(%) 12.70±2.79 13.38±2.78 −5.949 0.002 心脏 V30(%) 14.67±5.82 17.21±10.42 −0.937 0.392 V40(%) 9.42±4.19 11.70±8.04 −1.120 0.314 脊髓 Dmax(cGy) 4128.73±254.72 4112.12±304.66 0.377 0.722 正常组织 Dmean(cGy) 1209.37±466.66 1246.63±485.12 −3.363 0.020 V5(%) 54.87±22.60 58.46±24.31 −4.584 0.006 V10(%) 40.61±17.30 40.95±17.99 −0.383 0.717 V20(%) 24.42±10.44 24.45±10.43 −0.112 0.915 V30(%) 13.84±5.46 14.04±5.43 −0.977 0.374 V40(%) 5.89±2.63 6.38±2.67 −3.300 0.021 注:F-plan为锁铅门设计;B-plan为添加虚拟的“Block”设计;MLD为肺平均剂量;Vx为接受x Gy剂量照射的体积占总体积的百分比;Dmax为最大剂量;Dmean为平均剂量 表 2 中央型肺癌调强适形放射治疗中2种治疗计划的危及 器官受照剂量的比较(n=6,
)$\bar x \pm s $ Table 2. Dosimetric comparison of organs at risk between the two treatment plans types of intensity modulated radiotherapy in central lung cancer (n=6,
)$\bar x \pm s $
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
Effect of different optimization methods for the same beam angles on IMRT plan of central lung cancer
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摘要:
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。 -
关键词:
- 肺肿瘤 /
- 放射疗法,调强适形 /
- 放射治疗计划,计算机辅助 /
- 射野角度优化
Abstract: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. -
表 1 中央型肺癌调强适形放射治疗中2种治疗计划的靶区 覆盖结果的比较(n=6,
)$\bar x \pm s $ Table 1. Comparison of target coverage between the two plan types of intensity modulated radiotherapy in central lung cancer (n=6,
)$\bar x \pm s $ 评估参数 F-plan B-plan t值 P值 PGTV Dmean(cGy) 6245.55±27.55 6244.48±32.84 0.244 0.817 D2(cGy) 6464.21±46.10 6458.18±53.75 1.228 0.274 D50(cGy) 6258.60±28.25 6255.79±33.04 0.427 0.687 D95(cGy) 6023.78±21.96 6028.10±27.41 −0.738 0.494 D98(cGy) 5939.17±39.43 5944.32±43.07 −0.603 0.573 V95%(%) 99.84±0.23 99.78±0.42 0.745 0.490 V100%(%) 95.21±1.04 95.38±1.37 −0.503 0.636 V105%(%) 28.04±11.22 27.72±11.79 0.151 0.886 CI 0.780±0.045 0.778±0.048 0.237 0.822 HI 0.087±0.010 0.088±0.008 −1.000 0.363 PCTV Dmean(cGy) 5784.35±173.08 5784.60±171.99 −0.049 0.963 V95%(%) 99.35±0.33 99.29±0.30 0.626 0.559 V100%(%) 96.05±0.98 95.45±1.27 1.863 0.122 V105%(%) 78.46±14.42 78.62±12.83 −0.204 0.846 机器跳数 1106.67±111.28 1142.50±71.88 −1.383 0.225 注:F-plan为锁铅门设计;B-plan为添加虚拟的“Block”设计;PGTV为计划大体肿瘤体积;Dmean为平均剂量;Dx为x%的靶区体积所接受的照射剂量;Vx%为接受x%处方剂量照射的体积占总体积的百分比;CI为适形度指数;HI为均匀性指数;PCTV为计划临床靶体积 表 2 中央型肺癌调强适形放射治疗中2种治疗计划的危及 器官受照剂量的比较(n=6,
)$\bar x \pm s $ Table 2. Dosimetric comparison of organs at risk between the two treatment plans types of intensity modulated radiotherapy in central lung cancer (n=6,
)$\bar x \pm s $ 评估参数 F-plan B-plan t值 P值 双肺 MLD(cGy) 1546.45±152.98 1572.13±148.08 −5.951 0.002 V5(%) 60.66±5.34 62.58±5.91 −6.370 0.001 V10(%) 44.79±3.14 44.73±2.82 0.129 0.902 V13(%) 39.12±2.93 38.87±2.76 0.527 0.621 V15(%) 35.89±2.79 35.91±2.62 −0.069 0.948 V20(%) 29.12±2.15 29.46±1.76 −1.835 0.126 V25(%) 23.79±2.20 24.33±1.83 −2.601 0.048 V30(%) 19.59±2.71 20.14±2.43 −2.912 0.033 V40(%) 12.70±2.79 13.38±2.78 −5.949 0.002 心脏 V30(%) 14.67±5.82 17.21±10.42 −0.937 0.392 V40(%) 9.42±4.19 11.70±8.04 −1.120 0.314 脊髓 Dmax(cGy) 4128.73±254.72 4112.12±304.66 0.377 0.722 正常组织 Dmean(cGy) 1209.37±466.66 1246.63±485.12 −3.363 0.020 V5(%) 54.87±22.60 58.46±24.31 −4.584 0.006 V10(%) 40.61±17.30 40.95±17.99 −0.383 0.717 V20(%) 24.42±10.44 24.45±10.43 −0.112 0.915 V30(%) 13.84±5.46 14.04±5.43 −0.977 0.374 V40(%) 5.89±2.63 6.38±2.67 −3.300 0.021 注:F-plan为锁铅门设计;B-plan为添加虚拟的“Block”设计;MLD为肺平均剂量;Vx为接受x Gy剂量照射的体积占总体积的百分比;Dmax为最大剂量;Dmean为平均剂量 -
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