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放疗靶区和邻近的组织器官,特别是危及器官实际受到的照射剂量,即吸收剂量,是评估放疗疗效和不良反应或损伤的基础。由于直接计算的物理剂量(physical dose,PhD)受总剂量、分割计量、分次数等因素影响很大,难以进行比较,所以对预期疗效、不良反应和危及器官损伤的预测需要进行生物效应剂量(biological effective dose,BED)的换算。BED是指每次1.8~2.0 Gy,每周5次,总剂量60.0~70.0 Gy,即60.0~70.0 Gy/30~35次/6~7周的剂量分割模式下的剂量[1],一般以2.0 Gy计算,即常规2.0 Gy分次的等效剂量(equivalent dose in 2.0 Gy/f,EQD2)。这既是讨论肿瘤吸收剂量进行疗效判定的标准,也是靶区周围危及器官剂量控制的标准[2-4]。
在目前以适形和调强技术为主的精确放疗模式下,危及器官能够明确排除在靶区以外,所以每次的受照剂量较常规放疗明显减少[5-6]。常规分割模式下,危及器官每次的实际照射剂量明显低于2.0 Gy,因此危及器官特别是对分次剂量更为敏感器官的BED与PhD明显不同[7]。本研究结合L-Q(linear quadratic)模型[8],应用深圳市医诺智能科技发展有限公司的RTIS软件,在胸部肿瘤放疗患者中对这一问题进行探讨。
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评估显示1次剂量或总剂量下的PhD和BED等剂量曲线,从剂量-体积直方图可以看出,脊髓的BED曲线位于PhD曲线左侧,而PTV的BED曲线位于PhD曲线右侧(图 1中D、图 2中D)。
图 1 单次照射脊髓和PTV的PhD和BED(男性,54岁)
Figure 1. The results of physicat dose and biological effective dose in cord and planning target volume for single radiation
图 2 30次照射脊髓和PTV的PhD与BED(男性,54岁)
Figure 2. The results of physicat dose and biological effective dose in cord and planning target volume for 30 radiations
由表 1可见,脊髓的PhD和BED的最小、最大、平均剂量的差异均有统计学意义(t=0.826、6.143、5.234,均P<0.05);而PTV的PhD和BED的最小、最大、平均剂量的差异均无统计学意义(t=6.953、-2.164、-1.193,均P>0.05)。但由于脊髓是典型的串行器官,因此,最小剂量、平均剂量的参考价值较小,临床主要应用最大剂量。
名称 脊髓 PTV 最小剂量 最大剂量 平均剂量 最小剂量 最大剂量 平均剂量 PhD 80.41±274.75 3398.00±1200.95 1265.79±762.49 3615.51±1566.10 5505.26±1731.64 4984.33±1615.59 EQD2 74.71±249.34 3118.93±1181.96 1181.44±742.18 3500.97±1576.92 5672.93±1791.98 5047.63±1646.57 t值 0.826 6.143 5.234 6.953 -2.164 -1.193 P值 0.04 0 0 0.122 0.071 0.061 注:表中,PTV:计划靶体积;PhD:物理剂量;EQD2:2.0 Gy的等效剂量。 表 1 30 例胸部肿瘤患者脊髓和PTV的PhD与EQD2比较(x±s)
Table 1. The comparison of physical dose and biological effective dose in cord and planning target volume for 30 thoracic tumor patients(x±s)
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依据线性二次方程(L-Q模型)计算出2.0 Gy照射1次和30次时脊髓(α/β比值=3.0)在不同剂量曲线的PhD和BED。由表 2可见,随着剂量曲线下降,PhD和BED也随之降低,而且相同剂量曲线的BED较PhD更低。
剂量曲线/% 单次PhD/Gy 单次BED/Gy 30次PhD/Gy 30次BED/Gy 100 2 2 60 60 90 1.8 1.73 54 51.84 80 1.6 1.47 48 44.16 70 1.4 1.23 42 36.96 60 1.2 1.01 36 30.24 50 1 0.8 30 24 40 0.8 0.61 24 18.24 30 0.6 0.43 18 12.96 20 0.4 0.27 12 8.16 10 0.2 0.13 6 3.84 注:表中,PhD:物理剂量;BED:生物效应剂量。 表 2 30例胸部肿瘤患者接受2.0 Gy 1次和30次照射时脊髓在不同剂量曲线下的PhD和BED
Table 2. The data of physiacal dose and biological effective dose of cord in different dose curves with 2.0 Gy single and 30 radiations for 30 patients
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本研究应用的RTIS V2.13软件的治疗计划评估功能具有PhD显示和BED显示的双重模式,并且可以对照显示。在治疗计划评估中,可以选择单次治疗或全程治疗,软件以三维断面剂量曲线图和剂量-体积直方图形式显示PhD和BED(图 1、图 2)。
胸部肿瘤适形和调强常规分割放疗脊髓生物效应剂量研究
The study for biological effect dose of spinal cord in thoracic tumors with the model of conformal and intensity modulated technique and conventional fractionation
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摘要:
目的探讨对常规分割模式下胸部肿瘤适形和调强放疗技术进行脊髓生物效应剂量(BED)评估的必要性和可行性。 方法选取2016年5月16日至2016年12月31日于唐山市人民医院放化疗科收治的胸部肿瘤患者30例,应用医诺RTIS治疗计划评估模块对所有患者的治疗计划进行评估,并进行物理剂量(PhD)和BED的比较。依据线性二次方程(L-Q模型)计算2.0 Gy照射1次和30次时脊髓在不同剂量曲线的PhD和RED。组间比较采用t检验。 结果脊髓的RED曲线位于PhD曲线左侧,计划靶体积(PTV)的BED曲线位于PhD曲线右侧。30例患者的治疗计划中,脊髓的最小、最大、平均PhD与BED分别为(80.41±274.75)、(3398.00±1200.95)、(1265.79±762.49)cGy和(74.71±249.34)、(3118.93±1181.96)、(1181.44±742.18)cGy,差异均有统计学意义(t=0.826、6.143、5.234,P < 0.05);PTV的最小、最大、平均PhD和BED分别为(3615.51±1566.10)、(5505.26±1731.64)、(4984.33±1615.59)cGy和(3500.97±1576.92)、(5672.93±1791.98)、(5047.63±1646.57)cGy,差异均无统计学意义(t=6.953、-2.164、-1.193,均P>0.05)。随着剂量曲线的下降,PhD和BED也随之降低,而且相应剂量曲线的BED较PhD更低。 结论从增强靶区控制和脊髓保护的角度,胸部肿瘤精确常规分割放疗有必要进行脊髓的BED评估。 -
关键词:
- 胸部肿瘤 /
- 放射疗法, 调强适形 /
- 脊髓 /
- 常规分割 /
- 生物效应剂量
Abstract:ObjectiveTo investigate the necessity and feasibility of evaluation for spinal cord biological effect dose (BED) in clinical radiotherapy on thoracic tumors in the model of conformal or intensity modulated technique and conventional fractionation. MethodsFrom 16 May 2016 to 31 December 2016, 30 patients accepting thoracic radiotherapy were selected in the Radio-chemotherapy department of Tangshan City People's Hospital. Radiotherapy plans of these patients were evaluated by the evaluation module of the RTIS treatment plan system, and then the physical dose(PhD) and BED were compared, respectively. After that, the PhD and BED of the spinal cord in different dose curves for 2.0 Gy irradiation 1 and 30 times were calculated by the linear quadratic equation(L-Q model). T test was used for all comparison between groups in statistics. ResultsThe BED curve of the spinal cord was on the left of the PhD curve, and the BED curve of planning target volume(PTV) was on the right of the PhD curve. In the radiotherapy plans of the 30 patients, for the spinal cord, the minimum maximum, average doses of PhD and BED were (80.41±274.75), (3398.00±1200.95), (1265.79±762.49) cGy and (74.71±249.34), (3118.93±1181.96), (1181.44±742.18) cGy, separately, the differences of them were significantly(t=0.826, 6.143, 5.234, all P < 0.05). However, for the PTV of target the minimum, maximum, average doses of PhD and BED were (3615.51±1566.10), (5505.26±1731.64), (4984.33±1615.59) cGy and (3500.97±1576.92), (5672.93±1791.98), (5047.63±1646.57) cGy, all of them were no significances in statistics (t=6.953, -2.164, -1.193, all P>0.05). With the decline of the dose curve, the PhD and BED were reducing, and the BED were lower than the PhD in the curve for corresponding dose. ConclusionsIn the radiotherapy of thoracic tumors, considering potential enhancement of local target control and better spinal cord protection, it is necessary to evaluate the BED of the spinal cord. -
表 1 30 例胸部肿瘤患者脊髓和PTV的PhD与EQD2比较(x±s)
Table 1. The comparison of physical dose and biological effective dose in cord and planning target volume for 30 thoracic tumor patients(x±s)
名称 脊髓 PTV 最小剂量 最大剂量 平均剂量 最小剂量 最大剂量 平均剂量 PhD 80.41±274.75 3398.00±1200.95 1265.79±762.49 3615.51±1566.10 5505.26±1731.64 4984.33±1615.59 EQD2 74.71±249.34 3118.93±1181.96 1181.44±742.18 3500.97±1576.92 5672.93±1791.98 5047.63±1646.57 t值 0.826 6.143 5.234 6.953 -2.164 -1.193 P值 0.04 0 0 0.122 0.071 0.061 注:表中,PTV:计划靶体积;PhD:物理剂量;EQD2:2.0 Gy的等效剂量。 表 2 30例胸部肿瘤患者接受2.0 Gy 1次和30次照射时脊髓在不同剂量曲线下的PhD和BED
Table 2. The data of physiacal dose and biological effective dose of cord in different dose curves with 2.0 Gy single and 30 radiations for 30 patients
剂量曲线/% 单次PhD/Gy 单次BED/Gy 30次PhD/Gy 30次BED/Gy 100 2 2 60 60 90 1.8 1.73 54 51.84 80 1.6 1.47 48 44.16 70 1.4 1.23 42 36.96 60 1.2 1.01 36 30.24 50 1 0.8 30 24 40 0.8 0.61 24 18.24 30 0.6 0.43 18 12.96 20 0.4 0.27 12 8.16 10 0.2 0.13 6 3.84 注:表中,PhD:物理剂量;BED:生物效应剂量。 -
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