Bolus厚度和使用次数对乳腺癌根治术后调强放疗皮肤剂量影响

目的探讨Bolus厚度和使用次数对乳腺癌根治术后调强放疗皮肤剂量影响。方法选取20例乳腺癌根治术后患者固定野调强放疗计划进行回顾性分析,单独使用0.5 cm或1 cm厚Bolus次数为5 F、10 F、15 F、20 F、25 F和混合使用0.5 cm和1 cm厚Bolus来研究放疗计划靶区均匀性指数(homogeneity index,HI)、适形度指数(conformity index,CI)及皮肤剂量D_max、D_mean、D_min;拟合出皮肤剂量与Bolus使用次数的关系式。结果随着Bolus使用次数增加,皮肤剂量增加,靶区热点减小、低剂量体积降低。不同Bolus使用次数1 cm厚Bolus比0.5 cm厚Bolus靶区均匀性均更好(P <0.05),且随着Bolus使用次数增加,HI逐渐降低。0.5 cm和1 cm厚Bolus靶区CI随着Bolus使用次数增加先增大后减小,在15 F附近最大,仅在20 F和25 F 2种厚度Bolus的CI结果具有统计学意义(P <0.05)。0.5 cm厚Bolus...

Effects of bolus thickness and use frequency on skin dose in postmastectomy intensity-modulated radiotherapy

Objective To investigate the effects of bolus thickness and use frequency on skin dose in postmastectomy intensity-modulated radiotherapy. Methods We retrospectively reviewed 20 cases receiving postmastectomy fixed-field intensity-modulated radiotherapy, to analyze the homogeneity index (HI) and conformity index (CI) of the target volume and the skin dose (D_max, D_mean, and D_min) of radiotherapy plans with 0.5 cm-thick bolus or 1 cm-thick bolus alone at a use frequency of 5 F, 10 F, 15 F, 20 F, and 25 F versus a combination of 0.5 cm and 1 cm-thick bolus, and fit the relationship between skin dose and bolus use frequency. Results As the bolus use frequency increased, the skin dose increased, the hot spot of the target volume decreased, and the low-dose volume decreased. The HI of the target volume with the 1 cm bolus was better than that with the 0.5 cm bolus at all use frequencies (P < 0.05), and HI decreased with the increase of bolus use frequency. For both 0.5 cm and 1 cm bolus, the CI of the target volume increased initially and then decreased, reaching the maximum value at a frequency of around 15 F; the CI showed significant differences only at 20 F and 25 F between the two types of bolus (P < 0.05). The skin D_max and D_mean were significant higher with the 0.5 cm bolus than with the 1 cm bolus (P < 0.05). The equation for the relationship between skin dose (D) and bolus use frequency (F) was D = A×F + B×F² + C. The D_max and HI with the combination of 0.5 cm bolus (6 F) plus 1 cm bolus (8 F) fell between those with the 0.5 cm bolus (15 F) and those with the 1 cm bolus (15 F) (P < 0.05). Conclusion In postmastectomy fixed-field intensity-modulated radiotherapy, skin dose can be calculated based on bolus use frequency. Mixed use of bolus may be more suitable than use of 0.5 cm bolus or 1 cm bolus alone.