Department of Radiotherapy Physics, The Ipswich Hospital NHS Trust, Heath Road, Ipswich, Suffolk IP45PD, UK.
Br J Radiol. 2010 Feb;83(986):159-65. doi: 10.1259/bjr/65264916. Epub 2009 Sep 14.
Irregular surface compensation uses dynamic multileaf collimators to modify the fluence to an irregular surface along the cranio-caudal axis. The depth of the compensation surface can be varied by specifying a user-defined parameter called the transmission penetration depth (TPD). In our institution, a review has been carried out of 60 breast patients treated using irregular surface compensation of the tangent fields. The effect of changes in the TPD on the dose distribution was investigated, and the optimum TPD was correlated with the maximum field separation (S(max)) along the posterior border. Reducing the TPD below 50% pushes the dose towards the front of the breast. This reduces hot spots at the medial and lateral regions next to the posterior border of the tangential fields, particularly for patients with large separation. In 23/60 patients, with a mean S(max) of 23.9 +/- 1.6 cm, a TPD between 35% and 45% was used to reduce the proportion of the planning target volume receiving more than 107% of the prescribed dose by 3.4% +/- 2.8%. Our department protocol states that, subject to an acceptable dose distribution, a TPD of 40% is used if S(max) is greater than 24 cm; for smaller separations, a TPD of 50% is used.
不规则表面补偿使用动态多叶准直器来沿着颅尾轴修改不规则表面的剂量分布。补偿表面的深度可以通过指定一个名为透射穿透深度（TPD）的用户定义参数来改变。在我们机构中，对使用切线野不规则表面补偿治疗的 60 名乳腺癌患者进行了回顾性研究。研究了 TPD 变化对剂量分布的影响，并将最佳 TPD 与后边界的最大场间距（S(max)）相关联。将 TPD 降低到 50%以下会将剂量推向乳房的前部。这会降低切线野后边界附近内侧和外侧区域的热点，特别是对于间隔较大的患者。在 23/60 名患者中，S(max)平均值为 23.9 +/- 1.6 cm，使用 TPD 在 35%到 45%之间，将接受超过处方剂量 107%的计划靶区的比例降低了 3.4% +/- 2.8%。我们部门的方案规定，如果 S(max)大于 24 cm，则使用 TPD 为 40%；对于较小的间隔，使用 TPD 为 50%。
