Tamaki Tomoaki, Noda Shin-Ei, Ohno Tatsuya, Kumazaki Yu, Kato Shingo, Nakano Takashi
Department of Radiation Oncology, Fukushima Medical University, Fukushima, Japan; Department of Radiation Oncology, Gunma University Graduate School of Medicine, Gunma, Japan; Department of Radiation Oncology, Saitama Medical University International Medical Center, Saitama, Japan.
Department of Radiation Oncology, Gunma University Graduate School of Medicine, Gunma, Japan.
Brachytherapy. 2016 Sep-Oct;15(5):598-606. doi: 10.1016/j.brachy.2016.06.006. Epub 2016 Jul 27.
To analyze the dose-volume histogram of the central shielding technique for cervical cancer radiotherapy by computing the composite three-dimensional EQD2 dose distributions of external-beam radiotherapy plus intracavitary brachytherapy.
On a phantom, three patterns of high-risk clinical target volume (HR-CTV) with right-left diameters of 3, 4, and 5 cm were created using clinical data. Four patterns of combinations of whole-pelvis irradiation plus "pelvis irradiation using the central shielding technique" (CS) (shielding width, 3 or 4 cm) were created: 20 Gy/10 fractions + 30 Gy/15 fractions, 30 Gy/15 fractions + 20 Gy/10 fractions, 40 Gy/20 fractions + 10 Gy/5 fractions, and 50 Gy/25 fractions + 0 Gy. The intracavitary brachytherapy plan was set as 24 Gy/4 fractions prescribed to the Point A. The HR-CTV D90/D98 and modeled bladder/rectum D2cc were computed using the composite EQD2 dose distributions of all the treatment combinations.
If appropriate combinations of the treatment plans were selected on the basis of the CS doses and the HR-CTV sizes, the D90/D98 of HR-CTV 3 cm, HR-CTV 4 cm, and HR-CTV 5 cm were 89.7 Gy/80.6 Gy, 77.3 Gy/72.0 Gy, and 73.0 Gy/69.2 Gy in the case of CS width 3 cm, respectively; and 86.2 Gy/76.0 Gy, 73.3 Gy/67.6 Gy, and 70.9 Gy/67.1 Gy in the case of CS width 4 cm, respectively. The contributions of CS to the HR-CTV D90/bladder D2cc/rectum D2cc values were 24-56%/28-32%/9% of the CS plan doses for shielding width of 3 cm and were 13-35%/11-16%/5-6% for shielding width of 4 cm.
The dose contributions of CS were variable but not negligible when analyzing the total doses delivered to the HR-CTV.
通过计算外照射放疗加腔内近距离放疗的复合三维等效均匀剂量（EQD2）分布，分析宫颈癌放疗中心屏蔽技术的剂量体积直方图。
在体模上，利用临床数据创建了左右径分别为3、4和5 cm的三种高危临床靶区（HR-CTV）模式。创建了全盆腔照射加“使用中心屏蔽技术（CS）的盆腔照射”（屏蔽宽度为3或4 cm）的四种组合模式：20 Gy/10次+30 Gy/15次、30 Gy/15次+20 Gy/10次、40 Gy/20次+10 Gy/5次和50 Gy/25次+0 Gy。腔内近距离放疗计划设定为向A点给予24 Gy/4次。使用所有治疗组合的复合EQD2剂量分布计算HR-CTV的D90/D98以及模拟的膀胱/直肠D2cc。
如果根据CS剂量和HR-CTV大小选择合适的治疗计划组合，在CS宽度为3 cm的情况下，3 cm HR-CTV、4 cm HR-CTV和5 cm HR-CTV的D90/D98分别为89.7 Gy/80.6 Gy、77.3 Gy/72.0 Gy和73.0 Gy/69.2 Gy；在CS宽度为4 cm的情况下，分别为86.2 Gy/76.0 Gy、73.3 Gy/67.6 Gy和70.9 Gy/67.1 Gy。对于3 cm的屏蔽宽度，CS对HR-CTV D90/膀胱D2cc/直肠D2cc值的贡献分别为CS计划剂量的24 - 56%/28 - 32%/9%；对于4 cm的屏蔽宽度，分别为13 - 35%/11 - 16%/5 - 6%。
在分析给予HR-CTV的总剂量时，CS对剂量的贡献是可变的，但不可忽略。
