Shaikh Mubin Y, Tanny Sean
Department of Radiation Oncology, Rochester Regional, Rochester, NY.
Department of Radiation Oncology, SUNY Upstate Medical University, Syracuse, NY.
Brachytherapy. 2020 Mar-Apr;19(2):234-240. doi: 10.1016/j.brachy.2019.11.005. Epub 2019 Dec 24.
Breast intraoperative radiotherapy with electronic brachytherapy (eBT) sources, such as the Zeiss INTRABEAM and the Xoft Axxent, are used to treat the lumpectomy cavity using a stationary or a stepped 50 kVp X-ray source, respectively. For three comparable applicator sizes with volume differences <11%, we compare the dosimetry using clinical planning data.
A dosimetric comparison between the INTRABEAM and Axxent to the proximal 1.0 cm of tissue surrounding the applicator is performed using dose-volume parameters (DVPs): V, V, V, D, and Homogeneity Index (HI); HI was calculated as D/D. The dose-volume histograms of the INTRABEAM and Axxent were computed with measured percent depth dose data and with TG-43 parameters, respectively. The skin dose of 0.7-1.0 cm from the applicator surface was also computed.
The mean DVPs were 5.5 ± 0.8% V, 12.1 ± 1.5% V, 47.5 ± 5.8% V, 6.4 ± 0.6 Gy D, and 3.2 ± 0.3 HI for the INTRABEAM applicators compared with 7.4 ± 0.3% V, 14.7 ± 0.8% V, 55.2 ± 4.7% V, 4.0 ± 0.6 Gy D, and 6.4 ± 1.1 HI for the Axxent applicators. INTRABEAM skin doses ranged from 7.7 to 9.0 Gy at 0.7 cm to 5.5-6.8 Gy at 1.0 cm, whereas Axxent skin doses ranged from 10.7 to 13.0 Gy at 0.7 cm to 7.8 to 9.3 Gy at 1.0 cm.
We demonstrated ±5% comparable dosimetric coverage for tissue ≤0.5 cm from the cavity and higher skin dose for Axxent plans. The DVPs increased with applicator size and with stepped treatment delivery.
采用电子近距离放射治疗（eBT）源进行乳腺术中放疗，如蔡司INTRABEAM和Xoft Axxent，分别使用固定或步进式50 kVp X射线源来治疗乳房肿块切除腔。对于三种体积差异<11%的可比施源器尺寸，我们使用临床计划数据比较剂量测定。
使用剂量体积参数（DVPs）：V、V、V、D和均匀性指数（HI），对INTRABEAM和Axxent与施源器周围近端1.0 cm组织进行剂量测定比较；HI计算为D/D｡INTRABEAM和Axxent的剂量体积直方图分别根据测量的百分深度剂量数据和TG - 43参数计算得出。还计算了距施源器表面0.7 - 1.0 cm处的皮肤剂量。
INTRABEAM施源器的平均DVPs为：V 5.5±0.8%、V 12.1±1.5%、V 47.5±5.8%、D 6.4±0.6 Gy、HI 3.2±0.3，而Axxent施源器的平均DVPs为：V 7.4±0.3%、V 14.7±0.8%、V 55.2±4.7%、D 4.0±0.6 Gy、HI 6.4±1.1｡INTRABEAM在0.7 cm处的皮肤剂量范围为7.7至9.0 Gy，在1.0 cm处为5.5至6.8 Gy，而Axxent在0.7 cm处的皮肤剂量范围为10.7至13.0 Gy，在1.0 cm处为7.8至9.3 Gy。
我们证明对于距腔≤0.5 cm的组织，剂量测定覆盖范围可比，相差±5%，且Axxent计划的皮肤剂量更高。DVPs随施源器尺寸和步进式治疗递送而增加。
