A study of the distance between the upper and lower targets in subsection total body irradiation by helical tomotherapy
10.3760/cma.j.issn.1004-4221.2017.11.016
- VernacularTitle:HT在分段TBI中上下靶区间距研究
- Author:
Haiyang WANG
1
;
Yuexin GUO
;
Xudong ZHANG
;
Fanyang KONG
;
Yangguang MA
;
Fei JIA
;
Lele LIU
;
Fangna WANG
;
Dandan XU
Author Information
1. 450052,郑州大学第一附属医院放射治疗部
- Keywords:
Target gap distance;
Helical tomotherapy;
Total body irradiation
- From:
Chinese Journal of Radiation Oncology
2017;26(11):1318-1321
- CountryChina
- Language:Chinese
-
Abstract:
Objective To investigate the optimal distance between the upper and lower targets in the subsection total body irradiation(TBI)using helical tomotherapy,and to analyze the dose distribution of abutment regions. Methods A total of 8 patients with acute leukemia with a height of about 120 cm were involved in the study. All patients were scanned from the calvarium to the toe by computerized tomography (CT,Siemens)with a thickness of 5 mm,and a lead wire was placed at a point 10 cm above the patella as a marker of the boundary between the upper and lower targets. The delineation of target volumes and organs at risk(OAR)was performed in the Varian Eclipse 10.0 doctor workstation. The different distances between the lead wires and the boundary of the two targets were delineated, and images were transferred to the HT workstation to design the radiotherapy planning,including Jaw width(5 cm),modulation factor(1.8),and pitch(0.43). The plans were superimposed together, and then the dose distribution in abutment regions with different target gaps was analyzed to find the optimal distance. Results When the target gap was 5 cm, the dose distribution in abutment regions was satisfactory. However,the dose was obviously insufficient when the gap was more than 5 cm;the doses in abutment regions significantly exceeded the prescribed doses when the gap was less than 5 cm. Conclusions In the subsection TBI using HT, different parameters were designed,including Jaw width(5 cm), modulation factor(1.8), pitch(0.43), and slice thickness(5 mm). The upper and lower borders of the targets should be 2.5 cm away from the lead wire,that is,a gap of 5 cm,thus avoiding the dose-related hot or cold spots in the target convergence and ensuring a safer and more accurate radiotherapy.
