医科达ⅩⅥ锥形束CT头颈部扫描角度优化  

Optimizing gantry rotation of head and neck scanning for Elekta ⅩⅥ cone beam CT

作　　者：李正贤 赵晶晶 马永乐 王博生 杨立婷 周莉[2] 张艺宝[3] 

机构地区：[1]吉林国文医院放疗科,吉林公主岭136100 [2]四川大学华西医院肿瘤中心(生物治疗国家重点实验室)放射物理技术中心,四川成都610041 [3]北京大学肿瘤医院暨北京市肿瘤防治研究所放疗科/恶性肿瘤发病机制及转化研究教育部重点实验室,北京100142

出　　处：《中国医学物理学杂志》2017年第11期1106-1109,共4页Chinese Journal of Medical Physics

基　　金：国家自然科学基金(11505012);北京市医院管理局“青苗”计划专项经费(QML20151004);北京市卫生和计划生育委员会首都卫生发展科研专项;北京市自然科学基金(7172048,1174016);北京大学深化专业学位研究生教育综合改革项目(住院物理师规范化培训体系建设)

摘　　要：目的:比较医科达ⅩⅥ头颈部标准全弧和快速半弧模式的辐射剂量和图像质量,并优化扫描角度降低辐射敏感器官的剂量。方法:利用PTW静电计和CT电离室测量头颈CTDI模体正位0、3、9点方向,以及逆时针旋转模体45°后3、0点方向,模拟甲状腺,左、右腮腺和左、右晶体的辐射剂量。同时测量加权CT剂量指数(CTDI_w)。除测量标准全弧和半弧外,还通过修改半弧脚本将默认315°~160°机架旋转变更至335°~180°,并对顺/逆时针扫描分别测量。用Catphan503模体评估各参数图像质量。结果:全弧CTDI_w为0.81/0.81 m Gy(0°/45°),约是半弧的2倍。优化模式顺时针扫描剂量最低,快速模式顺时针最高,对于甲状腺、左腮腺、左晶体、右晶体、0°和45°CTDI_w,前者比后者低3.17%、3.55%、2.04%、1.75%、0.93%和4.18%。角度优化不会对图像质量产生明显影响,但可减少治疗前机架空转时间从而提高效率。结论:头颈快速模式较标准全弧模式剂量低且图像质量满足临床要求,角度优化后的快速模式可进一步降低敏感器官剂量并提高临床效率。Objective To compare the irradiation dose and image quality of Elekta XVI head and neck scans using standard full arc and fast partial arc protocols, and reduce the dose to sensitive organs by optimizing gantry rotation. Methods The standard head and neck CTDI phantom at 0, 3, 9 o’clock （upright setup）, and 3, 0 o’clock （rotating the phantom by 45o, counter clockwise） were measured using a PTW electrometer and a CT chamber to simulate the irradiation dose to thyroid, left and right parotid, left and right lenses. Weighted CT dose index （CTDIw） of each protocol was also measured. In addition to the measurement of standard full and partial arc scan, the configuration script of partial arc scan was modified, where the gantry rotation was changed from 315o-160o to 335o-180o, and the dose in clockwise and counter clockwise scans were measured, respectively. Image quality was assessed using Catphan 503 phantom. Results CTDIw of standard full arc scanning was 0.81/0.81 mGy （0o/45o）, which was about twice of that of partial arc scanning. The optimized partial arc clockwise scan and standard partial arc clockwise scan had the lowest dose and the highest, respectively, and compared with the latter, the former reduced dose to thyroid, left parotid, left lens, right lens, 0o and 45o CTDIw by 3.17%, 3.55%, 2.04%, 1.75%, 0.93% and 4.18%, respectively. Gantry rotation optimization did not affect image quality obviously, but improved clinical efficiency by reducing unnecessary gantry idle time. Conclusion Relative to standard full arc scan, partial arc XVI scan can achieve satisfactory image quality for head and neck at a lower dose. Optimized partial arc protocol can further reduce imaging dose to sensitive organs and improve clinical efficiency.

关 键 词：锥形柬CT 参数优化 影像引导放疗 成像剂量 放射防护 

分 类 号：R730.55[医药卫生—肿瘤] R811.1[医药卫生—临床医学]