Influence of Collimator Angle on Dose Verification of Portal Dosimetry
for Radiotherapy Plans of Cervical Carcinoma
SHI Feiyue1,2, WANG Min1, QIN Wei1, ZHAO Huanyu1, JIN Xun3
1. Radiation Therapy Center, Nanjing First Hospital, Nanjing Medical University, Nanjing Jiangsu 210006, China; 2. The Center
of Medical Physics with Nanjing Medical University, Nanjing Jiangsu 210029, China; 3. The Second Clinical Medical College,
Nangjing University of Chinese Medicine, Nanjing Jiangsu 210023, China
Abstract：Objective To investigate the influence of collimator angle on the results of portal dosimetry (PD) dose verification for
radiotherapy plans of cervical carcinoma. Methods Twenty-four treatment plans of cervical carcinoma were selected to carry out this
study. For each treatment plan, the field of G180 was selected to design two PD verification plans with two collimator angles (0° and
90°). Corresponding to two subfields (G180_0 and G180_1), one total filed (G180) and two collimator angles, there were six groups
of fields, G180_0-C0, G180_1-C0, G180-C0, G180_0-C90, G180_1-C90 and G180-C90. A Varian Clinac iX linear accelerator
was employed to deliver the 48 PD verification plans. Then the gamma pass rate and mean gamma value were analyzed by the
statistical analysis and comparative study. Results The values of gamma pass rate of G180_0-C0, G180_1-C0 and G180-C0 were
(99.06±0.68)%, (98.51±0.94)% and (96.28±1.66)%, respectively. The values of gamma pass rate of G180_0-C90, G180_1-C90
and G180-C90 were (98.61±0.68)%, (99.88±0.09)% and (96.58±1.37)%, respectively. For gamma pass rate, there was statistical
difference between G180_0-C0 and G180_0-C90 groups (P<0.05); there was significant statistical difference between G180_1-C0
and G180_1-C90 groups (P<0.05); but there was no statistical difference between G180-C0 and G180-C90 groups. For mean gamma
value, there were statistical difference between G180_0-C0 and G180_0-C90, G180_1-C0 and G180_1-C90, and G180-C0 and
G180-C90 (P<0.05). Conclusion For PD dose verification of cervical cancer plan, the collimator angle affects the gamma pass rate
of the subfield, and the mean gamma value of subfield and total field.
时飞跃1,2，王敏1，秦伟1，赵环宇1，金洵3. 准直器角度对宫颈癌计划Portal Dosimetry剂量验证的影响[J]. 中国医疗设备, 2019, 34(3): 48-50.
SHI Feiyue1,2, WANG Min1, QIN Wei1, ZHAO Huanyu1, JIN Xun3. Influence of Collimator Angle on Dose Verification of Portal Dosimetry
for Radiotherapy Plans of Cervical Carcinoma. China Medical Devices, 2019, 34(3): 48-50.
