Dosimetirc effects of carbon fiber couch on volumetric modulated arc therapy of cervical cancer(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2019年第1期
- Page:
- 37-42
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Dosimetirc effects of carbon fiber couch on volumetric modulated arc therapy of cervical cancer
- Author(s):
- KONG Wei; YE Hongqiang; HE Jianli; XIA Xinshe; ZHAO Ting; DING Wei; SHANG Jun
- Department of Radiotherapy, General Hospital of Ningxia Medical University, Yinchuan 750004, China
- Keywords:
- ; Keywords: cervical cancer; carbon fiber couch; volumetric modulated arc therapy; planning system; attenuation coefficient
- PACS:
- R815.6
- DOI:
- DOI:10.3969/j.issn.1005-202X.2019.01.008
- Abstract:
- Abstract: Objective To study the dosimetric effects of carbon fiber couch on the volumetric modulated arc therapy (VMAT) of cervical cancer and it’s correction methods. Methods Computed tomography (CT) electron density phantom was used to calibrate the CT value of large aperture CT, and the relative electron density-CT value curve was established with Eclipse 10.0 treatment planning system (TPS). After the carbon fiber couch on the medical electron linear accelerator was scanned with CT, the obtained CT image was transmitted to the Eclipse TPS and the CT value of the carbon fiber couch was measured. Base on the CT value, a carbon fiber couch model was established in the TPS. Under the same measurement conditions, the attenuation coefficients of the carbon fiber couch in the TPS and in the actual condition were measured and analysis. A total of 5 patients with stage IA or IIB cervical cancer were selected, and plans with no carbon fiber couch were designed using Eclipse TPS. Then, 3 models of carbon fiber couch of different thicknesses (Thin, Med and Thick) were established on the positioning image, and the plan with no couch was directly transplanted to the images of 3 different couches. Dose calculation was performed based on that the treatment center and machine unit remained unchanged. Finally, the dosimetric differences in planning target volume (PTV) and organs-at-risk (OAR) were compared between plan with and without carbon fiber couch and among plans with 3 different couches. Results For Thin and Thick carbon fiber couches, the deviation of attenuation coefficient between the actual measurement and TPS calculated results was not more than ±1%. There were statistical differences in the dose indexes of PTV and OAR between plans with no couch and those with couch (P<0.05). However, the thickness of carbon fiber couch has a certain effect on the accuracy of PTV and OAR dose evaluations. Conclusion Carbon fiber couch affects the dose distribution of VMAT plan for cervical cancer. Therefore, an appropriate model of carbon fiber couch should be established and participated in the dose calculation when VMAT is carried out. Moreover, the thickness of carbon fiber couch model should be determined according to the position relationship between PTV and carbon fiber couch.
Last Update: 2019-01-24