Dosimetric comparison of VMAT plans in different modes for cervical cancer: flatting filter free vs flattening filter(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2017年第11期
- Page:
- 1110-1116
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Dosimetric comparison of VMAT plans in different modes for cervical cancer: flatting filter free vs flattening filter
- Author(s):
- WANG Zhanyu; TAN Junwen; LONG Yusong; HE Xiantao; WEI Ting; LI Gang
- Room of Radiotherapy, Department of Oncology, Fourth Affiliated Hospital of Guangxi Medical University, Liuzhou 545005, China
- Keywords:
- ; Keywords: cervical cancer; flatting filter free; volumetric-modulated arc therapy; dosimetric comparison
- PACS:
- R815.6
- DOI:
- DOI:10.3969/j.issn.1005-202X.2017.11.007
- Abstract:
- Abstract: Objective To compare the dosimetric characteristics of flatting filter free (FFF) volumetric-modulated arc therapy (VMAT) plans and flattening filter VMAT plan for cervical cancer for analyzing the feasibility of VMAT plan in FFF mode for cervical cancer. Methods Ten patients with cervical cancer admitted between January 2016 and March 2017 were selected. Based on the CT image and clinical target areas of each patient, two plans with the same prescription dose of 50.4 Gy and the same parameters were designed in RayStation planning system, namely VMAT plan with 6 MV FFF X-ray (6FFF plan) and VMAT plan with 6 MV flattening filter X-ray (6X plan). The dosimetric characteristics, dose passing rate, monitor unit and delivery time were compared between 6FFF plan and 6X plan. Results The differences between 6X plan and 6FFF plan in the maximum dose (D2%), mean dose and minimum dose (D98%) of planning target volume, target coverage and conformity index of target areas were trivial (P>0.05). The V45 and Dmean of bladder and the V45 of small intestine were lower in 6FFF plan than in 6X plan. The irradiated volume of normal tissue in 6FFF plan was less than that in 6X plan. Both 6FFF plan and 6X plan met the requirements for dosimetric verification. The average gamma passing rate in 6FFF plan were (98.52±0.66)%, slightly lower than that in 6X plan. 6FFF plan increased the average monitor unit to 1.34 times of that in 6X plans (P=0.000), but reduced the average delivery time to the 95.5% of that in 6X plan (P=0.012). Conclusion Though both 6X plan and 6FFF plan meet the requirements for clinical dosimetric verification, 6FFF plan has more advantages in decreasing the dose to low dose area in normal tissue and protecting organs-at-risk, which can reduce the risk of cancer recurrence. The dosimetric verification also showed that 6FFF plan can achieve a gamma passing rate satisfying the clinical requirements. Compared with 6X plan, 6FFF plan increases the monitor units but shortens the delivery time, which means using VMAT plan in FFF mode wouldn’t reduce efficiency. How to evaluate the clinical effect of the VMAT plan in FFF mode for cervical cancer needs further study.
Last Update: 2017-11-23