Dosimetric comparison of helical tomotherapy and volumetric modulated arc therapy for latestage
nasopharyngeal carcinoma(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2018年第9期
- Page:
- 1005-1011
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Dosimetric comparison of helical tomotherapy and volumetric modulated arc therapy for latestage
nasopharyngeal carcinoma
- Author(s):
- CHENG Tingting1; ZHANG Yanqiu2; ZHANG Zijian1; HUANG Xinqiong1; JIN Zefu1; LIU Gui1; HU Yongmei1; LI Shan1; SHEN
Liangfang1
- 1. Department of Radiation Oncology, Xiangya Hospital, Central South University, Changsha 410008, China; 2. Department of
Radiotherapy, First Hospital of Qinhuangdao, Qinhuangdao 066000, China
- Keywords:
- Keywords: nasopharyngeal carcinoma; helical tomotherapy; volumetric modulated arc therapy; dosimetry
- PACS:
- R811.1
- DOI:
- 1005-202X（2018）09-1005-07
- Abstract:
- Abstract: Objective To compare the dosimetric characteristics of helical tomotherapy (HT) and volumetric modulated arc therapy
(VMAT) for late-stage nasopharyngeal carcinoma. Methods TomoHDTM planning system was used to design HT plans for 10
randomly selected patients who had been treated with VMAT for late-stage nasopharyngeal carcinoma. Under the condition of
meeting the same prescription dose requirements, the dosimetric indexes of planning target areas (PGTvnx, PGTVnd, PTV1 and
PTV2) and organs-at-risk (OAR) of the two plans were evaluated and compared. The dosimetric indexes of planning target areas
included minimum dose, maximum dose (Dmax), median dose, conformity index and homogeneity index, and V107 (%); and the
dosimetric indexes of OAR included the Dmax of spinal cord, brain stem, lens, optic nerve, optic chiasma and pituitary, the Dmax
andV60 of temporal lobe, the V30 of parotid gland, and the V50 of temporomandibular joint. The dose of normal tissues B-P and total monitor units were also compared between HT plans and VMAT plans. Results Paired sample t test was conducted on the
dosimetric indexes of target areas, OAR and normal tissues. No statistical differences were found in the dosimetric parameters
of PGTVnd between the two plans, except the Dmax and median dose of PGTVnd which were slightly decreased in HT plans
(t=-4.734, -3.341; P=0.001, 0.009) and conformity index which was better in HT plan (t=-0.403, P=0.026). All dosimetric
parameters of PGTVnx, PTV1 and PTV2 didn’t show any statistical differences. The comparison of OAR dose between VMAT
plans and HT plans showed that there were statistical differences in some dosimetric indexes, including the Dmax of brain stem
which was decreased in HT plan (t=-2.309, P=0.046), the Dmax of contralateral optic nerve which was increased in HT plan
(t=0.050, P=0.002), the Dmax on both sides of the temporal lobe which was decreased in HT plan (t=-4.929, -3.480; P=0.001,
0.007), the V30 on both sides of the parotid glands which was decreased in HT plan (t=-5.971, -5.603; P=0.000, 0.000). As for
the other dosimetric indexes of OAR, no statistical significance was found between the two plans. Moreover, the V5, V10, V15,
V20, V25 of normal tissues B-P were slightly increased in HT plans as compared with VMAT plans, with statistical significance
(t=9.141, 8.409, 7.100, 5.883, 3.560; P=0.000, 0.000, 0.000, 0.000, 0.049) and no statistical differences were found in the other
dosimetric indexes of normal tissues B-P. The sum of the monitor unit of each field in HT plans and VMAT plans was
6 345±210, 821±38, respectively, with statistical differences (t=-20.234, P=0.000), and the delivery time of the two plans was
(9.1±0.4), (6.9±0.3) min, respectively, with statistical differences (t=-10.236, P=0.000). Conclusion According to the dosimetric
characteristics of the two schemes, in general, HT scheme should be considered for the plan with high complexity, while VMAT
scheme for the plan with general complexity. In clinical practice, different plans should be selected based on different situations.
If the patient has poorer tolerance, VMAT plan should be considered. For the patient who has higher requirements for the protection
of normal organs, such as parotid gland, HT plan is more suitable.
Last Update: 2018-09-28