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| Impact of fluence smoothing on the dosimetry of cervical cancer radiotherapy |
| QIU Gang1, FANG Baoshuan1, WEI Qiang1, CHEN Li2, ZHANG Xiaoxiao2, CAO Can2, LI Qinghao2, HUAN Ran2, WANG Lu2 |
1. Hebei General Hospital, Shijiazhuang 050051 China;
2. Anshan Cancer Hospital, Anshan 114038 China |
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Abstract Objective To explore the dosimetric differences of radiotherapy plan for cervical cancer with 4 different fluence smoothing (FS) parameters using Monaco treatment planning system (Monaco TPS).Methods Fifteen patients with ⅠB2 stage cervical cancer in our hospital were enrolled in this study. And a 2 Volumetric Modulated Arc Therapy (VMAT) plan for each patient were completed by Monaco 5.11 TPS according to the X-Ray Voxel Monte Carlo (XVMC) method. For each plan was optimized by FS function, with the level of Off, Low, Medium and High. To compare the difference of plan optimization time, conformity index (CI), Homogeneity index (HI), Dmean, Dmin, D2% of PTV，dose to the organ at risk (OAR)，the number of Segments# and MU#，estimated total delivery time (ETDT), quantum Efficiency (QE) of the plans, the formation of Segments# with the same angle and verification of inserting 729 two-dimensional matrix into PTW octavius 4D module of different FS function levels, with the precondition of the Prescription isodose curve covering 95% of the target area. The data was analysed by multivariate factor analysis with the application of SPSS, and P < 0.05 was considered as statistically significant. And the Planned revenue score of different FS levels was also calculated.Results Except for the Dmin of PTV (the lowest value is (32.09 ±0.26) Gy for the Off group, and the highest value is (35.98 ±0.42) Gy for the High group), V40 of the rectum (the lowest value in the Medium group is 55.88% ±2.02%, and the highest value in the High group was 61.90% ±2.98%) and bladder (the lowest value was 45.01% ±2.08% in the Medium group, and the highest value is 50.45% ±1.98% in the High group), the V20 (the lowest value High group was 49.05% ±1.98%, the highest value Off group was 56.52%±1.75%) of femoral head (P < 0.05), there was no significant difference of the dose assessment results for PTV and OARs in 4 different FS function levels. In the High level, the ETDT, QE and MU# were showed better than other groups evidently, however, the number of Segments# showed no significant difference. The plan validation results was increased with the improvement of FS function level, and the level of High was considered to be the optimal. To compare the score of overall benefits of the plan, the level of Medium (-17.18 ±0.05) got the highest score, and the Low group (-17.58 ±0.05) and the High group (-17.42 ±0.06) have similar scores, and Off group (-18.81 ±0.08) has the lowest score.Conclusion Different FS levels of the Monaco 5.11 TPS can optimize the radiotherapy plan for cervical cancer, but the level of Medium is considered to be the most applicable.
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Received: 11 January 2021
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