Preliminary exploration of the influence of beam orientation and beam number on the optimization of IMRT plan with cervical cancer / 中华放射医学与防护杂志

Objective To explore the influence of the number and orientation of the beams on the optimization of IMRT plan.Methods Four IMRT plans were designed for 9 patients with cervical cancer,and 7 and 15 fields were applied.The 15-field plans had 30 segments and the 7-field plans had 55 segments.The initial beam angle degrees were 0° and 180°,respectively.Dose delivery time,MUs of plans,the dose distributions of the targets,organs at risk and normal tissues were analyzed and compared in the plans.Results Compared the plans with different beam directions under the same amount,no difference of the irradiation dosimetry in the target and organs at risk was found,except for irradiation dosimetry received by the 7-field 180° small intestine was about 4％ higher than the other three plans(F=6.164,P＜0.05).The terms of the volume of organs at risk got high dose irradiation(V40 and V30 of the rectum and bladder,V40 of the small intestine),which was similar in the 7-and 15-field plans.V20 and Dmean of organs at risk were significantly smaller(F=3.665-10.503,P＜0.05)in the 15-field plans.The 15-field plans needed a little longer treatment time(F=0.312,P＜0.05)and HI was slightly worse (F=12.933,P＜0.05),but the number of MUs was significantly reduced(F=4.650,P＜0.05).Conclusions Increasing the beam number will offset the negative impact of sub field reduction and get the similar dose distribution result.

Improved genetic algorithm in optimization of beam orientation in intensity modulated radiotherapy / 中华放射肿瘤学杂志

manual beam orientation selection, beam orientation optimization which is feasible in IMRT planning may significantly improve the efficiency and result.

Optimization of beam orientations in three-dimensional conformal radiotherapy with the genetic algorithm / 中华放射肿瘤学杂志

Objective To develop a beam orientation optimization algorithm for the gantry orientation in three-dimensional conformal radiotherapy(3 DCRT).Methods Patients' data were imported from the Pinnacle v 7.2 treatment planning system.including the DICOMRT and dose distribution files.These imported files were merged using a uniforiB coordinate system.The algorithm determined the optimized beam weight for each beam group and optimized the beam orientation with genetic algorithm.The optimized parameters,including the optimized beam orientations and weights,were exposed back to the Pinnacle v 7.2 to compare with the conventional 3DCRT plan.The optimized algorithm was implemented with our in-house program. The dose distributions, the DVH diagram and the conformity index of two lung cancer patients were compared. Results for the two lung cancer patients,the conformity index of the optimized plan(0.59 and 0.7)was higher than the conwentional 3DCRT plan(0.36 and 0.58).The maximum dose in spinal cord was reduced by 17.8%and 22.4%,the lung V20 reduced by 3.12%and 4.35%,and V30 reduced by 4.47%and 1.49%.For the brain tumor patient. the dose of lens and eyes was also decreased significantly. Conclusion This beam orientation optimization can be used as an assistant planning tool.

A Study on IMRT Beam Weight and Orientation Optimization based on Genetic Algorithm with Two Populations / 医疗卫生装备

Objective To study the application of the genetic algorithm with two populations in optimization of both IMRT beam weight and orientation.Methods The genetic algorithm with two populations was used to optimize IMRT beam weight and orientations with three dimensional pencil beam dose calculation model. The algorithm was implemented in Visual c#. Net. And the results were analyzed. Results The modest change of the beam orientation resulted in more conformal dose distribution in target volume, and large high dose area was included. Further more, genetic algorithm with two populations gave such a clinically acceptable computation time. Conclusion Little change had distinct influence on dose distribution when there were few beam orientations. The genetic algorithm with two populations was an effective and global optimization method because of its parallel, robust and global. It provided satisfying results when used to optimize IMRT beam weight and orientations

Influence of dose distribution selected from different beam orientation for a nasopharyngeal carcinoma IMRT plan / 中国癌症杂志

Purpose:To evaluate the different dose distribution created by three different plans on a nasopharyngeal carcinoma case with simultaneous integrated boost intensity modulated radiation therapy (SIB-IMRT). Methods:we designed three different SIB-IMRT plans on a nasopharyngeal carcinoma case, one was from anterior direction of the head, 5 non-equally spaced fields, another was from posterior direction of the head, 5 non-equally spaced fields also, third was 5 equally spaced fields around the head. Each plan had its dose distribution to the target and main critical structures.Results:No significant difference of dose distribution to the target when comparing the previous three different IMRT plans. However, dose to the parotids delivered from 5-equally spacd was obviously lower than the other plans, dose to the optic chiasm was much lower created by the plan designed from the posterior direction of the head with 5 non-equally spacea field.Conclusions:For a nasopharyngeal carcinoma case, there is no significant difference of dose distribution to the target compared with three different 5-beam orientation SIB-IMRT plans. To protect parotids, we recommend designing a plan with equal beam direction around the head. When the target is very close to the optic chiasm, plauning from posterior direction of the head should be better.