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Objective To explore the feasibility of using the optimization parameters modification and optimization processes modification to reduce the total monitor units ( MUs ) in the Eclipse radiotherapy treatment planning system (TPS). Methods Based on the radiotherapy plan of 10 patients with nasopharyngeal carcinoma, a total of 90 plans were designed for 9 groups using different optimization parameters and processes. The total MUs and the exposure dose of the organs among the different plans were compared. Results There was no significant difference in the doses of the organs at risk (class I) under the premise of target dose requirements (all P>0.05). The increase of the weight of the target area and the organs at risk will increase the total MUs. The increase of the preset limit value of the minimum MUs in the subfield will reduce the total MUs. The increase of the fluence smoothness in the X and Y directions will increase the total MUs. An unreasonable minimum MU value will increase the total MUs. Under the condition that the organ exposure is not changed significantly, the influencing factors of MU are ranked as weight>fluence smoothness>minimum MUs. Conclusions Parameter setting and process planning can reduce the total MUs to a certain extent. However, due to the complexity of the influence of optimization parameters on the plan, the optimization process should be preferred. Especially in the Eclipse TPS, the method of gradual optimization to achieve the final dose distribution requirement and then remove the fluence re-optimization is more convenient and effective for reducing the total MUs.
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Objective To explore the effects of improvements on setup error ( SE ) and clinical target ( CTV ) margin of supraclavicular field ( SCF ) by using moisture-cured resin cushion and breast bracket for lower neck fixation in breast cancer patients who underwent post-mastectomy radiotherapy. Methods Totally 13 patients with breast cancer who underwent post-mastectomy radiotherapy were enrolled. All patients were immobilized by breast bracket and moisture-cured resin cushion. Firstly, each patient′s lower neck and head was fixed well by moisture-cured resin cushion, filling the gap between the neck and breast bracket. Secondly,each patient underwent the cone-beam CT ( CBCT) at the first, tenth and twentieth treatment after positioning. Then these CBCT images were registered to the planning CT to determine setup errors in translational and rotational directions, and SCF CTV margins by the systematic and random errors were evaluated. Results The setup errors in x (left-right), y (superior-inferior), z (anterior-posterior) translational directions were (2. 16 ± 1. 25), (1. 50 ± 1. 28), (1. 94 ± 1. 12) mm and (1. 76 ±1. 87)°, (1. 82 ±1. 12)°, (0. 99 ±0. 58)°, respectively in θ (pitch degree),Ф(roll degree),ψ( yaw degree) rotational directions. Non-parametric rank test ( Mann-Whitney U test) was performed with previous data, the differences of the setup error in y, z,θ directions were statistically significant ( Z =4. 152, 3. 415, 2. 053, P<0. 05). The margins from CTV were 4. 07, 4. 03 and 3. 73 mm in x, y and z directions, respectively. Compared with the previous study on SCF, CTV margin required 8, 8 and 6 mm in x, y and z axis directions, the volume of CTV to PTV were decreased by 32. 73% on average. Conclusions Compared with plastic circular pillow alone, moisture-cured resin cushion with breast bracket locating method could reduce setup errors in SCF target region. The margins from CTV to PTV weredecreased to 4. 07, 4. 03 and 3. 73 mm in x, y and z axis directions at least.
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Objective To explore the effects of improvements on setup error ( SE ) and clinical target ( CTV ) margin of supraclavicular field ( SCF ) by using moisture-cured resin cushion and breast bracket for lower neck fixation in breast cancer patients who underwent post-mastectomy radiotherapy. Methods Totally 13 patients with breast cancer who underwent post-mastectomy radiotherapy were enrolled. All patients were immobilized by breast bracket and moisture-cured resin cushion. Firstly, each patient′s lower neck and head was fixed well by moisture-cured resin cushion, filling the gap between the neck and breast bracket. Secondly,each patient underwent the cone-beam CT ( CBCT) at the first, tenth and twentieth treatment after positioning. Then these CBCT images were registered to the planning CT to determine setup errors in translational and rotational directions, and SCF CTV margins by the systematic and random errors were evaluated. Results The setup errors in x (left-right), y (superior-inferior), z (anterior-posterior) translational directions were (2. 16 ± 1. 25), (1. 50 ± 1. 28), (1. 94 ± 1. 12) mm and (1. 76 ±1. 87)°, (1. 82 ±1. 12)°, (0. 99 ±0. 58)°, respectively in θ (pitch degree),Ф(roll degree),ψ( yaw degree) rotational directions. Non-parametric rank test ( Mann-Whitney U test) was performed with previous data, the differences of the setup error in y, z,θ directions were statistically significant ( Z =4. 152, 3. 415, 2. 053, P<0. 05). The margins from CTV were 4. 07, 4. 03 and 3. 73 mm in x, y and z directions, respectively. Compared with the previous study on SCF, CTV margin required 8, 8 and 6 mm in x, y and z axis directions, the volume of CTV to PTV were decreased by 32. 73% on average. Conclusions Compared with plastic circular pillow alone, moisture-cured resin cushion with breast bracket locating method could reduce setup errors in SCF target region. The margins from CTV to PTV weredecreased to 4. 07, 4. 03 and 3. 73 mm in x, y and z axis directions at least.
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Objective To evaluate the setup errors for lower neck with cone beam CT (CBCT) in breast cancer patients immobilized by breast bracket,and to probe the margins from supraclavicular clinical target volume (CTV) in 3 directions.Methods A total of 14 breast cancer patients with supraclavicular lymph node radiation were enrolled.All patients were immobilized by breast bracket,and each patient would undergo CBCT at the first,tenth and twentieth treatment after positioning,respectively.Then these CBCT images were registered to the planning CT to determine setup errors in translational and rotational direction,and evaluated correlation between them.At last,CTV margins were calculated from the systenatic and random errors.Results The setup errors on x (left-ring),y (superior-inferior),z (anterior-posterior) translational directions were (2.89 ±.2.52),(3.96 ±2.97),(4.21 ±2.24) mm and on θ (pitch degree),φ (roll degree),Ψ (yaw degree) rotational direction were (2.38 ± 1.97)°,(1.60±1.63) °,(1.91 ±1.54)°,respectively.The margins from CTV were 8.08,8.13,6.30mminx,y and z direction.On y and z directions translational errors were correlated significantly with φ and Ψ degree rotational errors(Pearson =-0.515,-0.509,P ＜ 0.05).In inter-fraction only on z direction the setup changes were considered as correlative with Ψ degree (Pearson =-0.583,P ＜ 0.05).Conclusions For supraclavicular region irradiation breast cancer patients immobilized with breast bracket,the margins from CTV were recommended as not less than 8.08,8.13,6.30 mm in x,y,z directions,respectively.The position immobilized method and the positioning workflow should be further improved in order to reduce the influence of the neck rotational on setup errors.
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Objective To study the effects of using jaw tracking technique with Smart LMC algorithm on the absorbing dose of planning target volume (PTV) and organs at risk (OARs) in dynamic intensity-modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC).Methods Field fluencies of 10 cases of NPC patients were optimized using DVO algorithm on Eclipse TPS (11.0),and according to the same optimal fluence,MLC operation files were calculated using jaw tracking technique and jaw fixing technique respectively,dose distribution was calculated with AAA algorithm and jaw tracking IMRT plan (JT-IMRT) and jaw fixing IMRT plan (JF-IMRT) were generated respectively.Collimators' position at the plan implementation was observed,and the total number of plans' monitor units (MU),the dose of PTV,the absorb dose of OARs,and the actual fluence verification pass rate were compared.Results The collimators' opening gap distances in 166 control points of the JT-IMRT reduced in both X and Y directions in the field,compared to that of the JF-IMRT.Total number of the JT-IMRT's MU increased by 3.59％-11.63％.There was no statistical significant difference between the doses of the PTV.Statistical significance was found in the differences between maximum dose (Dmax) of brainstem,spinal cord,crystal,optic nerve,the mean dose (Dmean) and D50％ of parotid and their decreased values after therapy (t=5.70-8.66,P＜0.05).The actual fluence verification pass rate of the JT-IMRT was higher than that of the JF-IMRT.There was a significant difference between the results (t=5.18,P＜0.05).Conclusions The JT-IMRT plan of the smart LMC algorithm is more tolerant to the radiation leakage between inter-and intra-leaf.The dose of OARs is lower,while the dose calculation precision and the verification pass rate are higher,the actual radiation dose is more accurate and reliable.Therefore it is more suitable for clinical applications.
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Objective To study the dosimetry and safety of the non-coplanar IMRT plan for advanced lung cancer.Methods The two groups IMRT plans were designed with coplanar (5,7F) and non-coplanar field (5,7F-n) for patients.To compare the dosimetry of two groups and perform 4 patients F7-n IMRT plan.Results With the increase of the fields in each group PTV's CI were improved (all P =0.000),especially the 7F-n plan PTV's Dmean,Dmax,V95％ and HI also were improved (P=0.001,0.001,0.009,0.000) ; in the coplanar group each lung' s V5 increased (P =0.000,0.002,0.000) and whole lung's Dmean increased (P =0.000),but non-coplanar group whole lung's and contralateral lung's V5 reduce (P =0.001,0.005).Between the groups,7F-n plan PTV's indicators were all improved to compared with 5F plan (all P =0.000),and each lung's V20 reduced (all P =0.000),and whole lung's Dmean,V30,contralateral lung' s V5 reduced (P =0.000,0.001,0.000),and spinal cord' s Dmax also reduced (P =0.033),but ipsilateral lung's V5 and heart's Dmean increased (P =0.000,0.003);with compared to 7F plan,the 7F-n's ipsilateral lung's V5 and heart's Dmean also increased (P =0.000,0.048),but whole lung' s and contralateral lung's V5 decreased (all P =0.000).Four patients were performed successfully non-coplanar IMRT treatment,no collision occurred.Conclusions 7 fields non-coplanar IMRT plan not only improve the dose distribution of PTV,but also effectively control the volume of low dose lung increase,lung V20 and Dmean reduce too.Thus recommended to use this design in patients with advanced lung cancer for radiotherapy
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Objective To study the probability safety assessment to analyze and evaluate radiation error risk in the external beam radiotherapy,so as to establish and strengthen the control and management of the radiotherapy process,continuous improvement of quality control and quality management.Methods To build the whole of radiotherapy flow chart and process tree,using the decision tree model to determine critical control points in the whole process,making risk assessment chart and analyzing 4 patients with potential safety hazards error.Results The whole process is divided into 22 missions in 3 functional areas,the entire cover 15 branches and 59 key and 11 key control point.The enumeration of error as risks and critical control points has certain correlation.Conclusions Probabilistic safety assessment method have strengthened manage,analyze and control to risk,and all these provide the basis for developing and improving radiotherapy process control management.Radiotherapy quality management for future multidisciplinary and high-level management personnel who take up provides a prospective study.