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Objective:To analyze the intensity-modulated radiotherapy (IMRT) process based on the TG100 report, aiming to improve the quality control method and guarantee the safety and quality of IMRT.Methods:Based on the TG100 report, a risk analysis team was established. The flow chart of overall and each sub-step of IMRT was constructed. The failure mode and effect analysis method were adopted to determine all potential error modes in the process. The probability of of the error mode, the probability of being checked out and the severity of the effect of the error mode on the clinical bed were evaluated based on the pre-set scoring standard. The priority value of each error mode was calculated and ranked from high to low priority value. The top 20% is defined as the high-risk error mode, which was analyzed by error tree to improve the quality control method.Results:IMRT consisted of 11 main steps and 41 sub-steps, and 180 failure modes were detected. The priority values were ranged from 30 to 178. A total of 36 high-risk failure modes were found. The top 5 high-risk failure modes (RPN) consisted of setup error (178), electronic portal imaging device (EPID) registration (172), contouring error (166), treatment delivery error (160) and prescription dose error (156).Conclusion:TG100 report is practical and convenient to utilize, which can effectively and systematically improve IMRT process and provide safety and quality assurance of IMRT process.
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Objective:To create AAPM TG 119 test plans for intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in order to evaluate the accuracy of the United Imaging Healthcare′s URT treatment planning system (URT-TPS). The plans were delivered to the phantom using the United Imaging Healthcare′s URT-Linac 506C.Methods:The overall accuracy of IMRT and VMAT planning, measurement, and analysis were evaluated for four test geometries provided by American Association of Physicists in Medicine (AAPM) Task Group Report 119(TG-119) on multi-target, prostate, head and neck and C-shape (easy). The dose distributions were measured in the coronal plane. The point measurements were measured by a Farmer type ion chamber and fluence measurements were completed with film and Delta4 phantom, respectively. Measured planar dose distributions were analyzed using gamma index with criteria 3%/3 mm.Results:For IMRT and VMAT plans, the planning results matched the TG-119 planning results. Measured point doses of IMRT and VMAT were within 2.62% and 3.90% of the planned doses, respectively. Measured film dosimetry gamma values of IMRT and VMAT were> 97.50% and> 93.27%, respectively.Conclusion:Based on these analyses which were performed in line with the TG119 recommendations, it is evident that the URT treatment planning system and URT-Linac 506C have commissioned IMRT and VMAT techniques with adequate accuracy.
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Objective@#To investigate postoperative recurrent pattern of the thoracic esophageal squamous cell carcinoma (TESCC), aiming to provide a basis for the delineation of postoperative radiotherapy volume for TESCC.@*Methods@#Clinical data of 66 TESCC patients who recurred after the radical esophagectomy in Zhongnan Hospital of Wuhan University from 2011 to 2017 were retrospectively analyzed. According to the AJCC 8th edition-defined classification of esophageal carcinoma, regional lymph node stations 1 to 8M were defined as the upper-middle mediastinum region (UMMR), and stations 8Lo, 9 and 15 were defined as the inferior mediastinum region (IMR), stations 16 to 20 were regarded as the upper abdominal lymph node region (UAR).@*Results@#Among all 66 patients, 41 cases (62%) experienced loco-regional recurrence alone, 25 cases (38%) presented with distant metastasis alone. A total of 54 patients with 148 lymph node recurred after treatment. The highest risk region of lymph node recurrence was UMMR (118/148, 80%), after that, followed by UAR (24/148, 17%). With regard to 9 cases of UAR, 6 patients had lower TESCC, and 8 patients (89%) were graded as ≥ pathological stage Ⅲ.@*Conclusions@#The highest risk region of lymph node recurrence is UMMR in TESCC patients undergoing radical esophagectomy, which should be considered as the target volume in postoperative radiotherapy. For patients with lower TESCC ≥ pathological stage Ⅲ, UAR might be the target volume with cautions. Anastomosis and IMR are probably not the routine treatment volumes.
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Objective To investigate postoperative recurrent pattern of the thoracic esophageal squamous cell carcinoma (TESCC),aiming to provide a basis for the delineation of postoperative radiotherapy volume for TESCC.Methods Clinical data of 66 TESCC patients who recurred after the radical esophagectomy in Zhongnan Hospital of Wuhan University from 2011 to 2017 were retrospectively analyzed.According to the AJCC 8th edition-defined classification of esophageal carcinoma,regional lymph node stations Ⅰ to 8M were defined as the upper-middle mediastinum region (UMMR),and stations 8Lo,9 and 15 were defined as the inferior mediastinum region (IMR),stations 16 to 20 were regarded as the upper abdominal lymph node region (UAR).Results Among all 66 patients,41 cases (62％) experienced locoregional recurrence alone,25 cases (38％) presented with distant metastasis alone.A total of 54 patients with 148 lymph node recurred after treatment.The highest risk region of lymph node recurrence was UMMR (118/148,80％),after that,followed by UAR (24/148,17％).With regard to 9 cases of UAR,6 patients had lower TESCC,and 8 patients (89％) were graded as ≥ pathological stage Ⅲ.Conclusions The highest risk region of lymph node recurrence is UMMR in TESCC patients undergoing radical esophagectomy,which should be considered as the target volume in postoperative radiotherapy.For patients with lower TESCC ≥ pathological stage Ⅲ,UAR might be the target volume with cautions.Anastomosis and IMR are probably not the routine treatment volumes.
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Objective To investigate the precision and stability of optical surface imaging (OSI)system Catalyst in guiding radiotherapy positioning.Methods A total of 52 patients with five different tumor sites who underwent cone-beam computed tomography (CBCT)-guided radiotherapy were recruited in this investigation.For the first treatment fraction,the setup error was recorded as C after online CBCT correction,and the surface images of patients taken by Catalyst were set as the reference images Cref.For the following treatment fraction,patients were pre-corrected according to the Catalyst Cref image with the acceptable errors within 2 mm/ 2,and the pre-corrected errors were recorded as C1.Then,after online CBCT correction,the setup errors were recorded as C.The errors between post-corrected Catalyst surface image and Cref image were recorded as C2.For each treatment fraction,the difference between Catalyst correction errors C1 and CBCT corrected errors C was recorded as d1,and the difference between the post-corrected Catalyst errors C2 and Cref image was recorded as d2.d3=d1-d2.The values of d1 and d3 in the 6 dimensions were analyzed using single sample t-test.The correlation between C-C1 and d1-d2 was statistically analyzed by Pearson correlation analysis.Results The mean value of d1 and d3 for 52 patients were within 2 mm/2 °.CBCT-C1 and d1-d2 were both significantly correlated (R =3,7,P=0.00,0.01).Conclusions OSI system yield high accuracy and stability in radiotherapy positioning,which is of certain significance in radiotherapy positioning for cancer patients.
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With the rapid development of radiotherapy technology, traditional quality management will shift from a device-centric strategy to a process involving multiple people. In recent years,failure mode and effect analysis(FMEA)based on predictive risk assessment has gradually been applied in the quality management of radiotherapy process. The FMEA approach mainly includes four steps: process tree management,FMEA, error tree analysis, and the design of scheme for process quality management. The specific methods and results are different due to the specificity of radiotherapy process and the subjectivity of participants. Its reliability and feasibility have also been considered and verified. This article reviews the application of FMEA approach in some radiotherapy centers.
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In vivo dosimetry (IVD) is currently the most direct and effective means of quality assurance.The electronic portal imaging device (EPID) has been widely used for IVD verification owing to its favorable dosimetric properties.In recent years,an increasing number of EPID-based IVD studies have emerged around the world.The purpose of this paper is to give an overview of the present progress in EPID-based IVD studies,and to provide a reference for the subsequent application of EPID in IVD.
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Independent check is one of the key measures of quality control (QC) in radiotherapy and is essential for the assurance of radiotherapy accuracy.In recent years,with the application of computer-aided system,the automaticity of independent check,as well as its accuracy and efficiency,increases.Meanwhile,QC has evolved from a device-centered to a process-centered program.Therefore,independent check has been increasingly systematic and specific.This review gives a brief summary of the implementation and development of independent check.
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Objective To analyze the impact of electronic portal imagingdevice (EPID) position error on three-dimensional dose verification of volumetric modulated arc therapy (VMAT).Metbods Five Suremark SL-20 lead points were fixed on Elekta tray,and EPID images were collected in 0-360° rotation,one image per 5°.The position error relative to the accelerator was analyzed via Matlab.Then the images position error was corrected according to the analysis,and the 3D dose was reconstructed with the corrected images.The dose distributions of double arcs,clockwise arc(arc 1),and counterclockwise arc (arc 2) of 16 nasopharyngeal carcinoma patients' VMAT plan were evaluated by γ analysis,and the results of before and after position error correction were compared.Results Compared to 0° gantry angle,the error of source to the image distance (SID) was maximum (1.20 cm) when the gantry angle was 180°.On account of the SID change,the maximum error along the up-down (y) direction in the iso-center planar was 2.28 mm and the left-right (x) direction error was within ± O.5 mm.The 3D γ analyses of 16 nasopharyngeal carcinoma in VMAT plans were obviously increased after the position error along y was corrected.The double arcs,arc1 and arc 2 were increased by (4.12 ±1.67) ％ (t =-9.86,P＜ 0.05),(3.47±1.64) ％ (t=-8.46,P＜ 0.05) and (5.08±1.30) ％ (t=-15.63,P＜ 0.05) in 5％/3 mm standard,respectively.However,in 3％/3 mm standard,γ value of the double arcs,arc 1 and arc2 were increased by (7.63 ±2.24) ％ (t =-13.63,P＜ 0.05),(6.03 ±2.07) ％ (t =-11.66,P＜ 0.05),(9.17 ±2.23) ％ (t =-16.41,P＜ 0.05),respectively.Since the EPID position error along x was corrected after y,the 3D γ analysis of reconstruction dose indicated that the average of the 5％/3 mm and 3％/3 mm γ value were increased by 0.23％ and 0.24％,respectively.Conclusions EPID motion error along the gantry to table direction of the accelerator can't be ignored.When reconstruct dose based on EPID,a modification should be made for rebuilding more accurate patients' 3D dose distribution.