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Objective To evaluate the clinical efficacy and adverse events of intensity-modulated radiotherapy ( IMRT ) in the treatment of intermediate risk localized prostate cancer, and analyze the significance of prostate-specific antigen ( PSA) level changes. Methods Clinical data of 66 patients with intermediate risk localized prostate cancer admitted to our hospital between 2007 and 2018 were retrospectively analyzed. Sixty patients were treated with endocrine therapy before radiotherapy. The radiation field covered the pelvic lymph node drainage area in 6 cases. Forty-seven patients received image-guided radiotherapy ( IGRT) . The median dose in the prostate and seminal vesicle was 78 Gy and 48 Gy in the pelvic lymph node drainage area. The survival rate was calculated using the Kaplan-Meier method. Results The median age was 77 years. The median follow-up time was 71. 3 months. The 5-year sample size was 47. The 3-and 5-year overall survival (OS) was 98％ and 90％.The 3-and 5-year cancer-specific survival (CSS) was 100％ and 93％.The 3-and 5-year biochemical relapse-free survival was 97％ and 86％. The mean time of PSA declining to the nadir was 5. 83 months. The median level of PSA nadir was 0. 06 ng/ml after IMRT. The incidence of grade I andⅡearly adverse events in the urinary system was 38％ and 6％. The incidence of grade I andⅡearly adverse events in the gastrointestinal system was 21％ and 3％. The incidence of grade I andⅡadvanced-stage adverse events in the urinary system was 9％ and 2％. The incidence of grade I advanced-stage adverse events in the gastrointestinal system was 5％. Conclusions IMRT yields high clinical efficacy in the treatment of intermediate risk localized prostate cancer with a low risk of adverse events in the early and advanced stage. The monitoring of PSA after IMRT contributes to the assessment of clinical prognosis.
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Objective To analyze the data from intensity-modulated radiotherapy ( IMRT) for prostate cancer guided by kilovoltage cone-beam computed tomography (CBCT), and to provide a clinical basis for selecting the optimal image registration method and reasonable target volume margins.Methods A total of 16 patients with prostate cancer who received radical IMRT were enrolled, and CBCT for online position verification was performed 214 times.The images were obtained after conventional skin marking and laser alignment, and automatic registration, bone registration, soft tissue registration, and manual registration were performed for CBCT images and planned CT images.The differences between these four registration methods were evaluated, and the margins for extending clinical target volume into planning target volume (PTV) were calculated.Results The setup errors in left-right, anterior-posterior, and cranial-caudal directions for automatic registration, bone registration, soft tissue registration, and manual registration were-0.6±2.8 mm/-0.6±4.5 mm/-0.6±3.8 mm,-0.7±2.7 mm/-0.9±4.5 mm/-0.8±4.1 mm,-0.8± 2.6 mm/-0.3±4.4 mm/-1.1±4.0 mm, and-0.6±2.9 mm/-0.7±5.1 mm/-0.9±3.9 mm, respectively. There were no significant differences between the four registration methods.The margins for extension in the left-right, anterior-posterior, and cranial-caudal directions were calculated as 4.7 mm, 5.2 mm, and 6.5 mm, respectively.Conclusions With a comprehensive consideration of various factors, a default setting of automatic registration and manual fine adjustment is appropriate for CBCT-guided radiotherapy for prostate cancer.The margins for extension in the left-right, anterior-posterior, and cranial-caudal directions are 4.7 mm, 5.2 mm, and 6.5 mm, respectively.
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Objective To observe the motions of the rectum and bladder by image?guided radiotherapy ( IGRT) and to analyze their impact on treatment. Methods Eighteen patients with prostate cancer undergoing intensity?modulated radiotherapy ( IMRT) were enrolled in the study and 247 cone?beam computed tomography ( CBCT) images were obtained from this study. The clinical target volume, bladder, and rectum were contoured on all simulated CT and CBCT to examine their volume and position changes. The dose distributions were recalculated based on the data of the x?, y?, and z?axis setup errors. The doses to planning target volume ( PTV) and organs at risk were calculated in the replanning, and their impact on treatment was analyzed. Comparison of the planning and replanning results was made by paired t?test. The effects of displacements and volumes of the bladder and rectum on target doses were analyzed by Pearson correlation method. Results Great changes in the volumes of the bladder and rectum were observed during the treatment. For the planning and replanning results, PTVD95% was 7777. 37 cGy vs. 7628. 56 cGy ( P=0. 027), PTV Dmin was 87. 91 cGy vs. 83. 35 cGy (P=0. 000), and RVP was 5. 89% vs. 8. 31%(P=0. 000). There were correlations between PTVD95% and the motions of the bladder and rectum, with correlation coefficients of 0. 296 and 0. 177, respectively. The correlation coefficient between rectal volume and PTVD95% was 0. 115, indicating a certain correlation. There is a certain correlation between and PTV Dmin and bladder volume, with a correlation coefficient of?0. 128. Conclusions The recovery of the state during localization for the bladder and rectum, especially the latter, has great significance to ensure the target dose and reduce exposure of the rectum in the IMRT for prostate cancer.
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Objective To investigate the set-up errors of super and middle part of esophageal cancer patients using cone-beam CT (CBCT) during intensity modulated radiotherapy (IMRT),hence determine various margins from CTV to PTV.The corresponding influence on the normal tissues (lung and spinal cord) was also discussed.Methods From December 2012 to December 2013,12 patients with upper and middle segment of esophageal cancer were chosen.Using their 60 sets of weekly acquired CBCT images prior to the treatment,the lateral,longitudinal,and vertical set-up errors of each patient were obtained.Based on these measured errors and the target motions,we adopted new margins to create new PTV.Then IMRT plans were created for the original PTV (5 mm margin in all directions on CTV) and new PTV respectively.On condition of the same target coverage (V95 ≥ 95％),the doses to lungs (V5,V20,V30,D) and spinal cord (D1 cm3) were compared statistically between the original and new plans.Results According to the 60 CBCT scans,the average left-right (RL),superior-inferior (SI),anterior-posterior (AP) set-up errors were (2.02 ± 1.74),(2.03 ± 1.93),and (2.02 ± 1.89) mm respectively.The margins were 5.6 mm (RL),8.5 mm (SI),and 4.7 mm (AP) for the upper esophagus and 6.2 mm (RL),11 mm (SI),and 5.0 mm (AP) for the middle esophagus.Comparison of both lungs and spinal cord suggested significant differences between the two plans (t =-8.23,-5.55,-4.66,-6.87,-4.67,P ＜0.05).Conclusions The margins from CTV to PTV should be created via CBCT-measured set-up errors and previous reports,which can be helpful for clinical treatment.
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Objective To study corrective method for displacement in the procedure of electronic portal imaging device (EPID)-based intensity-modulated radiotherapy dose valuation by studying the relative mechanical displacement of different vendor EPID (aS1000,Varian; aS500,Varian; iViewGT,Elekta).Methods A 5 cm × 5 cm field was set up to acquire portal images for three kinds of EPID,then a in house software was used to analysis the portal images.The relative displacement was acquired via analyzing a series of comparation between center positions of gantry angle ranging from 0° to 360° and gantry angle at 0°.Results In the lateral direction,the maximum relative displacement of EPID with aS1000,S500 and iViewGT were (-0.23 ±0.17) mm,(2.94±0.17) mm and (0.35 ±0.09) mm,respectively.In the longitude direction,the displacements were (-4.16 ± 0.20) mm,(-4.15 ± 0.25) mm and (-1.66 ±0.11) mm,respectively.As to longitude direction,the displacements could be well fitted with the usage of quadruplicate empiric function.Conclusions There is a significant difference at the aspect of relative displacement between different vendors EPID at different gantry angles.And the displacement in the longitude direction is obviously larger than in the lateral direction.The relative displacement should be corrected when applying EPID to the intensity-modulated radiotherapy dose verification at different gantry angles.
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ObjectiveTo test a three-dimensional dose verification system,which reconstructing dose to anatomy based on modeling and online measurements ( RDBMOM ),and to evaluate the accuracy and feasibility of its application in clinical intensity-modulated radiotherapy (IMRT) quality assurance.Methods Phantom plans of regular and irregular fields were selected for the testing.All test plans were implemented and the dose distributions were measured using the thimble ion-chamber and two-dimensional ion-chamber array,the accuracy of RDBMOM were then evaluated by comparing the corresponding results.Two practical treated nasopharyngeal carcinoma IMRT plans were verified with RDBMOM and the clinic significancy were valued.ResultsCompared with measurements of the thimble ion-chamber,deviations of RDBMOM were within 1％ in all tested cases except small field of 3 cm ×3 cm.The largest deviation of reconstructed dose in IMRT cases was 2.12％.The dose profile reconstructed by RDBMOM coincided with the measurement using two-dimensional ion-chamber array.The γ rates (3％/3 mm) were 94.56％ - 100％.The RDBMOM verification of IMRT cases shown that the γ rate ＞ 99％ in total and ＞ 98％ in planning target volume,deviation in D95 ＜0.4％,but the largest deviations in mean dose of the parotids and lens were 2.97％ and 59.58％ respectively.ConclusionsAccuracy of the tested system satisfies the demand of IMRT dose verification.RDBMOM is able to provide information of volumetric dosimctry and anatomical location of dose error,which is benefit for evaluating the clinical value of verification results.