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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 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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ObjectiveTo evaluate setup errors of image guided radiation therapy (IGRT) for body tumors immbilized with vacuum cushions and localized with final isocenter marked method using kilovoltage cone beam CT (KVCBCT).MethodsA retrospective study has been carried out for 223 patients from March 2009 to April 2011.All patients were immobilized with vacuum cushions and localized with final isocenter marked method in Philips PQS CT or Philips Brilliance CT Big Bore scanner,which were equipped with LAP movable laser systems. The CT images were transferred to a Varian Eclipse workstation for contouring and treatment planning.Before irradiation,a KVCBCT scan was performed and image registration was done on a Varian iX linear accelerator via OBI system.Each set of setup errors in right-left ( RL),superior-inferior (SI),and anterior-posterior (AP) directions were gathered.An independent-samples t-test statistical analysis was conducted with the 758 sets of data using SPSS 16.0.Results The statistical analysis showed that setup errors from the 758 datasets were depicted a Gaussian distribution.The system errors ± random errors in RL,SI and AP were ( -0.5 ±2.8) mm,(0.0±3.0) mm and (0.4±3.4)mm,respectively.Referring to the formula for planning target volume margin calculation,M =2.5Σ + 0.7δ,the margins were calculated as 3.2,2.1 and 3.4 mm,respectively.ConclusionsThe margins derived from this retrospective study have confirmed the premise that the treatment plans were executed in patients with high reliability,thereby created a high sense of confidence for the clinicians.
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Objective To evaluate the penumbra of a new multileaf collimator equipped with Elekta Synergy accelerator. Methods The penumbra were derived from beam profiles measured in air and water using PinPoint ion chamber with PTW MP3 water phantom. Variations of penumbra with X-ray beam energy, depth in water, and leaf position were investigated. Results The penumbra in air for 6 MV X-ray was 2 mm less than that at depth of maximal dose in water. The penumbra of leaf side was 1 mm less than that of the leaf end. The penumbra had close relationship with beam energy, depth in water and leaf position. Penumbra was increased with beam quality and water depth. The leaf position had great influence on the penumbra. Conclusions The penumbra of the multileaf collimator is related to its original design and radiation delivery technique. Special considerations should be taken into during treatment planning.Regular measurement should be performed to guarantee the delivery quality.
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Objective To evaluate the absorbed doses of lower-neck and supraclaviclar subclinical target and the normal tissues of nasopharyngeal carcinoma using three different intensity-modulated radiation therapy (IMRT) techniques. Methods Three radiotherapy techniques were single tangential low neck-supraclavicular field technique (tech1), seven portal IMRT in which the gantry angles are 180°, 150°, 120°, 90°, 270°, 210°(tech2) and 240°and eight portal IMRT in which the gantry angles are 180°, 150°, 120°,90°,0°,270°,210°and 240°(tech3). The dose distribution of lower-neck and supraclaviclar subclinical target and normal tissues were analyzed through the dose-volume histograms, high dose volumes were analyzed using V60 (volume of accepted > 60 Gy/all volume × 100%). The delivery efficiencies were evaluated by means of the total number of segments and MUs. Results The V60 of PTV2 were 65%, 10% and 3% in tech1, tech2 and teeh3 respectively. The maximum doses of spinal cord were 42.0, 48.9 and 45.1 Gy in techl, tech2 and tech3 respectively. The average doses of trachea were 32.92, 52.17 and 36.56 Gy in techl, tech2 and tech3 respectively. Conclusions Tech1 is simple method, but the dose distribution is very nonuniform. Tech2 is better than the Tech1, but the spinal cord and trachea receive the highest doses in three strategies. Tech3 uses less number of segments and MUs than Tech2, and has the best dose distribution.
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Objective To develop a measurement method of dosimetric parameters for Hi-ART tomotherapy unit. Methods Percentage depth doses and beam profiles were measured using the dedicated mini water phantom, and compared to the results of 6 MV X-ray from Primus accelerator. Following the AAPM TG51 protocol, absolute dose calibration was carried out under SSD of 85 cm at depth of 1.5 cm for field of 5 cm ×40 cm. The output linearity and reproducibility were evaluated. The output variation with the gantry rotation was also investigated using 0.6 cm3 ion chamber in cylindrical perplex phantom and on-board MVCT detectors. Leaf fluence output factors were quantified for the leaf of interest and its adjacent leaves.Results The buildup depth was around 1.0 cm. The PDD values at 10 cm for Hi-ART and Primus were 59.7% and 64.7%, respectively. Varying with the field width, the lateral and longitudinal beam profiles were not so homogeneous as the Primus fields. The measured dose rate was 848.38 cGy/min. The fitted lint(sec) ,with a relative coefficient of 0. 999. The maximum deviation and standard deviation of output were 1.6% and less than 0.5% ; The maximum deviation and standard deviation of output changed by gantry angle were 1.1% and 0.5 % , respectively. Leaf fluence output factors did not increase significantly when leaves were opened beyond the two adjacent leaves. Conclusions Hi-ART Tomotherapy unit has a very high dose output and inhomogeneous beam profiles owing to its special design of the treatment head. This may be useful in dose calculation and treatment delivery.
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Objective To evaluate the dosimetric effect of carbon fiber tabletop on the patient doses in radiotherapy. Methods The transmission factors of couch and inserts were measured in air and solid water phantom using 0.6 cm3 ion chamber and PTW 2D ion chamber array for 6 MV ,10 MV and 18 MV X-ray,respectively. Absorbed doses at depth of maximum dose ,5 cm and 10 cm in solid water were measured with the 2D ion chamber array. Absorbed doses fluctuations with different gantry angles and air gaps between phantom and couch were also measured. Results The posterior field measurement showed that the reductions of absorbed doses at the depth maximum dose,5 cm and 10 cm were within 5%. The ratios of the absorbed doses with to without couch increased with the oblique incident angles and varied slightly with the air gap at depth of 5 cm. The transmission factors of inserts were less than those of couch owing to its thinner thickness. Conclusion The carbon-fiber tabletop affects the absorbed doses and dose distributions of the target, and this effect changes with the gantry angle and air gap. Special considerations should be taken during treatment planning.
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Objective To evaluate the clinical feasibility of quality assurance of helical tomotherapy intensity modulated radiation therapy (IMRT) through a series of clinical case studies. Methods Tomotherapy planning system was used to provide optimized IMRT treatment plans. To verify the dose of IMRT plans,the cylindrical Virtual Water phantom,0.056cm3 AISL, ion chamber and EDR2 film were used for getting the absolute and relative doses from tomotherapy IMRT planning. The film and ion chamber were placed into the phantom. The doses of the interesting points and isodose distribution of the axial plane were measured,then the results were compared with those from the calculation in planning system for verification. Before the irradiation,kVCT images of the phantom were registered by tomotherapy MVCT images. So the setup of phantom was guided for verifying the position. Results The isedose distribution (on the axial plane) measured by the film was well consistent with that calculated by tomotherapy planning system. The error between the measured dose and predicted dose in the measured points was less than 3%. The setup error of the phantom was able to be kept within 1 mm. There was 2 mm offset along the vertical direction of couch from the virtual isocenter to beam isocenter,which should be considered during the phantom/patient setup. Conclusions The procedures for quality assurance of tomotherapy IMRT are feasible in our experience. And helical tomotherapy IMRT QA system has been constituted.