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Objective:To analyze and compare the dosimetric differences based on volumetric-modulated arc therapy (VMAT), fixed field intensity-modulated radiotherapy (F_IMRT), and electron irradiation combined with VMAT (E&VMAT) in radiotherapy for breast cancer after modified mastectomy, aiming to provide reference for clinical selection of treatment plan.Methods:Ten patients with the left breast cancer who received radiotherapy after modified mastectomy were randomly selected. The target areas included chest wall and supraclavicular region, and the prescribed dose was 43.5 Gy in 15 fractions (2.9 Gy/F). Based on the Pinnacle 3 planning system, the VMAT, F_IMRT and E&VMAT plans (electron beam for chest wall, VMAT for supraclavicular area) were designed for each patient. The conformity and homogeneity of the target areas, the dose of organs at risk and treatment time were compared. Results:The VMAT plan could improve the dose distribution of the target areas. The conformity index and homogeneity index of the target dose were significantly better than those of the F_IMRT and E&VMAT plans (all P<0.05). The average dose, V 30Gy, V 20Gy, V 10Gy of the left lung in the VMAT plan were significantly better than those in the F_IMRT and E&VMAT plans (all P<0.05). The V 5Gy of the left lung in the VMAT plan was significantly better than that in the F_IMRT plan ( P<0.05). There was no statistical difference in the V 5Gy of the left lung between the VMAT and E&VMAT plans ( P>0.05). The heart, right breast and right lung of the VMAT plan could meet the clinical dose limit requirements. The treatment time of the VMAT, F_IMRT and E&VMAT plans was (326±27) s, (1 082±169) s, and (562±48) s, respectively. Conclusions:Compared with the F_IMRT and E&VMAT plans, the VMAT plan has better quality and shorter treatment time. VMAT plan has higher value in clinical application compared with the F_IMRT and E&VMAT plans.
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Objective:To design and implement a plan data archiving system (PDAS) for radiotherapy treatment, in order to improve the efficiency of plan archiving and avoid plan data loss.Methods:The original plan file in the treatment planning system (TPS) was read and parsed, and the record and verification (R&V) system database was accessed to obtain the patient′s treatment record. PDAS processed all parameters involved in the plan archiving and saved the structured data into a local database. PDAS included two major modules, the plan archiving module and the plan loss detection module. The former could be divided into four parts, data sorting, data compression, archiving check and plan recovery. For different modules, we designed corresponding logic rules and wrote programs to realize the system. Compared with the plan data of manual archiving, the clinical application effect of PDAS was evaluated.Results:Each module of PDAS was developed and implemented. During 31 months of clinical application, the system was stable, and 17 614 plans were archived. Compared with manual archiving, PDAS improved the archiving efficiency significantly and reduced the plan loss rate from 0.004 or so to 0.Conclusions:PDAS can improve the efficiency of plan archiving and ensure the security and integrity of plan data.
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Objective To investigate the dose characteristics and outcomes of a single isocenter bilateral tangential fields (IBTF) combined with intensity-modulated radiotherapy (IMRT) in bilateral breast radiotherapy (BBR).Methods Fourteen female patients with synchronous bilateral breast cancer (SBBC) after breast-conserving surgery (BCS) were enrolled in this study.All patients received BBR using IBTF combined with IMRT at a conventional (50 Gy/25f) or hypofractionated (43.5 Gy/15f) dose.For patients with invasive cancer,the additional tumor bed boost was given with sequential electron radiation or simultaneously photon IMRT.The coverage,uniformity and short-term clinical efficacy were evaluated.Results The number of the irradiation field was 8-11,including 4-7 intensity-modulated fields.The bilateral breast PTV dose coverage reached 95％ in all plans.For the tumor bed,the mean dose coverage was (95.54± 1.33) ％ (left) and (94.19± 1.03) ％(right) using photon,and (90.25± 8.79) ％ (left) and (85.28± 8.35) ％(right) using electron.The average V20 of bilateral lungs was (16.69±3.90)％.The cardiac Dmean was 5.48 Gy.Three patients presented with grade Ⅱ acute skin toxicities.No ≥ grade Ⅱ pneumonitis was observed.No recurrence occurred with the median follow-up time of 30.1 months.Eleven patients showed excellent cosmetic results.Conclusion BBR using IBTF combined with IMRT is efficacious and safe for patients with SBBC after BCS.
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Objective The IAEA report No.483 describes the latest method of small field dosimetry.The field output factor measurement and correction methods are used to improve the accuracy and consistency of the measurement results for different type detectors.Methods The field output factors from 0.6 cm×0.6 cm to 10 cm× 10 cm were measured using IBA's CC13 ionization chamber,CC01 ionization chamber,PFD semiconductor detector,EFD semiconductor detector and Razor semiconductor detector,respectively.The field output correction factors were used to correct the measurement result.Results Compared with the corrected data,the results of ionization chamber are mainly affected by the volume averaging and the fluence perturbation effect,lead to the measurement result which is 4.70％ lower at 0.6 cm × 0.6 cm;The results of Shielded semiconductors are mainly affected by fluence perturbation effect,lead to the measurement result which is 4.80％ higher at 0.6 cm × 0.6 cm.The results of unshielded semiconductors are mainly affected by energy response and fluence perturbation effect,resulting in lower measurement results at the field size＞0.8 cm×0.8 cm,2.10％ lower at field size of 1.5 cm× 1.5 cm,higher measurement results at field size＜0.8 cm×0.8 cm and 1.1％ higher at field size of 0.6 cm×0.6 cm.Before the correction,the measurement results from different types of detectors are quite different,average standard deviation is 0.016 6.After the correction,the difference among the detectors is significantly reduced,average standard deviation is 0.006 6.Conclusions For detectors such as ionization chambers and semiconductors,the field output correction factors can be used to correct the output factors of the small field to improve the accuracy and consistency of the measurement results.
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Objective@#To investigate the dose characteristics and outcomes of a single isocenter bilateral tangential fields (IBTF) combined with intensity-modulated radiotherapy (IMRT) in bilateral breast radiotherapy (BBR).@*Methods@#Fourteen female patients with synchronous bilateral breast cancer (SBBC) after breast-conserving surgery (BCS) were enrolled in this study. All patients received BBR using IBTF combined with IMRT at a conventional (50 Gy/25f) or hypofractionated (43.5 Gy/15f) dose. For patients with invasive cancer, the additional tumor bed boost was given with sequential electron radiation or simultaneously photon IMRT. The coverage, uniformity and short-term clinical efficacy were evaluated.@*Results@#The number of the irradiation field was 8-11, including 4-7 intensity-modulated fields. The bilateral breast PTV dose coverage reached 95% in all plans. For the tumor bed, the mean dose coverage was (95.54±1.33)%(left) and (94.19±1.03)%(right) using photon, and (90.25±8.79)%(left) and (85.28±8.35)%(right) using electron. The average V20 of bilateral lungs was (16.69±3.90)%. The cardiac Dmean was 5.48 Gy. Three patients presented with grade Ⅱ acute skin toxicities. No ≥ grade Ⅱ pneumonitis was observed. No recurrence occurred with the median follow-up time of 30.1 months. Eleven patients showed excellent cosmetic results.@*Conclusion@#BBR using IBTF combined with IMRT is efficacious and safe for patients with SBBC after BCS.
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Objective@#To obtain the high-resolution dose distribution for the single source channel of Leksell 4C gamma knife.@*Methods@#A parallel computing platform based on the Message Passing Interface (MPI) and Monte Carlo Code MCNPX was established. The ring-shaped detector and two pre-validated variance reduction techniques (emission direction-biased sampling of source and termination of electron tracking in partial structures) were adopted to derive the high-resolution dose distribution for the single source channel of Leksell 4C gamma knife. The effect of cut-off energy for both photon and electron on the accuracy of simulation outcomes was evaluated and statistically compared.@*Results@#Compared with previous findings, the spatial resolution of the dose distribution for the single source channel obtained in this study was higher (radial resolution=0.1 mm) with less statistical error (<1%). The calculation time was acceptable (approximately 24 h). For the 4-, 8-, 14-and 18-mm variable collimators, the penumbra and full width at the half maximum (FWHM) for single side were 1.0, 1.1, 1.2, 1.3 mm and 2.2, 4.3, 7.3, 9.3 mm, respectively, which were consistent with previous studies. The difference of the simulation results was extremely small between different cut-off energy for photon (1 keV vs.10 keV). However, the simulation results significantly differ between 1 and 521 keV electronic cut-off energy.@*Conclusions@#The MCNPX parallel computing platform based on the MPI environment can be utilized to derive highly accurate dose distribution with high resolution in acceptable calculation time. The cut-off energy of the photon and electron should be cautiously set up during simulation.
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Objective improve the accuracy of the measurement results by using the field output factor measurement method based on daisy-chaining.Methods The Varian Edge Accelerator 6 MV X-ray data were measured using the IBA CC13 ionization chamber, IBA CC01 ionization chamber, IBA Razor semiconductor detector , IBA EFD semiconductor detector and Gafchromic EBT 3 film , respectively. Results Compared with the daisy-chaining measurement method,the results obtained by the conventional measurement method using CC13 were smaller. The deviation value was 16. 71% in the 1 cm × 1 cm field. The measurement results in a larger field via CC01 were bigger with a deviation of 8. 39% in the 40 cm × 40 cm filed. The measurement results via Razor in a larger field were larger with a deviation of 9. 40% in the 40 cm × 40 cm field. The measurement results were similar between EFD and Razor with a deviation of 9. 14% in the 40 cm × 40 cm field. The results of the film measurement were equivalent to those obtained from the daisy-chaining method in a field of＞ 1 cm × 1 cm with a deviation within 1. 60%,whereas the deviation was increased to 3. 13% in the 1 cm× 1 cm field. The results were consistent with daisy-chaining measurement if the 3 cm × 3 cm or 4 cm × 4 cm fields were selected as the intermediate fields with the maximum deviation of 0. 29%. Conclusions For the detectors with changing response along with the field size,daisy-chaining measurement method can be utilized to extend the measurement range and improve the accuracy of the measurement results.
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Objective To preliminarily observe the clinical efficacy of hippocampal-sparing prophylactic cranial irradiation (HS-PCI) using helical tomotherapy (HT) in patients with limited-stage small-cell lung cancer (LS-SCLC) after chemoradiotherapy,and compare HT with intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in dose distribution.Methods From April to June,2014,six patients with LS-SCLC who had achieved a complete remission after chemoradiotherapy were assigned to HS-PCI using HT within a month after brain metastasis was ruled out using brain magnetic resonance imaging (MRI).After fusing CT images and MRI images,the hippocampus was contoured in the fusion images and hippocampal avoidance regions were created using a volumetric expansion of 3 mm around the hippocampus.A dose of 25 Gy in 10 fractions to 95％ of planning target volume (PTV) was prescribed in HT,IMRT,and VMAT.The clinical efficacy,adverse reactions,neurocognitive function,and brain metastasis were evaluated for HT.The dose distribution in PTV and hippocampus were compared between HT,IMRT,and VMAT.Results There were one patient with abdominal wall and abdominal lymph node metastases,one patient with local recurrence,and no patient with brain metastasis during the observation period.The numbers of patients with grade 1 and grade 2 headache,dizziness,and hair loss reactions were 3 and 1,3 and 1,and 4 and 2,respectively.There were no significant differences in the average score of the Mini-Mental State Examination before treatment and at 3 and 6 months after treatment (29.7,29.2,and 29.3 ; P =0.083,0.317,and 0.157).The mean dose to the hippocampus was 16.85 Gy for IMRT and 17.59 Gy for VMAT.For HT,the mean doses to the hippocampus and avoidance regions were reduced to 5.26 Gy and 6.21 Gy,respectively.The prescribed dose for HT was reduced by 79％ and 71％ compared with IMRT and VMAT,respectively.The average coverage rate of the prescribed dose was 94.48％ for HT.Conclusions HT achieves promising dose distribution and target coverage in sparing of the hippocampus.Moreover,HT dose not increase the incidence of adverse reactions.The change in neurocognitive function needs to be further studied with longterm observation and large-scale sampling.