Objective:To determine under what conditions and criteria comparisons between calculations made with the current clinical treatment planning system(Syngo)and an in-house built TPS(TIMPS)would allow skipping of in-beam...Objective:To determine under what conditions and criteria comparisons between calculations made with the current clinical treatment planning system(Syngo)and an in-house built TPS(TIMPS)would allow skipping of in-beam portal-specific measurements.Methods:Measurements were made with an array of 24 ion chambers in a water phantom for 227 proton and 313 carbon ion portals with and without a range shifter(RS).These measurements were compared with calculations performed with Syngo and TIMPS using metrics of average dose difference and Gamma index.Results:For proton portals without RS,if a Gamma comparison between TIMPS and Syngo passed using criteria of 90%of tested points being within 3%and 3 mm,then 74%of measurements would agree with both TIMPS and Syngo.For proton portals with RS,more than 80%of measurements would agree with both calculations using the same criteria.For carbon ion portals without RS,if a Gamma evaluation between TIMPS and Syngo passed with criteria of 90%of tested points being within 2%and 2 mm,85%of measurements would agree with both cal-culations.For carbon ion portals with RS,if a Gamma evaluation between TIMPS and Syngo passed with criteria of 90%of tested points being within 3%and 3 mm,60%of measurements would agree with both calculations.Conclusions:Both the pencil beam algorithm in Syngo and the FDC algorithm in TIMPS can provide accurate dose calculations in water for most clinical portals.For about 75%of portals,physicists can perform comparisons of calculations instead of phantom measurements to verify Syngo calculations thereby saving a large amount of beam time.There are some portals,however,such as for low-energy protons without RS and high-energy carbon ions,where agreement between the two calculations and measurements are not yet satisfactory to allow the elimination of all measurements.展开更多
This study mainly focused on the key technologies,the photon dose calculation based on the Monte Carlo Finite-Size Pencil Beam(MCFSPB)model in the Accurate Radiotherapy System(ARTS).In the MCFSPB model,the acquisition...This study mainly focused on the key technologies,the photon dose calculation based on the Monte Carlo Finite-Size Pencil Beam(MCFSPB)model in the Accurate Radiotherapy System(ARTS).In the MCFSPB model,the acquisition of pencil beam kernel is one of the most important technologies.In this study,by analyzing the demerits of the clinical pencil beam dose calculation methods,a new pencil beam kernel model was developed based on the Monte Carlo(MC)simulation and the technology of medical accelerator energy spectrum reconstruction.which greatly improved the accuracy of calculated result.According to the axial symmetry principle,only part of simulation results was used for the data of pencil beam kernel,which greatly reduced the data quantity of the pencil beam and reduced calculated time.Based on the above studies,the MCFSPB method was designed and implemented by the Visual C++development tool.With several tests including the comparisons among the American Association of Physicists in Medicine(AAPM)No.55 Report sample and the ion chamber measurement of lung-simulating inhomogeneous phantom in clinical treatment plan,the results showed that the maximum error of most calculated point was less than 0.5%in the homogeneous phantom and less than 3%in the heterogeneous phantom.This method met the clinical criteria,and would be expected to be used as a fast and accurate dose engine for clinic TPS.展开更多
The spatial resolution of a commercial two-dimensional(2D)ionization chamber(IC)array is limited by the size of the individual detector and the center-to-center distance between sensors.For dose distributions with are...The spatial resolution of a commercial two-dimensional(2D)ionization chamber(IC)array is limited by the size of the individual detector and the center-to-center distance between sensors.For dose distributions with areas of steep dose gradients,inter-detector dose values are derived by the interpolation of nearby detector readings in the conventional mathematical interpolation of 2D IC array measurements.This may introduce significant errors,particularly in proton spot scanning radiotherapy.In this study,by combining logfile-based reconstructed dose values and detector measurements with the Laplacian pyramid image blending method,a novel method is proposed to obtain a reformatted dose distribution that provides an improved estimation of the delivered dose distribution with high spatial resolution.Meanwhile,the similarity between the measured original data and the downsampled logfilebased reconstructed dose is regarded as the confidence of the reformatted dose distribution.Furthermore,we quantify the performance benefits of this new approach by directly comparing the reformatted dose distributions with 2D IC array detector mathematically interpolated measurements and original low-resolution measurements.The result shows that this new method is better than the mathematical interpolation and achieves gamma pass rates similar to those of the original low-resolution measurements.The reformatted dose distributions generally yield a confidence exceeding 95%.展开更多
Background In the field of particle therapy,the method of pencil beam scanning is of great potential for clinical application,now and in the future.Purpose The authors made strong effort to develop a spot scanning sys...Background In the field of particle therapy,the method of pencil beam scanning is of great potential for clinical application,now and in the future.Purpose The authors made strong effort to develop a spot scanning system for Shanghai Proton Therapy Facility.Design parameters and basic layout of the system are introduced.Methods Functionalities and specifications of crucial devices are described in detail.Most of the devices in the system were designed in house by the authors themselves,including scanning nozzle,scanning magnets and their power supplies,beam monitors,irradiation control modules and safety interlock modules.During the technical commissioning stage in the fix beam room,the spot scanning system was tested and verified.Results Under conditions of the maximum dose rate and minimum dose rate,a)repeatability of the single spot dose is less than±0.1%;b)nonlinearity of the single spot dose is less than±0.1%;c)FWHM for spot size in air at isocenter varies from 8mm to 12mm for full energy,consistent with the design values;d)lateral dose distribution achieves a flatness of less than 2%for multiple proton energies.Conclusion According to the results of technical commissioning,the spot scanning system is capable of producing a pre-scribed 3D dose distribution for target tumor successfully.展开更多
In this paper, efficient, high gain and pencil beam grid antenna array is proposed for hyperthermia breast cancer therapy system. The proposed antenna bandwidth extends from 4.8 GHz to 4.9 GHz at resonant frequency of...In this paper, efficient, high gain and pencil beam grid antenna array is proposed for hyperthermia breast cancer therapy system. The proposed antenna bandwidth extends from 4.8 GHz to 4.9 GHz at resonant frequency of 4.86 GHz. This frequency band has been reported for the breast cancer hyperthermia therapy. The grid long and short sides are responsible for the undesired cross-polarized radiation and desired copolarized radiation, respectively. The unsuitability of the conventional grid antenna array is ensured by investigating its radiation properties. The proposed grid antenna array short side width is varied and its long side width is kept wide as possible to enhance the radiation properties and to reduce the losses. Also, a reflector has been used for gain enhancement purpose. The proposed grid antenna array achieves side lobe level and 3 dB beam width of —27.9 dB and 25.9° for the E-plane and —27.9 dB and 26.3° for the H-plane, respectively. The breast phantom is irradiated by both proposed and conventional grid antenna arrays for 10 minutes. The proposed grid antenna array achieves 8°C temperature increase within the breast phantom area compared to 2°C temperature increase for conventional one. The proposed grid antenna array is highly efficient, high gain and light weight, and it has a very suitable radiation property for hyperthermia breast cancer therapy.展开更多
The purpose of this study was to compare the Pencil Beam (PB) with Monte Carlo (MC) calculated dosimetric results using phantoms for air cavity region. Measurements in Tough water phantom with air gaps were used to ve...The purpose of this study was to compare the Pencil Beam (PB) with Monte Carlo (MC) calculated dosimetric results using phantoms for air cavity region. Measurements in Tough water phantom with air gaps were used to verify the calculated dose. The plane-parallel ionization chamber was moved from 2 mm to 20 mm behind air gap. Calculations were performed for various air gaps (1.0, 2.0, 3.0 and 4.0 cm) and field sizes (4.2 × 4.2, 6.0 × 6.0 and 9.8 × 9.8 cm2). The lateral missing tissue measurement was performed using the radiochromic RT-QA film. Dose difference between PB and chamber measurement near an air gap was greater for smaller field size, larger air gap thickness, and shallower depth behind air gap. As the distance from the phantom edge became shorter, the dose differences of the PB calculation and film measurement became larger. MC calculations were found within 3% agreement to the measured dose distributions. Our results demonstrate an excellent agreement between ionization chamber and radiochromic RT-QA film measurements and MC calculations.展开更多
文摘Objective:To determine under what conditions and criteria comparisons between calculations made with the current clinical treatment planning system(Syngo)and an in-house built TPS(TIMPS)would allow skipping of in-beam portal-specific measurements.Methods:Measurements were made with an array of 24 ion chambers in a water phantom for 227 proton and 313 carbon ion portals with and without a range shifter(RS).These measurements were compared with calculations performed with Syngo and TIMPS using metrics of average dose difference and Gamma index.Results:For proton portals without RS,if a Gamma comparison between TIMPS and Syngo passed using criteria of 90%of tested points being within 3%and 3 mm,then 74%of measurements would agree with both TIMPS and Syngo.For proton portals with RS,more than 80%of measurements would agree with both calculations using the same criteria.For carbon ion portals without RS,if a Gamma evaluation between TIMPS and Syngo passed with criteria of 90%of tested points being within 2%and 2 mm,85%of measurements would agree with both cal-culations.For carbon ion portals with RS,if a Gamma evaluation between TIMPS and Syngo passed with criteria of 90%of tested points being within 3%and 3 mm,60%of measurements would agree with both calculations.Conclusions:Both the pencil beam algorithm in Syngo and the FDC algorithm in TIMPS can provide accurate dose calculations in water for most clinical portals.For about 75%of portals,physicists can perform comparisons of calculations instead of phantom measurements to verify Syngo calculations thereby saving a large amount of beam time.There are some portals,however,such as for low-energy protons without RS and high-energy carbon ions,where agreement between the two calculations and measurements are not yet satisfactory to allow the elimination of all measurements.
基金the National Natural Science Foundation of China under grant No.30900386&No.81101132the Anhui Provincial Natural Science Foundation under grant No.11040606Q55.
文摘This study mainly focused on the key technologies,the photon dose calculation based on the Monte Carlo Finite-Size Pencil Beam(MCFSPB)model in the Accurate Radiotherapy System(ARTS).In the MCFSPB model,the acquisition of pencil beam kernel is one of the most important technologies.In this study,by analyzing the demerits of the clinical pencil beam dose calculation methods,a new pencil beam kernel model was developed based on the Monte Carlo(MC)simulation and the technology of medical accelerator energy spectrum reconstruction.which greatly improved the accuracy of calculated result.According to the axial symmetry principle,only part of simulation results was used for the data of pencil beam kernel,which greatly reduced the data quantity of the pencil beam and reduced calculated time.Based on the above studies,the MCFSPB method was designed and implemented by the Visual C++development tool.With several tests including the comparisons among the American Association of Physicists in Medicine(AAPM)No.55 Report sample and the ion chamber measurement of lung-simulating inhomogeneous phantom in clinical treatment plan,the results showed that the maximum error of most calculated point was less than 0.5%in the homogeneous phantom and less than 3%in the heterogeneous phantom.This method met the clinical criteria,and would be expected to be used as a fast and accurate dose engine for clinic TPS.
文摘The spatial resolution of a commercial two-dimensional(2D)ionization chamber(IC)array is limited by the size of the individual detector and the center-to-center distance between sensors.For dose distributions with areas of steep dose gradients,inter-detector dose values are derived by the interpolation of nearby detector readings in the conventional mathematical interpolation of 2D IC array measurements.This may introduce significant errors,particularly in proton spot scanning radiotherapy.In this study,by combining logfile-based reconstructed dose values and detector measurements with the Laplacian pyramid image blending method,a novel method is proposed to obtain a reformatted dose distribution that provides an improved estimation of the delivered dose distribution with high spatial resolution.Meanwhile,the similarity between the measured original data and the downsampled logfilebased reconstructed dose is regarded as the confidence of the reformatted dose distribution.Furthermore,we quantify the performance benefits of this new approach by directly comparing the reformatted dose distributions with 2D IC array detector mathematically interpolated measurements and original low-resolution measurements.The result shows that this new method is better than the mathematical interpolation and achieves gamma pass rates similar to those of the original low-resolution measurements.The reformatted dose distributions generally yield a confidence exceeding 95%.
基金supported by the Youth Innovation Promotion Association CAS(No.2016238)
文摘Background In the field of particle therapy,the method of pencil beam scanning is of great potential for clinical application,now and in the future.Purpose The authors made strong effort to develop a spot scanning system for Shanghai Proton Therapy Facility.Design parameters and basic layout of the system are introduced.Methods Functionalities and specifications of crucial devices are described in detail.Most of the devices in the system were designed in house by the authors themselves,including scanning nozzle,scanning magnets and their power supplies,beam monitors,irradiation control modules and safety interlock modules.During the technical commissioning stage in the fix beam room,the spot scanning system was tested and verified.Results Under conditions of the maximum dose rate and minimum dose rate,a)repeatability of the single spot dose is less than±0.1%;b)nonlinearity of the single spot dose is less than±0.1%;c)FWHM for spot size in air at isocenter varies from 8mm to 12mm for full energy,consistent with the design values;d)lateral dose distribution achieves a flatness of less than 2%for multiple proton energies.Conclusion According to the results of technical commissioning,the spot scanning system is capable of producing a pre-scribed 3D dose distribution for target tumor successfully.
文摘In this paper, efficient, high gain and pencil beam grid antenna array is proposed for hyperthermia breast cancer therapy system. The proposed antenna bandwidth extends from 4.8 GHz to 4.9 GHz at resonant frequency of 4.86 GHz. This frequency band has been reported for the breast cancer hyperthermia therapy. The grid long and short sides are responsible for the undesired cross-polarized radiation and desired copolarized radiation, respectively. The unsuitability of the conventional grid antenna array is ensured by investigating its radiation properties. The proposed grid antenna array short side width is varied and its long side width is kept wide as possible to enhance the radiation properties and to reduce the losses. Also, a reflector has been used for gain enhancement purpose. The proposed grid antenna array achieves side lobe level and 3 dB beam width of —27.9 dB and 25.9° for the E-plane and —27.9 dB and 26.3° for the H-plane, respectively. The breast phantom is irradiated by both proposed and conventional grid antenna arrays for 10 minutes. The proposed grid antenna array achieves 8°C temperature increase within the breast phantom area compared to 2°C temperature increase for conventional one. The proposed grid antenna array is highly efficient, high gain and light weight, and it has a very suitable radiation property for hyperthermia breast cancer therapy.
文摘The purpose of this study was to compare the Pencil Beam (PB) with Monte Carlo (MC) calculated dosimetric results using phantoms for air cavity region. Measurements in Tough water phantom with air gaps were used to verify the calculated dose. The plane-parallel ionization chamber was moved from 2 mm to 20 mm behind air gap. Calculations were performed for various air gaps (1.0, 2.0, 3.0 and 4.0 cm) and field sizes (4.2 × 4.2, 6.0 × 6.0 and 9.8 × 9.8 cm2). The lateral missing tissue measurement was performed using the radiochromic RT-QA film. Dose difference between PB and chamber measurement near an air gap was greater for smaller field size, larger air gap thickness, and shallower depth behind air gap. As the distance from the phantom edge became shorter, the dose differences of the PB calculation and film measurement became larger. MC calculations were found within 3% agreement to the measured dose distributions. Our results demonstrate an excellent agreement between ionization chamber and radiochromic RT-QA film measurements and MC calculations.
