• Journal of the Korean Society of Radiology
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• v.17 no.5
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• pp.633-640
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• 2023

With the recent development of static and dynamic modulated brachytherapy methods in brachytherapy, which use radiation shielding to modulate the dose distribution to deliver the dose, the amount of parameters and data required for dose calculation in inverse treatment planning and treatment plan optimization algorithms suitable for new directional beam intensity modulated brachytherapy is increasing. Although intensity-modulated brachytherapy enables accurate dose delivery of radiation, the increased amount of parameters and data increases the elapsed time required for dose calculation. In this study, a GPU-based CUDA-accelerated dose calculation algorithm was constructed to reduce the increase in dose calculation elapsed time. The acceleration of the calculation process was achieved by parallelizing the calculation of the system matrix of the volume of interest and the dose calculation. The developed algorithms were all performed in the same computing environment with an Intel (3.7 GHz, 6-core) CPU and a single NVIDIA GTX 1080ti graphics card, and the dose calculation time was evaluated by measuring only the dose calculation time, excluding the additional time required for loading data from disk and preprocessing operations. The results showed that the accelerated algorithm reduced the dose calculation time by about 30 times compared to the CPU-only calculation. The accelerated dose calculation algorithm can be expected to speed up treatment planning when new treatment plans need to be created to account for daily variations in applicator movement, such as in adaptive radiotherapy, or when dose calculation needs to account for changing parameters, such as in dynamically modulated brachytherapy.

• Journal of radiological science and technology
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• v.43 no.4
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• pp.265-272
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• 2020

The purpose of this study was to investigate the dose-volume indices and radiobiological indices according to the change in dose calculation grid size during the planning of nasopharyngeal cancer VMAT treatment. After performing the VMAT treatment plan using the 3.0 mm dose calculation grid size, dose calculation from 1.0 mm to 5.0 mm was performed repeatedly to obtain a dose volume histogram. The dose volume index and radiobiological index were evaluated using the obtained dose volume histogram. The smaller the dose calculation grid size, the smaller the mean dose for CTV and the larger the mean dose for PTV. For OAR of spinal cord, brain stem, lens and parotid gland, the mean dose did not show a significant difference according to the change in dose calculation grid size. The smaller the grid size, the higher the conformity of the dose distribution as the CI of the PTV increases. The CI and HI showed the best results at 3.0 mm. The smaller the dose calculation grid size, the higher the TCP of the PTV. The smaller the dose calculation grid size, the lower the NTCP of lens and parotid. As a result, when performing the nasopharynx cancer VMAT plan, it was found that the dose calculation grid size should be determined in consideration of dose volume index, radiobiological index, and dose calculation time. According to the results of various experiments, it was determined that it is desirable to apply a grid size of 2.0 - 3.0 mm.

• Progress in Medical Physics
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• v.31 no.3
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• pp.54-62
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• 2020

Dose calculation algorithms play an important role in radiation therapy and are even the basis for optimizing treatment plans, an important feature in the development of complex treatment technologies such as intensity-modulated radiation therapy. We reviewed the past and current status of dose calculation algorithms used in the treatment planning system for radiation therapy. The radiation-calculating dose calculation algorithm can be broadly classified into three main groups based on the mechanisms used: (1) factor-based, (2) model-based, and (3) principle-based. Factor-based algorithms are a type of empirical dose calculation that interpolates or extrapolates the dose in some basic measurements. Model-based algorithms, represented by the pencil beam convolution, analytical anisotropic, and collapse cone convolution algorithms, use a simplified physical process by using a convolution equation that convolutes the primary photon energy fluence with a kernel. Model-based algorithms allowing side scattering when beams are transmitted to the heterogeneous media provide more precise dose calculation results than correction-based algorithms. Principle-based algorithms, represented by Monte Carlo dose calculations, simulate all real physical processes involving beam particles during transportation; therefore, dose calculations are accurate but time consuming. For approximately 70 years, through the development of dose calculation algorithms and computing technology, the accuracy of dose calculation seems close to our clinical needs. Next-generation dose calculation algorithms are expected to include biologically equivalent doses or biologically effective doses, and doctors expect to be able to use them to improve the quality of treatment in the near future.

• Radiation Oncology Journal
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• v.2 no.1
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• pp.129-137
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• 1984

In brachytherapy, it is important to determine the positions of the radiation sources which are inserted into a patient and to estimate the dose resulting from the treatment. Calculation of the dose distribution throughout an implant is so laborious that it is rarely done by manual methods except for model cases. It is possible to calculate isodose distributions and tumor doses for individual patients by the use of a microcomputer. In this program, the dose rate and dose distributions are calculated by numerical integration of point source and the localization of radiation sources are obtained from two radiographs at right angles taken by a simulator developed for the treatment planning. By using microcomputer for brachytherapy, we obtained the result as following 1. Dose calculation and irradiation time for tumor could be calculated under one or five seconds after input data. 2. It was same value under$\pm2\%$ error between dose calculation by computer program and measurement dose. 3. It took about five minutes to reconstruct completely dose distribution for intracavitary irradiation. 4. Calculating by computer made remarkly reduction of dose errors compared with Quimby's calculation in interstitial radiation implantation. 5. It could calculate the biological isoffect dose for high and low dose rate activities.

• Journal of radiological science and technology
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• v.43 no.6
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• pp.431-441
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• 2020

The purpose of this study was to construct a model of MVCT(Megavoltage Computed Tomography) dose calculation by using Dosimetry Check™, a program that radiation treatment dose verification, and establish a protocol that can be accumulated to the radiation treatment dose distribution. We acquired sinogram of MVCT after air scan in Fine, Normal, Coarse mode. Dosimetry Check™(DC) program can analyze only DICOM(Digital Imaging Communications in Medicine) format, however acquired sinogram is dat format. Thus, we made MVCT RC-DICOM format by using acquired sinogram. In addition, we made MVCT RP-DICOM by using principle of generating MLC(Multi-leaf Collimator) control points at half location of pitch in treatment RP-DICOM. The MVCT imaging dose in fine mode was measured by using ionization chamber, and normalized to the MVCT dose calculation model, the MVCT imaging dose of Normal, Coarse mode was calculated by using DC program. As a results, 2.08 cGy was measured by using ionization chamber in Fine mode and normalized based on the measured dose in DC program. After normalization, the result of MVCT dose calculation in Normal, Coarse mode, each mode was calculated 0.957, 0.621 cGy. Finally, the dose resulting from the process for acquisition of MVCT can be accumulated to the treatment dose distribution for dose evaluation. It is believed that this could be contribute clinically to a more realistic dose evaluation. From now on, it is considered that it will be able to provide more accurate and realistic dose information in radiation therapy planning evaluation by using Tomotherapy.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.171-176
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• 2014

Purpose : Changing the calculation grid of AAA in Lung SABR plan and to analyze the changes in target dose, and investigated the effects associated with it, and considered a suitable method of application. Materials and Methods : 4D CT image that was used to plan all been taken with Brilliance Big Bore CT (Philips, Netherlands) and in Lung SABR plan($Eclipse^{TM}$ ver10.0.42, Varian, the USA), use anisotropic analytic algorithm(AAA, ver.10, Varian Medical Systems, Palo Alto, CA, USA) and, was calculated by the calculation grid 1.0, 3.0, 5.0 mm in each Lung SABR plan. Results : Lung SABR plan of 10 cases are using each of 1.0 mm, 3.0 mm, 5.0 mm calculation grid, and in case of use a 1.0 mm calculation grid $V_{98}$. of the prescribed dose is about $99.5%{\pm}1.5%$, $D_{min}$ of the prescribed dose is about $92.5{\pm}1.5%$ and Homogeneity Index(HI) is $1.0489{\pm}0.0025$. In the case of use a 3.0 mm calculation grid $V_{98}$ dose of the prescribed dose is about $90{\pm}4.5%$, $D_{min}$ of the prescribed dose is about $87.5{\pm}3%$ and HI is about $1.07{\pm}1$. In the case of use a 5.0 mm calculation grid $V_{98}$ dose of the prescribed dose is about $63{\pm}15%$, $D_{min}$ of the prescribed dose is about $83{\pm}4%$ and HI is about $1.13{\pm}0.2$, respectively. Conclusion : The calculation grid of 1.0 mm is better improves the accuracy of dose calculation than using 3.0 mm and 5.0 mm, although calculation times increase in the case of smaller PTV relatively. As lung, spread relatively large and low density and small PTV, it is considered and good to use a calculation grid of 1.0 mm.

• Journal of radiological science and technology
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• v.39 no.3
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• pp.305-312
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• 2016

This study were compared with the direct measurement and indirect dose methods through various dose calculation in head and wrist. And, the modified equation was proposed considering equipment type, setting conditions, tube voltage, inherent filter, added filter and its accompanied back scatter factor. As a result, it decreased the error of the direct measurement than the existing dose calculation. Accordingly, diagnostic radiography patient dose comparison would become easier and radiogrphic exposure control and evaluation will become more efficient. The study findings are expected to be useful in patients' effective dose rate evaluation and dose reduction.

• Nuclear Engineering and Technology
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• v.36 no.1
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• pp.1-11
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• 2004

Two approximate methods for a cosmic radiation shielding calculation in low earth orbits were developed and assessed. Those are a sectoring method and a chord-length distribution method. In order to simulate a change in cosmic radiation environments along the satellite mission trajectory, IGRF model and AP(E)-8 model were used. When the approximate methods were applied, the geometrical model of satellite structure was approximated as one-dimensional slabs, and a pre-calculated dose-depth conversion function was introduced to simplify the dose calculation process. Verification was performed with mission data of KITSAT-1 and the calculated results were also compared with detailed 3-dimensional calculation results using Monte Carlo calculation. Dose results from the approximate methods were conservatively higher than Monte Carlo results, but were lower than experimental data in total dose rate. Differences between calculation and experimental data seem to come from the AP-8 model, for which it is reported that fluxes of proton are underestimated. We confirmed that the developed approximate method can be applied to commercial satellite shielding calculations. It is also found that commercial products of semi-conductors can be damaged due to total ionizing dose under LEO radiation environment. An intensive shielding analysis should be taken into account when commercial devices are used.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1769-1780
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• 2022

A new method of dose calculation algorithm, called GPU-accelerated Monte Carlo and collapsed cone Convolution (GMCC) was developed to improve the calculation speed of BNCT treatment planning system. The GPU-accelerated Monte Carlo routine in GMCC is used to simulate the neutron transport over whole energy range and the Collapsed Cone Convolution method is to calculate the gamma dose. Other dose components due to alpha particles and protons, are calculated using the calculated neutron flux and reaction data. The mathematical principle and the algorithm architecture are introduced. The accuracy and performance of the GMCC were verified by comparing with the FLUKA results. A water phantom and a head CT voxel model were simulated. The neutron flux and the absorbed dose obtained by the GMCC were consistent well with the FLUKA results. In the case of head CT voxel model, the mean absolute percentage error for the neutron flux and the absorbed dose were 3.98% and 3.91%, respectively. The calculation speed of the absorbed dose by the GMCC was 56 times faster than the FLUKA code. It was verified that the GMCC could be a good candidate tool instead of the Monte Carlo method in the BNCT dose calculations.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.41-41
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• 2003

Purpose: Even if the wedge filter is widely used for the radiation therapy to modify the photon beam intensity, the wedged photon beam dose calculation is not so easy. Radiation therapy planning systems (RTPS) have been used the empirical or semi-analytical methods such as attenuation method using wedge filter parameters or wedge filter factor obtained from measurement. However, these methods can cause serious error in penumbra region as well as in edge region. In this study, we propose the dose calculation algorithm for wedged field to minimize the error especially in the outer beam region. Materials and Method: Modified intensity by wedge filter was calculated using tissue-maximum ratio (TMR) and scatter-maximum ratio (SMR) of wedged field. Profiles of wedged and non-wedged direction was also used. The result of new dose calculation was compared with measurement and the result from attenuation method. Results: Proposed algorithm showed the good agreement with measurement in the high dose-gradient region as well as in the inner beam region. The error was decreased comparing to attenuation method. Conclusion: Although necessary beam data for the RTPS commissioning was increased, new algorithm would guarantee the improved dose calculation accuracy for wedged field. In future, this algorithm could be adopted in RTPS.