• 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.

• Journal of Radiation Protection and Research
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• v.33 no.4
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• pp.151-160
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• 2008

In Korean nuclear power plants (NPPs), two thermoluminescent dosimeters (TLD) were provided to workers who work in an inhomogeneous radiation field; one on the chest and the other on the head. In this way, the effective dose for radiation workers at NPPs was determined by the high deep dose between two radiation dose from these TLDs. This represented a conservative method of evaluating the degree of exposure to radiation. In this study, to prevent the overestimation of the effective dose, field application experiments were implemented using two-dosimeter algorithms developed by several international institutes for the selection of an optimal algorithm. The algorithms used by the Canadian Ontario Power Generation (OPG) and American ANSI HPS N13.41, NCRP (55/50), NCRP (70/30), EPRI (NRC), Lakslumanan, and Kim (Texas A&M University) were extensively analyzed as two-dosimeter algorithms. In particular, three additional TLDs were provided to radiation workers who wore them on the head, chest, and back during maintenance periods, and the measured value were analyzed. The results found no significant differences among the calculated effective doses, apart from Lakshmanan's algorithm. Thus, this paper recommends the NCRP(55/50) algorithm as an optimal two-dosimeter algorithm in consideration of the solid technical background of NCRP and the convenience of radiation works. In addition, it was determined that a two-dosimeter is provided to a single task which is expected to produce a dose rate of more than 1 mSv/hr, a difference of dose rates depending on specific parts of the body of more than 30%, and an exposure dose of more than 2 mSv.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.1
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• pp.11-19
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• 2014

Purpose : To derive the most appropriate factors by considering the effects of the major factors when applied to the optimization algorithm, thereby aiding the effective designing of a ideal treatment plan. Materials and Methods : The eclipse treatment planning system(Eclipse 10.0, Varian, USA) was used in this study. The PBC (Pencil Beam Convolution) algorithm was used for dose calculation, and the DVO (Dose Volume Optimizer 10.0.28) Optimization algorithm was used for intensity modulated radiation therapy. The experimental group consists of patients receiving intensity modulated radiation therapy for the head and neck cancer and dose prescription to two planned target volume was 2.2 Gy and 2.0 Gy simultaneously. Treatment plan was done with inverse dose calculation methods utilizing 6 MV beam and 7 fields. The optimal algorithm parameter of the established plan was selected based on volume dose-priority(Constrain), dose fluence smooth value and the impact of the treatment plan was analyzed according to the variation of each factors. Volume dose-priority determines the reference conditions and the optimization process was carried out under the condition using same ratio, but different absolute values. We evaluated the surrounding normal organs of treatment volume according to the changing conditions of the absolute values of the volume dose-priority. Dose fluence smooth value was applied by simply changing the reference conditions (absolute value) and by changing the related volume dose-priority. The treatment plan was evaluated using Conformal Index, Paddick's Conformal Index, Homogeneity Index and the average dose of each organs. Results : When the volume dose-priority values were directly proportioned by changing the absolute values, the CI values were found to be different. However PCI was $1.299{\pm}0.006$ and HI was $1.095{\pm}0.004$ while D5%/D95% was $1.090{\pm}1.011$. The impact on the prescribed dose were similar. The average dose of parotid gland decreased to 67.4, 50.3, 51.2, 47.1 Gy when the absolute values of the volume dose-priority increased by 40,60,70,90. When the dose smooth strength from each treatment plan was increased, PCI value increased to $1.338{\pm}0.006$. Conclusion : The optimization algorithm was more influenced by the ratio of each condition than the absolute value of volume dose-priority. If the same ratio was maintained, similar treatment plan was established even if the absolute values were different. Volume dose-priority of the treatment volume should be more than 50% of the normal organ volume dose-priority in order to achieve a successful treatment plan. Dose fluence smooth value should increase or decrease proportional to the volume dose-priority. Volume dose-priority is not enough to satisfy the conditions when the absolute value are applied solely.

• Progress in Medical Physics
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• v.10 no.2
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• pp.103-114
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• 1999

In this study, as a preliminary study for developing a full 3D photon dose calculation algorithm, We developed 2.5D photon dose calculation algorithm by extending 2D calculation algorithm to allow non-coplanar configurations of photon beams. For this purpose, we defined the 3d patient coordinate system and the 3d beam coordinate system, which are appropriate to 3d treatment planning and dose calculation. and then, calculate a transformation matrix between them. For dose calculation, we extended 2d "Clarkson-Cunningham" model to 3d one, which can calculate wedge fields as well as regular and irregular fields on arbitrary plane. The simple Batho's power-law method was implemented as an inhomogeneity correction. We evaluated the accuracy of our dose model following procedures of AAPM TG#23; radiation treatment planning dosimetry verifications for 4MV of Varian Clinac-4. As results, PDDs (percent depth dose) of cubic fields, the accuracy of calculation are within 1% except buildup region, and $\pm$3% for irregular fields and wedge fields. And for 45$^{\circ}$ oblique incident beam, the deviations between measurements and calculations are within $\pm$4%. In the case of inhomogeneity correction, the calculation underestimate 7% at the lung/water boundary and overestimate 3% at the bone/water boundary. At the conclusions, we found out our model can predict dose with 5% accuracy at the general condition. we expect our model can be used as a tool for educational and research purpose.. purpose..

• 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.

• The Journal of Korean Society for Radiation Therapy
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• v.13 no.1
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• pp.38-46
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• 2001

Purpose : The aim of this study is to investigate the effect of tissue inhomogeneities when appling to contrast medium among Homogeneous, Batho and ETAR dose calculation method in RTP system. Method and Material : We made customized heterogeneous phantom it filled with water or contrast medium slab. Phantom scan data have taken PQ 5000 (CT scanner, Marconi, USA) and then dose was calculated in 3D RTP (AcQ-Plan, Marconi, USA) depends on dose calculation algorithm (Homogeneous, Batho, ETAR). The dose comparisons were described in terms of 2D isodose distribution, percent depth dose data, effective path length and monitor unit. Also dose distributions were calculated with homogeneous and inhomogeneous correction algorithm, Batho and ETAR, in each patients with different clinical sites. Results : Result indicated that Batho and ETAR method gave rise to percent depth dose deviation $1.5{\sim}2.7\%,\;2.3{\sim}3.5\%$ (6MV, field size $10{\times}10cm^2$) in each status with and without contrast medium. Also show that effective path lengths were more increase in contrast status (23.14 cm) than Non-contrast (22.07 cm) about $4.9\%$ or 10.7 mm (In case Hounsfield Unit 270) and these results were similary showned in each patient with different clinical site that was lung. prostate, liver and brain region. Concliusion : In conclusion we shown that the use of inhomogeneity correction algorithm for dose calculation in status of injected contrast medium can not represent exact dose at GTV region. These results mean that patients will be more irradiated photon beam during radiation therapy.

• Journal of the Korean Society of Radiology
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• v.13 no.3
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• pp.481-487
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• 2019

Based on the scan conditions and algorithms that are generally applied during examinations during head CT examinations, the results of dose reduction through the application of algorithm changes were investigated through experiments. As a result, the dose reduction effect was more meaningful for the change of perfusion than for the tube voltage, and the quality evaluation using the brain phantom was relatively less reduced when the dose was reduced after the application of the Bone algorithm, especially for the application of the Bone algorithm, and the deviation of the mean CT number or Pixel value was measured relatively significantly. In other words, the conditions under which dose was reduced and quality was maintained to reduce the patient's exposure dose and obtain images of the same quality were obtained with the application of the Smooth algorithm and the resulting values of 120 kVp, 160 mA. At this point, doses were reduced by about 28%, and the mean CT number or Pixel value was also measured with relatively little error. If the results are applied to patients who visit the hospital for examination or follow-up after applying various algorithms and follow up scan conditions, the results are considered to be very useful in reducing patient exposure dose.

• Journal of Radiation Protection and Research
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• v.34 no.4
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• pp.165-169
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• 2009

Two dosimeters are provided to radiation workers participating in tasks where high radiation exposure is expected during maintenance at nuclear power plants. At Korean nuclear power plants, two dosimeters are currently provided for tasks where exposure rates exceed 1 mSv/hr, the difference of equivalent dose to specific parts of the body is more than 30% and an exposure of more than 2 mSv is expected in a single task. These conditions for the provisioning of two dosimeters are based on previous field test results, and it is recommended that the dosimeters be worn on the chest and back. It was also found that the workers felt it was more convenient when they wore two dosimeters on chest and back rather than on chest and head. After the application of previous field test results to practice, it was found that the calculated effective dose for workers during radiation work was lower than the maximum dose of chest or back dosimeter by approximately 10%-30%. This performance is regarded not only to meet the international guideline but also to provide convenience for workers during radiation work.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.208-210
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• 2002

In a treatment planning for actual patients with a complex internal structure, we often expect that proton beams, which pass through both a bolus and the heterogeneity in body, will form complex dose distributions. Therefore, the accuracy of the calculated dose distributions has to be verified for such a complex object. Then dose distributions formed by proton beams passing through both the bolus and phantoms simulating a clinical heterogeneity in patients were measured using a silicon semiconductor detector. The calculated results by the range-modulated pencil beam algorithm (RMPBA) produced large errors compared with the measured dose distributions since dose calculation using the RMPBA could not predict accurately the edge-scattering effect both in the bolus and in clinical heterogeneous phantoms. On the other hand, in spite of this troublesome heterogeneity, calculated results by the simplified Monte Carlo (SMC) method reproduced the experimental ones well. It is obvious that the dose-calculations by the SMC method will be more useful for application to the treatment planning for proton therapy.

• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.1966-1973
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• 2023

Virtual reality technology has been widely used in the field of nuclear and radiation safety, dose rate computing in virtual environment is essential for optimizing radiation protection and planning the work in radioactive-controlled area. Because the CPU-based gamma dose rate computing takes up a large amount of time and computing power for voxelization of volumetric radioactive source, it is inefficient and limited in its applied scope. This study is to develop an efficient gamma dose rate computing code and apply into fast virtual simulation. To improve the computing efficiency of the point kernel algorithm in the reference (Li et al., 2020), we design a GPU-based computing framework for taking full advantage of computing power of virtual engine, propose a novel voxelization algorithm of volumetric radioactive source. According to the framework, we develop the GPPK(GPU-based point kernel gamma dose rate computing) code using GPU programming, to realize the fast dose rate computing in virtual world. The test results show that the GPPK code is play and plug for different scenarios of virtual simulation, has a better performance than CPU-based gamma dose rate computing code, especially on the voxelization of three-dimensional (3D) model. The accuracy of dose rates from the proposed method is in the acceptable range.