• Journal of Sensor Science and Technology
• /
• v.25 no.1
• /
• pp.41-45
• /
• 2016

In this study, LET (Linear Energy Transfer) calibration of CR-39 SSNTD (Solid State Nuclear Track Detector) was performed using 500 MeV/u Fe heavy ions in HIMAC (Heavy Ion Medical Accelerator) for high LET radiation dosimetry. The irradiated CR-39 SSNDT were etched according JAXA (Japan Aerospace Exploration Agency) etching conditions. And the etched SSNTD were analyzed by using Image J. Determined dose-mean lineal energy ($\overline{y_D}$) of 500 MeV/u Fe is about 283.3 keV/um by using the CR-39 SSNTD. This value is very similar result compare to the results calculated by GEANT4 Monte Carlo simulation and measured with TEPC active radiation detector. We confirmed that the CR-39 SSNTD was useful for high LET radiation dosimetry such as heavy iron ions.

• Journal of Radiopharmaceuticals and Molecular Probes
• /
• v.3 no.1
• /
• pp.18-24
• /
• 2017

Patient-specific image-based internal dosimetry involves using the patient's individual anatomy and spatial distribution of radioactivity over time to obtain an absorbed dose calculation. Individual absorbed dose was calculated by accumulated activity multiply S-value of each organs. The aim of this study was to calculate the S-values using Monte Carlo simulation in monkey and mouse and evaluation of absorbed dose in each organ. Self-irradiation S-value of monkey heart self-irradiation was 3.15E-03 mGy-g/MBq-s, lung self-irradiation was 8.94E-04 mGy-g/MBq-s and liver self-irradiation S-value was 2.23E-03 mGy-g/MBq-s. Mouse heart self-irradiation S-value was 1.95E-01 mGy-g/MBq-s, lung was 9.59E-02 mGy-g/MBq-s, and liver was 1.40E-03 mGy-g/MBq-s. The results of this study show that the calculation protocol of image based individual absorbed dose of each organ using Monte Carlo simulation. Therefore, this study may be applied to calculate human specific absorbed dose.

• Progress in Medical Physics
• /
• v.27 no.2
• /
• pp.72-78
• /
• 2016

A CCD camera and an LED light source were combined to fabricate a compact optical CT scanner for the therapeutic radiation dose evaluation of a polymer gel dosimeter. After the collimated beam emitted by the LED passed through aquarium, gel phantom, and telecentric lens, an image was collected by the CCD camera and reconstructed using MATLAB. By using a stepping motor and LabVIEW, the gel dosimeter was rotated at every $0.72^{\circ}$, and the time for collecting 500 slice images per a revolution was within 20 min. At a spatial frequency of 4.5 lp/mm of the optical CT scanner, the modulation transfer function value was 72%. The linear correlation coefficient of the optical CT scanner for the polymer gel dosimeter was 0.987.

• Progress in Medical Physics
• /
• v.28 no.1
• /
• pp.33-38
• /
• 2017

Creating individualized build-up material for superficial photon beam radiation therapy at irregular surface is complex with rice or commonly used flat shape bolus. In this study, we implemented a workflow using 3D printed patient specific bolus and describe our clinical experience. To provide better fitted build-up to irregular surface, the 3D printing technique was used. The PolyLactic Acid (PLA) which processed with nontoxic plant component was used for 3D printer filament material for clinical usage. The 3D printed bolus was designed using virtual bolus structure delineated on patient CT images. Dose distributions were generated from treatment plan for bolus assigned uniform relative electron density and bolus using relative electron density from CT image and compared to evaluate the inhomogeneity effect of bolus material. Pretreatment QA is performed to verify the relative electron density applied to bolus structure by gamma analysis. As an in-vivo dosimetry, Optically Stimulated Luminescent Dosimeters (OSLD) are used to measure the skin dose. The plan comparison result shows that discrepancies between the virtual bolus plan and printed bolus plan are negligible. (0.3% maximum dose difference and 0.2% mean dose difference). The dose distribution is evaluated with gamma method (2%, 2 mm) at the center of GTV and the passing rate was 99.6%. The OSLD measurement shows 0.3% to 2.1% higher than expected dose at patient treatment lesion. In this study, we treated Mycosis fungoides patient with patient specific bolus using 3D printing technique. The accuracy of treatment plan was verified by pretreatment QA and in-vivo dosimetry. The QA results and 4 month follow up result shows the radiation treatment using 3D printing bolus is feasible to treat irregular patient skin.

• Radiation Oncology Journal
• /
• v.11 no.1
• /
• pp.175-181
• /
• 1993

Radiosurgery requires integral procedure where special devices and computer systems are needed for localization, dose planning and treatment. The aim of this work is to verify the overall mechanical accuracy of our LINAC and develop dose calculation algorithm for LINAC radiosurgery. The alignment of treatment machine and the performance testing of the entire system were extensively carried out and the basic data such as percent depth dose, off-axis ratio and output factor were measured. A three dimensional treatment planning system for stereotactic radiosurgery has been developed. We used an IBM personal computer with C programming language (IBM personal system/2, Model 80386, IBM Co., USA) for calculating the dose distribution. As a result, deviations at isocenter on gantry and table rotation for our treatment machine were acceptable since they were less than 2 mm. According to the phantom experiments, the focusing isocenter were successful by the error of less than 2 mm. Finally, the mechanical accuracy of our three dimensional planning system was confirmed by film dosimetry in sphere phantom.

• Progress in Medical Physics
• /
• v.30 no.4
• /
• pp.112-119
• /
• 2019

Purpose: The advantages of ocular proton therapy are that it spares the optic nerve and delivers the minimal dose to normal surrounding tissues. In this study, it developed a solid eye phantom that enabled us to perform quality assurance (QA) to verify the dose and beam range for passive single scattering proton therapy using a single phantom. For this purpose, a new solid eye phantom with a polymethyl-methacrylate (PMMA) wedge was developed using film dosimetry and an ionization chamber. Methods: The typical beam shape used for eye treatment is approximately 3 cm in diameter and the beam range is below 5 cm. Since proton therapy has a problem with beam range uncertainty due to differences in the stopping power of normal tissue, bone, air, etc, the beam range should be confirmed before treatment. A film can be placed on the slope of the phantom to evaluate the Spread-out Bragg Peak based on the water equivalent thickness value of PMMA on the film. In addition, an ionization chamber (Pin-point, PTW 31014) can be inserted into a hole in the phantom to measure the absolute dose. Results: The eye phantom was used for independent patient-specific QA. The differences in the output and beam range between the measurement and the planned treatment were less than 1.5% and 0.1 cm, respectively. Conclusions: An eye phantom was developed and the performance was successfully validated. The phantom can be employed to verify the output and beam range for ocular proton therapy.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2002.09a
• /
• pp.241-243
• /
• 2002

New types of protocols have been recently in development, all based on an absorbed dose-to-water with the aim of improving the accuracy of measurements of absorbed dose to water. IAEA TRS-277, the air-kerma standard-based present protocol, and IAEA TRS-398 and AAPM TG-51, the absorbed dose-to-water standard-based new one, were studied and compared theoretically and experimentally for photon beams of 6, 10, and 15 MV. NE 2571 and 3 Farmer types of ionization chambers in widely commercial use were used to determine an absorbed dose to water at the reference depth in water. Two different kinds of calibration factors were given respectively for every chamber calibrated in $\^$60/CO gamma ray beams from a Korean Secondary Standard Dosimetry Laboratory (KFDA). This work shows that there is around 1 % of difference of absorbed doses measured between two different types of calibration systems owing to different physical parameters and reference conditions used. We hope this work to help form the basis on development of new type of protocol in Korea.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2002.09a
• /
• pp.68-73
• /
• 2002

In standard teletherapy, a treatment plan is generated with the aid of a treatment planning system, but it is common to perform an independent monitor unit verification calculation (MUVC). In exact analogy, we propose and demonstrate that a simple and accurate MUVC in Intensity Modulated Radiotherapy (IMRT) is possible. We introduce a concept of Modified Clarkson Integration (MCI). In MCI, we exploit the rotational symmetry of scattering to simplify the dose calculation. For dose calculation along a central axis (CAX), we first replace the incident IMRT fluence by an azimuthally averaged fluence. Second, the Clarkson Integration is carried over annular sectors instead of over pie sectors. We wrote a computer code, implementing the MCI technique, in order to perform a MUVC for IMRT purposes. We applied the code to IMRT plans generated by CORVUS. The input to the code consists of CORVUS plan data (e.g., DMLC files, jaw settings, MU for each IMRT field, depth to isocenter for each IMRT field), and the output is dose contribution by individual IMRT field to the isocenter. The code uses measured beam data for Sc, Sp, TPR, (D/Mu)$\_$ref/ and includes effects from MLC transmission, and radiation field offset. On a 266 MHZ desktop computer, the code takes less than 15 sec to calculate a dose. The doses calculated with MCI algorithm agreed within +/- 3% with the doses calculated by CORVUS, which uses a 1cm x 1cm pencil beam in dose calculation. In the present version of MCI, skin contour variations and inhomogeneities were neglected.

• Journal of radiological science and technology
• /
• v.43 no.6
• /
• pp.443-451
• /
• 2020

This study is to evaluate absorbed dose from right lung for brachytherapy and to estimate the effects of tissue heterogeneities on dose distribution for Iridium-192 source using Monte Carlo simulation. The study employed Geant4 code as Monte Carlo simulation to calculate the dosimetry parameters. The dose distribution of Iridium-192 source in solid water equivalent phantom including aluminium plate or steel plate inserted was calculated and compared with the measured dose by the ion chamber at various distances. And the simulation was used to evaluate the dose of gamma radiation absorbed in the lung organ and other organs around it. The dose distribution embedded in right lung was calculated due to the presence of heart, thymus, spine, stomach as well as left lung. The geometry of the human body was made up of adult male MIRD type of the computational human phantom. The dosimetric characteristics obtained for aluminium plate inserted were in good agreement with experimental results within 4%. The simulation results of steel plate inserted agreed well with a maximum difference 2.75%. Target organ considered to receive a dose of 100%, the surrounding organs were left the left lung of 3.93%, heart of 10.04%, thymus of 11.19%, spine of 12.64% and stomach of 0.95%. When the statistical error is performed for the computational human phantom, the statistical error of value is under 1%.

• Progress in Medical Physics
• /
• v.9 no.3
• /
• pp.185-192
• /
• 1998

It is necessarily to evaluate the energy of X-ray emitted from linear accelerator in order to determine the accurate absorbed dose. The method of direct measurement for x-ray energy is very difficult and impractical. Therefore the method of using beam quality index is generally used. Several dosimetry protocols recommend the use of quality indices such as depth of dose maximum at radiation central axis, dose gradient, and dose level. The linear accelerator manufactures follow the recommendation as dosimetry protocols. The study was performed for us to select the most suitable parameter among the Quality indices as described above. For photon beams of 4, 6, 10, 15, and 21 MV nominal energies produced by four kinds of accelerators(Mitsubishi, Scanditronix, Siemens, Varian) in eleven institutions, We evaluated the x-ray energies obtained by the Quality indices as recommended by several dosimetry protocols and manufactures. Results showed that there were energy spreads according to the same accelerators and Quality indices even though nominal energies were same. It appeared that the percent depth dose at 10 cm (D$_{10}$(%)) gave the smallest deviation and spread of energies. As energies increased, the energy deviation increased for all the quality indices. It is desirable for the use of unified quality index to compare the evaluation of beam quality at different institutions.