• Nuclear Engineering and Technology
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• v.56 no.7
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• pp.2516-2523
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• 2024

This study aims to validate the dosimetric characteristics of Low Dose Rate (LDR) I-125 source Geant4-based Monte Carlo code. According to the recommendation of the American Association of Physicists in Medicine (AAPM) task group report (TG-43), the dosimetric parameters of a new brachytherapy source should be verified either experimentally or theoretically before clinical procedures. The simulation studies are very important since this procedure delivers a high dose of radiation to the tumor with only a minimal dose affecting the surrounding tissues. GEANT4 Monte Carlo simulation toolkit associated brachytherapy example was modified, adapted and several updated techniques have been developed to facilitate and smooth radiotherapy techniques. The great concordance of the current study results with the consensus data and with the results of other MC based studies is promising. It implies that Geant4-based Monte Carlo simulation has the potential to be used as a reliable and standard simulation code in the field of brachytherapy for verification and treatment planning purposes.

• Radiation Oncology Journal
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• v.21 no.2
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• pp.158-166
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• 2003

Purpose: To propose a conceptual design of a novel source for intensity modulated brachytherapy. Materials and Methods: The source design incorporates both radioactive and shielding materials (stainless steel or tungsten), to provide an asymmetric dose intensity in the azimuthal direction. The intensity modulated intravascular brachytherapy was performed by combining a series of dwell positions and times, distributed along the azimuthal coordinates. Two simple designs for the beta-emitting sources, with similar physical dimensions to a $^{90}Sr/Y$ Novoste Beat-Cath source, were considered in the dosimetric feasibility study. In the first design, the radioactive and materials each occupy half of the cylinder and in the second, the radioactive material occupies only a quater of the cylinder. The radial and azimuthal dose distributions around each source were calculated using the MCNP Monte Carlo code. Results: The preliminary hypothetical simulation and optimization results demonstrated the 87$\%$ difference between the maximum and minimum doses to the lumen wall, due to off-centering of the radiation source, could be reduced to less than 7$\%$ by optimizing the azimuthal dwell positions and times of the partially shielded intravascular brachytherapy sources. Conclusion: The novel brachytherapy source design, and conceptual source delivery system, proposed in this study show promising dosimetric characteristics for the realization of intensity modulated brachytherapy in intravascular treatment. Further development of this concept will center on building a delivery system that can precisely control the angular motion of a radiation source in a small-diameter catheter.

• The Journal of Korean Society for Radiation Therapy
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• v.10 no.1
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• pp.30-44
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• 1998

Accurate delivery of doses using a high dose rate(HDR) brachytherapy, remote afterloading system(RALS) depends on knowing the strength of the radioactive source at the time of treatment, the precision and consistency of the timer, and the ability of the unit to position the source at the proper dwell location along the applicator. Periodic Quality Assurance(QA) on HDR machines is a part of the standard protocol of any user. The safety of the patient & staff, positional accuracy, temporal accuracy, and dose delivery accuracy are periodically(weekly, quarterly, monthly) estimated using HDR source(Ir-192), treatment planning devices, measurement devices, and overall treatment devices with regard to treatment delivery. The overall measurement results are estimated successfully and assessed its clinical significance. As a result, our HDR brachytherapy units has been very accurate until now. The QA program protocol permits routine clinical use and provides a high confidence level in the accurate operation of HDR units. Therefore, regular QA of HDR brachytherapy is essential for successful treatment.

• Progress in Medical Physics
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• v.32 no.2
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• pp.25-39
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• 2021

Brachytherapy, along with external beam radiation therapy (EBRT), is an essential and effective radiation treatment process. In brachytherapy, in contrast to EBRT, the radiation source is radioisotopes. Because these isotopes can be positioned inside or near the tumor, it is possible to protect other organs around the tumor while delivering an extremely high-dose of treatment to the tumor. Brachytherapy has a long history of more than 100 years. In the early 1900s, the radioisotopes used for brachytherapy were only radium or radon isotopes extracted from nature. Over time, however, various radioisotopes have been artificially produced. As radioisotopes have high radioactivity and miniature size, the application of brachytherapy has expanded to high-dose-rate brachytherapy. Recently, advanced treatment techniques used in EBRT, such as image guidance and intensity modulation techniques, have been applied to brachytherapy. Three-dimensional images, such as ultrasound, computed tomography, magnetic resonance imaging, and positron emission tomography are used for accurate delineation of treatment targets and normal organs. Intensity-modulated brachytherapy is anticipated to be performed in the near future, and it is anticipated that the treatment outcomes of applicable cancers will be greatly improved by this treatment's excellent dose delivery characteristics.

• Radiation Oncology Journal
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• v.6 no.2
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• pp.277-281
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• 1988

Although widely used in external beam treatment planning, computed tomography scans are infrequent in incranial tumors by implanting of Radioactive isotope. This incranial brachytherapy has only become possible by using CT scans and stereotaxic operation methods. The coincidence of single source and tumor axes in brachytherapy is very important to determine the therapeutic dosages. Eventhough using the CT scan, according to spatial location of tumor tying, the section of tumor will be seen enlargement, cause the tumor will be cut off with slight angle to its axes. Correct analysis of tumor size from source is required for rotated axes in analytical geometry.

• Progress in Medical Physics
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• v.23 no.4
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• pp.326-332
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• 2012

Recently, there are difficulties in operating brachtherapy machine in the radiotherapy department because of increasing the source price with decreasing nuclear reactor in the world. The development and technical features of the Ir-192 HDR sources (4.5 mm, 1.1 mm in diameter) in Korea were described in this report. We expect that this report will be helpful for hospitals to make the long-term plan for operating and managing HDR brachytherapy machine.

• Progress in Medical Physics
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• v.27 no.4
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• pp.213-219
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• 2016

The position verification of the radiation source utilized in brachytherapy forms a critical factor in determining the therapeutic efficiency. Currently, films are used to verify the source position; however, this method is encumbered by the lengthy time interval required from film scanning to analysis, which makes real-time position verification difficult. In general, the source position accuracy is usually tested in a monthly quality assurance check. In this context, this study investigates the feasibility of the real-time position verification of the radiation source in high dose rate (HDR) brachytherapy with the use of scintillating fibers. To this end, we construct a system consisting of scintillating fibers and a silicon photomultiplier (SiPM), optimize the dosimetric software setup and radiation system characteristics to obtain maximum measurement accuracy, and determine the relative ratio of the measured signals dependent upon the position of the scintillating fiber. According to the dosimetric results based on a treatment plan, in which the dwell time is set at 30 and 60 s at two dwell positions, the number of signals is 31.5 and 83, respectively. In other words, the signal rate roughly doubles in proportion to the dwell time. The source position can also be confirmed at the same time. With further improvements in the spatial resolution and scintillating fiber array, the source position can be verified in real-time in clinical settings with the use of a scintillating fiber-based system.

• Progress in Medical Physics
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• v.24 no.3
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• pp.171-175
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• 2013

Applicator of various kind of number ten kinds is used to raise from efficiency of brachytherapy to maximum. The compatibility of radiation source and applicator is very important subject for safety brachytherapy. Developed high dose rate brachytherapy source through Hanaro nuclear reactor in Korea Atomic Energy Research Institute and improve compatibility with using equipment in present. In this research, we wished to evaluate stability mechanical safety of radiation source and we developed phantom for evaluate several quality about Ir-192 sealed source that improve newly in Korea Atomic Energy Research Institute and is improved. The result for suitability of Ir-192 HDR source with brachytherapy tools that did normal operation in 2.2~2.7 cm extent about change of equal curvature and consider change of sudden curvature that did normal operation in radius 1.5~1.8 cm extent.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2006.08a
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• pp.115-115
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• 2006

• Progress in Medical Physics
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• v.9 no.4
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• pp.259-266
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• 1998

To achieve the 2D dose distribution around the designed high dose rate Ir-192 source substitution for Co-60 brachytherapy source, we determined the exposure rate constant and tissue attenuation factors as a large depth as a 20 cm from source center. The exposure rate constant is used for apparent activity in designed source with self-absorption and encapsulation steel wall. The tissue dose delivered from the 4401 segments of 2.5 mm in a diameter and 2.5 mm height of disk-type source layer. In the experiments, the tissue attenuation factors include the tissue attenuation and multiple scattering in a medium surrounding the source. The fitted the polynomial regression with 4th order for the tissue attenuation factors are very closed to the experimental measurement data within ${\pm}$1% discrepancy. The Meisberger's constant showed the large uncertainty in large distance from source. The exposure rate constant 4.69 Rcm$^2$/mCi-hr was currently used for determination of apparent activity of source and air kerma strength was obtained 0.973 for tissue absorbed dose from the energy spectrum of Ir-192 source. In our experiments with designed high dose rate brachytherapy source, the apparent activity of Ir-192 source was delivered from the 54.6 % of actual physical source activity through the self-absorption and encapsulation wall attenuations. This paper provides the 2-dimensional dose tabulation from unit apparent activity in a water medium for dose planning includes the multiple scattering, source anisotropy effect and geometric factors.