• Radiation Oncology Journal
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• v.33 no.3
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• pp.226-232
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• 2015

Purpose: Toxicity of mucosa is one of the major concerns of radiotherapy (RT), when a target tumor is located near a mucosal lined organ. Energy of photon RT is transferred primarily by secondary electrons. If these secondary electrons could be removed in an internal cavity of mucosal lined organ, the mucosa will be spared without compromising the target tumor dose. The purpose of this study was to present a RT dose reduction in near target inner-surface (NTIS) of internal cavity, using Lorentz force of magnetic field. Materials and Methods: Tissue equivalent phantoms, composed with a cylinder shaped internal cavity, and adjacent a target tumor part, were developed. The phantoms were irradiated using 6 MV photon beam, with or without 0.3 T of perpendicular magnetic field. Two experimental models were developed: single beam model (SBM) to analyze central axis dose distributions and multiple beam model (MBM) to simulate a clinical case of prostate cancer with rectum. RT dose of NTIS of internal cavity and target tumor area (TTA) were measured. Results: With magnetic field applied, bending effect of dose distribution was visualized. The depth dose distribution of SBM showed 28.1% dose reduction of NTIS and little difference in dose of TTA with magnetic field. In MBM, cross-sectional dose of NTIS was reduced by 33.1% with magnetic field, while TTA dose were the same, irrespective of magnetic field. Conclusion: RT dose of mucosal lined organ, located near treatment target, could be modulated by perpendicular magnetic field.

• Journal of radiological science and technology
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• v.46 no.6
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• pp.509-517
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• 2023

This study analyzed imaging conditions and exposure index through clinical information collection and dose calculation programs in coronary angiography examinations. Through this, we aim to analyze the effective dose according to examination conditions and provide basic data for dose optimization. In this study, ALARA(As Low As Reasonably Achievable)-F(Fluoroscopy), a program for evaluating the radiation dose of patients and the collected clinical data, was used. First, analysis of imaging conditions and exposure index was performed based on the data of the dose report generated after coronary angiography. Second, after evaluating organ dose according to 9 imaging directions during coronary angiography, with the LAO fixed at 30°, dose evaluation was performed according to tube voltage, tube current, number of frames, focus-skin distance, and field size. Third, the effective dose for each organ was calculated according to the tissue weighting factors presented in ICRP(International Commission on Radiological Protection) recommendations. As a result, the average sum of air kerma during coronary angiography was evaluated as 234.0±112.1 mGy, the dose-area product was 25.9±13.0 Gy·cm², and the total fluoroscopy time was 2.5±2.0 min. Also, the organ dose tended to increase as the tube voltage, milliampere-second, number of frames, and irradiation range increased, whereas the organ dose decreased as the FSD increased. Therefore, medical radiation exposure to patients can be reduced by selecting the optimal tube voltage and field size during coronary angiography, maximizing the focal-skin distance, using the lowest tube current possible, and reducing the number of frames.

• Radiation Oncology Journal
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• v.20 no.1
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• pp.41-52
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• 2002

Purpose : 3D conformal radiotherapy, the optimum dose delivered to the tumor and provided the risk of normal tissue unless marginal miss, was restricted by organ motion. For tumors in the thorax and abdomen, the planning target volume (PTV) is decided including the margin for movement of tumor volumes during treatment due to patients breathing. We designed the respiratory gating radiotherapy device (RGRD) for using during CT simulation, dose planning and beam delivery at identical breathing period conditions. Using RGRD, reducing the treatment margin for organ (thorax or abdomen) motion due to breathing and improve dose distribution for 3D conformal radiotherapy. Materials and Methods : The internal organ motion data for lung cancer patients were obtained by examining the diaphragm in the supine position to find the position dependency. We made a respiratory gating radiotherapy device (RGRD) that is composed of a strip band, drug sensor, micro switch, and a connected on-off switch in a LINAC control box. During same breathing period by RGRD, spiral CT scan, virtual simulation, and 3D dose planing for lung cancer patients were peformed, without an extended PTV margin for free breathing, and then the dose was delivered at the same positions. We calculated effective volumes and normal tissue complication probabilities (NTCP) using dose volume histograms for normal lung, and analyzed changes in doses associated with selected NTCP levels and tumor control probabilities (TCP) at these new dose levels. The effects of 3D conformal radiotherapy by RGRD were evaluated with DVH (Dose Volume Histogram), TCP, NTCP and dose statistics. Results : The average movement of a diaphragm was 1.5 cm in the supine position when patients breathed freely. Depending on the location of the tumor, the magnitude of the PTV margin needs to be extended from 1 cm to 3 cm, which can greatly increase normal tissue irradiation, and hence, results in increase of the normal tissue complications probabiliy. Simple and precise RGRD is very easy to setup on patients and is sensitive to length variation (+2 mm), it also delivers on-off information to patients and the LINAC machine. We evaluated the treatment plans of patients who had received conformal partial organ lung irradiation for the treatment of thorax malignancies. Using RGRD, the PTV margin by free breathing can be reduced about 2 cm for moving organs by breathing. TCP values are almost the same values $(4\~5\%\;increased)$ for lung cancer regardless of increasing the PTV margin to 2.0 cm but NTCP values are rapidly increased $(50\~70\%\;increased)$ for upon extending PTV margins by 2.0 cm. Conclusion : Internal organ motion due to breathing can be reduced effectively using our simple RGRD. This method can be used in clinical treatments to reduce organ motion induced margin, thereby reducing normal tissue irradiation. Using treatment planning software, the dose to normal tissues was analyzed by comparing dose statistics with and without RGRD. Potential benefits of radiotherapy derived from reduction or elimination of planning target volume (PTV) margins associated with patient breathing through the evaluation of the lung cancer patients treated with 3D conformal radiotherapy.

• Radiation Oncology Journal
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• v.27 no.4
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• pp.240-248
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• 2009

Purpose: To provide a simple research tool that may be used to analyze a dose volume histogram from different radiation therapy planning systems for NTCP (Normal Tissue Complication Probability), OED (Organ Equivalent Dose) and so on. Materials and Metohds: A high-level computing language was chosen to implement Niemierko's EUD, Lyman-Kutcher-Burman model's NTCP, and OED. The requirements for treatment planning analysis were defined and the procedure, using a developed GUI based program, was described with figures. The calculated data, including volume at a dose, dose at a volume, EUD, and NTCP were evaluated by a commercial radiation therapy planning system, Pinnacle (Philips, Madison, WI, USA) for comparison. Results: The volume at a special dose and a dose absorbed in a volume on a dose volume histogram were successfully extracted using DVH data of several radiation planning systems. EUD, NTCP and OED were successfully calculated using DVH data and some required parameters in the literature. Conclusion: A simple DVH analyzer program was developed and has proven to be a useful research tool for radiation therapy.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.206-207
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• 2002

The effective dose due to the X-Ray radiography in the patient positioning for the heavy ion radiotherapy was measured on three regions, chest, upper-abdomen and pelvis. All the radiographic systems and the conditions used in the measurements were same as the clinical trial being performed in National Institute of Radiological Sciences, Japan. The organ or tissue for measurements was selected by following ICRP60$^1$ and the effective dose was calculated from measured organ doses and the surface dose.

• Korean Journal of Digital Imaging in Medicine
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• v.14 no.2
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• pp.9-14
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• 2012

Exposed dose of young child should be managed necessarily. Young child is more sensitive than adult of a Radioactivity, especially, and lives longer than adult. Must reduce exposed dose which follows The ALARA(As Low As Reasonably Achievable)rule is recommended by ICRP(International Commission on Radiological Protection)within diagnostic useful range. Therefore, We have to prepare Pediatric DRL(Diagnostic Reference Level) in Korea as soon as possible. Consequently, in this study, wish to estimate organ dose and effective dose using PCXMC Program(a PC-Based Monte Carlo Program), and measure ESD(Entrance surface dose)and organ dose using Glass dosimeter, and then compare with DRL which follows EC(European Commission)and NRPB(National Radiological Protection Board). Using glass dosimeter and PCXMC programs conforming to the International Committee for Radioactivity Prevention(ICRP)-103 tissue weighting factor based on the item before the organs contained in the Chest, Skull, Pelvis, Abdomen in the organ doses and effective dose and dose measurements were evaluated convenience. In a straightforward way to RANDO phantom inserted glass dosimeter(GD352M)by using the hospital pediatric protocol, and in a indirect way was PCXMC the program through a virtual simulation of organ doses and effective dose were calculated. The ESD in Chest PA is 0.076mGy which is slightly higher than the DRL of NRPB(UK) is 0.07mGy, and is lower than the DRL of EC(Europe) which is 0.1mGy. The ESD in Chest Lateral is 0.130mGy which is lower than the DRL of EC(Europe) is 0.2mGy. The ESD in Skull PA is 0.423mGy which is 40 percent lower than the DRL of NRPB(UK) is 1.1mGy and is 28 percent lower than the DRL of EC(Europe) is 1.5mGy. The ESD in Skull Lateral is 0.478mGy which is half than the DRL of NRPB(UK) is 0.8mGy, is 40 percent lower than the DRL of EC(Europe) is 1mGy. The ESD in Pelvis AP is 0.293mGy which is half than the DRL of NRPB(UK) is 0.60mGy, is 30 percent lower than the DRL of EC(Europe)is 0.9mGy. Finally, the ESD in Abdomen AP is 0.223mGy which is half than the DRL of NRPB(UK) is 0.5mGy, and is 20 percent lower than the DRL of EC is 1.0mGy. The six kind of diagnostic radiological examination is generally lower than the DRL of NRPB(UK)and EC(Europe) except for Chest PA. Shouldn't overlook the age, body, other factors. Radiological technician must realize organ dose, effective dose, ESD when examining young child in hospital. That's why young child is more sensitive than adult of a Radioactivity.

• The Journal of the Korean dental association
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• v.53 no.8
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• pp.558-568
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• 2015

Objective: The objectives of this study were to measure pediatric organ and effective doses of cone-beam computed tomography (CBCT) for orthodontic analysis and to compare them to those of panoramic and lateral cephalometric radiography, the conventional radiography for orthodontic analysis. Materials and Methods: Alphard VEGA for CBCT, Planmeca Proline XC for panoramic radiography and Orthophos CD for cephalometric radiography were used for this study. Thermoluminescent dosimeter (TLD) chips were located at 24 anatomic sites of 10-year-old anthropomorphic phantom and exposed during CBCT (C-mode; $200{\times}179mm$ FOV), panoramic and lateral cephalometric radiographic procedures at the clinical exposure settings for 10-year-old patient. Pediatric organ and effective doses were measured and calculated using ICRP 2007 tissue weighting factors. Results: Effective doses of CBCT, panoramic radiography and lateral cephlometric radiography in pediatric clinical exposure settings were $292.5{\mu}Sv$, $19.3{\mu}Sv$, and $4.4{\mu}Sv$ respectively. The thyroid gland contributed most significantly to the effective dose in all the radiographic procedures. Conclusion: Effective dose of CBCT was about 12 times to conventional radiographic procedures for orthodontic analysis in pediatric patient. The use of CBCT for orthodontic analysis should be fully justified over conventional radiography and dose optimization to decrease thyroid dose is needed in pediatric patients.

• The Journal of the Korea Contents Association
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• v.14 no.4
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• pp.249-255
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• 2014

Total body irradiation use one of the pre-treatment as hematopoietic stem cell transplantation in the treatment of leukemia. According to the study of Korean network for organ sharing 2013 report, continue to increase the number of hematopoietic stem cell transplantation. however, the current dose evaluation fall short before treatment. So purpose of this study is Surface dose and deep organ dose evaluation and then find the most ideal conditions when change of the thickness on tissue compensator in TBI. Result, surface dose in 4 MV, SSD 280 cm, compensators thickness 0.5 cm, was measured the highest dose 5.84 mGy/min. And the ideal dose showed when compensator thickness less than 1 cm.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.25 no.1
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• pp.27-38
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• 1995

The organ or tissue doses were determined with head and neck phantom measurement for multiple axial scans (36 slices), multiple coronal scans (13 slices), 3 types of single axial scans(orbit, maxillary sinus and mandibular canal) and single coronal scan (maxillary sinus). For each scan sequence 30 TLDs were placed in selected sites(16 internal sites and 14 external sites) in a tissue-equivalent phantom. The exposure was made at 120kVp, 500mAs with 5 mm slice width. The results were as follows : 1. In multiple axial scans, the greatest effective dose recorded was that delivered to the thyroid glands(2.77 mSv) and the least was that received by the skin(0.05 mSv). From these data, stochastic effects were 202.2x10/sup -6/ and 3.7×10/sup -6/, respectively. 2. In multiple coronal scans, the greatest effective dose recorded was that delivered to the salivary glands(0.58 mSv) and the least was that received by the skin(0.01 mSv). From these data, stochastic effects were 42.2×10/sup -6/ and 0.7×10/sup -6/, repectively. 3. Among single axial scans, the greatest effective dose recorded was that delivered to the salivary gland(0.38 mSv) in maxillary sinus scan. From this data, stochastic effect was 27.7×10/sup -6/. 4. In single coronal scan, the greatest effective dose recorded was that delivered to the salivary gland(0.01 mSv). From this data, stochastic effect was 1.0×10/sup -6/. 5. The equivalent dose measured that delivered to the lens of the eyes was 69.64 mSv in multiple axial scan, 39.32 mSv in multiple coronal scan and 36.77 mSv in single axial scan(orbit).

• Journal of radiological science and technology
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• v.40 no.1
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• pp.49-55
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• 2017

In the case of nuclear medicine practitioners in medical institutions, a wide range of exposure dose to individual workers can be found, depending on the type of source, the amount of radioactivity, and the use of shielding devices in handling radioactive isotopes. In this regard, this study evaluated the organ dose on practitioners as well as the dose reduction effect of the L-block shielding device in handling the diagnostic radiation source through the simulation based on the Monte Carlo method. As a result, the distribution of organ dose was found to be higher as the position of the radiation source was closer to the handling position of a practitioner, and the effective dose distribution was different according to the ICRP tissue weight. Furthermore, the dose reduction effect according to the L-block thickness tended to decrease, which showed the exponential distribution, as the shielding thickness increased. The dose reduction effect according to each radiation source showed a low shielding effect in proportion to the emitted gamma ray energy level.