• Journal of the Korean Society of Radiology
• /
• v.16 no.5
• /
• pp.603-609
• /
• 2022

The dose distribution in the human body was evaluated and analyzed through dosimetry data using water phantom, ionization chamber and simulated by Monte Carlo simulation for ^99mTc and ¹⁸F sources, which are frequently used in the nuclear medicine in this study. As a result of this study, it was found that the dose decreased exponentially as the distance from the radioisotope increased, and it particularly showed a tendency to decrease sharply when the radioisotope was separated by 5 cm. It means that a large amount of dose is delivered to an organ located within 4 cm of source's movement path when a source uptake in the human body. Numerically, it was formed in the rage of 0.16 to 2.16 pC/min for ^99mTc and 0.49 to 9.29 pC/min for ¹⁸F. In addition, the energy transfer coefficient calculated using the result was found to be similar to the measured value and the simulation value in the range of 0.240 to 0.260. Especially, when the measured data and the simulation value were compared, there was a difference is within 2%, so the reliability of the data was secured. In this study, the distribution of radiation generated from a source was calculated to quantitatively evaluate the internal dose by radioisotopes. It presented reliable results through comparative analysis of the measurement value and simulation value. Above all, it has a great significance to the point that it was presented by directly measuring the distribution of radiation in the human body.

• Journal of the Korean Society of Radiology
• /
• v.13 no.6
• /
• pp.889-894
• /
• 2019

Upper gastrointestinal series is an examination that uses X-rays. It is important to defend against exposure to radiation during upper gastrointestinal examination because the organs, such as thyroid gland, lens, breasts, and gonads, with relatively high biological sensitivity to radiation are distributed on the examination area. We have made a whole body phantom that can change the depth of organs. radiation dose of eye, thyroid gland, breast and gonads were measured by the same procedure as the actual upper gastrointestinal examination. When performed only fluoroscopy the mean dose reduction of lens, thyroid gland, breast and gonads was 62.2%. The mean dose reduction of lens, thyroid gland, breast and gonads was 59.0% when both fluoroscopy and spot shoot were performed. Therefore, when performed upper gastrointestinal examination it was confirmed that shielding of the lens, thyroid gland, breast and gonads was effective in decreasing the exposure dose. The manufactured human phantom can be used in measuring radiation dose for deep organ because it can adjust the height corresponding to the organs located in the human body.

• The Journal of Korean Society for Radiation Therapy
• /
• v.35
• /
• pp.7-13
• /
• 2023

Purpose: In this study, we evaluated the effect of using a customized bolus on dose delivery in the treatment plan when cervical cancer protruded out of the body along with the uterus and evaluated reproducibility in patient set-up. Materials & Methods: The treatment plan used the Eclipse Treatment Planning System (Version 15.5.0, Varian, USA) and the treatment machine was VitalBeam (Varian Medical Systems, USA). The radiotherapy technique used 6 MV energy in the AP/PA direction with 3D-CRT. The prescribed dose is 1.8 Gy/fx and the total dose is 50.4 Gy/28 fx. Semiflex TM31010 (PTW, Germany) was used as the ion chamber, and the dose distribution was analyzed and evaluated by comparing the planned and measured dose according to each position movement and the tumor center dose. The first measurement was performed at the center by applying a customized bolus to the phantom, and the measurement was performed while moving in the range of -2 cm to +2 cm in the X, Y, and Z directions from the center assuming a positional error. It was measured at intervals of 0.5 cm, the Y-axis direction was measured up to ±3 cm, and the situation in which Bolus was set-up incorrectly was also measured. The measured doses were compared based on doses corrected to CT Hounsfield Unit (HU) 240 of silicon instead of the phantom's air cavity. Result: The treatment dose distribution was uniform when the customized bolus was used, and there was no significant difference between the prescribed dose and the actual measured value even when positional errors occurred. It was confirmed that the existing sheet-type bolus is difficult to compensate for irregularly shaped tumors protruding outside the body, but customized Bolus is found to be useful in delivering treatment doses uniformly.

• Journal of the Korean Society of Radiology
• /
• v.16 no.7
• /
• pp.851-856
• /
• 2022

The purpose of this study is to confirm the effect of reducing the surface dose around the radiation field in breast cancer radiotherapy using the Field-in-Field (FIF) technique. X-ray was exposed from a linear accelerator (Linac) was used for irradiation, and the surface dose was measured with a glass dosimeter. The source-to-surface distance (SSD) was 90 cm, the field size is 10 × 10 cm², and the X-ray energy was 6 MV and 10 MV, respectively. The surface dose of the FIF was compared with the dose measured in the physical wedge (PW) and dynamic wedge (DW). Wedge angles of 15° and 30° were used in the PW and DW, respectively. Surface dose was measured at 1 cm, 3 cm, and 5 cm from the center of the field size, respectively. According to the results, FIF showed lower surface dose compared to PW and DW regardless of the energy of the X-ray beam, wedge angle, and dose measurement point. Since FIF could reduce the radiation dose in periphery of the field size in breast cancer treatment, it is expected to be able to reduce the secondary damage caused by the radiation beam as well as to obtain a uniform dose distribution on the target.

• Progress in Medical Physics
• /
• v.17 no.3
• /
• pp.131-135
• /
• 2006

A commercial ion chamber matrix was examined the characteristics and its performance for radiotherapy qualify assurance. The device was the I'mRT 2D-MatriXX (Scanditronix-Wellhofer, Schwarzenbruck, Germany). The 2D-MatriXX device consists of a 1020 vented ion chamber array, arranged in $24{\times}24cm^2$ matrix. Each ion chamber has a volume of $0.08cm^3$, spacing of 0.762 cm and minimum sampling time of 20 ms. For the investigation of the characteristics, dose linearity, output factor, short-term reproducibility and dose rate dependency were tested. In the testing of dose linearity. It has shown a good signal linearity within 1% in the range of $1{\sim}800$cGy. Dose rate dependency was found to be lower than 0.4% (Range: 100-600 Mu/min) relative to a dose rate of 300 Mu/min as a reference. Output factors matched very well within 0.5% compared with commissioned beam data using a ionization chamber (CC01, Scanditronix-Wellhofer, Schwarzenbruck, Germany) in the range of field sizes $3{\times}3{\sim}24{\times}24cm^2$. Short-term reproducibility (6 times with a interval of 15 minute) was also shown a good agreement within 0.5%, when the temperature and the pressure were corrected by each time of measurement. in addition, we compared enhanced dynamic wedge (EDW, Varian, Palo Alto, USA) profiles from calculated values in the radiation planning system with those from measurements of the MatriXX. Furthermore, anon-uniform IMRT dose fluence was tested. All the comparison studies have shown good agreements. In this study, the MatriXX was evaluated as a reliable dosimeter, and it could be used as a simplistic and convenient tool for radiotherapy qualify assurance.

• Radiation Oncology Journal
• /
• v.19 no.4
• /
• pp.301-305
• /
• 2001

Purpose : This study was peformed for the evaluation of the feasibility and toxicity of hypofractionated radiation therapy for early glottic cancer Methods and Materials : From February 1999 to February 2000, 20 patients with Histologically confirmed Stage I, II glottic cancer were enrolled into this study. There were 18 males and 2 females, the median age of the patients was 59 years. The distribution of stage distribution was as fellows; T1aN0-16 patients, T1bN0-1 patient, T2N0-3 patients. Eighteen patients underwent laryngomicroscopic biopsy only, and two patients underwent laser cordectomy. All patients received radical radiation therapy (2.5 Gy per fraction, 24 fractions, total 60 Gy). Median duration of treatment was 36 days (range $31\~45\;days$). Results : Radiation therapy were well tolerated. Most common acute reactions were odynophagia and hoarseness, and these reactions resolved after radiation therapy. There were one case of RTOG grade 3 odynophagia $(5\%)$, six cases of grade 3 hoarseness $(30\%)$. Response of radiation therapy was evaluated one month after completion of treatment. All patients revealed complete response. During follow up, total three cases of treatment failure were detected. two cases were local recurrence in 10 and 13 months of radiation therapy and one case was local recurrence and distant metastasis in 2 months of radiation therapy. Conclusion : This hypofractionated radiation therapy schedule was feasible and effective for control of early glottic cancer But longer follow up time would be required to assess the long-term disease control and the late complication by shortening radiation therapy duration.

• Journal of the Korean Society of Radiology
• /
• v.12 no.4
• /
• pp.443-450
• /
• 2018

The Geant 4 simulated the linear accelerator (VARIAN CLINAC) based on the previously implemented BEAMnrC data, using the head structure of the linear accelerator. In the 10 MV photon flux, Geant4 was compared with the measured value of the percentage of the deep dose and the lateral dose of the water phantom. In order to apply the dose calculation to the body part, the actual patient's lung area was scanned at 5 mm intervals. Geant4 dose distributions were obtained by irradiating 10 MV photons at the irradiation field ($5{\times}5cm^2$) and SAD 100 cm of the water phantom. This result is difficult to measure the dose absorbed in the actual lung of the patient so the doses by the treatment planning system were compared. The deep dose curve measured by water phantom and the deep dose curve calculated by Geant4 were well within ${\pm}3%$ of most depths except the build-up area. However, at the 5 cm and 20 cm sites, 2.95% and 2.87% were somewhat higher in the calculation of the dose using Geant4. These two points were confirmed by the geometry file of Genat4, and it was found that the dose was increased because thoracic spine and sternum were located. In cone beam CT, the dose distribution error of the lungs was similar within 3%. Therefore, if the contour map of the dose can be directly expressed in the DICOM file when calculating the dose using Geant4, the clinical application of Geant4 will be used variously.

• Progress in Medical Physics
• /
• v.13 no.1
• /
• pp.1-8
• /
• 2002

Accurate knowledge of the distribution of contamination electrons ( which comes from mainly gantry head by Compton scattering, pair production, and tray: henceforth called leptons ) at the surface and in the first centimeters of tissue is essential for the clinical practice of radiation oncology. Such lepton tends to reduce or eliminate the ‘skin-sparing’ advantage of megavoltage photon beam radiotherapy, This information is needed to prescribe a absorbed dose to a skin volume at a few millimeter depth in high energy therapeutic radiation photon beam All experiments were done with 15 MV photon beam from a dual energy linear accelerator (Clinac 1800, Varian). Field size is defined by ranged from 10.0$\times$10.0 to 30.0$\times$30.0 $\textrm{cm}^2$. The absorbed dose and distribution of leptons in therapeutic radiation beam (15 MV) are investigated by means of variable blocked beams of 30.0$\times$30.0 $\textrm{cm}^2$ and dose beam profiles partly removed leptons with a copper plate. A numerous leptons mainly are distributed as shape of broad cone in the central photon beam and leptons path length in the water are shorter than 2.5 cm because of the leptons energy having around 3.0 MeV. These results clearly appears that the subtraction of leptons from the total depth dose curve not only lower the absolute dose in the buildup region and surface dose, it also causes a shift of d$_{max}$ to a deeper depth.

• The Journal of Korean Society for Radiation Therapy
• /
• v.17 no.1
• /
• pp.9-17
• /
• 2005

Purpose : Uniform dose distribution of the target volume is very important in the radiation treatment. We will evaluate the usefulness of Field-in-Field Technique use to get uniform dose distribution of the target volume and try to find Apply possibility out to a whole brain treatment patient of various thickness. Material and method : We compare the dose distribution when we applied Field-in-Field Technique and parallel opposed fields technique. establish the treatment plan to a phantom(acryl 16cm spheral phantom) and do the measurement, assessment use the TLD and Low sensitivity film. Also the assessment did Apply possibility of Field-in-Field Technique to 20 patient object of various thickness. Result : In the case to use the parallel opposed fields at the whole brain treatment $10-12\%$ high dose region appeared but reduce to $3-4\%$ lesses when we used the Field-in-Field technique. We could get similar numerical value the film and TLD measurement result also. The change of the dose distribution appeared to its ${\pm}1{\sim}2\%$ although it applied such Field-in-Field technique to various patient so that we were identical. Conclusion : We can get uniform dose distribution of in the treatment region if we apply the Field-in-Field technique at the whole brain treatment. Also alternate can play the role of the wedge filter and 3D compensator and We are thought by minimizing the obstacle to be happened due to the high dose region when radiation treatment.

• Progress in Medical Physics
• /
• v.22 no.1
• /
• pp.3-11
• /
• 2011

The purpose of this study was to evaluate feasibility of Vertical Multileaf Collimator for determination of irradiation size using Vertical Multileaf Collimator and lead block to determine 4 different irradiation shape in case of Co-60 gamma-ray and 6 MV X-ray. We chose ion chamber, glass dosimeter and EBT chromic film to compare with Vertical Multileaf Collimator results and lead block results. In case of Co-60 gamma-ray and 6 MV X-ray, the central axis point dose normalized at reference field of lead block with ion chamber results for Vertical Multileaf Collimator were estimated higher than lead block about 5.1%, 4.2%. In case of Co-60 gamma-ray, the central axis point dose normalized at reference field of lead block with glass dosimeter results for Vertical Multileaf Collimator were estimated higher than lead block about 2.2%, 7.8%, 7.2%, 4.0% for reference, circle, triangle, cross field, respectively. In case of 6 MV X-ray, the central axis point dose normalized at reference field of lead block with glass dosimeter results for Vertical Multileaf Collimator were estimated higher than lead block about 6.7%, 6.2%, 3.8%, 6.2% for reference, circle, triangle, cross field, respectively. The results of EBT chromic film, Vertical Multileaf Collimator of penumbra size for all irradiation shape was smaller than lead block of those size that 2.0~3.5 mm for Co-60 gamma-ray, 0.5~1.0 mm for 6 MV X-ray. The results from this study, radiation treatment volume that results in shielding block can be minimized. In addition, during radiation treatment for 2, 3-dimensional radiation therapy using a Vertical Multileaf Collimator of this survey can be used to determine variety of irradiation fields.