• Journal of the Korean Society of Radiology
• /
• v.15 no.2
• /
• pp.239-246
• /
• 2021

Portal Dosimetry was verified using EPID to secure the clinical application and reliability of the existing research dose evaluation. The dose distribution of Geant4 was compared with the measured value by 360° rotational irradiation with a 2.5 cm cone for stereotactic brain surgery. To confirm the dose distribution of patients with brain metastasis, the dose distribution investigated by inserting a Gafchromic EBT film into the parietal phantom and the dose distribution obtained from the parietal phantom using VMAT are compared and applied to actual patients. As a result of the analysis, it was confirmed that the accuracy of the beam center and the center of the couch coincide accurately with an error within 1mm as a result of QA through a pin ball. In addition, it was confirmed that the EBT3 film has excellent linearity in the range of 0 to 10 Gy according to various dose irradiation. In the same setting as the two cervical phantoms, we confirm that the implementation and simulation results calculations of dose calculations based on Geant4 using photon beams match the experimental data within the treatment planning volume (PTV). Therefore, volume modulated arc treatment (VMAT) 360° rotational irradiation was performed, and the result of iso-dose distribution analysis by rotational irradiation confirmed that it is appropriate to include a virtual tumor.

• Journal of the Korean Society of Radiology
• /
• v.12 no.7
• /
• pp.879-886
• /
• 2018

A 3-dimensional (D) printer is a device capable of outputting a three-dimensional solid object based on data modeled in a computer. These features are utilized in the bone model X - ray phantom production etc using CT data by fusing with the radiation science field. A bone model phantom was made using data obtained by CT scan of an existing Pelvis phantom, using PLA, Wood, XT-CF20, Glow fill, Steel filaments which are materials of Fused Filament Fabrication (FFF) 3D printer.Measure Hounsfield Unit (HU) with images obtained by CT scan of the existing Pelvis phantom and five material phantoms made with 3D printer under the same conditions,SI and SNR were measured using a diagnostic X-ray generator, and each phantom was compared and analyzed.As a result, the X - ray phantom in the X - ray examination condition of the limb was found to be most suitable for the glow fill filament.The characteristics of the filament can be known to the base of this research and the practicality of X - ray phantom fabrication was confirmed.

• Journal of the Korean Society of Radiology
• /
• v.12 no.6
• /
• pp.793-799
• /
• 2018

As interest in artificial intelligence has increased, artificial intelligence has been actively studied in the medical field. In Korea, artificial intelligence has been applied to medical imaging devices such as X-ray imaging, Computer Tomography and Magnetic Resonance Imaging and artificial intelligence capable of acquiring radiation images of patients without radiologists in the future Medical devices are expected to be invented. This study was an initial study on the automation of patient positioning in X - ray imaging. We used x-ray equipment and human phantoms to evaluate the positioning. The program used Visual Studio 2010 MFC and the image was in the size $1450{\times}1814$. The pixel values were converted to contrasts with values of 0 to 255 that can be visually recognized and output to the monitor. We developed a procedure algorithm program that predicts the angle of the output image through three pixel coordinate values and induces the patient to perform correct positioning according to the voice guidance according to the angle. In the next study, we will study the artificial intelligence to grasp the structure itself and calculate the angle, rather than conveying the reference of coordinates to artificial intelligence. In the future, it is expected that it will be helpful in the study of artificial intelligence from shooting to positioning through the automation of positioning.

• Journal of the Korean Society of Radiology
• /
• v.13 no.5
• /
• pp.675-681
• /
• 2019

The purpose of this study was to investigate the effect of increasing the amount of 3D volume imaging on the hand, knee, and foot human phantom in CT, After analyzing the data, three - dimensional volumetric images were implemented using MMWP program to evaluate reproducibility. First, the data amount of three human phantoms according to each increment was analyzed. Secondly, the reproducibility evaluation and the measured length were compared. As a result of analyzing the amount of image data for each phantom according to the increment, it was confirmed that the amount of data is reduced to about 1/10 when the increment is set to 1.0 mm as compared with the case where the increment is set to 0.1 mm. In the evaluation of the feasibility, gap was generated from 0.7mm for hand phantom, 0.6mm for knee phantom and foot phantom, and it was confirmed that even when the actual phantom and actual length were compared, the length was much different and the implementation was lowered. As the increment is closer to 1.0mm, the number of images is small and the 3D implementation time is small. Therefore, it is best to determine the increase before the gap of the image is generated and to apply the Increment for preoperative diagnosis. We hope that this study will be an indicator of the accurate increment setting when implementing 3D image through VRT Rendering after CT scan.

• Journal of Radiation Protection and Research
• /
• v.47 no.3
• /
• pp.158-166
• /
• 2022

Background: The effects of radiation on the health of radiation workers who are constantly susceptible to occupational exposure must be assessed based on an accurate and reliable reconstruction of organ-absorbed doses that can be calculated using personal dosimeter readings measured as H_p(10) and dose conversion coefficients. However, the data used in the dose reconstruction contain significant biases arising from the lack of reality and could result in an inaccurate measure of organ-absorbed doses. Therefore, this study quantified the biases involved in organ dose reconstruction and calculated the bias-corrected H_p(10)-to-organ-absorbed dose coefficients for the use in epidemiological studies of Korean radiation workers. Materials and Methods: Two major biases were considered: (a) the bias in H_p(10) arising from the difference between the dosimeter calibration geometry and the actual exposure geometry, and (b) the bias in air kerma-to-H_p(10) conversion coefficients resulting from geometric differences between the human body and slab phantom. The biases were quantified by implementing personal dosimeters on the slab and human phantoms coupled with a Monte Carlo method and considered to calculate the bias-corrected H_p(10)-to-organ-absorbed dose conversion coefficients. Results and Discussion: The bias in H_p(10) was significant for large incident angles and low energies (e.g., 0.32 for right lateral at 218 keV), whereas the bias in dose coefficients was significant for the posteroanterior (PA) geometry only (e.g., 0.79 at 218 keV). The bias-corrected H_p(10)-to-organ-absorbed dose conversion coefficients derived in this study were up to 3.09- fold greater than those from the International Commission on Radiological Protection publications without considering the biases. Conclusion: The obtained results will aid future studies in assessing the health effects of occupational exposure of Korean radiation workers. The bias-corrected dose coefficients of this study can be used to calculate organ doses for Korean radiation workers based on personal dose records.

• Progress in Medical Physics
• /
• v.32 no.4
• /
• pp.99-106
• /
• 2021

Purpose: In this study, we aimed to manufacture a patient-specific gel phantom combining three-dimensional (3D) printing and polymer gel and evaluate the radiation dose and dose profile using gel dosimetry. Methods: The patient-specific head phantom was manufactured based on the patient's computed tomography (CT) scan data to create an anatomically replicated phantom; this was then produced using a ColorJet 3D printer. A 3D polymer gel dosimeter called RTgel-100 is contained inside the 3D printing head phantom, and irradiation was performed using a 6 MV LINAC (Varian Clinac) X-ray beam, a linear accelerator for treatment. The irradiated phantom was scanned using magnetic resonance imaging (Siemens) with a magnetic field of 3 Tesla (3T) of the Korea Institute of Nuclear Medicine, and then compared the irradiated head phantom with the dose calculated by the patient's treatment planning system (TPS). Results: The comparison between the Hounsfield unit (HU) values of the CT image of the patient and those of the phantom revealed that they were almost similar. The electron density value of the patient's bone and brain was 996±167 HU and 58±15 HU, respectively, and that of the head phantom bone and brain material was 986±25 HU and 45±17 HU, respectively. The comparison of the data of TPS and 3D gel revealed that the difference in gamma index was 2%/2 mm and the passing rate was within 95%. Conclusions: 3D printing allows us to manufacture variable density phantoms for patient-specific dosimetric quality assurance (DQA), develop a customized body phantom of the patient in the future, and perform a patient-specific dosimetry with film, ion chamber, gel, and so on.

• Journal of Radiation Protection and Research
• /
• v.48 no.4
• /
• pp.167-174
• /
• 2023

Background: A nondestructive test is commonly used to inspect the surface defects and internal structure of an object without any physical damage. X-rays generated from an electron accelerator or a tube are one of the methods used for nondestructive testing. The high penetration of X-rays through materials with low atomic numbers makes it difficult to discriminate between these materials using X-ray imaging. The interaction characteristics of neutrons with materials can supplement the limitations of X-ray imaging in material discrimination. Materials and Methods: The radiation image acquisition process for air-cargo security inspection equipment using X-rays and neutrons was simulated using a GEometry ANd Tracking (Geant4) simulation toolkit. Radiation images of phantoms composed of 13 materials were obtained, and the R-value, representing the attenuation ratio of neutrons and gamma rays in a material, was calculated from these images. Results and Discussion: The R-values were calculated from the simulated X-ray and neutron images for each phantom and compared with those obtained in the experiments. The R-values obtained from the experiments were higher than those obtained from the simulations. The difference can be due to the following two causes. The first reason is that there are various facilities or equipment in the experimental environment that scatter neutrons, unlike the simulation. The other is the difference in the neutron signal processing. In the simulation, the neutron signal is the sum of the number of neutrons entering the detector. However, in the experiment, the neutron signal was obtained by superimposing the intensities of the neutron signals. Neutron detectors also detect gamma rays, and the neutron signal cannot be clearly distinguished in the process of separating the two types of radiation. Despite these differences, the two results showed similar trends and the viability of using simulation-based radiation images, particularly in the field of security screening. With further research, the simulation-based radiation images can replace ones from experiments and be used in the related fields. Conclusion: The Korea Atomic Energy Research Institute has developed air-cargo security inspection equipment using neutrons and X-rays. Using this equipment, radiation images and R-values for various materials were obtained. The equipment was reconstructed, and the R-values were obtained for 13 materials using the Geant4 simulation toolkit. The R-values calculated by experiment and simulation show similar trends. Therefore, we confirmed the feasibility of using the simulation-based radiation image.

• Korean Journal of Acupuncture
• /
• v.40 no.4
• /
• pp.184-193
• /
• 2023

Objectives : The purpose of this study is to understand the temperature characteristics depending on the thickness and material of the needle used with the Electronic Warm Acupuncture Device (EWAD). Methods : We controlled experimental environment and measured temperature changes of a silicon phantom in which K-type thermocouples were inserted at depths of 2, 7 mm. EWAD perfomed with acupuncture needles of various thicknesses (0.25×60 mm, 0.40×60 mm, and 0.50×60 mm) and materials (Gold 0.40×50 mm). We set non-needle (only heated with EWAD skin heater) group as a control group. Results : The maximum temperature and temperature changes of 0.40 mm, 0.50 mm needle group were significantly higher than the non-needle group. The highest temperature range in all needle groups was 0.50 mm needle group (41.44±0.31℃). However, the 0.25 mm needle group was not significantly different from the non-needle group. Maximum temperature of gold needle group was significantly higher than stainless steel needle group. Temperature changes of gold needle group were higher than stainless steel group at the depth of 7 mm. Conclusions : It was found that needle thickness and material of acupuncture had an effect on the temperature of the EWAD. When performing EWAD treatment, consideration of thickness and material of acupuncture is needed. Future research is needed using phantoms that can reflect actual clinical situations and better mimic the human body.

• Journal of the Korean Society of Radiology
• /
• v.17 no.6
• /
• pp.919-927
• /
• 2023

Elastography utilizes the fact that the tissue of a malignant tumor is harder than that of a benign tumor and increases the specificity of diagnosis according to the elastic modulus of the tumor, helping to reduce unnecessary biopsies. However, the reliability of elastography can be influenced by the equipment used and the examiner's skills. In this study, the researchers analyzed the reproducibility of elastography by evaluating phantom images when measuring the elasticity values repeatedly. Phantoms were created using silicone and gelatin with different levels of stiffness, and they were inserted at varying depths from the surface. The elasticity values were measured using shear wave elastography. The study aimed to determine whether the reproducibility of elasticity values remains consistent depending on the stiffness and depth of the lesions. The experimental results showed that there was no statistically significant correlation between the elasticity values obtained through shear wave elastography and the depth or stiffness of the lesions. However, in the lesions with the lowest stiffness, the elasticity values were statistically significant (p<0.001) and showed a high correlation with the depth of the lesions. Although there were variations in the measured elasticity values based on the differences in lesion stiffness and depth, these differences did not significantly impact the diagnosis. Therefore, shear wave elastography remains a reliable diagnostic method, and it is suggested that it can be helpful in the diagnosis of breast lesions.

• Journal of the Korean Society of Radiology
• /
• v.17 no.6
• /
• pp.985-991
• /
• 2023

A tissue-equivalent phantom is necessary for quality control of hyperthermia therapy. However, since there is no phantom for this purpose, phantoms made from agar are being used in various studies. The tissue-equivalent properties of the agar phantom were confirmed by comparison with the tissue-equivalent material bolus in this study. CT images of the agar phantom and bolus were acquired, and tissue equivalent characteristics were analyzed with image analysis and dose calculation using a computerized radiation therapy planning system. The average pixel value was 96.960±10.999 in bolus, 108.559±8.233 in 3% agar phantom, and 111.844±8.651 in 4% agar phantom. Using the SSD technique, 100 cGy was prescribed at a depth of 1.5 cm and 6 MV X -ray was set to irradiated to 10x10 cm2, and the absorbed dose according to depth was calculated from the central axis of the beam. The intraclass correlation coefficient of dose distribution of bolus, 3% agar phantom, and 4% agar phantom was 0.979 (p<.001, 95%CI .957-.991). The density (g/cm3) at the point where the absorbed dose was calculated was 0.990±0.020 at the bolus, 1.018±0.020 at the 3% agar phantom, and 1.035±0.024 at the 4% agar phantom. In this study, the internal density distribution and uniformity of the agar phantom were confirmed to be appropriate as a tissue equivalent material by analysis of CT images and a computerized radiation therapy planning system.