• Journal of the Korean Society of Radiology
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• v.13 no.4
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• pp.565-572
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• 2019

In this study, shielding analysis of material and thickness of 3D printer filaments was performed for the manufacture of custom shielding by radiation workers during outdoor radiographic test. The shielding was attached to the ICRU Slab Phantom after selecting the voxel source $^{192}Ir$ and $^{75}Se$ through simulation using MCNPX, and the distance between the source and the slab Phantom was set at 100 cm. The 12 shielding materials were divided into 5 mm units up to 200 mm from the absence of shielding materials to evaluate the energy absorbed per unit mass of each shielding material. The results showed that the shielding effect was high in the order of ABS + Tungsten, ABS + Bismuth, PLA + Copper, PLA + Iron from all sources of radiographic test. However, compared to lead, the shielding effect was somewhat lower. Based on this study in the future, further study of the atomic number and the high density filament material is necessary.

• 대한방사선방어학회:학술대회논문집
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• 2009.11a
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• pp.120-121
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• 2009

• Journal of radiological science and technology
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• v.45 no.5
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• pp.423-431
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• 2022

The purpose of this study is to present objective information in applying 3D printing technology for PET/CT (Positron Emission Tomography/Computed Tomography) performance evaluation and use it as a basic research that can be applied to various purposes in the future. Phantoms were manufactured with step wedge of ABS(Acrylonitrile Butadiene Styrene) and ACR(Acrylic acid) material. The counts for each ROI(Region of Interest) were analyzed through image acquisition in PET/CT. And the variation rate of counts and CNR(Contrast Noise Ratio) was evaluated. In the counts analysis, the effect of thickness occurred. In addition, in the variation rate analysis, the thickness setting of steps wedge 4 to 5 levels should be considered first. These results minimize quantitative and qualitative changes in the phantom manufactured based on 3D printing, and enable more stable PET/CT performance evaluation. Based on 3D printing in PET/CT, various phantoms are expected to be produced in the future. If the characteristics of each material are considered and applied through the basic research such as this research, the result of the phantom manufactured through 3D printing can be more meaningful and will be used in a wide range.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.322-323
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• 2002

Partial volume averaging effect of PET data influences on the accuracy of quantitative measurements of regional brain metabolism because spatial resolution of PET is limited. The purpose of this study was to evaluate the accuracy of partial volume correction carried out on $^{18}$ F-PET images using Hoffman brain phantom. $^{18}$ F-PET Hoffman phantom images were co-registered to MR slices of the same phantom. All the MR slices of the phantom were then segmented to be binary images. Each of these binary images was convolved in 2 dimensions with the spatial resolution of the PET. The original PET images were then divided by the smoothed binary images in slice-by-slice, voxel-by-voxel basis resulting in larger PET image volume in size. This enlarged partial volume corrected PET image volume was multiplied by original binary image volume to exclude extracortical region. The evaluation of partial volume corrected PET image volume was performed by region of interests (ROI) analysis applying ROIs, which were drawn on cortical regions of the original MR image slices, to corrected and original PET image volume. From the ROI analysis, range of regional mean values increases of partial volume corrected PET images was 4 to 14%, and average increase for all the ROIs was about 10% in this phantom study. Hoffman brain phantom study was useful for the objective evaluation of the partial volume correction method. This MR-based correction method would be applicable to patients in the. quantitative analysis of FDG-PET studies.

• ETRI Journal
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• v.41 no.6
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• pp.850-862
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• 2019

This work investigated three-dimensional (3D) focused microwave thermotherapy (FMT) at 925 MHz for a human tissue mimicking phantom using the time reversal (TR) principle for musculoskeletal disorders. We verified the proposed TR algorithm by evaluating the possibility of 3D beam focusing through simulations and experiments. The simulation, along with the electromagnetic and thermal analyses of the human tissue mimicking phantom model, was conducted by employing the Sim4Life commercial tool. Experimental validation was conducted on the developed FMT system using a fabricated human tissue mimicking phantom. A truncated threshold method was proposed to reduce the unwanted hot spots in a normal tissue region, wherein a beam was appropriately focused on a target position. The validation results of the simulation and experiments obtained by utilizing the proposed TR algorithm were shown to be acceptable. Effective beam focusing at the desired position of the phantom could be achieved.

• Journal of radiological science and technology
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• v.33 no.4
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• pp.341-348
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• 2010

By accessing the current status of FPD system use in the hospitals located in Seoul and Gyeonggi Province as well as the entrance skin dose and the image quality evaluation realized by C-D Phantom, and the image assessment by the medical professionals regarding the radiography for the extremity, the following results were derived. 1. According to the evaluation made in the actual use of FPD system (12 machines), the grid ratio varied from 8:1 to 13:1, and 6 machines used the grid ratio with 12:1, realizing the largest number. Among the machines, there were 8 machines that allowed a removable grid while 3 machines did use a removable grid (25.0%). 2. When it came to the equipments used for the experiment, it showed that the amount of the entrance skin dose increased from 4.13 times up to 4.79 times with the grid use. 3. The difference in the entrance skin dose depending on the changes in the exposure condition(0.5times or 2.0times) was not significantly different regardless of the patients' thickness. 4. In terms of the image quality depending on C-D Phantom, the grid use was distinguished well. However, the images were well distinguishable as the exposure condition got increased. 5. In the clinical assessment, the grid use was less effective for the Hand PA, which was considered to shoot a thin body part. It was evaluated that the grid use was preferred for the Knee AP, which was shooting for a relatively thick body part. Nonetheless, 3 out of 5 people said that they would not use the grid if the entrance skin dose to reduced.

• The Journal of Korean Society for Radiation Therapy
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• v.22 no.2
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• pp.135-144
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• 2010

Purpose: The purpose of this study is that through production of phantom for respiration gated radiotherapy, assessing appropriacy of exposure dose for the therapy using RPM (Real-time Position Management). Materials and Methods: We located measurement object on the phantom for respiration gated radiotherapy made of 2 linear actuator, acrylic panel, stanchion, iron plate ets. to drive (up, down, front, back). Using 4D CT scan, we analyzed patient's respiration and reproduced the movement by computer. On the phantom, we located a 2D-Array (PTW) and an White water phantom (4.5 cm) and used DMLC (interval 2 cm) in the field size $10{\times}10\;cm$, then exposed 21EX X-ray 100 MU, in the case of phantom was (1) static (2) moving (3) gated using RPM respectively gantry $0^{\circ}$ and $90^{\circ}$ We measured with a 0.125 CC ionization chamber (PTW) on the phantom (7.5 cm) in the same condition. Results: Ionization chamber: There were within 0.3% of error with gating respiration and approximately 2% of error without gating in the same condition. 2D-Array: Gantry $90^{\circ}$, field size $10{\times}10\;cm$, using DMLC. There were within 3% of error with gating respiration and approximately 16% of error without gating. Conclusion: The phantom for respiration gated radiotherapy makes plans considering patient's movement, quantitative analysis of exposure dose and proper assessment therapy for IMRT patients using RPM possible.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.529-535
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• 2020

Geant4 is compatible with the Windows operating system in C++ language use, enabling interface functions that link DICOM or software. It was simulated to address the basic structure of the simulation using Geant4/Gate code and to specifically verify the density composition and lung cancer process in the human phantom. It was visualized using the Gate Graphic System, i.e. openGL, Ray Tracer: Ray Tracing by Geant4 Tracing, and using Geant4/Gate code, lung cancer is modeled in the human phantom area in 3D, 4D to verify the simulation progress. Therefore, as a large number of new functions are added to the Gate Code, it is easy to implement accurate human structure and moving organs.

• The Korean Journal of Nuclear Medicine Technology
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• v.13 no.1
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• pp.57-62
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• 2009

Purpose: Brain SPECT study is more sensitive to motion than other studies. Especially, when applying 1-day subtraction method for Diamox SPECT, it needs shorter study time in order to prevent reexamination. We were required to have new study condition and analysing method on dual detector system because triple head camera in Seoul National University Hospital is to be disposed. So we have tried to increase image quality and make the dual and triple head to have equivalent study time by using a new analysing program. Materials and Methods: Using IEC phantom, we estimated contrast, SNR and FWHM. In Hoffman 3D brain phantom which is similar with real brain, we were on the supposition that 5% of injected doses were distributed in brain tissue. To compare with existing FBP method, we used fan-beam collimator. And we applied 15 sec, 25 sec/frame for each SEPCT studies using LEHR and LEUHR. We used OSEM2D and Onco-flash3D reconstruction method and compared reconstruction methods between applied Gaussian post-filtering 5mm and not applied as well. Attenuation correction was applied by manual method. And we did Brain SPECT to patient injected 15 mCi of $^{99m}Tc$-HMPAO according to results of Phantom study. Lastly, technologist, MD, PhD estimated the results. Results: The study shows that reconstruction method by Flash3D is better than exiting FBP and OSEM2D when studied using IEC phantom. Flowing by estimation, when using Flash3D, both of 15 sec and 25 sec are needed postfiltering 5 mm. And 8 times are proper for subset 8 iteration in Flash3D. OSEM2D needs post-filtering. And it is proper that subset 4, iteration 8 times for 15sec and subset 8, iteration 12 times for 25sec. The study regarding to injected doses for a patient and study time, combination of input parameter-15 sec/frame, LEHR collimator, analysing program-Flash3D, subset 8, iteration 8times and Gaussian post-filtering 5mm is the most appropriate. On the other hands, it was not appropriate to apply LEUHR collimator to 1-day subtraction method of Diamox study because of lower sensitivity. Conclusions: We could prove that there was also an advantage of short study time effectiveness in Dual camera same as Triple gamma camera and get great result of alternation from existing fan-beam collimator to parallel collimator. In addition, resolution and contrast of new method was better than FBP method. And it could improve sensitivity and accuracy of image because lesser subjectivity was input than Metz filter of FBP. We expect better image quality and shorter study time of Brain SPECT on Dual detector system.

• The Korean Journal of Nuclear Medicine Technology
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• v.15 no.2
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• pp.60-64
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• 2011

Purpose: The brain perfusion SPECT is the examination which is able to know adversity information related brain disorder. But brain perfusion SPECT has also high failure rates by patient's motions. In this case, we have to use two days method and patients put up with many disadvantages. We think that we don't use two days method in brain perfusion SPECT, if we can use registration method. So this study has led to look over registration method applications in brain perfusion SPECT. Materials and Methods: Jaszczak, Hoffman and cylindrical phantoms were used for acquiring SPECT image data on varying degree in x, y, z axes. The phantoms were filled with $^{99m}Tc$ solution that consisted of a radioactive concentration of 111 MBq/mL. Phantom images were acquired through scanning for 5 sec long per frame by using Triad XLT9 triple head gamma camera (TRIONIX, USA). We painted the ROI of registration image in brain data. So we calculated the ROIratio which was different original image counts and registration image counts. Results: When carring out the experiments under the same condition, total counts differential was from 3.5% to 5.7% (mean counts was from 3.4% to 6.8%) in phantom and patients data. In addition, we also run the experiments in the double activity condition. Total counts differential was from 2.6% to 4.9% (mean counts was from 4.1% to 4.9%) in phantom and patients data. Conclusion: We can know that original and registration data are little different in image analysis. If we use the image registration method, we can improve disadvantage of two days method in brain perfusion SPECT. But we must consider image registration about the distance differences in x, y, z axes.