• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.651-660
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• 2020

The purpose of this study was to create a phantom with a HU value similar to that of the human Femur using a 3D printer to replace the existing pig bone. A total of 372 people were analyzed to determine the HU value of human Femur. Using a 3D printer, a human bone model phantom was fabricated using PLA-Cu 20% and subjected to CT examination. Pig bones were 6 months old pigs, and bones 2 days after slaughter were used. As a result of the examination, the 3D printing phantom made with 80% of the internal filling showed a similar value to all data of the human body (p<0.05), and there was a difference from the pig bone (p>0.05). In addition, in the case of the HU value of Femur by age group, it was confirmed that the value of HU decreased as the age group increased (p<0.05). 3D printing and HU values confirmed a weak negative correlation with respect to the stacking height, but confirmed a strong positive correlation (R² = 0.996) with 182.13±1.290 in the inner filling (p<0.05). In conclusion, it was confirmed that the human body model phantom using 3D printing can exhibit a similar level of HU value to the human body compared to the existing pig bone phantom, and this study will provide basic data for the production of a human body model phantom using a 3D printer.

• Radiation Oncology Journal
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• v.6 no.1
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• pp.85-91
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• 1988

For the physical characterization of neutron beam, dosimetric measurements had been performed to obtain physical data of KCCH cyclotron-produced neutrons for clinical use. The results are presented and compared with the data of other institutions from the literatures. The central axis percent depth dose, build-up curves and open and wedge isodose curve values are intermediate between that of a 4 and 6 MV X-rays. The build-up level of maximum dose was at 1.35cm and entrance dose was approximately $40\%$. Flatness of the beam was $9\%$ at Dmax and less $than{\pm}3\%$ at the depth of $80\%$ isodose line. Penumbra begond the $20\%$ line is wider than corresponding photon beam. The output factors ranged 0.894 for $6\times6cm$ field to 1.187 for $30\times30cm$ field. Gamma contamination of neutron beam was $4.9\%$ at 2 cm depth in $10\times10cm$ field.

• Progress in Medical Physics
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• v.12 no.1
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• pp.95-102
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• 2001

The intracavitary cones were designed which were made of stainless steel and have scratched inside cone to be generated electron scatter and designed to be attached easily to the LINAC collimator and controlled cones length to be contacted smoothly between the patient and the cone tip. Two types of intracavitary cones were designed. One is the straight end cones with circular opening on the distal end and the other is 30 degree beveled end cones with elliptical opening on the distal end. Each type of intracavitary cone ranged in daimeter from 2.5 cm to 3.5 cm and required a separate set of lower trimmer annulias cone diameter. The film phantom was designed with an internal cassette that accurately aligned the film edge with the film phantom surface. Film optical density data were measured by photodensitometer(Wellhofer 700i) Dosimetry measurements were made to commission the LINAC for 6 - 20 MeV electron using the intracavitary cones. Isodose curves were measured for all energy and cones combinations. Output is defined as the maximum dose per MU along the clinical central axis in water at 113 cm SSD. Calibration output, defined to be the output for the 15cm$\times$15cm diameter straight cone, was adjusted to 1.00 cGy/MU at each energy according to the TG-21 protocol.

• Journal of the Korean Society of Radiology
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• v.14 no.2
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• pp.111-120
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• 2020

Research should be actively conducted for the ability of X-ray equipment and Retrospective image analysis of X-ray equipment used in hospitals. Retrospective image analysis of X-ray machines, CT and MRI of radiology and medical equipment has been actively conducted. However, image quality measurement using angiography equipment of angiography room is mostly measured with phantom, and image quality measurement on image after being taken by actual patient is insufficient and researches on accurate image quality measurement method are remarkable. It is in short supply. Therefore, through this study, the researcher devised a method to measure the image quality of the acquired image after coronary angiography, and to provide a high quality image to the operator. The equipment and programs used were angiographic examination equipment (Axiom Artis Zee Ceiling) and Image J program. Subjects were images automatically saved in PACS program after coronary angiography.For image quality measurement, selected the AP Caudal 30° image that show the LCA vessel well and the LAO 30° image that show the RCA vessel well during the coronary angiography. In order to measure the background and ROI of the selected image by selecting an image, a criterion on how to find and measure a section where the overlap of the shadow, such as blood vessel, liver and lung is minimized, is presented. In conclusion, there is no exact standard for analyzing an image quality measurement method of angiography image. Therefore, in order to provide quality images to the practistioners, not only the technicians of the equipment but also the users who actually use them should become researchers and conduct research on image quality measurement in various ways. Thus, it is expected to provide excellent images to patients.

• Journal of the Korean Society of Radiology
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• v.8 no.1
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• pp.43-49
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• 2014

PACS is needed medical imaging with large-capacity storage device. Slower transmission degrades the performance of the PACS. Thus, the image read by the reading of the long-term stored image without compromising the quality of the video, which does not affect future readings in the range will be compressed and stored. Compression and video storage, and video transport Noise generated during storage and transmission of medical images and the resulting loss of information that occurs when the monitor output from many problems. The study estimates server display monitor and client display monitor of philips DSA system, and suggests that the evaluation and improvement about PSNR, process from server display signal obtaining to client display monitor. P company DSA is used in the test. Two monitors that are $1280{\times}1024$ pixel monitor of P company and 1536x2048 pixel monitor of Wide are used displaying angiography picture. MARO-view is taken in PACS program, and Visual $C^{++}$ is taken as accomplishing PSNR measurement program. As a result of experiment, no change in No 1, 3 of PSNR appear that there is no error in telephotograph and display. In terms of compressibility, low compressibility has small change of definition, and there was not remarkable drawback of compressibility which has little change in definition.

• Journal of the Korean Society of Radiology
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• v.3 no.1
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• pp.29-39
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• 2009

In this paper has proposed to the recognition of the disease on medical images using neural network. The neural network is constructed as three-layers of the input-layer, the hidden-layer and the output-layer. The training method applied for the recognition of disease region is adaptive error back-propagation. The low-frequency region analyzed by DWT are expressed by matrix. The coefficient-values of the characteristic polynomial applied are n+1. The normalized maximum value +1 and minimum value -1 in the range of tangent-sigmoid transfer function are applied to be use as the input vector of the neural network. To prove the validity of the proposed methods used in the experiment with a simulation experiment, the input medical image recognition rate the evaluation of areas of disease. As a result of the experiment, the characteristic polynomial coefficient of low-frequency area matrix, conversed to 4 level DWT, was proved to be optimum to be applied to the feature parameter. As for the number of training, it was marked fewest in 0.01 of learning coefficient and 0.95 of momentum, when the adaptive error back-propagation was learned by inputting standardized feature parameter into organized neural network. As to the training result when the learning coefficient was 0.01, and momentum was 0.95, it was 100% recognized in fifty-five times of the stomach image, fifty-five times of the chest image, forty-six times of the CT image, fifty-five times of ultrasonogram, and one hundred fifty-seven times of angiogram.

• Radiation Oncology Journal
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• v.13 no.3
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• pp.285-289
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• 1995

Purpose : We compared the calcualted percent depth dose curves of 6 MeV electron beam to that of measured to evaluate the usefulness of Monte-carlo simulation method in radiation physics. Materials and Methods : The radiation dose values of 6 MeV electron beam using EGS4 code with one million histories in water were compared values that were measured from the depth dose curve of electron beam irradiated by medical accelerator ML6M. The central axis dose values were calculated according to the changing field size. such as $5{\times}5,\;10{\times}10,\;15{\times}15,\;20{\times}20cm^2$. Results : The value calculated showed a very similar shape to depth dose curve. The calculated and measured value of $D_max$ at $10{\times}10cm^2$ cone is 15mm and 14mm respectively. The calculated value of the surface radiation dose rate is $65.52\%$ and measured one is $76.94\%$. The surface radiation dose rate has varied from $64.43\%$ to $66.99\%$. The calculated values of $D_max$ are in the range between 15mm and 18mm. The calculated value was fitted well with measured value around the $D_max$ area, excluding build up range and below the $90\%$ depth dose area. Conclusion : This result suggested that the calculation of dose value can be replace the direct measurement of the dose for radiation therapy. Also, EGS4 may be a very convenient program to assess the effect of radiation dose using by personal computers.

• Journal of the Korean Society of Radiology
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• v.13 no.6
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• pp.841-846
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• 2019

Effect of misalignment on the performance was evaluated for the development of time-of-flight(TOF)-PET detector. A pair of TOF-PET detector consists of Lutetium-yttrium oxyorthosilicate(LYSO) scintillation crystal with a volume of 3 mm × 3 mm × 20 mm and Geiger-mode avalanche photodiodes(GAPD) photo-sensor with a active area of 3.07 mm × 3.07 mm. Analog output signals from TOF-PET detector were sent to the pre-amplifier and then fed into the gain adjust circuit for achievement of gain homogeneity for each detector. The amplified signals were recorded and digitized by data acquisition system based on oscilloscope. The effect of the detector misalignment between LYSO and GAPD was examined for four different alignment offsets of 0.0 mm, 0.5 mm, 1.0 mm and 1.5 mm for a pair of TOF-PET detector. The photopeak position decreased from ~400 mV to ~250 mV with increasing detector misalignment. the energy resolution and time resolution were degraded from 11.6% to 16.2%, and from 477 ps to 632 ps, respectively. This study demonstrated that PET detector performance was degraded considerably depending on the detector misalignment, which would be a critical issue for the development of TOF-PET detector.

• Progress in Medical Physics
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• v.22 no.4
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• pp.216-223
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• 2011

Recently PTW developed a MicroLion liquid ionization chamber which is water_equivalent and has a small sensitive volume of $0.002cm^3$. The aim of this work is to investigate such dosimetric characteristics as dose linearity, dose rate dependency, spatial resolution, and output factors of the chamber for the external radiotherapy photon beam. The results were compared to those of Semiflex chamber, Pinpoint chamber and Diode chamber with the sensitive volumes of $0.125cm^3$, $0.03cm^3$ and $0.0025cm^3$, respectively and evaluated to be suitable for small fields. This study was performed in the 6MV photon energy from a Varian 2300 C/D linac accelerator and the MP3 water phantom (PTW, Freiburg) was used. Penumbras in the varios field sizes ranged from $0.5{\times}0.5cm^2$ to $10{\times}10cm^2$ were used to evaluate the spatial resolution. Output factors were measured in the field sizes of $0.5{\times}0.5$ to $40{\times}40cm^2$. Readings of the chamber was linearly proportional to dose. Dose rate dependency was measured from 100 MU/min to 600 MU/min, showed a maximum difference of 5.0%, and outputs decreased with dose rates. The spatial resolutions determined with comparing profiles for the field sizes of $0.5{\times}0.5cm^2$ to $10{\times}10cm^2$ agreed between every detector except the Semiflex chamber to within 2%. Outputs of detectors were compared to that of Semiflex chamber and showed good agreements within 2% for every chamber. This study shows that MicroLion chamber characterized by a high signal-to-noise ratio and water equivalence could be suitable for the small field dosimetry.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.4
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• pp.61-67
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• 2017

Low-dose X-ray fluoroscopic image sequences to avoid radiation exposure risk are contaminated by quantum noise. To restore these noisy sequences, we propose a 3D nonlocal means (NLM) filter based on stochastic distancesed can be applied to the denoising of X-ray fluoroscopic image sequences. The stochastic distance is obtained within motion-compensated noise filtering support to remove the Poisson noise. In this paper, motion-adaptive weight which reflected the frame similarity is proposed to restore the noisy sequences without motion artifact. Experimental results including comparisons with conventional algorithms for real X-ray fluoroscopic image sequences show the proposed algorithm has a good performance in both visual and quantitative criteria.