• Journal of Digital Convergence
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• v.13 no.1
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• pp.331-339
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• 2015

The purpose of this study is to evaluate utility of rotating adjustment using Xsight spine tracking system in 3D DOF location adjusting method, to minimize error between 6D DOF and 3D DOF in fiducial tracking system. In this study, the result of 6D DOF target location error is $0.124{\pm}0.058mm$, using fiducial inside tumor 3D DOF $0.673{\pm}0.142mm$, outside tumor $1.126{\pm}0.253mm$, apply with Xsight spine tracking system 3D DOF $0.542{\pm}0.103mm$. As the experiment shows, it was demonstrated that rotating adjustment through Xsight spine tracking system is valuable in case of treatment in 3D DOF location error that makes increasing accuracy and dose distribution each approximately 48% and 3%. In accordance with result of this study is useful rotation.

• Progress in Medical Physics
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• v.20 no.4
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• pp.290-297
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• 2009

In case of radiation treatment using small field high-energy photon beams, an accurate dosimetry is a challenging task because of dosimetrically unfavorable phenomena such as dramatic changes of the dose at the field boundaries, dis-equilibrium of the electrons, and non-uniformity between the detector and the phantom materials. In this study, the absorbed dose in the phantom was measured by using an ion chamber and a diode detector widely used in clinics. $GAFCHROMIC^{(R)}$ EBT films composed of water equivalent materials was also evaluated as a small field detector and compared with ionchamber and diode detectors. The output factors at 10 cm depth of a solid phantom located 100 cm from the 6 MV linear accelerator (Varian, 6 EX) source were measured for 6 field sizes ($5{\times}5\;cm^2$, $2{\times}2\;cm^2$, $1.5{\times}1.5\;cm^2$, $1{\times}1\;cm^2$, $0.7{\times}0.7\;cm^2$ and $0.5{\times}0.5\;cm^2$). As a result, from $5{\times}5\;cm^2$ to $1.5{\times}1.5\;cm^2$ field sizes, absorbed doses from three detectors were accurately identified within 1%. Wheres, the ion chamber underestimated dose compared to other detectors in the field sizes less than $1{\times}1\;cm^2$. In order to correct the observed underestimation, a convolution method was employed to eliminate the volume averaging effect of an ion chamber. Finally, in $1{\times}1\;cm^2$ field the absorbed dose with a diode detector was about 3% higher than that with the EBT film while the dose with the ion chamber after volume correction was 1% lower. For $0.5{\times}0.5\;cm^2$ field, the dose with the diode detector was 1% larger than that with the EBT film while dose with volume corrected ionization chamber was 7% lower. In conclusion, the possibility of $GAFCHROMIC^{(R)}$ EBT film as an small field dosimeter was tested and further investigation will be proceed using Monte Calro simulation.

• Radiation Oncology Journal
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• v.28 no.3
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• pp.133-140
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• 2010

Purpose: We retrospectively investigated the effect of irradiation using helical tomotherapy in recurrent pelvic tumors that underwent prior irradiation. Materials and Methods: Fourteen patients with recurrent pelvic tumors consisting of rectal cancer (57.1%), cervical cancer (35.7%) and cancer with an unknown origin (7.1%) were treated with tomotherapy. At the time of irradiation, median tumor size was 3.5 cm and 7 patients complained of pain originating from a recurrent tumor. The median radiation dose delivered to the gross tumor volume, clinical target volume, and planning target volume was 50 Gy, 47.8 Gy and 45 Gy, respectively and delivered at 5 fractions per week over the course of 4 to 5 weeks. Treatment response and duration of local disease control were evaluated using the Response Evaluation Criteria in Solid Tumors (ver. 1.0) and the Kaplan-Meyer method. Treatment-related toxicities were assessed through Common Terminology Criteria for Adverse Events (ver. 3.0). Results: The median follow-up time was 17.3 months, while the response rate was 64.3%. Symptomatic improvement appeared in 6 patients (85.7%). The median duration time of local disease control was 25.8 months. The rates of local failure, distant failure, and synchronous local and distant failure were 57.1%, 21.4%, and 7.1%, respectively. Acute toxicities were limited in grade I or II toxicities, except for one patient. No treatment related death or late toxicity was observed. Conclusion: Helical tomotherapy could be suggested as a feasible palliative option in recurrent pelvic tumors with prior radiotherapy. However, to increase treatment effect and overcome the limitation of this outcome, a large clinical study should be performed.

• Progress in Medical Physics
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• v.25 no.1
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• pp.46-52
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• 2014

Liquid ionization chamber is filled with liquid equivalent material unlike air filled ionization chamber. The high density material allow very small-volume chamber to be constructed that still have a sufficiently high sensitivity. However liquid ionization chamber should be considered for both initial recombination and general recombination. We, therefore, studied using the Co-60 beam as the continuous beam and the microLion chamber (PTW) for comparing the ion collection efficiency by Greening theory, two-dose rate method and our experiment method. The measurements were carried out using Theratron 780 as the cobalt machine and water phantom and 0.6 cc Farmer type ionization chamber was used with microLion chamber in same condition for measuring the charge of microLion chamber according to the dose rates. Dose rate was in 0.125~0.746 Gy/min and voltages applied to the microLion chamber were +400, +600 and +800 V. As the result, the collection efficiency by three method was generally less than 1%. In particular, our experimental collection efficiency was in good agreement within 0.3% with Greening theory except the lowest two dose rates. The collection efficiency by two-dose rate method also agreed with Greening theory generally less than 1%, but the difference was about 4% when the difference of two dose rates were lower. The ion recombination correction factors by Greening theory, two-dose rate method and our experiment were 1.0233, 1.0239 and 1.0316, respectively, in SSD 80 cm, depth 5 cm recommended by TRS-398 protocol. Therefore we confirmed that the loss by ion recombination was about 3% in this condition. We think that our experiment method for ion recombination correction will be useful tool for radiation dosimetry in continuous beam.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.2
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• pp.29-34
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• 2012

Purpose : Presently, hardwares and softwares for reducing radiation exposure are continually developed for PET/CT examination. Purpose of this study is to evaluate effectiveness of reducing radiation exposure dose of CT and SUV changes of PET when applied each kernel to ACCT (Attenuation Correction Computed Tomography) according to adopted IRIS (Iterative Reconstruction in Image Space) software. Materials and Methods : Biograph mCT (Siemens, Germany) was used as a PET/CT scanner. Using AAPM CT performance phantom, from standard (120 kVp, 100 mAs), 7 scans were conducted by reducing 15 mAs each. After image reconstruction by FBP (Filtered Back Projection) and IRIS, noise and spatial resolution were evaluated. The same method was applied to anthropomorphic chest phantom and acquired images were compared. NEMA IEC body phantom was used for SUV evaluation. Injected dose rate for hot sphere (hot) and background cylinder (BKG) were 1:8. CT dose condition (120 kVp, 50 mAs) was the same for each scan and PET scan durations were 1, 2, 3 and 4min. After scanning, each kernel of IRIS was applied to ACCT. And PET images were reconstructed by ACCT adopted IRIS for comparing SUV changes. Results : AAPM phantom test for noise evaluation, SD for FBP 100 mAs, IRIS 55 mAs were 8.8 and 8.9. FBP 85 mAs, IRIS 40 mAs were 9.5 and 9.7. FBP 70 mAs, IRIS 25 mAs were 11.9 and 11.1. Above mAs condition for FBP and IRIS, SD showed similar values. And for spatial resolution test, there was no significant difference. For chest phantom test, when applied the same mAs and kernel to both of FBP and IRIS, every applied kernels showed reduced noise. Lower mAs and higher kernel value showed higher noise reduction. There was no considerable difference only except for I70 very sharp kernel for SUV comparison using NEMA IEC body phantom. Conclusion : In this study, low mAs (55 mAs) applied IRIS and standard mAs (100 mAs) applied FBP showed similar noise. And only except for I70 kernel, there was no significant SUV changes. It is possible to reduce needless radiation exposure and acquire better image quality than FBP's through applying appropriate kernel of IRIS to PET/CT.

• Progress in Medical Physics
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• v.22 no.1
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• pp.12-17
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• 2011

This study has its own goal to deliver the accurate dose on the target volume by calculating and modifying the attenuation rate of photon beam transmitting the couch top with geometric model. The experiment was that the transmission rate and attenuation rate of photon beam transmitting the couch top was predicted by the geometric model, then compared and analyzed with what was measured experimentally based on that. The result showed that the predicted value by the geometric model accorded closely with the experimental value. In addition, in order to judge whether the practical clinical application is available, the point dose, measured after modifying the attenuation rate modelinged according to the treatment plan of a patient of spine radiosurgery, was compared with the one done nothing. The result was that the former showed decreased error range with treatment planned one than the latter. This papers calculated the transmission and attenuation rate with the geometric model transmitting the couch top and verified it experimentally. This method is expected to be very useful in not only the radiosurgery using Novalis but also the general radiation therapy.

• Journal of radiological science and technology
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• v.40 no.4
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• pp.639-646
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• 2017

The purpose of this study is to present the algorithm to minimize the image noise caused by deterioration of high X-ray container inspection equipment and the faulty detection sensors, and to improvement quality of the container inspection images using MATLAB Toolbox. The daily checking images for the container inspection were used with the subject images and the noise caused by the horizontal and vertical images was evaluated with Root Mean Square (RMS) method, which is the most basic evaluation method of digital radiation image. Also, quality of the improved images was evaluated compared to quality of the orignal images. As a result, all RMS value of the improved images was lower then the original images by a mean of 13.5% in the horizontal images and 18.2% in the vertical images respectively. Also so did RMS value of the improved container images, by a mean of 13.4% in the horizontal images and 19.1% in the vertical images respectively. These findings can be verified objectively and visually and they would help the reading process of the container images be effective in Korea Customs Service.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.13
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• pp.5171-5174
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• 2014

Background: The increase in breast cancer awareness and widespread use of mammographic screening has led to an increased detection of (non-palpable) breast cancers that cannot be discovered through physical examination. One of the methods used in the diagnosis of these cancers is vacuum-assisted core biopsy, which prevents a considerable number of patients from undergoing surgical procedures. The aim of this study was to present the results of stereotactic vacuum-assisted core biopsy for suspicious breast lesions. Materials and Methods: Files were retrospectively scanned and data on demographic, radiological and pathological findings were recorded for patients who underwent stereotactic vacuum-assisted core biopsy due to suspicious mammographic findings at the Interventional Radiology Centre of the Florence Nightingale Hospital between January 2010, and April 2013. Statistical analysis was carried out using Pearson's Chi-square, continuity correction, and Fisher's exact tests. Results: The mean age of the patients was 47 years (range: 36-70). Biopsies were performed due to BIRADS 3 lesions in 8 patients, BIRADS 4 lesions in 77 patients, and BIRADS 5 lesions in 3 patients. Mammography elucidated clusters of microcalcifications in 73 patients (83%) and focal lesions (asymmetrical density, distortion) in 15 patients (17%). In terms of complications, 1 patient had a hematoma, and 2 patients had ecchymoses (3/88; 3.3%). The histopathologic results revealed benign lesions in 63 patients (71.6%) and malignant lesions in 25 patients (28.4%). The mean duration of the procedure was 37 minutes (range: 18-55). Although all of the BIRADS 3 lesions were benign, 22 (28.6%) of the BIRADS 4 lesions and all of the BIRADS 5 lesions were malignant. Among the malignant cases, 80% were in situ, and 20% were invasive carcinomas. These patients underwent surgery. Conclusions: In cases where non-palpable breast lesions are considered to be suspicious in mammography scans, the vacuum-assisted core biopsy method provides an accurate histopathologic diagnosis thus preventing a significant number of patients undergoing unnecessary surgical procedures.

• The Korean Journal of Nuclear Medicine
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• v.34 no.4
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• pp.322-335
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• 2000

Purpose: For quantitative estimation of cerebrovascular reserve (CVR), we estimated the cerebral blood flow (CBF) using Lassen's nonlinearity correction algorithm and Tc-99m HMPAO brain SPECT images acquired with consecutive acquisition protocol. Using the values of CBF in basal and acetaBolamide (ACZ) stress states, CBF increase was calculated. Materials and Methods: In 9 normal subjects (age; $72{\pm}4$ years), brain SPECT was performed at basal and ACZ stress states consecutively after injection of 555 MBq and 1,110 MBq of Tc-99m HMPAO, respectively. Cerebellum was automatically extracted as reference region on basal SPECT image using threshold method. Assuming basal CBF of cerebellum as 55 ml/100g/min, CBF was calculated lot every pixel at basal states using Lassen's algorithm. Cerebellar blood flow at stress was estimated comparing counts of cerebellum at rest and ACZ stress and Lassen's algorithm. CBF of every pixel at ACZ stress state was calculated using Lassen's algorithm and ACZ cerebellar count. CVR was calculated by subtracting basal CBF from ACZ stress CBF for every pixel. The percent CVR was calculated by dividing CVR by basal CBF. The CBF and percentage CVR parametric images were generated. Results: The CBF and percentage CVR parametric images were obtained successfully in all the subjects. Global mean CBF were $49.6{\pm}5.5ml/100g/min\;and\;64.4{\pm}10.2ml/100g/min$ at basal and ACZ stress states, respectively. The increase of CBF at ACZ stress state was $14.7{\pm}9.6ml/100g/min$. The global mean percent CVR was 30.7% and was higher than the 13.8% calculated using count images. Conclusion: The blood flow at basal and ACZ stress states and cerebrovascular reserve were estimated using basal/ACZ Tc-99m-HMPAO SPECT images and Lassen's algorithm. Using these values, parametric images for blood flow and cerebrovascular reserve were generated.

• Korean Journal of Remote Sensing
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• v.39 no.5_1
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• pp.637-654
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• 2023

In recent years, the number of users has been increasing with the rapid development of earth observation satellites. In response, the Committee on Earth Observation Satellites (CEOS) has been striving to provide user-friendly satellite images by introducing the concept of Analysis Ready Data (ARD) and defining its requirements as CEOS ARD for Land (CARD4L). In ARD, a mask called an Unusable Data Mask (UDM), identifying unnecessary pixels for land analysis, should be provided with a satellite image. UDMs include clouds, cloud shadows, terrain shadows, etc. Terrain shadows are generated in mountainous terrain with large terrain relief, and these areas cause errors in analysis due to their low radiation intensity. previous research on terrain shadow detection focused on detecting terrain shadow pixels to correct terrain shadows. However, this should be replaced by the terrain correction method. Therefore, there is a need to expand the purpose of terrain shadow detection. In this study, to utilize CAS500-4 for forest and agriculture analysis, we extended the scope of the terrain shadow detection to shaded areas. This paper aims to analyze the potential for terrain shadow detection to make a terrain shadow mask for South and North Korea. To detect terrain shadows, we used a Hill-shade algorithm that utilizes the position of the sun and a surface's derivatives, such as slope and aspect. Using RapidEye images with a spatial resolution of 5 meters and Sentinel-2 images with a spatial resolution of 10 meters over the Korean Peninsula, the optimal threshold for shadow determination was confirmed by comparing them with the ground truth. The optimal threshold was used to perform terrain shadow detection, and the results were analyzed. As a qualitative result, it was confirmed that the shape was similar to the ground truth as a whole. In addition, it was confirmed that most of the F1 scores were between 0.8 and 0.94 for all images tested. Based on the results of this study, it was confirmed that automatic terrain shadow detection was well performed throughout the Korean Peninsula.