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Intensity Modulated Radiation Therapy Commissioning and Quality Assurance: Implementation of AAPM TG119.

Korean Journal of Medical Physics.2011;22(2):99-105.

The purpose of this study is to evaluate the accuracy of IMRT in our clinic from based on TG119 procedure and establish action level. Five IMRT test cases were described in TG119: multi-target, head&neck, prostate, and two C-shapes (easy&hard). There were used and delivered to water-equivalent solid phantom for IMRT. Absolute dose for points in target and OAR was measured by using an ion chamber (CC13, IBA). EBT2 film was utilized to compare the measured two-dimensional dose distribution with the calculated one by treatment planning system. All collected data were analyzed using the TG119 specifications to determine the confidence limit. The mean of relative error (%) between measured and calculated value was 1.2+/-1.1% and 1.2+/-0.7% for target and OAR, respectively. The resulting confidence limits were 3.4% and 2.6%. In EBT2 film dosimetry, the average percentage of points passing the gamma criteria (3%/3 mm) was 97.7+/-0.8%. Confidence limit values determined by EBT2 film analysis was 3.9%. This study has focused on IMRT commissioning and quality assurance based on TG119 guideline. It is concluded that action level were +/-4% and +/-3% for target and OAR and 97% for film measurement, respectively. It is expected that TG119-based procedure can be used as reference to evaluate the accuracy of IMRT for each institution.
Film Dosimetry ; Prostate

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A Study of Characteristics of MicroLion Liquid Ionization Chamber for 6 MV Photon Beam.

Sang Hyoun CHOI ; Hyun Do HUH ; Seong Hoon KIM ; Young Hoon JI ; Kum Bae KIM ; Woo Chul KIM ; Hun Jeong KIM ; Dong Oh SHIN ; Chan Hyeong KIM

Korean Journal of Medical Physics.2011;22(4):216-223.

Recently PTW developed a MicroLion liquid ionization chamber which is water_equivalent and has a small sensitive volume of 0.002 cm3. 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 0.125 cm3, 0.03 cm3 and 0.0025 cm3, 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 0.5x0.5 cm2 to 10x10 cm2 were used to evaluate the spatial resolution. Output factors were measured in the field sizes of 0.5x0.5 to 40x40 cm2. 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 0.5x0.5 cm2 to 10x10 cm2 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.
Dependency (Psychology) ; Reading ; Signal-To-Noise Ratio ; Spatial Analysis ; Water

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A Pilot Research for Real-Time Specific Patient Quality Assurance Using the Hybrid Optimized Vmat Phantom (Hovp) in Volume Modulated Arc Therapy.

Hyun Do HUH ; Sang Hyoun CHOI ; Woo Chul KIM ; Hun Jeong KIM ; Kum Bae KIM ; Seong Hoon KIM ; Sam Ju CHO ; Chul Kee MIN ; Kwang Hwan CHO ; Sang Hoon LEE ; Suk LEE ; Jang Bo SHIM ; Dong Oh SHIN ; Young Hoon JI

Korean Journal of Medical Physics.2011;22(4):206-215.

The purpose of this was to investigate the measurement of fluence dose map for the specific patient quality assurance. The measurement of fluence map was performed using 2D matrixx detector. The absorbed dose was measured by a glass detector, Gafchromic film and ion chamber in Hybrid Optimized VMAT Phantom (HOVP). For 2D Matrixx, the results of comparison were average passing rate 85.22%+/-1.7 (RT_Target), 89.96%+/-2.15 (LT_Target) and 95.14%+/-1.18 (G4). The dose difference was 11.72%+/-0.531, -11.47%+/-0.991, 7.81%+/-0.857, -4.14%+/-0.761 at the G1, G2, G3, G4. In HOVP, the results of comparison for film were average passing rate (3%, 3 mm) 93.64%+/-3.87, 90.82%+/-0.99. We were measured an absolute dose in steep gradient area G1, G2, G3, G4 using the glass detector. The difference between the measurement and calculation are 8.3% (G1), -5.4% (G2), 6.1% (G3), 7.2% (G4). The using an Ion-chamber were an average relative dose error -1.02%+/-0.222 (Rt_target), 0.96%+/-0.294 (Lt_target). Though we need a more study using a transmission detector. However, a measurement of real-time fluence map will be predicting a dose for real-time specific patient quality assurance in volume modulated arc therapy.
Chimera ; Glass ; Humans

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Evaluation of Dose Distribution Using a Radiophotoluminescence Glass Dosimeter in Biobeam8000 Gamma Irradiation Device.

Sang Hun SHIN ; Sunghyun LEE ; Kihong SON ; Hyun Ho LEE ; Kum Bae KIM ; Haijo JUNG ; Young Hoon JI

Korean Journal of Medical Physics.2011;22(4):198-205.

Gamma irradiator is widely used for cell, animal experiment, irradiation for blood, dose measurement, and education. Biobeam8000 gamma irradiator (STS Steuerungstechnik &. Strahlenschutz GmbH, Braunschweig, Germany, Cs137, 81.4 TBq) that KIRAMS (Korea Institute of Radiological and Medical Science) has is a irradiation device that enables to be used in large-capacity of 7.5 L and extensive area. Cs-137 source moves range of 24 cm back-and-forth in a regular cycle in beaker for uniform irradiation and a beaker that puts a specimen like existing radiation irradiator such as Gammacell3000 rotates 360degrees during irradiation. Precise dose information according to the location of radiation source would be needed because of the movement of radiation source, whereas radiation could be uniformly irradiated in comparison with existing gamma irradiator. In this study, dose distribution of the inside beaker located in Biomeam8000 gamma irradiator was measured using glass dosimeter, and dose evaluation and distribution regarding dose linearity and dose reproducibility were implemented based on measurement results. This aims to show guideline for efficient use of irradiator based on measurement result when doing experiment or radiation exposure.
Animal Experimentation ; Germany ; Glass

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Evaluation of Factors Used in AAPM TG-43 Formalism Using Segmented Sources Integration Method and Monte Carlo Simulation: Implementation of microSelectron HDR Ir-192 Source.

Woo Sang AHN ; Won Woo JANG ; Sung Ho PARK ; Sang Hoon JUNG ; Woon Kap CHO ; Young Seok KIM ; Seung Do AHN

Korean Journal of Medical Physics.2011;22(4):190-197.

Currently, the dose distribution calculation used by commercial treatment planning systems (TPSs) for high-dose rate (HDR) brachytherapy is derived from point and line source approximation method recommended by AAPM Task Group 43 (TG-43). However, the study of Monte Carlo (MC) simulation is required in order to assess the accuracy of dose calculation around three-dimensional Ir-192 source. In this study, geometry factor was calculated using segmented sources integration method by dividing microSelectron HDR Ir-192 source into smaller parts. The Monte Carlo code (MCNPX 2.5.0) was used to calculate the dose rate D(r,theta) at a point (r,theta) away from a HDR Ir-192 source in spherical water phantom with 30 cm diameter. Finally, anisotropy function and radial dose function were calculated from obtained results. The obtained geometry factor was compared with that calculated from line source approximation. Similarly, obtained anisotropy function and radial dose function were compared with those derived from MCPT results by Williamson. The geometry factor calculated from segmented sources integration method and line source approximation was within 0.2% for r> or =0.5 cm and 1.33% for r=0.1 cm, respectively. The relative-root mean square error (R-RMSE) of anisotropy function obtained by this study and Williamson was 2.33% for r=0.25 cm and within 1% for r>0.5 cm, respectively. The R-RMSE of radial dose function was 0.46% at radial distance from 0.1 to 14.0 cm. The geometry factor acquired from segmented sources integration method and line source approximation was in good agreement for r> or =0.1 cm. However, application of segmented sources integration method seems to be valid, since this method using three-dimensional Ir-192 source provides more realistic geometry factor. The anisotropy function and radial dose function estimated from MCNPX in this study and MCPT by Williamson are in good agreement within uncertainty of Monte Carlo codes except at radial distance of r=0.25 cm. It is expected that Monte Carlo code used in this study could be applied to other sources utilized for brachytherapy.
Anisotropy ; Brachytherapy ; Organothiophosphorus Compounds ; Uncertainty ; Water

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The Comparison of Usefulness between MDCT Angiography and DSA in the Diagnosis of Intracranial Aneurysm.

Hyun Soo KHANG ; Sun Youl SEO ; Dong Kyoon HAN ; Soo Il KWON ; Su Jung SHIM ; Sam Ju CHO

Korean Journal of Medical Physics.2011;22(4):184-189.

The purpose of this study was to compare the image between DSA and MDCT Angiography and to examine whether MDCT Angiography could be useful as a screening test for the diagnosis of cerebral aneurysm in patients who were diagnosed with cerebral aneurysm on DSA. Of patients who were diagnosed with cerebral aneurysm DSA at University Hospital, 194 patients who concomitantly underwent MDCT Angiography were enrolled in the current retrospective study. The methods for analyzing cerebral aneurysm were to analyze the presence of cerebral aneurysm on DSA and MDCT Angiography. In cases in which it exceeded 1, the corresponding cases were classified as narrow-neck aneurysms. In otherwise cases, they were classified as wide-neck aneurysms. Thus, a comparative analysis could be performed to ascertain if cases were narrow-neck or wide-neck aneurysms. As compared with DSA, the sensitivity of MDCT Angiography for cerebral aneurysm was measured to be 97.4%. The degree of consistency between narrow-neck and wide-neck aneurysms was 90.2% and the proportion of undetectable an at MDCT Angiography was 2.54%. mean size was 2.4 mm. It is expected that a non-invasive diagnostic modality for a screening test for cerebral aneurysm, MDCT Angiography might be a very useful regimen as compared with an invasive one, DSA.
Aneurysm ; Angiography ; Humans ; Intracranial Aneurysm ; Mass Screening ; Retrospective Studies

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Analysis on the Calculated Dose in the Lung Radiation Surgery Planning Using TomoTherpay.

Ju Young SONG ; Jae Uk JUNG ; Mee Sun YOON ; Sung Ja AHN ; Woong Ki CHUNG ; Byung Sik NAH ; Taek Keun NAM

Korean Journal of Medical Physics.2011;22(4):178-183.

The applicability and feasibility of TomoTherapy in the lung radiation surgery was analyzed by comparison of the calculated dose distribution in TomoTherapy planning with the results of conventional IMRS (intensity modulated radiation surgery) using LINAC (linear accelerator). The acquired CT (computed tomograph) images of total 10 patients whose tumors' motion were less than 5 mm were used in the radiation surgery planning and the same prescribed dose and the same dose constraints were used between TomoTherapy and LINAC. The results of TomoTherapy planning fulfilled the dose requirement in GTV (gross tumor volume) and OAR (organ at risk) in the same with the conventional IMRS using LINAC. TomoTherapy was superior in the view point of low dose in the normal lung tissue and conventional LINAC was superior in the dose homogeneity in GTV. The calculated time for treatment beam delivery was long more than two times in TomoTherapy compared with the conventional LINAC. Based on the results in this study, TomoTherapy can be evaluated as an effective way of lung radiation surgery for the patients whose tumor motion is little when the optimal planning is produced considering patient's condition and suitability of dose distribution.
Humans ; Lung

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Small Animal PET Imaging Study of 68Ga-BAPEN.

Ji Who KIM ; Jae Sung LEE ; Bo Yeun YANG ; Su Jin KIM ; Joong Hyun KIM ; Jae Min JEONG ; Dong Soo LEE

Korean Journal of Medical Physics.2011;22(4):172-177.

The purpose of this study was to analyze 68Ga-BAPEN dynamic PET image in rat myocardium to evaluate potential of this radiotracer as a perfusion imaging agent. Animal PET/CT scan was done in 9 rats during 120 minutes. Especially we synthesized 68Ga-BAPEN with kit which is simple and low cost method. PET images showed the in vivo dynamic distribution of 68Ga-BAPEN in the chest region of rats. Initially 68Ga-BAPEN PET images showed aorta and liver activities and a few minutes later, 68Ga-BAPEN moved to myocardium. Regions of interest were drawn on myocardium, liver, lung and blood pool. Time-activity curves showed significant uptake of 68Ga-BAPEN in myocardium. The contrast ratios of myocardial to blood pool, lung and liver at 60 minutes after injection were 1.66, 2.82 and 0.60. To estimate accurate kinetic parameters, 60 minutes after injection was required to PET scan as myocardium image contrast ratios reached to constant values. As a result, 68Ga-BAPEN would be suitable radiotracer for PET which can applied to diagnosis of myocardial perfusion diseases after further preclinical and clinical investigations.
Animals ; Aorta ; Liver ; Lung ; Myocardium ; Perfusion ; Perfusion Imaging ; Positron-Emission Tomography ; Rats ; Thorax

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Survey of Technical Parameters for Pediatric Chest X-ray Imaging by Using Effective DQE and Dose.

Hye Suk PARK ; Ye Seul KIM ; Sang Tae KIM ; Ok Seob PARK ; Chang Woo JEON ; Hee Joung KIM

Korean Journal of Medical Physics.2011;22(4):163-171.

The purpose of this study was to investigate the effect of various technical parameters for the dose optimization in pediatric chest radiological examinations by evaluating effective dose and effective detective quantum efficiency (eDQE) including the scatter radiation from the object, the blur caused by the focal spot, geometric magnification and detector characteristics. For the tube voltages ranging from 40 to 90 kVp in 10 kVp increments at the FDD of 100, 110, 120, 150, 180 cm, the eDQE was evaluated at the same effective dose. The results showed that the eDQE was largest at 60 kVp when compares the eDQE at different tube voltage. Especially, the eDQE was considerably higher without the use of an anti-scatter grid on equivalent effective dose. This indicates that the reducing the scatter radiation did not compensate for the loss of absorbed effective photons in the grid. When the grid is not used the eDQE increased with increasing FDD because of the greater effective modulation transfer function (eMTF). However, most of major hospitals in Korea employed a short FDD of 100 cm with an anti-scatter grid for the chest radiological examination of a 15 month old infant. As a result, the entrance surface air kerma (ESAK) values for the hospitals of this survey exceeded the Korean DRL (diagnostic reference level) of 100 microGy. Therefore, appropriate technical parameters should be established to perform pediatric chest examinations on children of different ages. The results of this study may serve as a baseline to establish detailed reference level of pediatric dose for different ages.
Child ; Humans ; Infant ; Korea ; Photons ; Thorax

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Investigation of Varied MR Spectra by TE and Metabolite Amount in the Localized Voxel using the MR Cone-shape Phantom.

Dong Cheol WOO ; Sang Soo KIM ; Hyang Shuk RHIM ; Geon Ho JAHNG ; Bo Young CHOE

Korean Journal of Medical Physics.2007;18(3):179-185.

The purpose of this study is to investigate the spectra of a magnetic resonance spectroscopy (MRS) in accordance with the variance of TE and the volumes of metabolites in a localized voxel for the quality assurance using a designed single voxel spectroscopy QA phantom. Because a cone-shape phantom is designed as the volume of metabolite in a localized voxel is changeable, we try to analyze the peaks of each metabolite (NAA, Cr, Cho, Lac, etc.) in accordance with metabolite volume in a localized voxel as well as echo time (TE). All data were obtained using a 3T MRI/MRS machine and analyzed using jMRUI(R). The results of this study show that TE is in inverse proportion to the noise of MRS and the longer TE and the less metabolite volume in the localized voxel, the peak intensities of each metabolite decrease. In case of the lactate, its peak was observed on the all TE only if the greatest metabolite is included in the localized voxel. Then, the intensity of a metabolite is more sensitive to the metabolite volume in the localized voxel than the TE. These obtained in vitro MRS data is provide the guideline that is important for in vivo metabolite quantification. But, in the edge of cone-shape vial air bubbles were observed and spectrum could not obtained. Therefore our cone-shape MRS phantom needs to be modified in order to solve these problems.
Lactic Acid ; Magnetic Resonance Spectroscopy ; Noise ; Spectrum Analysis

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