• Journal of radiological science and technology
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• v.39 no.2
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• pp.157-161
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• 2016

The purpose of this study is that in measures the acoustic propagate characteristics and temperature sensitivity of ultrasound tissue mimicking phantom(TM phantom). TM phantom manufacture according to the International Electronical Committee(IEC) guidelines for acoustic propagate characteristics of soft tissue. TM phantom was observed to have the image brightness and the image depth penetration decreases changes convergence which was the subject of ultrasound image characteristics in accordance with an external temperature that the change is reduced in temperature below $22^{\circ}C$. This study provide a basis t o create another TM Phantom and TM Phantom has been determined that it is appropriate for use in more than $22^{\circ}C$.

• Journal of Radiation Protection and Research
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• v.34 no.3
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• pp.137-143
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• 2009

This study was conducted to evaluate the accuracy of CyberKnife $Synchrony^{TM}$ respiratory tracking system which was applied to Stereotactic Radiosurgery (SRS) for moving tumors in chest and abdomen with breathing motion. For accurate evaluation, gold fiducial marks were implanted into a moving phantom. The moving phantom was a cube imbedding an acryl ball as a target. The acryl ball was prescribed to 20 Gy at 70% of isodose curve in a virtual treatment and radiochromic films were inserted into the acryl ball for dose verification and tracking accuracy evaluation. The evaluation of position tracking consists of two parts: fiducial mark tracking in a stationary phantom and $Synchrony^{TM}$ respiratory tracking in a moving phantom. Each measurement was done in three directions and was repeated to 5 times. Range of position error was 0.1957 mm to 0.6520 mm in the stationary phantom and 0.4405 mm to 0.7665 mm in the moving phantom. Average position error was 0.3926 mm and 0.5673 mm in the stationary phantom and the moving phantom respectively. This study evaluates the accuracy of CyberKnife $Synchrony^{TM}$ Respiratory tracking system, and confirms the usefulness when it's used for Stereotactic Radiosurgery of body organs.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2004.11a
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• pp.166-169
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• 2004

In the International Code of Practice for dosimetry TRS-398 published by International Atomic Energy Agency(IAEA), water equivalency plastic phantom may be used under certain circumstances for electron beam dosimetry for beam quality E0${\leq}$ 10 MeV. In this study, Palstic Water$^{TM}$ and Virtual Water$^{TM}$ were evaluated in order to determine fluence scaling factor hpl. Plastic phantom was evaluated for five electron energy from 6 MeV to 20 MeV. From the measured data of Palstic Water$^{TM}$, the fluence scaling factor hpl was found to be average 0.9964 and Virtual Water$^{TM}$ fluence scaling factor was 1.0156.

• The Journal of Korean Society for Radiation Therapy
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• v.32
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• pp.31-39
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• 2020

Purpose: The aims of this study were to compare the superficial dose with Optically Stimulated Luminescence Dosimeter(OSLD) measurement and Treatment Planning System(TPS) calculation for 6MV-Flattening Filter Free(FFF) energy using HalcyonTM and TrueBeamTM. Materials and methods: Phantom study was performed using the CT images of human phantom. In the treatment planning system, the Planning Target Volume(PTV) was contoured which is similar to Glottic cancer. Furthermore, Point(M), Point(R), and Point(L) were contoured at the iso-center of head and neck region and 5mm bolus was applied to the body contour. Each treatment plans using 6MV-FFF energy from HalcyonTM and TrueBeamTM with static Intensity Modulated Radiation Therapy(IMRT) and Volumetric Modulated Arc Therapy(VMAT) were established with eclipse. To reproduce the same position as the TPS, OSLDs were placed at the iso-center point and 5mm bolus was applied to compare the error rate after the dose delivery. Result: The results of the study using human phantom are as follows. In case of HalcyonTM, the mean absolute error rates of the point dose using the treatment planning system and the dose measured by OSLD were 1.7%±1.2% for VMAT and 4.0±2.8% for IMRT. Also TrueBeamTM was identified as 2.4±0.4% and 8.6±1.8% respectively for VMAT and IMRT. Conclusion: Through the results of this study, TrueBeamTM confirmed that the average error rate was 2.4 times higher for VMAT and 3.6 times higher for IMRT than HalcyonTM. Therefore, based on the results of this study, If we need a more accurate dose assessment for the superficial dose, It is expected that using HalcyonTM would be better than TrueBeamTM.

• Imaging Science in Dentistry
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• v.37 no.3
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• pp.157-163
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• 2007

Purpose: To evaluate the characteristics of (widely used) cone beam computed tomography (CBCT) images. Materials and Methods: Images were obtained with CT performance phantoms (The American Association of Physicists in Medicine; AAPM). CT phantom as the destination by using PSR $9000N^{TM}$ dental CT system (Asahi Roentgen Ind. Co., Ltd., Japan) and i-CAT CBCT (Imaging Science International Inc., USA) that have different kinds of detectors and field of view, and compared these images with the CT number for linear attenuation, contrast resolution, and spatial resolution. Results: CT number of both PSR $9000N^{TM}$ dental CT system and i-CAT CBCT did not conform to the base value of CT performance phantom. The contrast of i-CAT CBCT is higher than that of PSR $9000N^{TM}$ dental CT system. Both contrasts were increased according to thickness of cross section. Spatial resolution and shapes of reappearance was possible up to 0.6 mm in PSR $9000N^{TM}$ dental CT system and up to 1.0 mm in i-CAT CBCT. Low contrast resolution in region of low contrast sensitivity revealed low level at PSR $9000N^{TM}$ dental CT system and i-CAT CBCT. Conclusion: CBCT images revealed higher spatial resolution, however, contrast resolution in region of low contrast sensitivity was the inferiority of image characteristics.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2935-2940
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• 2023

A polystyrene phantom was developed following the guidance of the International Atomic Energy Association (IAEA) for gamma knife (GK) quality assurance. Its performance was assessed by measuring the absorbed dose rate to water and dose distributions. The phantom was made of polystyrene, which has an electron density (1.0156) similar to that of water. The phantom included one outer phantom and four inner phantoms. Two inner phantoms held PTW T31010 and Exradin A16 ion chambers. One inner phantom held a film in the XY plane of the Leksell coordinate system, and another inner phantom held a film in the YZ or ZX planes. The absorbed dose rate to water and beam profiles of the machine-specific reference (msr) field, namely, the 16 mm collimator field of a GK Perfexion^TM or Icon^TM, were measured at seven GK sites. The measured results were compared to those of an IAEA-recommended solid water (SW) phantom. The radius of the polystyrene phantom was determined to be 7.88 cm by converting the electron density of the plastic, considering a water depth of 8 g/cm². The absorbed dose rates to water measured in both phantoms differed from the treatment planning program by less than 1.1%. Before msr correction, the PTW T31010 dose rates (PTW Freiberg GmbH, New York, NY, USA) in the polystyrene phantom were 0.70 (0.29)% higher on average than those in the SW phantom. The Exradin A16 (Standard Imaging, Middleton, WI, USA) dose rates were 0.76 (0.32)% higher in the polystyrene phantom. After msr correction factors were applied, there were no statistically significant differences in the A16 dose rates measured in the two phantoms; however, the T31010 dose rates were 0.72 (0.29)% higher in the polystyrene phantom. When the full widths at half maximum and penumbras of the msr field were compared, no significant differences between the two phantoms were observed, except for the penumbra in the Y-axis. However, the difference in the penumbra was smaller than variations among different sites. A polystyrene phantom developed for gamma knife dosimetry showed dosimetric performance comparable to that of a commercial SW phantom. In addition to its cost effectiveness, the polystyrene phantom removes air space around the detector. Additional simulations of the msr correction factors of the polystyrene phantom should be performed.

• The Journal of Korean Society for Radiation Therapy
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• v.33
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• pp.47-54
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• 2021

Purpose : In order to evaluate the usefulness of clinical application of the Pause & Resume methods by comparing and analyzing the data stability and dose reduction effect when repeat scan assuming irregular breathing and using the Pause & Resume method during chest 4D CT using Quasar^TM Phantom. Materials and Methods : Using the Quasar^TM Phantom, set the breathing rate per minute to 15 BPM and 7.5 BPM, and set the S15 point as an irregular breathing section, and then placed OSLD to this point and use the Pause & Resume method to measure the dose of S15. CTDIvol, DLP, and ALARA-CT were used for comparative analysis of radiation dose between Pause & Resume method and Repeat-scan. In order to evaluate the stability and usability of the data applying the Pause & Resume method, the captured images were sorted by Advanced Workstation Volume Share7 and then sent to Eclipse^TM, the diameter and volume were analyzed by forming a contour on the iron ball in the Quasar^TM Phantom Results : When using Pause & Resume, the dose of OSLD measurement increased by 1.97 times in the section of S15. As a result of image evaluation, the average value of all volumes measured with and without the Pause & Resume method at 15 BPM and 7.5 BPM was 15.2 cm3±0.5%.Allthemeasuredvaluesfor the radius of iron ball were 3.1 cm regardless of whether Pause & Resume method was used or not. In the case of using Pause & Resume, 33% decreased from the lowest DLP value and 38% decreased from the highest DLP value of repeat scan, and the effective dose also decreased 32.1% from the minimum value and 37.6% from the maximum value. Conclusion: Irradiation dose was increased by Pause & Resume method because of the repeat scan on the S15 site where assuming irregular breathing occurred, However Pause & Resume method led to a significant reduction in dose on overall scan range. It also proved the usefulness of clinical application of the Pause & Resume method as a result of similar diameters and volumes of iron ball measurement.

• The Journal of Korean Society for Radiation Therapy
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• v.34
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• pp.73-82
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• 2022

Purpose: The purpose of this study is to evaluate the effectiveness of reducing the absorbed dose to the ovaries and the quality of the CBCT image when using the Halcyon^TM Fast kV CBCT of cervical cancer patients of child-bearing age who performed ovarian transposition Materials and Methods : Contouring of the cervix and ovaries required for measurement was performed on the computed tomography images of the human phantom (Alderson Rando Phantom, USA), and three Optically Stimulated Luminescence Dosimeter(OSLD) were attached to the selected organ cross-section, respectively. In order to measure the absorbed dose to the cervix and ovaries in the Truebeam^TM pelvis mode (Hereinafter referred to as TP), The Halcyon^TM Pelvis mode (Hereinafter referred to as HP) and The Halcyon^TM Pelvis Fast mode (Hereinafter referred to as HPF), An image was taken with a scan range of 17.5 cm and also taken an image that reduced the Scan range to 12.5cm. A total of 10 cumulative doses were summed, It was replaced with a value of 23 Fx, the number of cervical cancer treatments, and compared In additon, uniformity, low contrast visibility, spatial resolution, and geometric distortion were compared and analyzed using Catphan 504 phantom to compare CBCT image quality between equipment. Each factor was repeatedly measured three times, and the average value was obtained by analysing with the Doselab (Mobius Medical Systems, LP. Versions: 6.8) program. Results: As a result of measuring absorbed dose by CBCT with OSLD, TP and HP did not obtain significant results under the same conditions. The mode showing the greatest reduction value was HPF versus TP. In HPF, the absorbed dose was reduced by 39.8% in the cervix and 19.8% in the ovary compared to the TP in the scan range of 17.5 cm. the scan range was reduced to 12.5 cm, absorbed dose was reduced by 34.2% in the cervix and 50.5% in the ovary. In addition, result of evaluating the quality of the image used in the above experiment, it complied with the equipment manufacturer's standards with Geometric Distortion within 1mm (SBRT standard), Uniformity HU, LCV within 2.0%, Spatial Resolution more than 3 lp/mm. Conclusion: According to the results of this experiment, Halcyon^TM can select more various conditions than Truebeam^TM in treatment of fertility woman who have undergone ovarian Transposition , because it is important to reduce the radiation dose by CBCT during radiation therapy. So finally we recommend Halcyon^TM Fast kV CBCT which maintains image quality even at low mAs. However, it is consider that the additional exposure to low doses can be reduced by controlling the imaging range for patients who have undergone ovarian transposition in other treatment machines.

• Imaging Science in Dentistry
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• v.39 no.3
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• pp.115-120
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• 2009

Purpose : The purpose of this study was to determine a conversion coefficient for Hounsfield Units(HU) to material density ($g\;cm^{-3}$) obtained from cone-beam computed tomography ($CBMercuRay^{TM}$) data and to measure the hard tissue density based on the Hounsfield scale on dental head phantom. Materials and Methods : CT Scanner Phantom (AAPM) equipped with CT Number Insert consists of five cylindrical pins of materials with different densities and teflon ring was scanned by using the $CBMercuRay^{TM}$ (Hitachi, Tokyo, Japan) volume scanner. The raw data were converted into DICOM format and the HU of different areas of CT number insert measured by using $CBWorks^{TM}$. Linear regression analysis and Student t-test were performed statistically. Results : There was no significant difference (P > 0.54) between real densities and measured densities. A linear regression was performed using the density, $\rho$($g\;cm^{-3}$), as the dependent variable in terms of the HU (H). The regression equation obtained was $\rho=0.00072H-0.01588$ with an $R^2$ value of 0.9968. Density values based on the Hounsfield scale was $1697.1{\pm}24.9\;HU$ in cortical bone, $526.5{\pm}44.4\;HU$ in trabecular bone, $2639.1{\pm}48.7\;HU$ in enamel, $1246.1{\pm}39.4\;HU$ in dentin of dental head phantom. Conclusion : CBCT provides an effective option for determination of material density expressed as Hounsfield Units.

• Journal of the Korean Society of Radiology
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• v.9 no.7
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• pp.509-513
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• 2015

In this study, we evaluated the thermal denaturation characteristics of reusable NIPAM tissue mimicking (TM) Phantom by measuring the thermal sensitivity. And the changes of acoustic characteristic and thermal denaturation shape in NIPAM TM phantom according to the number of re-use time and re-use period were observed. With the result, as the sonication time is increased, the sound velocity of NIPAM phantom was decreased by 100 m/s and the attenuation was increased slightly. However, the changes according to the re-use period was not observed. In the thermal denaturation shape and size observation by ultrasound sonicaton, the remarkable changes have not been confirmed. With the result of this study, NIPAM Phantom was considered appropriate to evaluate and predict the effect of therapeutic ultrasound by in repeated sonication test.