• Journal of radiological science and technology
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• v.5 no.1
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• pp.21-34
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• 1982

When unattenuated x-ray radiation passes through the object it is transmitted and scattered from objectes and impinging on the film. During this process certain radiation is absorbed within the object and others transmitted in reduced scattering. The scattering radiation influence upon radiation image quality, confining x-ray beam which means scattering radiation produce increased fog on x-ray film image and as a consequence decrease contrast and less detail of the film there for the elimination of fog and for absorbing scattered radiation, the grid has been used between the object and the film in order to rid of scattering rays. Using grid is good method for the qualification of the better image as well as in using air gap technique. The grid is easy to manipulate and promote good efficiency which is defined by ICRU and JIS. It is the purpose to study for eliminating scattered radiation from the tissue equivalent acryl phantom using grid, we have studied and evaluated the grid permeability about the x-ray exposure, the selection of grid ratio according to phantom thickness, on x-ray exposure are performed as follows. 1. The penetrating ratio of primary x-ray is remarkably decreased by increasing of the grid ratio, but it is almost not influenced in KVP difference and phantom thickness. 2. The scattered radiation is proportionaly increased by thickness of the phantom, having nothing to do with grid ratios. 3. The relative between the penetration rate of primary and secondary x-ray is improved by increasing grid ratio, and decreased by phantom thickness, and slightly decreased by high tube voltage. 4. The grid of 5:1 and 10:1 ratio are adequate to the phantom of 10cm and 15cm thickness, respectively.

• Nuclear Engineering and Technology
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• v.43 no.4
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• pp.399-404
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• 2011

A LEGO-type multi-purpose dosimetry phantom was developed for intensity-modulated radiation therapy (IMRT), which requires various types of challenging dosimetry. Polystyrene, polyethylene, polytetrafluoroethylene (PTFE), and polyurethane foam (PU-F) were selected to represent muscle, fat, bone, and lung tissue, respectively, after considering the relevant mass densities, elemental compositions, effective atomic numbers, and photon interaction coefficients. The phantom, which is composed of numerous small pieces that are similar to LEGO blocks, provides dose and dose distribution measurements in homogeneous and heterogeneous media. The phantom includes dosimeter holders for several types of dosimeters that are frequently used in IMRT dosimetry. An ion chamber and a diode detector were used to test dosimetry in heterogeneous media under radiation fields of various sizes. The data that were measured using these dosimeters were in disagreement when the field sizes were smaller than $1.5{\times}1.5\;cm^2$ for polystyrene and PTFE, or smaller than $3{\times}3\;cm^2$ for an air cavity. The discrepancy was as large as 41% for the air cavity when the field size was $0.7{\times}0.7\;cm^2$, highlighting one of the challenges of IMRT small field dosimetry. The LEGO-type phantom is also very useful for two-dimensional dosimetry analysis, which elucidates the electronic dis-equilibrium phenomena on or near the heterogeneity boundaries.

• Journal of Biomedical Engineering Research
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• v.43 no.4
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• pp.271-279
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• 2022

Functional cosmetics containing various ingredients that improve skin health are currently being developed. In addition, technologies that help increase the absorption rate of such cosmetics have recently gained significant attention. Sonophoresis is a method to increase the transdermal absorption of cosmetics using ultrasound. A skin-mimicking phantom was fabricated using polydimethylsiloxane, Strat-M^TM membrane, and thermochromic pigments. Gel-type cosmetics used in skin mask packs and epidermal-growth-factor-based nano-cosmetics were tested for their absorption rates at ultrasound frequencies of 1, 3, and 10 MHz in the single frequency mode, and 1/3 and 3/10 MHz in the dual frequency mode. The gel-type cosmetics and epidermal-grow-factor-based nano-cosmetics showed the highest absorption rate at 3/10MHz dual frequency. The size of the cosmetic particles decreased by 5-9 %. Furthermore, the temperature rise caused by ultrasound could be visually recognized by the thermochromic pigment in the phantom turning white. We presented a skin-mimicking phantom. The device can be customized according to the size of the ultrasound probe and has the advantage of quantitatively evaluating the transdermal permeability of cosmetics at a low cost. The development of the skin-mimicking phantom will be useful for determining the suitable conditions required to increase the absorption rate of cosmetics using ultrasound.

• The Journal of Korean Society for Radiation Therapy
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• v.15 no.1
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• pp.53-60
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• 2003

I. Purpose It is essential to have the correct body contour information for the calculation of dose distribution. The role of CT images in the radiation oncology field has been increased. But there still exists a method to use cast or lead wire for the body contour drawing. This traditional method has drawbacks such as in accurate and time consuming procedure. This study has been designed to overcome this problem. II. Materials and Methods A digital camera is attached to a pole which stands on the opposite side of the gantry. Positional information was acquired from an image of the phantom which is specially designed for this study and located on the isocenter level of the simulator Laser line on the patients skin or on the phantom surface was digitized and reconstructed as the contour. Verification of usefulness this technique has been done with various shape of phantoms and a patients chest III. Results and Conclusions Contours from the traditional method with the cast or lead wire and the digital image method showed good agreement within experimetal error range. This technique showed more efficiente in time and convenience. For irregular shaped contour, like H&N region, special care are needed. The results suggest that more study is needed. To use of the another photogrammatory techinique with two camera system may be better for the actual clinical application

• The Journal of Korean Society for Radiation Therapy
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• v.9 no.1
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• pp.40-45
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• 1997

When therapeutic irradiation is indicated for the orbital tumors, the greatest concern is the risk of radiation-induced cataract. Conjunctival lymphoma is one of the good examples. We would like to report the procedure of the lens shielding device(L.S.D) and the result of irradiated dose to the lens. L.S.D. consistes of two parts : load alloy to attenuate electron beam, and dental acryl which completely covers the lead alloy to avoid discomfort of cornea from contacting directly with cerrobend and side scattering by cerrobend. And for easy location and removal, side bars were made on each side. Radiation doses were meaured with TLD(TLD 3500 Hawshaw). Markus chamber in a polystyrene phantom. The phantom was irradiated with 9MeV electron beams from Clinac 2100C with $6{\times}6cm$ electron cone. The relative dose at 6mm depth where the lens is located was $4.2\%$ with TLD and $5.1\%$ with Markus chamber clinically when 2600 cGy are irradiated to the eyeball, the mapinary dose to the lens will be 109 cGy or 132 cGy, which will significently reduce the cataract.

• Journal of radiological science and technology
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• v.43 no.2
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• pp.115-121
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• 2020

In a digital radiation system using a Flat Panel Detector, we attempted to the quality control of digital radiography system using the Exposure Index and Deviation Index. Calibration was performed with the radiation quality suggested by the International Electrotechnical Commission, and through an experiment using a phantom, appropriate inspection radiation conditions applicable to medical institutions were selected. The study was conducted using the selected radiation conditions. Through those chest posterior anterior image, information such as examination conditions and exposure index was obtained. The deviation index was derived by analyzing the exposure index based on the target exposure index calculated by the phantom study. As for the analyzed exposure index, 97.1% was distributed within the range of ± 2.0 based on the deviation index. Quality control of medical images should be performed through management of inspection conditions through exposure index and deviation index and management of medical images.

• Journal of the Korean Applied Science and Technology
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• v.15 no.4
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• pp.11-20
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• 1998

The propagation of light radiation in a turbid medium is an important problem that confronts dosimetry of therapeutic laser delivery and the development of diagnostic spectroscopy. Scattered light is measured as a function of the position(distance r, depth z) between the axis of the incident beam and the detection spot. Turbid sample yields a very forward-directed scattering pattern at short range of position from source to detector, whereas the thicker samples greatly attenuated the on-axis intensity at long range of position. The portions of scattered light reflected from or transmitted throughphantom depend upon internal reflectance and absorption properties of the phantom. Monte Carlo simulation method for modelling light transport in tissue is applied. It uses the photon is moved a distance where it may be scattered, absorbed, propagated, internally reflected, or transmitted out of tissue. The photon is repeatedly moved until it either escape from or is absorbed by the phantom. In order to obtain an optimum therapeutic ratio in phantom material, optimum control the light energy fluence rate is essential. This study is to discuss the physical mechanisms determining the actual light dose in phantom. Permitting a qualitative understanding of the measurements. It may also aid in designing the best model for laser medicine and application of medical engineering.

• Korean Journal of Digital Imaging in Medicine
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• v.11 no.2
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• pp.63-68
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• 2009

Among various physical or subjective assessments of the quality of X-ray images, physical assessments can be quantitative but they are eventually judged by the view of observers thus subjective assessments including the aspect of observers are required. The changes in the ability to detect lesions caused by changes in the thickness of acrylic plates were tested with the ROC interpretation method that has taken into consideration, all the features of physical assessments as well as observers' ability to observe and mental stages and even surrounding environments using an Alvim phantom and the result indicated that as the thickness of acrylic plates increased, the amount of noises occurred increased compared to signals and thus the ability to detect signals as well as the sensitivity that is an ability to signals accurately and the ability to distinguish noises from signals thus it is considered that more efforts of radiologic technologists will be required to detect small lesions of fat patients with diagnostic X-ray generating apparatus.

• Progress in Medical Physics
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• v.1 no.1
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• pp.61-68
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• 1990

We have designed the calculation model(AMC method) of electron output for the cut-out fieldsand studied the influence of shielding block size. The output of electron was measured in the water phantom at dmax, for 20 $\times$ 20cm$^2$ cone size electron beams from CL/1800 linear accelerator(Varian, USA), Which generates the energy of 6, 9, 12, 15 and 18MeV electron beams. The shielding blocks were rectangular or squre shaped, low melting point alloy. We can predict the output from the arbitrarily rectangular shaped block within 1% error. by using the AMC method, which considers the contribution of the collimator(block) scatter and the phantom scatter.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.302-304
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• 2002

In linac-based stereotactic radiosurgery, assuring the quality of the planning and delivery of external photon beam requires accurate evaluation of beam parameters, usually including output factors, tissue-phantom ratio and off-axis ratios, and measurement of actual dose distributions from simulated treatment. We're going to test the use of calibrated radio chromic film (Gafchromic film; type MD-55, Nuclear associate) using a Lumiscan 75 digitizer to measure absolute dose and relative dose distributions for linac-based radiosurgery unit Relative dose distribution of a human-style spherical acryl phantom were measured using radiochromic film and calculated by treatment planning system. The absolute dose at the sphere center was measured by radiochromic film and micro chamber (Exradin A-14, 0.009cc). What we want to demonstrate in this work, the 'well selected' radiochromic films when external photon beam are used in linac-based stereotactic radiosurgery are very accurate detector for dosimetry.