• Journal of the Korean Society of Radiology
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• v.17 no.4
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• pp.507-514
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• 2023

The purpose of this study is to find a formula that can easily calculate the effective photon energy in the X-ray beam of mammography. The tube voltage measured for each set tube voltage was obtained using the X2 MAM Sensor. The mass attenuation coefficient for aluminum of the aluminum filter was obtained from the half value layer measurement from each measured tube voltage X-ray beam. The mass attenuation coefficient of aluminum obtained from each measured tube voltage X-ray beam was corresponded to the mass attenuation coefficient of aluminum for each photon energy obtained from NIST. The photon energy corresponding to the matching mass attenuation coefficient was determined as the effective photon energy. The formula for calculating the determined effective photon energy was obtained by polynomial matching of the effective photon energy for each tube voltage in the Origin pro 2019b statistical program as y = 28.98968-1.91738x + 0.07786x2-0.000946717x3. Here, x is the measuring tube voltage and y is the effective photon energy. The calculation formula of the effective photon energy of the mammography X-ray beam obtained in this study is considered to be very useful in obtaining the interaction coefficient between the X-ray beam and a certain substance in clinical practice.

• Journal of the Korean Society of Radiology
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• v.9 no.6
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• pp.375-379
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• 2015

The purpose of this study is to determine the effective energy of a polyenegetic X-ray beam. The half value layer(HVL) of aluminum for 80 kVp X-ray beam was measured by using optically stimulated luminescent nanoDot dosimeters(OSLnDs). The linear attenuation coefficient(${\mu}$) was calculated using the measured HVL. And the mass attenuation coefficient(${\mu}/{\rho}$) was obtained by dividing the linear attenuation coefficient by the density(${\rho}$) of aluminum. The effective energy($E_{eff}$) of the obtained mass attenuation coefficient was determined using data of the X-ray mass attenuation coefficients for photon energies of aluminum given by National Institute of Standards and Technology(NIST). As a result, the HVL value is 2.262 mmAl. The ${\mu}$ value is $3.06cm^{-1}$. The ${\mu}/{\rho}$ value is $1.114cm^2/g$. And the $E_{eff}$ value was determined at 29.79 keV.

• Journal of the Korean Society of Radiology
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• v.15 no.6
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• pp.869-875
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• 2021

The purpose of this study is to derive a formula for calculating the effective energy of an X-ray beam generated by a CT simulator. Under 90, 120, and 140 kVp X-ray beams, the CT number calibration insert part of the AAPM CT performance phantom was scanned 5 times with a CT simulator. The CT numbers of polyethylene, polystyrene, water, nylon, polycarbonate, and acrylic were measured for each CT slice image. The average value of CT number measured under a single tube voltage and the linear attenuation coefficients corresponding to each photon energy calculated from the data of the National Institute of Standards and Technology were linearly fitted. Among the obtained correlation coefficients, the photon energy having the maximum value was determined as the effective energy. In this way, the effective energy of the X-ray beam generated at each tube voltage was determined. By linearly fitting the determined effective energies(y) and tube voltages(x), y=0.33026x+30.80263 as an effective energy calculation formula was induced.

• Journal of the Korean Society of Radiology
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• v.16 no.1
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• pp.61-66
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• 2022

The purpose of this study is to derive photon energy fluence and mass energy absorption coefficient for 1 Gy of absorbed dose of water in brachytherapy using an Ir¹⁹² source. From the radiotherapy physics written by Khan, the half-value of lead for the gamma ray beam of the Ir¹⁹² source was obtained. The linear attenuation coefficient and the mass attenuation coefficient were calculated from the obtained half-value layer of lead. By matching the calculated lead mass attenuation coefficient with the NIST mass attenuation coefficient data, the photon energy of the matching mass attenuation coefficient was determined as the effective energy. By matching the determined effective energy with the photon energy of the NIST data on the mass energy absorption coefficient of water, the mass energy absorption coefficient of water was obtained as 0.03273 cm²/g(32.73 cm²/kg). The photon energy fluence was calculated as 0.03055 J/cm² by dividing the obtained mass energy absorption coefficient (32.73 cm²/kg) by the absorbed dose of water 1 Gy.

• Journal of the Korean Society of Radiology
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• v.13 no.4
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• pp.517-522
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• 2019

The purpose of this study is to determine the effective energy of CT X-ray beams by using the CT slice images of a CT number calibration insert part in the AAPM CT performance phantom. The CT number calibration insert part in the AAPM CT performance phantom was scanned five times by using a CT canner for 80, 100 and 120 kVp X-ray beams. The average value of CT numbers of each pin were measured for each CT slice image. The correlation coefficients were obtained by linear fit between the average value of CT numbers measured and liner attenuation coefficient under different energy at each pin calculated from data of NIST. A photon energy corresponding to the maximum value of the obtained correlation coefficient was determined as an effective energy. As a result, the effective energy was 56, 62 and 66~67 keV, respectively, for 80, 100 and 120 kVp X-ray beams.

• Journal of the Korean Society of Radiology
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• v.16 no.6
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• pp.771-778
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• 2022

The purpose of this study is to present a method of measuring noise by the percentage of effective line attenuation coefficient of water that can be used for quality control of CT image noise using AAPM CT performance phantom in clinical practice. In the CT images obtained by scanning the AAPM CT performance phantom with a 120 kVp CT X-ray beam, the mean CT number was measured for each pin and water in the CT number linearity insert part. The effective energy was determined as the photon energy with the largest correlation coefficient from the correlation coefficients of the linear regression analysis of the measured mean CT number for each pin and water and the linear attenuation coefficient for each photon energy. And for water and acrylic, the contrast scale was calculated as 0.000188 cm^-1 · HU^-1 from the measured mean CT number and effective line attenuation coefficient. Using the calculated contrast scale, the effective line attenuation coefficient of water, and the standard deviation measured in the water of the alignment pin part of the AAPM CT performance phantom, The noise measurement value by the percentage of effective line attenuation coefficient of water obtained 0.31 ~ 0.52% in the range of 100 ~ 300 mAs.

• Journal of Radiation Protection and Research
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• v.31 no.4
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• pp.165-171
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• 2006

In Korea, a real-time effective dose measurement system is in development. The system uses 32 high-sensitivity MOSFET dosimeters to measure radiation doses at various organ locations in an anthropomorphic physical phantom. The MOSFET dosimeters are, however, mainly made of silicon and shows some degree of energy and angular dependence especially for low energy photons. This study determines the correction factors to correct for these dependences of the MOSFET dosimeters for accurate measurement of radiation doses at organ locations in the phantom. For this, first, the dose correction factors of MOSFET dosimeters were determined for the energy spectrum in the steam generator channel of the Kori Nuclear Power Plant Unit #1 by Monte Carlo simulations. Then, the results were compared with the dose correction factors from 0.652 MeV and 1.25 MeV mono-energetic photons. The difference of the dose correction factors were found very negligible $(\leq1.5%)$, which in general shows that the dose corrections factors determined from 0.662 MeV and 1.25 MeV can be in a steam general channel head of a nuclear power plant. The measured effective dose was generally found to decrease bit $\sim7%$ when we apply the dose correction factors.

• Progress in Medical Physics
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• v.13 no.2
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• pp.55-61
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• 2002

In this work, EPM (effective point of measurement) of parallel plate ionization chamber with three different spacing were investigated. If the plate separation is less than 2 mm one generally assumes that the effective point of measurement is just behind the front window of the parallel plate ionization chamber. For chamber with relatively large separation, such as the ones used for very accurate exposure measurements, this assumption breaks down and the EPM depends on plate separation and thickness of the front window. For parallel plate chambers, conventional theoretical analyses suggest that the EPM is the inner front wall and that it shifts towards the geometric centre of the chamber as the plate separation increases. The PP-IC (parallel plate ionization chamber) is fabricated using acrylic plate for the chamber medium and printed circuit board for electrical configuration. The various sizes of the sensitive volumes designed so far are 0.9, 1.9, and 3.1 cc. The gap between two electrodes ranges from 3, 6, and 10mm. Also the charge-to-voltage converter is designed to collect the electrons produced in the ionization chamber cavity. As the result of our experiment, the EPM shift was within 0.6 mm in photon beams and 0.4 mm to 2.5 mm in electron beams for the plate separation of 6 mm and 10 mm. EPM shifts towards the geometric center of the chamber as the plate separation increases.

• Journal of Radiation Protection and Research
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• v.31 no.4
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• pp.181-186
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• 2006

A radiophotoluminescent glass rod detector (GRD) system has recently become commercially available. We investigate the dosimetric properties of the GRD regarding the reproducibility of signal, dose linearity and energy dependence. The reproducibility of five measurements for 50 GRDs is presented by an average of one standard deviation of each GRD and it is ${\pm}1.2%$. It is found to be linear in response to doses of $^{60}Co$ beam in the range 0.5 to 50 Gy with a coefficient of linearity of 0.9998. The energy dependence of the GRD is determined by comparing the dose obtained using cylindrical chamber to that by using the GRD. The GRD response for each beam is normalized to the response for a $^{60}Co$ beam. The responses for 6 and 15 MV x-ray beams are within ${\pm}1.5%$ (1SD). The energy response of GRD for high-energy photon is almost the same as the energy dependence of LiF:Mg:Ti (TLD-100)and shows little energy dependence unlike p-type silicon diode detector. The GRDs have advantages over other detectors such diode detector, and TLD: linearity, reproducibility and energy dependency. It has been verified to be an effective device for small field dosimetry for stereotactic radiosurgery.

• Journal of the Korean Magnetics Society
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• v.6 no.3
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• pp.158-164
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• 1996

The magnetic and magneto-optical properties of the Tb/Co multilayers as a function of the layer thickness and the ratio of Tb/Co thicknesses were studied. When the thickness of Tb layer was $12{\AA}$, the maximum perpendicular anisotropy energy and the maximum thickness ratio which displays the perpendicular anisotropy were obtained. This result indicated that the Tb-Tb and Co-Co pairs as well as the Tb-Co pairs contribute to the perpendicular anisotropy. The Kerr rotation angle, $({\theta}_k)$ was proportional to the perpendicular anisotropy energy and was inversely proportional to the average spin dispersion angle, $(\alpha)$. The maximum $({\theta}_k)$ of $0.28^{\circ}$ was obtained in the film of $12{\AA}$ Tb and the thickness ratio of 1.55. The abnormal hysteresis loops were appeared during the aging treatment because the coercivity difference between the Co layer and the Tb layer was increased by the preferential oxidation of Tb.