• 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.2 no.1
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• pp.17-28
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• 1991

Generally, it is an accurate radiation measurement technique for processors fo thermoluminescent dosimenters(TLDs) to characterize each element they use by producing element correction factors(FCFs). TLDs are classified into three groups such as reference. control, and field TLDs. Reference TLDs are used only for the production of ECFs for the control and field TLDs. They are kept locked in a safe place except when it is necessary to use a subset of them to produce ECFs for the control and field TLDs. The ECF of a given element is a measure of the response of the element relative to the mean response of an arbitrarily selected group of reference elements. As TLDs are used in the field, their relative responses to radiation might be decreased due to muliple readings and physical abuse. Therefore, the producditon of ECFs are performed initially and periodically during the field use. This element correction method provides an excellent tool to examine new TLDs and to monitor the reliability of old TLDs. This paper discuss the 10 step procedures developed to produce and examine ECFs.

• Journal of Radiation Protection and Research
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• v.31 no.2
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• pp.97-104
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• 2006

In recent years, the MOSFET dosimeter has been widely used in various medical applications such as dose verification in radiation therapeutic and diagnostic applications. The MOSFET dosimeter is, however, mainly made of silicon and shows some energy dependence for low energy Photons. Therefore, the MOSFET dosimeter tends to overestimate the dose for low energy scattered photons in a phantom. This study determines the correction factors to compensate these dependences of the MOSFET dosimeter in ATOM phantom. For this, we first constructed a computational model of the ATOM phantom based on the 3D CT image data of the phantom. The voxel phantom was then implemented in a Monte Carlo simulation code and used to calculate the energy spectrum of the photon field at each of the MOSFET dosimeter locations in the phantom. Finally, the correction factors were calculated based on the energy spectrum of the photon field at the dosimeter locations and the pre-determined energy and directional dependence of the MOSFET dosimeter. Our result for $^{60}Co$ and $^{137}Cs$ photon fields shows that the correction factors are distributed within the range of 0.89 and 0.97 considering all the MOSFET dosimeter locations in the phantom.

• Journal of the Korean Society of Radiology
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• v.5 no.5
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• pp.261-265
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• 2011

The purpose of this study is to calculate correction factors for energy dependence of a nanoDotdosimeter to measure patient's skin dose in diagnostic radiography. The correction factors were calculated by using the values of mean energy for the RQR standard radiation qualities of IEC publicated by Rosado et al. and the energy response graph of dosimeter relative X-ray on phantom calibration provided by landaur corporation. Results showed the correction factors of 1-1.33 over the tube voltage range of 40-50 kVp. Acquired correction factors are considered to be useful in the clinics for the measurement of accurate skin dose at each tube voltage.

• Journal of Radiation Protection and Research
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• v.30 no.4
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• pp.231-236
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• 2005

Dosimeters are manufactured from same process in the manufacturer but the deviation of TL raw counts exists among the dosimeters. TL raw counts are also gradually degrade due to multiple readings and physical abuse. ECF (Element Correction Factor) correct the degradation and deviation of TL raw counts to the average TL raw counts of reference dosimeters. Procedures for producing ECF of thermoluminescent dosimeters were described In detail. ECFs of 319 reference, control and field dosimeters were measured three times and average of three ECF values was calculated. Also, % CV(Coefficient of Variation) of three ECF values was calculated to verify ECF. ECF & % CV distributions for the field and control dosimeters are presented. TL raw counts of field dosimeters, being used about 6 times for the past 3 years, were almost unchanged, but those of control dosimeters being used more frequently, were degraded about 4.7 %.

• Progress in Medical Physics
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• v.14 no.2
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• pp.69-73
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• 2003

In this study, we measured shielding block correction factors for irregular fields and compared them with published data for the square blocked field. We devised a methods to measure the factors at an arbitrary depth in phantom. The measurements were performed for 12 shielding blocks used in radiation therapy. The measured correction factors for irregular blocked fields were consistent within $\pm$0.5% with those of the square blocked fields. Our results show that the shielding block correction factors for the typical square blocked fields can be used in clinical dose calculations for irregular blocked fields. However, for small fields, we suggest that verification be done by measurement.

• Journal of Radiation Protection and Research
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• v.16 no.2
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• pp.17-26
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• 1991

Beta ray $(^{90}Sr+^{90}Y)$ absorbed dose at tissue surface was measured from the distance of 30cm by use of extrapolation chamber. In the measurement, following factors were considered: effective area of collecting electrode, polarity effect, ion recombination and window attenuation. The measured absorbed dose rate at tissue surface was $1.493{\mu}Gy/sec$ with ${\pm}2.9%$.

• Progress in Medical Physics
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• v.12 no.2
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• pp.133-140
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• 2001

The dose calculations for blocked fields were studied. The shielding block correction factors(K$_{b}$) as a function of collimator and blocked field size(r$_{c}$ and r$_{b}$) were measured. A simplified $K_{b}$ as a function of $A_{r}$ (the A/P ratio of r$_{b}$ to r$_{c}$) was determined by measured data and a fitting function for $K_{b}$ was obtained. We found that the corrections of $K_{b}$ for blocked fields in MU(monitor units) calculations need not take into account in common case of $A_{r}$ \ulcorner1 but the errors will be 3.5% in particular case such as $A_{r}$ = 0.5. These results imply that the shielding block correction for blocked fields in clinical dose calculations must be considered.

• 대한방사선방어학회:학술대회논문집
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• 2011.11a
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• pp.198-199
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• 2011

• Journal of the Korean Society of Radiology
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• v.12 no.1
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• pp.79-83
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• 2018

In this paper, we measured and analyzed the dose correction factor, absorbed dose linearity, peak voltage X-ray response, angular dependence. Exposure dose correction factor, absorbed dose linearity, and peak voltage linearity using the medical X-ray generator were all in accordance with IEC-62387-1 (2007). The reference to the dosimetry direction at 0, 30, and 60 degrees relative to baseline radiation exposure was -29% (${\pm}30^{\circ}$) and + 67% (${\pm}60^{\circ}$). The values measured at $30^{\circ}$ were -8% lower than the standard and -18% lower than the standard at $60^{\circ}$. Therefore, the effect of direction should be corrected when using OSL dot dosimeter.