• Journal of the Optical Society of Korea
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• v.6 no.4
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• pp.180-184
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• 2002

In this study, we investigated mask errors, photo errors with attenuated phase shift mask and off-axis illumination, and etch errors in dry etch conditions. We propose that total process proximity correction (TPPC), a concept merging every process step error correction, is essential in a lithography process when minimum critical dimension (CD) is smaller than the wavelength of radiation. A correction rule table was experimentally obtained applying TPPC concept. Process capability of controlling gate CD in DRAM fabrication should be improved by this method.

• Journal of radiological science and technology
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• v.45 no.6
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• pp.523-529
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• 2022

Gamma spectroscopy analysis is widely used for radioactivity analysis, and various factors are required for radioactivity calculations. Among the factors, K3 for each sample significantly influences the results. The previous methods of correcting the self-absorption effect include a computational simulation method and a method that requires making a CRM(certified reference material) identical to the sample medium. However, the above methods have limitations when used in small institutions because they require specialized program utilization skills or high manufacturing costs and large facilities. The aim of this study is to develop a method that can be easily and rapidly applied to radioactivity analysis. After filling the beaker with water, we placed the radiation source in a uniform position and used the measured value as the benchmark. Next, a correction factor was derived based on the difference in the radiation source count of the benchmark and the identically measured sample. For the radiation source, Eu-152, which emits a broad range of energy within the measurement range of gamma rays, and Cs-134 and Cs-137, which are indicator nuclides in environmental radiation analysis, were used. The sample was selected within the density range of 0.26-2.11 g/cm³, and the correction factor was derived by calculating the count difference of each sample compared to the reference value of water. This study presents a faster and more convenient method than the existing research methods for determining the self-absorption effect correction, which has become increasingly necessary.

• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2317-2323
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• 2024

Medical linear accelerators with an energy of 8 MV or higher are radiated owing to photonuclear reactions and neutron capture reactions. It is necessary to quantitatively evaluate the concentration of radioactive isotopes when replacing or disposing them. HPGe detectors are commonly used to identify isotopes and measure radioactivity. However, because the detection efficiency is generally calibrated using a standard material with a density of 1.0 g/cm³, a self-absorption effect occurs if the density of the measured material is high. In this study, self-absorption correction factors were calculated for tungsten, lead, copper, and SUS-303, which are the main materials of medical linear accelerator head parts, for each gamma-ray energy using MCNP 6.2 code. The self-absorption effect was more pronounced as the energy of the emitted gamma rays decreased and the density of the measured materials increased. These correction factors were applied to the radioactivity measurements of the in-built and portable HPGe detectors. Furthermore, compared to the surface dose rate measured by the survey meter, the accuracy of the measurements of radioactivity improved by an average of 124.31 and 100.53 % for inbuilt and portable HPGe detectors, respectively. The results showed a good agreement, with an average difference of 3.70 and 5.24 %.

• Radiation Oncology Journal
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• v.36 no.3
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• pp.248-253
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• 2018

Radiation protection in the scrotum to reduce the risk of genetic effect in the future is very important. This study aimed to measure the scrotal dose outside the treatment fields by using the radio-photoluminescence glass dosimeter (RPLGD). The characteristics of RPLGD model GD-302M were studied. Scattered dose to scrotum was measured in one liposarcoma case with the prescribed dose of 60 Gy. RPLGDs were placed in three different locations: one RPLGD was positioned at the posterior area which closer to the scrotum, and the other two RPLGDs were placed between the penis and the scrotum. Three RPLGDs were employed in each location. The scattered doses were measured in every fraction during the whole course of treatment. The entire number of 100 RPLGDs showed the uniformity within ±2%. The signal from RPLGD demonstrated linear proportion to the radiation dose (r = 0.999). The relative energy response correction factor was 1.05. The average scrotal dose was 4.1 ± 0.9 cGy per fraction. The results presented a wide range since there was a high uncertainty during RPLGD placement. The total scrotal dose for the whole course of treatment was 101.9 cGy (1.7% of the prescribed dose). The RPLGD model GD-302M could be used to measure scattered dose after applying the relative energy correction factor.

• Journal of Radiation Protection and Research
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• v.23 no.4
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• pp.267-271
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• 1998

It is required to measure air density correction factor at the time of absorbed dose calibration or measurement. In general, thermometer and barometer are widely used for air density correction. However, this can be done using the radioactive check device with better accuracy. The measurements of air density correction were performed by using the radioactive check device, Unidos electrometer, and 0.6 cc Farmer-type ion chamber of PTW under the different environmental conditions. Above experiments were repeated with thermometer and barometer. By comparing the two methods, they were within the difference of 0.2 %. The overall uncertainty for the dose found in thermometer and barometer was 1.2 - 1.6 %, depending upon either one step or two, whereas the overall uncertainty for the radioactive check device was 1.02 %. This method may reduce the possible error which could occur when thermometer and barometer are not calibrated at regular basis.

• The Journal of Korean Society for Radiation Therapy
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• v.18 no.2
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• pp.75-80
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• 2006

Purpose: In radiation therapy, precise calculation of dose toward malignant tumors or normal tissue would be a critical factor in determining whether the treatment would be successful. The Radiation Treatment Planning (RTP) system is one of most effective methods to make it effective to the correction of dose due to CT number through converting linear attenuation coefficient to density of the inhomogeneous tissue by means of CT based reconstruction. Materials and Methods: In this study, we carried out the measurement of CT number and calculation of mass density by using RTP system and the homemade inhomogeneous tissue Phantom and the values were obtained with reference to water. Moreover, we intended to investigate the effectiveness and accuracy for the correction of inhomogeneous tissue by the CT number through comparing the measured dose (nC) and calculated dose (Percentage Depth Dose, PDD) used CT image during radiation exposure with RTP. Results: The difference in mass density between the calculated tissue equivalent material and the true value was ranged from $0.005g/cm^3\;to\;0.069g/cm^3$. A relative error between PDD of RTP and calculated dose obtained by radiation therapy of machine ranged from -2.8 to +1.06%(effective range within 3%). Conclusion: In conclusion, we confirmed the effectiveness of correction for the inhomogeneous tissues through CT images. These results would be one of good information on the basic outline of Quality Assurance (QA) in RTP system.

• Molecules and Cells
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• v.27 no.1
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• pp.125-125
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• 2009

• Journal of Radiation Protection and Research
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• v.31 no.4
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• pp.173-179
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• 2006

The Monte Carlo simulation code CEARPPU has been developed and updated to provide pulse pile-up correction spectra for high counting rate cases. For neutron activation analysis, CEARPPU correction spectra were used in library least-squares method to give better isotopic activity results than the convention library least-squares fitting with uncorrected spectra.

• Progress in Medical Physics
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• v.32 no.4
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• pp.122-129
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• 2021

Purpose: This study aimed to design a multipurpose dose verification phantom for external audits to secure safe and optimal radiation therapy. Methods: In this study, we used International Atomic Energy Agency (IAEA) LiF powder thermoluminescence dosimeter (TLD), which is generally used in the therapeutic radiation dose assurance project. The newly designed multipurpose phantom (MPP) consists of a container filled with water, a TLD holder, and two water-pressing covers. The size of the phantom was designed to be sufficient (30×30×30 cm³). The water container was filled with water and pressed with the cover for normal incidence to be fixed. The surface of the MPP was devised to maintain the same distance from the source at all times, even in the case of oblique incidence regardless of the water level. The MPP was irradiated with 6, 10, and 15 MV photon beams from Varian Linear Accelerator and measured by a 1.25 cm³ ionization chamber to get the correction factors. Monte Carlo (MC) simulation was also used to compare the measurements. Results: The result obtained by MC had a relatively high uncertainty of 1% at the dosimetry point, but it showed a correction factor value of 1.3% at the 5 cm point. The energy dependence was large at 6 MV and small at 15 MV. Various dosimetric parameters for external audits can be performed within an hour. Conclusions: The results allow an objective comparison of the quality assurance (QA) of individual hospitals. Therefore, this can be employed for external audits or QA systems in radiation therapy institutions.

• Radiation Oncology Journal
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• v.8 no.1
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• pp.125-131
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• 1990

In X-ray irradiation, dose distribution depends on multiple parameters, one of them being tissue inhomogeneity to change the dose significantly. considerable dose attenuation through the mid-cranial fossa is expected because of various bony structures in it. Dose distribution around the mid-cranial fossa, following irradiation with 6 MV photon beam, was measured with LiF TLD micro-rod, and compared with the expected dose inthe same sites. In our calculation with $C_f$(correction factor), the expected dose attenuation revealed about $3.74\%$ per 1 cm thickness of bone tissue. And the differences between the expected dose with correction for bone tissue and the measured dose by TLD was small, agreeing within an average variation of $\pm0.21\%$.