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A cylindrical free-air ionization chamber is used as the medium X-ray air kerma primary standard at the Institute of Nuclear Energy Research (INER, Taiwan). Photon-scattering, electron-loss and shadow-effect correction factors are taken into account for the measurement of air kerma by the cylindrical free-air ionization chamber. The photon-scattering correction factor is used to deduct the ionizations caused by scattered photons. The electron-loss correction factor compensates for the loss of electrons striking the electrode shell without fully depositing their energies to charges in the air. The shadow-effect correction factor compensates for the loss of electrons striking the collecting rod inside the chamber. The photon scattering and electron loss correction factors previously used at INER were based on a least-squares fit with experimental data published in the NBS Handbook 64. The shadow-effect correction factor was not considered. In this study, photon-scattering, electron-loss and shadow-effect correction factors for each mono-energetic photon were calculated by a Monte Carlo code, EGS5. Then, the mono-energetic correction factors were substituted into the ISO 4037 radiation qualities spectrum, and the energy weighted correction factors were calculated. Comparing the calculated correction factors with the previous correction factors, the maximum differences were 0.51% and 1.22% for IN-250 and IN-300 radiation qualities, respectively. In a report detailing an international comparison of air kerma standards for the ISO 4037 narrow spectrum series (EUROMET.RI(I)-S3), which was conducted from 2004 to 2005, the ratio of differences and expanded uncertainties (Di/Ui) for INER's IN-250 and IN-300 radiation qualities were 0.9 and 1.8, respectively. If the correction factors obtained in this study are substituted, the differences can be reduced, and the (Di/Ui) ratios become 0.36 and 0.6 for IN-250 and IN-300, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Monte Carlo method was used to simulate the correction factors for electron loss and scattered photons for two improved cylindrical free-air ionization chambers (FACs) constructed at the Institute of Nuclear Energy Research (INER, Taiwan). The method is based on weighting correction factors for mono-energetic photons with X-ray spectra. The newly obtained correction factors for the medium-energy free-air chamber were compared with the current values, which were based on a least-squares fit to experimental data published in the NBS Handbook 64 [Wyckoff, H.O., Attix, F.H., 1969. Design of free-air ionization chambers. National Bureau Standards Handbook, No. 64. US Government Printing Office, Washington, DC, pp. 1–16; Chen, W.L., Su, S.H., Su, L.L., Hwang, W.S., 1999. Improved free-air ionization chamber for the measurement of X-rays. Metrologia 36, 19–24]. The comparison results showed the agreement between the Monte Carlo method and experimental data is within 0.22%. In addition, mono-energetic correction factors for the low-energy free-air chamber were calculated. Average correction factors were then derived for measured and theoretical X-ray spectra at 30–50kVp. Although the measured and calculated spectra differ slightly, the resulting differences in the derived correction factors are less than 0.02%. [Copyright &y& Elsevier]

We compared the Monte Carlo evaluation and GafChromic MD-55 film experimental measurement of 188Re liquid-filled balloons in intravascular brachytherapy using two phantoms of 6 mm vascular diameter, a phantom of 4 mm vascular diameter and a phantom of 3 mm vascular diameter. A dose-evaluation interface program was developed and was shown to be capable of quickly providing information such as the necessary 188Re source irradiation time to deliver a prescribed dose. [Copyright &y& Elsevier]

Diagnostic X-ray air kerma standards were established at the Institute of Nuclear Energy Research (INER, Taiwan) in accordance with the recommendations of IEC 61267. The radiation qualities established by INER include IEC 61267 RQR (RQR 3-10), RQA (RQA 3-10) and RQT. Among them, RQR is used to simulate the energy spectrum generated from the X-ray machine, RQA is used to simulate the energy spectrum after passing through the human body, and RQT is used to simulate the energy spectrum in computed tomography (CT). A tungsten target X-ray machine, 99.9% pure aluminum and copper filters were used to build the IEC 61267 radiation qualities. A cylindrical free-air chamber (FAC) is used as the X-ray air kerma primary standard. The FAC correction factors, including air attenuation, window attenuation, ion recombination, photon-scattering, electron-loss and shadow-effect, were evaluated by experiments or Monte Carlo methods. The half value layers (HVL) of these radiation qualities were measured by FAC, and the HVL differences between INER and IEC 61267 are less than 3%. The uncertainty of measurement was evaluated according to ISO GUM, and the relative standard uncertainty of primary standard is 0.53% (k = 1). An ionization chamber (Exradin A5) was sent to PTB and calibrated with IEC 61267 RQR and RQA qualities. When comparing the calibration factors between PTB and INER, the differences are less than 1.25%. The air kerma standard of diagnostic X-ray has been established at INER, and it will provide dose calibration services in Taiwan to improve medical quality. • The air kerma primary standard for diagnostic X-ray in Taiwan is introduced. • The methods for evaluating the correction factor of a free air chamber are described. • An informal comparison between PTB and INER shows that the two calibration results are close. [ABSTRACT FROM AUTHOR]

The purpose of this investigation is to re-evaluate primary dosimetry standards at the National Radiation Standard Laboratory (NRSL/INER) according to the recommendation of the International Commission on Radiation Units and Measurements Report 90 (ICRU Report 90). These standards are air kerma (K air) in X-rays, 60Co and 137Cs beams, absorbed dose to water (D W) in 60Co beam, as well as reference air kerma (RAKR) in 192Ir beam for brachytherapy in Taiwan. However, the Consultative Committee for Ionizing Radiation (CCRI) summarized the expected changes in ICRU Report 90 to primary standards. These include modifications to the mean excitation energy of water (I w) and graphite (I g), the application of the density effect correction for graphite, new combined correction factors and the uncertainty related to the average energy required to create an ion pair in air (W air), improved calculations of the stopping power, and the adoption of renormalized photoeffect cross-section. The recommendations of the CCRI were adopted for recalculation regarding correction factors and radiation-matter interaction constants for NRSL/INER primary standards. Furthermore, a newer version of Monte Carlo software and the alternative measurements with new ionization chambers (ICs) of a similar design were used to reassess the impact on the NRSL/INER standards. Consequently, the impact of the new ICRU recommendation on dosimetry standards ranged from -0.8% to 0.1%. The changes to the primary standards are in good correlation with similar changes implemented for the BIPM primary standards. For international comparisons of these standards, adoption of the ICRU Report 90 would not change significantly the degree of equivalence stated in the Asia-Pacific Metrology Programme (APMP) key and supplementary comparison database considering the impacts of the BIPM standards in the comparisons of APMP.RI(I)-K3, APMP.RI(I)-K1.1, APMP.RI(I)-K4, APMP.RI(I)-K8 and APMP.RI(I)-S3. Therefore, the NRSL/INER has formally implemented the re-evaluation standards on the 1st January 2024. • The NRSL/INER re-evaluated several primary dosimetry standards according to the ICRU Report 90. • The self-made ionization chambers and its measurement theory are introduced for air karma or absorbed dose to water. • The physical constants, correction factors and the changes are presented for standards in X-ray, Co-60, Cs-137 and Ir-192. [ABSTRACT FROM AUTHOR]

This study investigated the series of proficiency testing held by the Institute of Nuclear Energy Research (INER) from 2010 to 2017 and the benchmark of one type of dose evaluation system for personnel dosimeters in Taiwan. Based on the latest American National Standard Institute/Health Physics Society (ANSI/HPS) N13.11–2009 (R2015) performance testing standard, the personnel dose equivalent, H p (d) data of the proficiency testing programs were reanalyzed to research the dose assessment ability and the criteria update feasibility. The results showed that the tolerance level (L), absolute of bias (|B|) and standard deviation (S) for all categories of all the 8 laboratories and 4 types of dosimeter well met the latest ANSI/HPS N13.11 criteria. In addition, the measurements of the H p (d) with LiF: Mg, Ti-based TLD personnel dosimeters were also demonstrated by comparing with the MCNP6 Monte Carlo code. The dose responses were satisfactory in M100, M150 X-ray and 137Cs (including the angle tests) beams produced by INER for radiation protection level application. • In Taiwan, all 8personal dosimeter laboratories met the ANSI/HPS N13.11–2009 (R2015) criteria based on the reanalysis of pervious performance test. • The results could improve measurement quality and traceability for service laboratory using 4 different types of dosimeters. • The simulated model of Harshaw LiF:Mg, Ti-based TLD personnel dosimeter were established with MCNP6 code. • For irradiation verification, the results of equivalent dose comparison agreed within 5%–26% in the 137Cs, M100 and M150 X-ray beams. [ABSTRACT FROM AUTHOR]

Since the accident of Fukushima Daiichi nuclear power plant, the environmental radiation dose was increasingly concerned as a global issue. In Taiwan, the detection capability of the all calibration laboratories is just about 50 times the naturally occurring environmental radiation for environmental radiation protection detectors. Undoubtedly the use of environmental radiation detector shows relative low performance in accuracy and the public are very sensitive to the amount of environmental radiation. Thus, the National Radiation Standard Laboratory (NRSL) of the Institute of Nuclear Energy Research (INER) designed a multi-source of low air kerma rate calibration system to respond to the measurement and calibration needs in Taiwan. The system was verified to meet the needs of measurement and calibration through a series of evaluations and comparisons based on ISO 4037-1 criteria (ISO 4037, 1996). This environmental-level dose rate measurement and calibration system contains three radioactive sources respectively penetrating by sets of filter of three different thicknesses and then producing radiation fields of three different strengths. A total of nine standard radiation fields are provided with intensity ranges from 1746.6 μGy/h to 0.092 μGy/h, and the expanded uncertainties of the system were from 1.02% to 5.77% (k = 2). • A pressure-adjustable 10 L-nitrogen-filled ion chamber was used for air kerma determination. • A multi sources irradiator produced the irradiation field from 0.06 to 1.25 MeV gamma rays and 0.1–∼1700 μGy/h. • The tunnel-shaped shielding could reduce background interference to one tenth at the reference point. • A movable collimator and multi filters devices respectively adjust the suitable field size and air kerma rate. [ABSTRACT FROM AUTHOR]

At the Chang Gung Memorial Hospital, a wobbled beam together with a set of single scatterers produces a uniform proton field at the first and second gantries for proton radiotherapy. Conformal field shaping was accomplished by using only a multileaf collimator (MLC) or a combination of an MLC and a brass aperture (downstream of the MLC). The MLC-only technique typically delivered extra low dose tails in penumbra compared to the dose delivered using both the MLC and brass aperture/block. This study attempted to provide a physical explanation of this phenomenon by Monte Carlo simulation and phase space analysis. The Particle Therapy System Simulation Framework was used as the Monte Carlo tool for beam propagation simulation. This research team investigated four possible causes for low dose tails including, (a) same-side MLC scattering; (b) opposite-side MLC scattering; (c) MLC transmission; and (d) proton angular distribution broadened by the wobbling magnets. The results indicated that the proton angular distribution broadened by the wobbling magnets is the single cause of low dose tails and can be stopped by inserting a downstream brass aperture. • MLC-only technique typically delivered extra low dose tails in penumbra. • PTSim was an accurate tool for simulation a wobbling system within 2 mm/2%. • Broadened proton deflection angle by wobbling magnets causes low dose tails. • Low dose tails can be removed by inserting a downstream brass aperture. [ABSTRACT FROM AUTHOR]

Single event effects of secondary particles produced in silicon by proton and neutron irradiations were studied using a silicon equivalent proportional counter (SEPC), constructed for the measurements of linear energy transfer (LET). For optimal measurements, a silicon equivalent gas in the cavity of SEPC was needed. In the present work, Monte Carlo Geant4 simulations were performed to analyse the LET spectra and the secondary particle yields in several candidate gases of a silicon equivalent gas. Among all candidate gases, including propane (C 3 H 8), carbon dioxide (CO 2), carbon tetrachloride (CCl 4) and noble gases, CCl 4 gas seemed the best choice of a silicon equivalent gas. • Silicon equivalent gas in silicon equivalent proportional counter was studied. • Propane, carbon dioxide and carbon tetrachloride were simulated using Geant4 code. • LET spectra and secondary particle yields were calculated for proton/neutron beams. • Carbon tetrachloride gas was found the best choice of a silicon equivalent gas. [ABSTRACT FROM AUTHOR]