Energy responses of the LiF series TL pellets to high-energy photons in the energy range from 1.25 to 21 MV.

Kim, J L,Lee, J I,Ji, Y H,Kim, B H,Kim, J S,Chang, S Y Nuclear Technology Pub 2006 Radiation Protection Dosimeetry Vol.119 No.1

<P>The energy responses for the KLT-300(LiF:Mg,Cu,Na,Si, Korea), GR-200(LiF:Mg,Cu,P, China) and MCP-N(LiF:Mg,Cu,P, Poland) thermoluminescence(TL) pellets were studied for a photon radiation with energies from 1.25 MeV((60)Co) to 21 MV (Microtron) to verify the usefulness of the calibration for the radiotherapy beams. The International Atomic Energy Agency (IAEA) and the World Health Organization (WHO) have performed thermoluminescence dosimetry (TLD) audits to verify the calibration of the beams by TL powder, but TL pellets were used in this study because the element correction factor (ECF), defined as the factor to correct the variations that all TL dosemeters cannot be manufactured to have exactly the same TL efficiency, for each TL pellet could be accurately derived and be handled conveniently when compared with the powder. Also several works for the energy response of the TLDs were done for the low-energy photon beams up to (60)Co, but they will be extended in this experiment to the high photon energies (up to 20 MV), which are widely used in the therapy level of a radiation. The PTW 30006 ionisation chamber was calibrated by the Korea primary standards to establish the air-kerma rates and the TL pellets were irradiated in a specially designed waterproof pellet holder in a water phantom (30 x 30 x 30 cm(3)) just like the IAEA postal audits programme. This result was compared with that of another type of phantom [10 (W) x 10 (L) x 10 (H) cm(3) PMMA Perspex phantom for the (60)Co and 6 MV photon, and 10 x 10 x 20 (H) cm(3) for the 10 and 21 MV photon] for its convenient use and easy handling and installation in a hospital. The results show that the differences of the responses for the water phantom and PMMA Perspex phantom were negligible, which is contrary to the general conception that a big difference would be expected. For an application of these results to verify the therapy beams, an appropriate energy correction factor should be applied to the energies and phantom types in use.</P>

Estimation of absorbed organ doses and effective dose based on body mass index in digital radiography.

Kim, Hyunji,Park, MinSeok,Park, Songyi,Jeong, Hoiwoun,Kim, Jungmin,Kim, Youhyun Nuclear Technology Pub 2013 Radiation protection dosimetry Vol.153 No.1

<P>With the introduction of digital radiography, patients undergoing radiographic procedures are subject to being overexposed to radiation. Therefore, it is necessary to estimate the absorbed organ dose and the effective dose, which are significant for patient health, along with body type. During chest radiographic examinations conducted in 899 patients for screening, the absorbed dose of the 13 major organs, the average whole-body dose, and two effective doses weighted by factors published in ICRP 60 and ICRP 103 were calculated on the basis of patient information such as height, weight and examination condition, including kilovolt potential, focus-skin distance and entrance surface dose (ESD), using a PC-based Monte Carlo program simulation. It was found that dose per unit ESD had a tendency to decrease with body mass index (BMI). In particular, the absorbed dose for most organs was larger at high voltages (140 kVp) than at low voltages (120 kVp, 100 kVp). In addition, the effective dose which was based on ICRP 60 and ICRP 103 also represented the same tendency in respect of BMI and tube voltage.</P>

Comparison of the dose-response relationship of radiation-induced apoptosis in the hippocampal dentate gyrus and intestinal crypt of adult mice.

Kim, J S,Yang, M,Kim, J,Lee, D,Kim, J C,Shin, T,Kim, S H,Moon, C Nuclear Technology Pub 2012 Radiation protection dosimetry Vol.148 No.4

<P>The present study compared the dose-response curves for the frequency of apoptosis in mouse hippocampal dentate gyrus (DG) and intestinal crypt using whole-body gamma irradiation. The incidence of gamma-ray-induced apoptosis was measured using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end-labelling (TUNEL) method. TUNEL-positive apoptotic nuclei in the DG and intestinal crypt were increased in a dose-dependent pattern (0-2 Gy). The dose-response curves were linear-quadratic, with a significant relationship between the appearance of apoptosis and irradiation dose. The slopes of the dose-response curves in the DG were much steeper (~5-6-fold) than those in the intestinal crypt within the range of 0-1 Gy exposure. Hippocampal DG might be a more effective and sensitive evaluation structure than the intestinal crypt to estimate the degree of radiation exposure in damaged organs of adult mice exposed to low irradiation dose.</P>

Radon exposure assessment for underground workers: a case of Seoul Subway Police officers in Korea.

Song, Myeong Han,Chang, Byung-Uck,Kim, Yongjae,Cho, Kun-Woo Nuclear Technology Pub 2011 Radiation protection dosimetry Vol.147 No.3

<P>The objective of this study is the systematic and individual assessment of the annual effective dose due to inhaled radon for the Seoul Subway Police officers, Korea. The annual average radon concentrations were found to be in the range of 18.9-114 Bqm(-3) in their workplaces. The total annual effective doses which may likely to be received on duty were assessed to be in the range of 0.41-1.64 mSvy(-1). These were well below the recommended action level 10 mSvy(-1) by ICRP. However, the effective doses were higher than subway station staff in Seoul, Korea.</P>

Dose reduction in CT using bismuth shielding: measurements and Monte Carlo simulations.

Chang, Kyung-Hwan,Lee, Wonho,Choo, Dong-Myung,Lee, Choon-Sik,Kim, Youhyun Nuclear Technology Pub 2010 Radiation Protection Dosimeetry Vol.138 No.4

<P>In this research, using direct measurements and Monte Carlo calculations, the potential dose reduction achieved by bismuth shielding in computed tomography was evaluated. The patient dose was measured using an ionisation chamber in a polymethylmethacrylate (PMMA) phantom that had five measurement points at the centre and periphery. Simulations were performed using the MCNPX code. For both the bare and the bismuth-shielded phantom, the differences of dose values between experiment and simulation were within 9%. The dose reductions due to the bismuth shielding were 1.2-55% depending on the measurement points, X-ray tube voltage and the type of shielding. The amount of dose reduction was significant for the positions covered by the bismuth shielding (34 - 46% for head and 41 - 55% for body phantom on average) and negligible for other peripheral positions. The artefact on the reconstructed images were minimal when the distance between the shielding and the organs was >1 cm, and hence the shielding should be selectively located to protect critical organs such as the eye lens, thyroid and breast. The simulation results using the PMMA phantom was compared with those using a realistically voxelised phantom (KTMAN-2). For eye and breast, the simulation results using the PMMA and KTMAN-2 phantoms were similar with each other, while for thyroid the simulation results were different due to the discrepancy of locations and the sizes of the phantoms. The dose reductions achieved by bismuth and lead shielding were compared with each other and the results showed that the difference of the dose reductions achieved by the two materials was less than 2-3%.</P>

Thyroid dose estimation with potassium iodide (KI) administration in a nuclear emergency.

Jang, M,Kim, H K,Choi, C W,Kang, C S Nuclear Technology Pub 2008 Radiation protection dosimetry Vol.132 No.3

<P>In a breach-of-containment nuclear reactor accident, the near-field exposure is primarily through inhalation of radioiodine. Thyroid blockade by oral potassium iodide (KI) is a practical and effective protective measure for the general public in such an emergency. The retention functions incorporating the thyroid blocking effects by KI have been derived using a standard three-compartment model of iodine metabolism. This allows more accurate estimation of the thyroid dose by calculating the blocking factor.</P>

Development of a fibre-optic dosemeter to measure the skin dose and percentage depth dose in the build-up region of therapeutic photon beams.

Kim, K-A,Yoo, W J,Jang, K W,Moon, J,Han, K-T,Jeon, D,Park, J-Y,Cha, E-J,Lee, B Nuclear Technology Pub 2013 Radiation protection dosimetry Vol.153 No.3

<P>In this study, a fibre-optic dosemeter (FOD) using an organic scintillator with a diameter of 0.5 mm for photon-beam therapy dosimetry was fabricated. The fabricated dosemeter has many advantages, including water equivalence, high spatial resolution, remote sensing and real-time measurement. The scintillating light generated from an organic-dosemeter probe embedded in a solid-water stack phantom is guided to a photomultiplier tube and an electrometer via 20 m of plastic optical fibre. Using this FOD, the skin dose and the percentage depth dose in the build-up region according to the depths of a solid-water stack phantom are measured with 6- and 15-MV photon-beam energies with field sizes of 10 10 and 20 20 cm(2), respectively. The results are compared with those measured using conventional dosimetry films. It is expected that the proposed FOD can be effectively used in radiotherapy dosimetry for accurate measurement of the skin dose and the depth dose distribution in the build-up region due to its high spatial resolution.</P>