Browsing by Author "Meriaty, H"

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    An Australian secondary standard dosimetry laboratory participation in IAEA postal dose audits
    (Springer Nature, 2013-02-12) Davies, JB; Izewska, J; Meriaty, H; Baldock, C
    For over 30 years, the International Atomic Energy Agency (IAEA) and the World Health Organization (WHO) have jointly monitored activities of secondary standard dosimetry laboratories (SSDLs) through postal dose audits with the aim of achieving consistency in dosimetry throughout the world. The Australian Nuclear Science and Technology Organisation (ANSTO) maintains an SSDL and is a member of the IAEA/WHO SSDL Network. Postal dose audit results at this Australian SSDL from 2001 to 2011 demonstrate the consistency of absorbed dose to water measurements, underpinned by the primary standard maintained at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA).© 2020 Springer Nature
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    Characterisation of the neutron field at the ANSTO instrument calibration facility
    (Australian Nuclear Science and Technology Organisation, 2009-12-01) Meriaty, H
    ANSTO’s Instrument Calibration Facility (ICF) provides calibration services to radiation monitors, used in radiation protection applications. The facility has a large calibration room that accommodates the neutron source rig and the monitor table, which is remotely controlled. The room also hosts the gamma calibration services. Determination of the free field (direct) and scattered components of neutron field in a calibration room was essential to obtain an accurate response of the neutron monitor under testing. The free field fluence response and the fractional room return scatter, caused by the interaction of neutron fluence with the room structure, were determined. The fluence response was 1.210x10-4 μSv/h per n/m2; and the neutron field has a fractional room scatter of 0.044 at 1 m and increases linearly versus square of distance. The standard calibration methods, described by ISO-10647, IAEA-TR285, NCRP-112 and NPL-RS(EXT)5, were utilized in this characterisation and gave comparable results. The shadow-shield (truncated cone) were found more suitable to describe the neutron field compared with the other methods e.g. the polynomial fitting, semi-empirical due to the fact of the size, shape of the ICF room and source/monitor positions. Nevertheless; all methods resulted in good response curves with correlation coefficients of fitting greater than 0.97. The shadow shield consisted of two stacked conical sections. The first section was made from iron of 200mm height and the second section was a hollow and made from aluminium of 350mm height. The hollow section was then filled with neutron-moderating/absorbing materials i.e. water solution of LiBr 24% w/w. A performance test was conducted on the shield and gave a very satisfactory result e.g. the readings of fluence response to the free field neutron did follow the inverse square law with correlation >=0.999. It is worth noticing that at the completion of this characterisation and report, the calibration results with the Physikalische-Technische Bundesanstalt (PTB) in Germany became available. As a result, the neutron characterisation at ICF calibration room did agree with the BTP calibration within five percent. Consequently, the neutron field in ICF rig calibration room is now traceable to BTP standard laboratory in Germany. Also, this agreement confirms the integrity of the current neutron source e.g. anisotropy stability, which should save substantial cost and efforts in replacing the source or sending it overseas for re-certification.
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    Occupational dose assessment of iodine intake at Australian Nuclear Science & Technology Organisation
    (Australian Nuclear Science and Technology Organisation, 2009-05-10) Meriaty, H
    The iodine activity taken up by thyroid is measured by a collimated 7.6x7.6cm NaI crystal, usually following an Iodine incident. To perform a dose assessment of the subject, the ICRP biokinetic retention model, given in ICRP54 publication, is applied to estimate the activity intake in thyroid and whole boy. The dose/activity conversion factors from ICRP68 are then applied to obtain the corresponding committed doses (effective & equivalent) of the subject. The 5um AMAD for inhalation route is applied in most cases. Follow up measurements are usually carried out when the Intake exceeds 5 kBq. The results are then compared with the predicted dose by the biokinetic model; adjustment to the model is applied to fit the measured data of individual (if required). The ICRP biokinetic model provides a satisfactory estimate to all encountered cases.
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    Prediction of synergistic antitumour effect of gefitinib and radiation in vitro
    (The International Institute of Anticancer Research, 2011-09-01) Lin, HQ; Meriaty, H; Katsifis, A
    AIM: This study investigated the potential of a series of biomarkers in predicting the interaction of gefitinib and radiation in tumour treatment. MATERIALS AND METHODS: In vitro assays were performed on human skin cancer and melanoma cell lines. The antitumour effect was measured by using the MTT assay. Total and phosphorylated epidermal growth factor receptor (EGFR and pEGFR) levels were determined by cell-based ELISA. RESULTS: Gefitinib and radiation interacted to inhibit tumour cell proliferation in a cell line-dependent manner. Synergism dominated the interaction (76%), followed by additive effect (20%) and a few instances of antagonism (4%). Correlation analyses revealed a significant correlation between the median combination index (CI) and gefitinib IC950), radiation ID(50, gefitinib- or EGF-modulated EGFR and/or pEGFR expression (all p ≤ 0.05). CONCLUSION: A potential role of gefitinib efficacy, radiation efficacy and gefitinib- or EGF-modulated EGFR and/or pEGFR expression in the prediction of interaction between gefitinib and radiation is supported. Copyright © 2011 The International Institute of Anticancer Research.
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    Tumour response to gefitinib is associated with EGF- and gefitinib- but not radiation-modulated EGFR expression
    (International Institute of Anticancer Research, 2010-12-01) Lin, HQ; Katsifis, A; Meriaty, H
    Aim: This study was conducted to explore the relationship between different treatment-modulated EGFR expression and gefitinib sensitivity. Materials and Methods: Gefitinib-sensitive (A431) and -resistant (A375, MALME-3M, and SK-MEL 5) tumour cell lines were treated with epidermal growth factor (EGF), gefitinib or radiation in vitro, and EGFR expression levels were measured by using ELISA. Results: EGF, and gefitinib treatment resulted in significantly higher levels of total and/or phosphorylated EGFR in sensitive than in resistant tumours and this was associated with gefitinib IC50. In contrast, radiation-modulated EGFR expression, both total and phosphorylated, did not correlate with the efficacy of gefitinib. Stimulation of proliferation by EGF was significantly stronger in A431 than in the other three lines, indicating sensitive tumours were more EGFR-dependent than resistant tumours for cell proliferation. Conclusion: These findings imply a potential role of EGF- and gefitinib-modulated EGFR expression in predicting gefitinib sensitivity. © 2010, International Institute of Anticancer Research