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Enhancing Biodosimetry Capabilities in the Philippines for Nuclear Incident

Preparedness --------------------------------

Celia O. Asaad

Philippine Nuclear Research Institute

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The Cytogenetics Laboratory of the Philippine Nuclear Research Institute is the only laboratory in the country which offers

Chromosome Aberration Analysis for Overseas Filipino workers

serving as : • NDT (Non destructive testing) technicians • industrial radiographers Karyotype evaluation (referred by physicians) of individuals with: Down’s syndrome Turner’s syndrome Klinefelter’s syndrome ambiguous genitalia (sex chromosome confirmation) Habitual abortion cases Amenorrhea cases

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How is the test done?

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With the nuclear incident at Fukushima, Japan, attention was focused on strengthening the Biological Dosimetry capability of the country: The first step was the requested visit of Dr. Firrous Daroudi as IAEA Expert to the Philippines. Requested the consultancy services of two (2) retired Cytogenetics personnel to serve as local experts

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Healthy individuals without any prior medical/occupational exposure to ionizing radiation in the last 6 months (age: 25-45 y/o, male and female) were recruited / volunteered for blood sampling. Informed consent forms & medical questionnaires were answered and signed by all volunteers.

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Each volunteer donor was extracted with 10 ml of blood. 1 ml portion was transferred to sterile glass vials (8 vials) as blood containment vessels for irradiation. Each vial was placed in a 6-inch cylindrical thermal polyvinyl container filled with water level just enough to immerse the vial containing the blood and maintain temperature at 37°C +/- 1.

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0.5ml of irradiated samples was then added to 5ml PB-Max Karyotyping medium within two hours from irradiation time, in duplicates. Cultures were incubated in water bath for 48 hours at 37°C +/- 1. Harvesting followed standard procedure in “IAEA EPR- Biodosimetry 2011”. Four slides were prepared per dose for each person.

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Vials were positioned at the center of the sample holder of the Gammacell 220 at all times to ensure uniform irradiation of the sample. Temperature for surrounding water was measured immediately before and after loading the vial in the Gammacell 220.

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Blood samples were irradiated using Co-60 source (Gammacell 220). The doses include: 0.25, 0.5, 0.75, 1, 2, 4 and 6 Gy. Irradiation time for the samples ranged from 30secs- 13.3mins, depending on the dose rate of the source at the time of irradiation.

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The current dose rate as of Jan. 2013 is 27.33 Gy/hr. or 0.4555 Gy/min. Thus, 0.5 Gy would be approximately 1 minute (based on dose rate computation). This is the lowest dose that can be delivered. There is a 6-second period that should be considered, wherein the dose delivered to the blood sample is inaccurate because during this time, the source is moving from its resting position to its working position. Therefore, during the 6-second period, distance of the source from the sample is not fixed with possibility of lower or higher actual dose delivered to the sample than the computed dose.

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Slides were analyzed using a Nikon digital microscope and Carl Zeiss microscope. Only metaphase spreads with chromosome count of 44 or greater were included. Spreads with 44 or 45 chromosomes, having dicentric / ring / tricentric but without associated fragments were excluded from the count

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DOSE (Gy) Sample size

Total # of Cells scored

Dicentric

0 2 322 0 0.25 0.5 2 345 0 0.75 2 304 8 1 2 212 10 2 2 252 45 4 2 135 82 6 2 131 122

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Problem: Current set up can only measure Physical dosimeter as low as 50Gy. Solution: Requested the help of our Institute’s Radiation Protection Section, in charged of processing Physical dosimeters of hospital personnel.

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SOLUTION: Ordered OSL Nanodot dosimeter from Nagase Landauer Ltd., Japan C0-60 irradiation of Calibration cards at the Veterans Memorial Hospital (PMMA, SCD=80 cm Dmax Dose rate: 112.22 cGy/min

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The nanoDots dosimeters that we need for the calibration of the Micro Star Reader were irradiated at the Co-60 Radiation therapy facility near PNRI which has been calibrated, traceable to PNRI Secondary Standard Dosimetry Lab.

We irradiated the nanoDots using a water phantom so that we can simulate the experimental set-up for our blood samples. The nanoDots were water-tight sealed in plastic, immersed in the water phantom and placed at about 5-7cm from the Co-60 source.

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POSITIONING OF OSL NANODOTS

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C0-60 irradiation of Calibration cards at the Veterans Memorial Hospital (PMMA, SCD=80 cm Dmax Dose rate: 112.22 cGy/min Unexposed – 0 minute 10 cGy - 0.09 min 100 cGy - 0.89 minutes 300 cGy - 2.67 minutes 500 cGy - 4.46 minutes 800 cGy - 7.13 minutes 1000 cGy - 8.91 minutes 1300 cGy - 11.58 minutes

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2nd Irradiation at Veterans Memorial Hospital Dmax dose rate: Cobalt 60 112.22 cGy /min IN AIR: 100 cGy - 0.89 minutes 300 cGy - 2.67 minutes 600 cGy - 5.35 minutes 1,300 cGy - 11.58 minutes IMMERSED IN WATER 10 cGy - 0.09 minutes 100 cGy - 0.89 minutes 1000 cGy - 8.91 minutes

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OSL NANODOT DOSIMETER IN AIR IN WATER

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USE AND PROCESSING OF NANODOTS ANNEAL (At least 8 hours). Allow for 3 hours stabilization after annealing before reading the nanodots GET INITIAL READING Allow for 10-15 minutes stabilization after exposure before reading the nanodots IRRADIATE GET FINAL READINGS EVALUATE READINGS (Initial and Final, with control)

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NON-LINEAR calibration of the MicroStar Reader EXPOSURE OF THE CALIBRATION CARDS Co-60 source, Dose rate = 112.46 cGy/min. Using PMMA, we placed Nanodots at Dmax with build-up cup 0.5cm thick We used 3 Nanodots for each dose and 3 readings for every dosimeter, arriving at 9 readings for each dose point: Unexposed, 10, 100, 300, 500, 800, 1000 and 1300 cGy

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The calibration curve that we made cannot read below 10 cGy. Thus, initial readings of dosimeters cannot be performed since values for these are below 0.01cGy. Initial readings need to be subtracted from the final readings (using the excel/algorithm given by our Radiation Protection Group) every time we irradiate the dosimeter. We have 2 options: 1) We again irradiate calibration cards in Veterans at selected doses, maybe 3-4 sets.; or 2) we compute for the correction factor needed to convert a read value from X-ray calibration curve to Co-60 calibration curve. The reader actually has been calibrated with X-ray exposed cards and we can read some x-ray exposed xas using the two calibration curves and then compute for the ratio. The 2nd option looks feasible.

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PNRI submitted National Technical Cooperation Project proposal to IAEA for the 2014-2015 cycle on Emergency Preparedness. One component is on Enhancing Biological Dosimetry for Better Nuclear Emergency Preparedness (PHI2012001). Project design stage has been finalized with the following: 3 fellowship trainings (2 months per fellowship): • Dicentric assay • FISH-based translocation assay • Premature chromosome condensation assay 1 week IAEA Expert mission to the Philippines 2 Scientific Visits (1 week each) 1 unit Fluorescence microscope

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