EPR dosimetry of cortical bone and tooth enamel irradiated with X and gamma rays: Study of energy dependence
- Johns Hopkins Univ., Baltimore, MD (United States)
- National Institute of Standards and Technology, Gaithersburg, MD (United States)
Previous investigators have reported that the radiation-induced EPR signal intensity in compact or cortical bone increases up to a factor of two with decreasing photon energy for a given absorbed dose. If the EPR signal intensity was dependent on energy, it could limit the application of EPR spectrometry and the additive reirradiation method to obtain dose estimates. We have recently shown that errors in the assumptions governing conversion of measured exposure to absorbed dose can lead to similar [open quotes]apparent[close quotes] energy-dependence results. We hypothesized that these previous results were due to errors in the estimated dose in bone, rather than the effects of energy dependence per se. To test this hypothesis we studied human adult cortical bone from male and female donors ranging in age from 23 to 95 years, and bovine tooth enamel, using 34 and 138 keV average energy X-ray beams and [sup 137]Cs (662 keV) and [sup 60]Co (1250 keV) [gamma] rays. In a femur from a 47-year-old male (subject 1), there was a difference of borderline significance at the [alpha] = 0.05 level in the mean radiation-induced hydroxyapatite signal intensities as a function of photon energy. No other statistically significant differences in EPR signal intensity as a function of photon energy were observed in this subject, or in the tibia from a 23-year-old male (subject 2) and the femur from a 75-year-old female (subject 3). However, there was a trend toward a decrease (12-15%) in signal intensity at the lowest energy compared with the highest energy in subjects 1 and 3. Further analysis of the data from subject 1 revealed that this trend, which is in the opposite direction of previous reports but is consistent with theory, is statistically significant. There were no efforts of energy dependence in the tooth samples. 16 refs., 7 figs., 5 tabs.
- OSTI ID:
- 6441311
- Journal Information:
- Radiation Research; (United States), Vol. 138:1; ISSN 0033-7587
- Country of Publication:
- United States
- Language:
- English
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63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BONE TISSUES
DOSIMETRY
RADIATION DOSES
ELECTRON SPIN RESONANCE
ENERGY DEPENDENCE
EPR SPECTROMETERS
ACCURACY
ERRORS
FEMUR
GAMMA RADIATION
TIBIA
X RADIATION
ANIMAL TISSUES
BODY
CONNECTIVE TISSUE
DOSES
ELECTROMAGNETIC RADIATION
IONIZING RADIATIONS
MAGNETIC RESONANCE
MEASURING INSTRUMENTS
ORGANS
RADIATIONS
RESONANCE
SKELETON
SPECTROMETERS
TISSUES
560101* - Biomedical Sciences
Applied Studies- Radiation Effects- Dosimetry & Monitoring- (1992-)
560151 - Radiation Effects on Animals- Man