Midori Iwasaki

Human tooth dosimetry for gamma-rays and dental x-rays using ESR

The effect of secondary electron equilibrium on the ESR dosimetry of x- and gamma-ray irradiation has been studied by using acrylic plates to simulate the soft tissue of the human mouth. Dental x-rays create a different ESR signal pattern at the front surface of the tooth vs the back surface. The effect on radiation build-up of the acrylic plate on gamma-irradiation is dominant at the front but is not appreciable at the back side of the tooth.

Conversion from Tooth Enamel Dose to Organ Doses for Electron Spin Resonance Dosimetry

Conversion from tooth enamel dose to organ doses was analyzed to establish a method of retrospective individual dose assessment against external photon exposure by electron spin resonance (ESR) dosimetry. Dose to tooth enamel was obtained by Monte Carlo calculations using a modified MIRD-type phantom with a teeth part. The calculated tooth enamel doses were verified by measurements with thermo-luminescence dosimeters inserted in a physical head phantom. Energy and angular dependences of tooth enamel dose were compared with those of other organ doses. Additional Monte Carlo calculations were performed to study the effect of human model on the tooth enamel dose with a voxel-type phantom, which was based on computed tomography images of the physical phantom. The data derived with the modified MIRD-type phantom were applied to convert from tooth enamel dose to organ doses against external photon exposure in a hypothesized field, where scattered radiation was taken into account. The results indicated that energy distribution of photons incident to a human body is required to evaluate precisely an individual dose based on ESR dosimetry for teeth.

Dental ESR dosimetry of a medical physicist who received occupational radiation exposure for almost 40 Y.

Abstract— Dose distribution in the oral region of a medical physicist who received occupational radiation exposure for almost 40 y was determined retrospectively by electron spin resonance measurements of 24 tooth enamel samples using a calibration curve method. The result is considered to agree well with the value estimated from the record of his occupational exposure, including the measured values of personnel monitors. Doses to twelve of the above samples were determined by the additive re-irradiation method. The measured values obtained by the two methods agreed with the exception of one sample.

Analysis of Absorbed Dose to Tooth Enamel for ESR Dosimetry

Absorbed dose to tooth enamel was quantitatively correlated to organ doses by Monte Carlo calculations using the Electron Gamma Shower Code Version 4 for the Electron Spin Resonance (ESR) dosimetry using teeth. A region for teeth was newly added to a mathematical human model. Kerma coefficients for whole tooth and enamel part were prepared to estimate the dose to tooth enamel. Experiments were also carried out with a physical head phantom, which is made of tissue equivalent materials. Tooth samples and thermo-luminescence dosimeters (TLDs) of CaSO4 crystal were set at the teeth position in the head phantom. Additional Monte Carlo calculations were performed to verify the results of the experiments by using a Voxel-type phantom reconstructed from computed tomographic (CT) images of the physical phantom. The obtained data are to be useful for retrospective dose assessments in past radiation events by the ESR dosimetry with teeth.