Narrow Results

Analysis of cultural heritage samples by PIXE involves the risk of damaging precious samples due to MeV-proton irradiation. To investigate appropriate methods to detect invisible damage due to PIXE analysis, we analyzed the change in chemical bonding of the sample surface subjected to PIXE and RBS measurement by Fourier Transform InfraRed spectroscopy (FT-IR). We used Japanese hemp paper as a simulated cultural property sample. The proton irradiation for the PIXE/RBS measurement was performed in a vacuum with an incident beam energy of 2.5 MeV, a beam current of 1 nA, and an irradiation time up to 10 min. The corresponding beam flux and fluence were 0.06 nA/mm² and 4 $\mu$Coulomb/cm², respectively. When the irradiation time was 10 min, the absorbed dose was 480 kGy on the sample surface. We identified neither change of elemental composition nor visible change such as discoloration due to irradiation. However, we found changes in peak heights in the measured FT-IR spectra, which suggest the destruction of chemical bonds such as O–H and C–O due to proton-induced radiation damage.

Subject: This study assessed the absorbed dose for patients who underwent Tc-99m Methylene Diphosphonates (MDP) bone scan examination based on a series of personal dosimeter measurements and a derived semi-empirical formula. Material and methods: 210 volunteers among the patients, who were administrated 925 MBq Tc-99m MDP for the bone scan examination in the Department of Nuclear Medicine in the Dalin Tuzchi Hospital, Taiwan, underwent personal dosimeter measurements at 30, 120, and 180min after the injection. A personal dosimeter was held at a 30cm distance from the patient’s stomach. The acquired data were analyzed to derive the residence time of Tc-99m radionuclide in the patient’s body. Five biological parameters (gender, age, BMI, eGFR, and creatinine) of these 210 patients were collected and processed by the STATISTICA program, yielding a nonlinear 16-term first-order semi-empirical formula for the radionuclide residence time prediction. The respective four- and three-factor calculations, excluding creatinine and eGFR, provided poor correlation. Results and Conclusion: According to the phantom concept, treating a patient’s body as a homogenous spherical ball, a simplified formula was used to assess the absorbed dose rate and magnitude. Therefore, the derived residence time, dose rate, and absorbed dose were $146.1\pm 36.3$min, $8.3\pm 1.0\mu$Sv/min, and $1211.7\pm 354.2\mu$Sv, respectively. These results were lower than those obtained in previous studies, which can be attributed to accelerated radionuclide excretion of patients who drank 2000 cc of water after the procedure, yielding shorter residence times.

In this chapter, radiation quantities and units and the induction and repair of radiation-induced DNA damage are briefly reviewed. Results of the authors' theoretical studies of DNA damage induction and outcomes from the excision repair of clustered DNA lesions are reported for selected types of low- and high-LET (linear energy transfer) radiation. Models for the conversion of clusters into small-scale mutations and aberrations are presented and used to illustrate trends in mutagenesis as a function of dose and particle LET.