Response of alanine and barium dithionate EPR dosimeters.

The response of alanine and barium dithionate EPR dosimeters to proton irradiation with energies ranging from 6.6-25 MeV has been investigated. EPR dosimeters were calibrated using calibrated gamma sources. Alanine dosimeters show a value 29% higher than those obtained by a Markus chamber at the same energy, and barium dithionate shows a value 22% smaller. The response of the EPR dosimeters to irradiation at a mean dose of about 40 Gy depends on the proton energy. Using experimental data, the yield of the radicals in the tracks for the alanine pellets was calculated. The yield of the radicals was determined to be proportional to the linear energy transfer (LET) on the straight-line length of the proton track, and the proportional coefficient for alanine is equal to 0.109 eV-1. In the area of the Bragg peak, the probability of recombination of the ionized electrons with cations is increased. As a result, approximately 4.6 MeV of proton energy is used for ionization that results in electron-cation recombination instead of formation of radicals, and maximum LET does not coincide with the maximum concentration of the radicals.

Raman spectroscopy of tissue samples irradiated by protons.

PURPOSE: Since the number of cancer patients treated by proton irradiation has increased in the last few years, it seems appropriate to study dose-dependent effects of proton irradiation on mammalian tissues in more detail. MATERIALS AND METHODS: Tissue samples of normal skin of mouse and swine, of a human tumour model xenograph, and of normal skin and a skin tumour (basal cell carcinoma) of a human patient of about 1 mm thickness were irradiated by 24 MeV protons (uniform delivered doses of 1, 7 and 50 Gy: skin of mouse and a human tumour model xenograph, and 0.5, 5 and 50 Gy: swine and human skin). Raman spectra of non-irradiated and irradiated samples were recorded and analysed. RESULTS: Amide I, P=O and C-O bond vibrations and aromatics were sensitive to the proton irradiation dose. In the C-H stretching region, the irradiation-mediated change of Raman spectra was significant only in the case of the skin tumour. CONCLUSIONS: It has been shown that Raman spectroscopy is suited to assess the radiation damage done to biological samples by protons. Proteins of the human skin tumour seem to be more sensitive to proton irradiation than proteins of normal human skin.

The effect of proton-irradiation on the Raman spectroscopy of tissue samples.

Tumor and healthy tissue samples were irradiated by 24 MeV protons. The samples were exposed to doses from 0 to 50 Gy and subsequently examined by Raman spectroscopy. The analysis of the intensity of characteristic peaks as a function of radiation dose exhibits different trends for the two types of tissue.