DETERMINATION OF RADIATION-DOSE DISTRIBUTION BY MAGNETIC-RESONANCE-IMAGING IN THE NEW TISSUE-EQUIVALENT GEL

A new tissue-equivalent substance for the MR dosimetry has been develo ped. It is composed of water, bovine serum albumin, acrylamide with N, N'-methylene-bis-acrylamide, ammonium ferrous sulphate and sulphuric a cid. The elemental composition, mass density, and electron density of the PIRA gel are closer to real tissue than those of dosimeter gels pr eviously investigated. Irradiation causes the changes in the NMR prope rties of the gel. The dose dependence of NMR longitudinal relaxation r ate, R1, is reproducible (less than 2% variation) and is linear up to about 30 Gy, with a slope of 0.023 s(-1)Gy(-1) at 0.48 T. The gel, ref erred to as PIRA, can be used to obtain accurate radiation dose distri bution with conventional magnetic resonance imaging devices.