Comparison of Skin Responses of Mice after Single or Fractionated Exposure to Cyclotron-Accelerated Helium Ions and 230 kV X-Irradiation

Abstract

Mouse skin was irradiated with either cyclotron-accelerated helium ions or 230 kV X-rays. Single-dose exposures to helium ions were performed in the plateau region and in the Bragg peak region of ionization after modification of the peak region by insertion of a moving copper ridge filter into the beam path (spread-out Bragg peak). The degree of recovery occurring between equal fractions of helium ions (using the spread-out Bragg peak) given with an interval of 24 hr was compared to recovery after X-irradiation also with a 24-hr interval. Single doses of helium ions in the plateau portion of ionization gave skin responses not significantly different from X-ray responses, as determined by comparing average skin responses over the period of 8-30 days postirradiation. Helium ion irradiations in the spread-out Bragg peak region of ionization yielded a relative biological effectiveness of about 1.3 as compared to that yielded by X-irradiation. Recovery after helium ion irradiation in the Bragg peak region wa...