title: An analysis of particle track effects on solid mammalian tissues.
abstract: Relative biological effectiveness (RBE) and quality factor (Q) at extreme values of linear energy transfer (LET) have been determined on the basis of experiments with single-cell systems and specific tissue responses. In typical single-cell systems, each heavy particle (Ar or Fe) passes through a single cell or no cell. In experiments on animal tissues, however, each heavy particle passes through several cells, and the LET can exceed 200 keV micrometers-1 in every cell. In most laboratory animal tissue systems, however, only a small portion of the hit cells are capable of expressing the end-point being measured, such as cell killing, mutation or carcinogenesis. The following question was therefore addressed: do RBEs and Q factors derived from single-cell experiments properly account for the damage at high LET when multiple cells are hit by HZE tracks? A review is offered in which measured radiation effects and known tissue properties are combined to estimate on the one hand, the number of cells at risk, p3n, per track, where n is the number of cells per track based on tissue and organ geometry, and p3 is the probability that a cell in the track is capable of expressing the experimental end-point. On the other hand, the tissue and single-cell responses are compared by determining the ratio RBE in tissue/RBE in corresponding single cells. Experimental data from the literature indicate that tissue RBEs at very high LET (Fe and Ar ions) are higher than corresponding single-cell RBEs, especially in tissues in which p3n is high.
authors.affiliation: 2595 Vassar Drive, Boulder, CO 80303, USA.
authors.forename: P
authors.initials: P
authors.lastname: Todd
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000166:cytology / Q000528:radiation effects; D002477:Cells / Q000528:radiation effects*; D002478:Cells, Cultured; D003359:Cosmic Radiation; D046508:Culture Techniques; D007583:Jejunum / Q000166:cytology / Q000528:radiation effects; D018499:Linear Energy Transfer; D008297:Male; D051379:Mice; D011836:Radiation Tolerance; D051381:Rats; D012062:Relative Biological Effectiveness; D012542:Scattering, Radiation; D013737:Testis / Q000166:cytology / Q000528:radiation effects