title: Multiple cell hits by particle tracks in solid 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 tissue end-point experiments each heavy particle passes through several cells, and the LET can exceed 200 keV/micrometer 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 of interest to the investigator, such as cell killing, mutation or carcinogenesis.  The following question must therefore be addressed:  Do RBE's and Q factors derived from single-cell experiments properly account for the increased probability of multiple-cell damage by HZE tracks?  A model is offered in which measured radiation effects and known tissue properties are combined to estimate the value of a multiplier of damage effectiveness on the basis of number of cells at risk, p3n, per track containing a hit cell, 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.
authors.affiliation: Boulder CO 80303, USA.
authors.forename: P
authors.initials: P
authors.lastname: Todd
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000528:radiation effects; D001854:Bone Marrow Cells; D002477:Cells / Q000528:radiation effects*; D002478:Cells, Cultured; D003359:Cosmic Radiation / Q000009:adverse effects*; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D006243:Harderian Gland / Q000166:cytology / Q000528:radiation effects; D007583:Jejunum / Q000166:cytology / Q000528:radiation effects; D018499:Linear Energy Transfer; D008297:Male; D051379:Mice; D008954:Models, Biological; D011853:Radiobiology / Q000379:methods; D051381:Rats; D012062:Relative Biological Effectiveness; D012208:Rhabdomyosarcoma / Q000473:pathology; D018874:Spheroids, Cellular / Q000528:radiation effects; D013737:Testis / Q000166:cytology / Q000528:radiation effects; D014407:Tumor Cells, Cultured