In order for the memory model (2) to reproduce the radioadaptive response, the probability for a cell to become permanently altered by radiation exposure, <i>p</i>, must increase sufficiently at the higher radiation dose, <i>α</i>.

Abstract

<p>In other words, the radioadaptive response is not observed in the model if the increase in the parameter <i>p</i> at the higher value of <i>α</i> lies below a threshold. The graph plots the number of permanently altered cells in the presence of priming divided by the number of altered cells generated in the absence of priming, as a function of <i>n</i>-fold increase in the value of <i>p</i> at high <i>α</i>. If the value of <i>p</i> for high α is not increased sufficiently, more permanently altered cells are generated in the presence of priming. In contrast, if the value of <i>p</i> is increased by a threshold amount at high <i>α</i>, then priming lowers the total number of altered cells relative to the scenario where no low-dose priming is given. The horizontal line represents the ratio of one, where priming makes no difference. Base parameters are given as follows: <i>α = 0.1</i> for priming low dose radiation, and <i>α = 100</i> for higher dose radiation, <i>c = 1</i>, <i>η = 0.01</i>, <i>x₀ = 100</i>, <i>y₀ = 0</i>, <i>z₀ = 0</i>, <i>w₀ = 0</i>. For low-dose priming, <i>p = 0.05</i>. For high dose challenge, the value of <i>p</i> is increased <i>n</i>-fold, the horizontal axis of the graph.</p