Illustration of common experiments investigating radiation-induced signalling.

<p>Top: Schematic illustration of experimental approaches modelled in this paper. Intercellular communication is investigating by transferring media from irradiated cells to unirradiated cells (media transfer, a) or by exposing cell populations to spatially varying doses (modulated field, b), and measuring changes in survival in populations not exposed to radiation. Bottom: Illustration of signal kinetics expected in each system. Probability of response is governed by the time t<sub>exp</sub>, for which the signal is above the threshold. Due to prolonged signal production, this is significantly longer in modulated field exposures (d) than in media-transfer experiments (c).</p>