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PubMed1987

Common misinterpretations of the "linear, no-threshold" relationship used in radiation protection.

Absorbed dose D is shown to be a composite variable, the product of the fraction of cells hit (IH) and the mean "dose" (hit size) z to those cells. D is suitable for use with high level exposure (HLE) to radiation and its resulting acute organ effects because, since IH = 1.0, it approximates closely enough the mean energy density in the cell as well as in the organ. However, with low level exposure (LLE) to radiation and its consequent probability of cancer induction from a single cell, stochastic delivery of energy to cells results in a wide distribution of hit sizes z, and the expected mean value, z, is constant with exposure. Thus, with LLE, only IH varies with D so that the apparent proportionality between "dose" and the fraction of cells transformed is misleading. This proportionality therefore does not mean that any (cell) dose, no matter how small, can be lethal. Rather, it means that, in the exposure of a population of individual organisms consisting of the constituent relevant cells, there is a small probability of particle-cell interactions which transfer energy. The probability of a cell transforming and initiating a cancer can only be greater than zero if the hit size ("dose") to the cell is large enough. Otherwise stated, if the "dose" is defined at the proper level of biological organization, namely, the cell and not the organ, only a large dose z to that cell is effective.

Cells↗
PubMed2001

Radiation protection at low energy proton accelerators.

A sample is provided of the radiological safety issues particular to low energy proton accelerators. 'Low' energy in this context is taken to mean proton energies of less than about 1 GeV. Many of the radiation issues are common to all particle accelerators. Here, those issues are addressed that may require perhaps not unique treatment but those which benefit from a different approach. Among the problems discussed are the generation of prompt radiation and its transmission through shielding, the estimation of induced radioactivity, and the assessments of both the off-site prompt radiation hazard and the effect of releases of radioactive effluents to the environment.

Dose-Response Relationship, Radiation↗
PubMedDate not supplied

[Radiation protective efficacy of alpha-adrenomimetics during local gamma irradiation of the skin].

In experiment with mice and rats radioprotective properties of direct alpha-adrenomimetic drugs: indraline, mesaton (phenylephrine) and naphthyzine (naphazoline) have been investigated by local early and late radiation injuries. The drugs were S. C. and C. administrated at the site of the thigh of the hind of the animal at intervals of 5-8 min locally was irradiated with gamma-60Co-rays in the doses of 26.3-53.7 Gy at a rate of the dose of 1.31-1.54 Gy/min. When S. C. injected the topical effect of the adrenomimetics was higher than the systemic one. In experiment with mice radioprotective efficiency of topical indraline (S. C. 50 and 100 mg/kg) in term of DRF was equal to 1.34 and 1.67 for radiation burn of the skin, 1.56 and 1.91 for 3rd month radiation contracture of the hind and 1.10 and 1.50 for partial amputation of the one. In the same condition the effect of topical mesaton (S. C. 1, 2.5, 5 mg/kg) in term of DRF was accordingly equal to 1.29, 1.49 and 1.62 for early radiation injury, 1.08, 1.20 and 1.46 for 3th month radiation contracture of the hind and 1.0, 1.14, 1.33 for partial amputation of the one; the effect of topical naphthyzine (5 mg/kg) in the term of DRF was 1.36 for early radiation injury. In experiment with rats radioprotective property of systemic indraline (I. M. 100 mg/kg) in the term of DRF was equal to 1.39 for radiation burn of the skin, 1.39 for 6th month radiation contracture of the hind, 1.41 for partial amputation of the one. When C. administrated the effect of topical indraline (5% solution in 50% DMSO or ethyl alcohol solution) in term of DRF was accordingly equal to 1.17 and 1.18 for radiation burn ot the skin, 1.50 and 1.35 for radiation contracture of the hind, 1.41 and 1.28 for amputation of the one. When S. C. administrated the effect of topical and systemic mesaton (2.5 mg/kg) in term of DRF was accordingly equal to 1.30 and 1.04 for radiation burn ot the skin. 1.25 and 1.0 for radiation contracture of the hind, 1.30 and 1.0 for amputation of the one.

Administration, Cutaneous↗