Two-component model in the theory of RBE
From 4th symposium on microdosimetry; Pallanza, Italy (24 Sep 1973). Many investigators have sought to represent cellular survival after gamma-ray irradiation by a two-component model, according to the equation N/N/sub o/ = e/ sup -D/D/1 STA1 -- (1 - e/sup -D/D//sub m/)/sup m/! where D is the dose of gamma- rays, D/sub 1/ is the characteristic dose of the 1-hit component and D/sub m/ is the characteristic dose of the m-target component. Typically D/sub 1//D/sub m/ is about 2. Following the procedures of the delta-ray theory of track structure, the inactivation crosssection of a detector was calculated whose sensitive elements have an appropriate range of sizes, and of values of D/sub 1//D/sub m/ and m. For values of D/sub 1//D/sub m/ less than 10, the 1-hit component dominates the response of the detector to heavy ions, with the result that the RBE of such a detector should decrease with an increase in the value of z/sup 2// BETA /sup 2/ of the incident radiation. Only whe n D/sub 1/ is very much greater than D/sub m/ does the multi-target component dominate the result. Then the inactivation cross-section displays a plateau in the transition from the grain- count regime to the track-width regime. The result is only weakly dependent on the explicit use of the two-component model. It must be expected to arise from any survival curve after gamma-ray irradiation which displays a non-zero initial slope. The inference must be drawn that there is an inherent incompatibility among the following three conditions: (1) the response of a homogeneous population of targets to gamma-radiation may be described by a two-component model with D/sub 1//D/sub m/ less than 10, -(2) this population displays an RBE greater than 1 after any irradiation (including neutrons) and (3) the delta-ray theory of track structure is applicable to this system without modification for dose-rate effects or for repair mechanisms. (auth)
- Research Organization:
- Nebraska Univ., Lincoln (USA)
- NSA Number:
- NSA-29-006748
- OSTI ID:
- 4375779
- Report Number(s):
- COO-1671-50; CONF-730952-2
- Resource Relation:
- Conference: 4. symposium on microdosimetry, Pallanza, Italy, 24 Sep 1973; Other Information: Orig. Receipt Date: 30-JUN-74
- Country of Publication:
- United States
- Language:
- English
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