Particle detection and cellular inactivation: a unified theory of track structure
The response of many detectors, dosimeters, and biological cells in culture to energetic heavy- ions is described by a model of track structure in which the effect of radiation is attributed to the interaction of the ''electron flux spectrnm'' with the sensitive elements of the detector. In small subvolumes of the detector, and on the average, the response of the detector to the energy deposited by''delta rays'' is asserted to be the same as it is to irradiation with gamma rays in a uniformly irradiated second detector. Differences in the response of the detector to gammarays and to the delta rays from heavy ions is attributed to the spatial and temporal differences in the energy deposition. Thus the sensitive element of a scintillator excited by one delta ray from an ion cannot respond to a second delta ray from the same ion, though conceivably it could respond to Compton electrons from two gamma-ray protons in the time of irradiation of a block of material with gamma rays. The theory considers the gamma-ray dose-effect relation as a transfer function, to be applied to the spatial distribution of local dose about the path of a heawy ion, so as to convert the dose distribution to a distribution in effect. Such a procedure yields the spatial distribution of developed emulsion grains about the path of an ion in nuclear emulsion, to simulate the track of a heawy ion. Integration of the effect over all possible radial distances yields the pulse height, for a scintillation counter, or the inactivation cross-section when enzymes are bombarded, or the ion-kill cross section for the inactivation of a biological cell by a single heavy ion, as in the passage of a cosmic ray particle through biological mntter. For biological matter, where it is possible to accumulate sublethal damage, there is a second possible inactivation mode, called the gamma-kill mode because of its resemblance to the way in which secondary eiectrons from many gamma-ray photons inactivate cells) through which delta rays from several ions in a beam can collectively inactivate cells. The theory is one whose functional form is dictated by its internal logic, but whose parameters must be determined experimentally. Once these are known, the res- ponse of the detector to any specified radiation environment may be calculated. The model suggests that many accepted concepts of radiation science must be carefully reevaluated. (auth)
- Research Organization:
- Nebraska Univ., Lincoln (USA)
- NSA Number:
- NSA-29-011682
- OSTI ID:
- 4398193
- Report Number(s):
- COO-1671-47; CONF-730345-1
- Resource Relation:
- Conference: Regional conference on radiation protection, Jerusalem, Israel, 5 Mar 1973; Other Information: Orig. Receipt Date: 30-JUN-74
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
N46110 -Instrumentation-Radiation Detection Instruments-General Detectors & Monitors
N46120 -Instrumentation-Radiation Detection Instruments-Radiation Dosimeters
*HEAVY IONS- RADIATION DETECTION
*RADIATION DETECTORS- PERFORMANCE
COMPTON EFFECT
GAMMA RADIATION
MATHEMATICAL MODELS