| Popis: |
Biophysical studies indicate that the mechanisms responsible for radiation effects involve injury to cell substructures much smaller than a cell nucleus. Therefore, in order to understand the molecular mechanisms responsible, it is important to know the amount of dose deposited in the microscopic volumes of interest for a particular biological endpoint. In the case of heavy ion passage through tissue, the local pattern of energy deposition in critical volumes is strongly influenced by the structure of the track. At the Bevalac in Berkeley, a small proportional counter mounted in a large vacuum chamber was used to measure single event energy deposition distributions as a function of the distance radially outward from the primary ion path, for a 1.3 μm diameter site. It was found that the distribution of energy deposited only by delta-rays in the site resembled that of 170 kVp X-rays, and also that the specific energy (microscopic dose) for those sites exceeded the calculated average radial dose by two orders of magnitude at large radial distances. |
