THE STOCHASTICS OF THE POSITIVE-ION PENUMBRA

Authors
Citation
We. Wilson, THE STOCHASTICS OF THE POSITIVE-ION PENUMBRA, Radiation research, 140(3), 1994, pp. 375-381
Citations number
27
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Radiology,Nuclear Medicine & Medical Imaging
Journal title
ISSN journal
0033-7587
Volume
140
Issue
3
Year of publication
1994
Pages
375 - 381
Database
ISI
SICI code
0033-7587(1994)140:3<375:TSOTPP>2.0.ZU;2-#
Abstract
Statistical analysis of Monte Carlo simulations of positive ion track structure is presented for 1 MeV protons passing outside an absorbing region of interest. Energy deposition and production of ionization wit hin the region occur only by delta-ray transport from the ion's path. Depositions in spherical absorber regions of 2 to 100 nm diameter in u nit density tissue were scored. It is shown that production of delta r ays sufficiently energetic to reach the region is infrequent and the d elta rays are therefore relatively far apart along the ion path compar ed to their average range. The probability for any delta-ray energy de position in a distant site is small and proportional to the solid angl e intercepted by the site. The functional dependence of the frequency density distributions in energy imparted and in ionization number, con ditional on there being some interaction, is approximately exponential , and the first and second moments of the distributions are largely in dependent of distance from the ion path. These findings confirm simila r conclusions from experimental measurements on the track structure of germanium, iron and uranium ions.