Experimental determination of the angular dependence of the directional dose equivalent, H’(d), for ISO “narrow” X ray fields and 137Cs γ-rays measured in a PMMA sphere and a PMMA slab phantom
1993 (Swedish)Report (Other academic)
For the purpose of calibrating individual dosimeters in X-ray fields conversion factors from air kerma free in air to dose equivalent at a specified depth in a phantom have been calculated among others by Grosswendt (1991, 1992). By means of Monte Carlo calculations the angular dependence factor for photon beams of oblique incidence is also studied for different phantom shapes and compositions as well as for different X-ray qualities. However, till now there has been a lack of experimental verification of the angular dependence factors.
In this investigation the conversion factor from air kerma to Hp(10) has been determined for the following X-ray qualities: 40 kV, 80 kV, and 295 kV, ISO "narrow" spectra and for 137Cs γ-rays using thermoluminescent (TL) dosimeters. The angular dependence factor H'(10,α)/H'(10,0o) has also been experimentally determined for the same X-ray and γ -ray qualities and for different angles between 0o and 180o.
The conversion factors are found to be in good agreement with the calculated ones for the PMMA sphere phantom, while some minor discrepancies are found between the experimental and calculated angular dependence factors for the 30x30x15cm3 PMMA slab phantom.
The difference in angular dependence obtained for the slab and the sphere is discussed as well as the possibility to underestimate the personal dose equivalent, Hp(10), compared to effective dose, E.
Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 1993. , 27 p.
Report / Department of Radiology, Linköping University, 1990-1997, ISSN 1102-1799 ; 76
Radiology, Nuclear Medicine and Medical Imaging
IdentifiersURN: urn:nbn:se:liu:diva-57757ISRN: LIU-RAD-R-076OAI: oai:DiVA.org:liu-57757DiVA: diva2:327715