%A"Van der Linden, P M [Catharina Ziekenhuis, Eindhoven (Netherlands). Radiotherapy Dept.]" %A"Tiourina, T B" %A"Dries, W" %D1995 %I; Ghent Rijksuniversiteit (Belgium). Kliniek voor Radiotherapie en Kerngeneeskunde %2 %J[] %K55 BIOLOGY AND MEDICINE, BASIC STUDIES, PHOTON BEAMS, SCATTERING, RADIOTHERAPY, BEAM OPTICS, BIOMEDICAL RADIOGRAPHY, COLLIMATORS, CONFORMAL MAPPING, DELAYED RADIATION EFFECTS, DOSIMETRY, IMAGE PROCESSING, IMAGE SCANNERS, ISODOSE CURVES, NEOPLASMS, QUALITY ASSURANCE, TOMOGRAPHY %PMedium: ED; Size: pp. 22 %TMeasurement of the primary and scatter dose in high energy photon beams %XA method is presented to measure the primary and scatter components separately in a water tank using a small cylindrical absorber. Results from this experiment are compared with Monte Carlo calculations. The measurement setup consists of a small cylindrical absorber placed on a central axis of the beam a few centimetres above the radiation detector. Both absorber and detector move along the central axis while absorbed dose is registered. As the primary radiation is fully blocked, only scatter component is measured when a cylindrical absorber is used. Measurements in open fields result in the total absorbed dose being the sum of primary and scatter components. The primary dose component can be derived by substraction. Absorbers with different diameters are used. With decreasing dimensions the relative contribution of the dose due to scatter radiation increases. A steep increase is observed when the range of laterally scattered electrons becomes comparable with the radius of the absorber. Two different Monte Carlo simulations have been performed: with and without secondary electron transport. The data obtained for the former case perfectly agrees with the experiment. The situation where the secondary electron is assumed zero (i.e. local energy deposition) simulates the Cunningham model. Our results show that the Cunningham model predicts lower scatter component under the block edge which can be important for these applications. %0Conference %NINIS-BE-0001; CONF-951246-;Journal ID: ISSN 0167-8140; Other: ON: DE97622340; TRN: BE9700044034244 %1 %CBelgium %Rhttps://doi.org/10.1016/0167-8140(96)80631-1 Journal ID: ISSN 0167-8140; Other: ON: DE97622340; TRN: BE9700044034244 BEN %GEnglish