title: Measurement of the source size of a 6- and 18-MV radiotherapy linac.
abstract: The quality of portal imaging is strongly affected by the source size of the radiotherapy machine. The effective source size of the dual-energy clinac 1800 (6 and 18 MV) was measured with a 50 microns wide and 120 mm long slit formed by two tungsten-copper alloy blocks. A series of slit images were obtained by translating the slit horizontally. The images were analyzed using a microdensitometer. The measured data was simulated using an analytical model of the source and its size was derived by a best-fit analysis. For both energies the FWHM was found to be 1.5 +/- 0.1 mm.
authors.affiliation: Clinical Oncology and Radiation Therapy, Hadasa Hospital, Ein Kerem, Israel.
authors.forename: E
authors.initials: E
authors.lastname: Loewenthal
authors.forename: E
authors.initials: E
authors.lastname: Loewinger
authors.forename: E
authors.initials: E
authors.lastname: Bar-Avraham
authors.forename: G
authors.initials: G
authors.lastname: Barnea
mesh_terms: D006801:Humans; D008433:Mathematics; D008962:Models, Theoretical; D011878:Radiotherapy / Q000295:instrumentation / Q000379:methods*; D011879:Radiotherapy Dosage; D014965:X-Rays