title: An electronic portal imaging device for transit dosimetry.
abstract: An electronic portal imaging device has been designed and constructed. It consists of an array of 128 CsI scintillation crystals coupled to photodiodes which is scanned across the field in 4 seconds. The linac is operated at a dose rate of 400 cGy min-1 and the dose delivered for image acquisition is approximately 27 cGy. The data acquisition controller is a stand-alone STE computer located within the scan arm. Sample images are presented showing contrast and spatial resolution of the system together with a humanoid phantom image and a clinical image of a breast cancer patient. The phantom images show the detector has a contrast resolution of 0.3% (at 15 mm diameter) and a spatial resolution of 2.5-3.2 mm. Images of uniform Perspex blocks have also been calibrated for thickness, indicating the system can measure radiological thickness to an accuracy of 2-3 mm of water. These results indicate the detector may be used for transit dosimetry applications including compensator design.
authors.affiliation: Joint Department of Physics, Institute of Cancer Research, Sutton, Surrey, UK.
authors.forename: J R
authors.initials: JR
authors.lastname: Symonds-Tayler
authors.forename: M
authors.initials: M
authors.lastname: Partridge
authors.forename: P M
authors.initials: PM
authors.lastname: Evans
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D005260:Female; D006257:Head / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D008327:Mammography; D019047:Phantoms, Imaging; D011881:Radiotherapy, Computer-Assisted / Q000295:instrumentation*