Optical scattering in camera-based electronic portal imaging

• Published in: Physics in medicine & biology 1999-10, Vol.44 (10), p.2381-2396
• Main Authors: Partridge, Mike, Evans, Philip M, Symonds-Tayler, J Richard N
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Diagnostic Imaging - instrumentation; Diagnostic Imaging - methods; Humans; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Miscellaneous. Technology; Models, Theoretical; Radionuclide investigations; Radiotherapy Planning, Computer-Assisted - instrumentation; Radiotherapy Planning, Computer-Assisted - methods; Scattering, Radiation; Scintillation Counting - instrumentation; Scintillation Counting - methods
• ISSN: 0031-9155; 1361-6560
• DOI: 10.1088/0031-9155/44/10/302

An investigation of scintillation light scattering within camera-based electronic portal imaging devices is presented. A simple analytical scatter model is adapted for the precise geometries of two different camera-based imaging systems and the results of modelling and experimental measurements are compared. The results of the study strongly suggest that the main source of optical scattering is multiple reflection between the scintillation screen and 45 degree mirror in both systems. The scattered light has a highly non-uniform distribution, which is strongly dependent upon field size. For large radiation fields the scatter contribution can be over 20% of the primary signal scintillation light intensity in the centre of the field. A purely optical method of removing the scattered light signal using a louvre grid on the surface of the scintillation screen is then presented and experimentally demonstrated to be effective.