Portal Imaging

Amorphous silicon (a-Si:H) flat panel detectors are commonly used as electronic portal imaging devices (EPIDs) on linear accelerators. They are main prerequisite for numerous applications like image guided radiotherapy. However, the high energetic radiation leads to damages of the detector’s electronics components and related image artifacts. Also the panel specific characteristics like its temperature dependency might be affected. For this reason calibration routines and correction methods are integrated in open-radART for improving image quality and increasing the detector life span on a software basis. Comparing the image quality shows that our correction methods achieve a tremendous improvement.

a) b)  c)  d)

Fig.1: Irradiation of a female breast with 6MV photons: a) open segment after two-point gain-offset correction, b) image improvement by applying our in-house developed offset separation correction c) wedged field after two-point gain-offset correction, d) again image improvement by applying the offset separation correction – The method works also at lower dose rates!

a)  b)

Fig.2: Portal image of a hip, acquired with a two and a half year old panel: a) open segment after offset separation correction b) further image improvement after applying a more advanced multi level gain calibration and correction

a)   b)

Fig.3: Further developments towards in vivo dosimetry and dose back-projection 


 Key Personnel:

  • DI Mitterlechner B., Institute for Research and Development on Advanced RadiationTechnologies (radART), Paracelsus Medical University, Salzburg, Austria
  • Mag. Deutschmann H., Institute for Research and Development on Advanced RadiationTechnologies (radART), Paracelsus Medical University, Salzburg, Austria




Oral Presentations:

  • Phantomfreie Qualitätssicherung mit dem EPID, Mitterlechner B.2, Mooslechner M.2, Weichenberger H.1,2, Huber S.1, Deutschmann H.1,2 (Bodensee-Physikertreffen, Feldkirch 2011)
  • Absolute dose accuracy with the help of an aSi:H flat-panel detector, Mooslechner M.2, Mitterlechner B.2, Weichenberger H.1,2, Huber S.1, Sedlmayer F.1,2, Deutschmann H.1,2 (Drei-Länder-Tagung der ÖGMP, DGMP, SGSMP, Wien 2011)
  • How to improve image quality of electronic portal imaging devices with MLG calibration and temperature correction, Huber S.1, Mooslechner M.2, Mitterlechner B.2, Sedlmayer F.1,2, Deutschmann H.1,2 (ESTRO, London 2011)
  • Kalibrierung und temperaturabhängige Korrektur von aSi:H Flat-Panel Detektoren, Mooslechner M.2 (Tagung der Österreichischen Gesellschaft für Medizinische Physik – ÖGMP, Salzburg 2010)
  • Image quality improvement of damaged a-Si:H flat panel detectors: Temperature surrogate and enhanced temperature correction, Mooslechner M.2 (Paracelsus Science Come Together 2009)

1 Institute for Research and Development on Advanced RadiationTechnologies (radART), Paracelsus Medical University, Salzburg, Austria

2 Department of Radiotherapy and Radio-Oncology at the Salzburger Landeskliniken, Salzburg, Austria