title: Monitoring external beam radiotherapy using real-time beam visualization.
abstract: OBJECTIVE
  To characterize the performance of a novel radiation therapy monitoring technique that utilizes a flexible scintillating film, common optical detectors, and image processing algorithms for real-time beam visualization (RT-BV).
  
  
  METHODS
  Scintillating films were formed by mixing Gd2O2S:Tb (GOS) with silicone and casting the mixture at room temperature. The films were placed in the path of therapeutic beams generated by medical linear accelerators (LINAC). The emitted light was subsequently captured using a CMOS digital camera. Image processing algorithms were used to extract the intensity, shape, and location of the radiation field at various beam energies, dose rates, and collimator locations. The measurement results were compared with known collimator settings to validate the performance of the imaging system.
  
  
  RESULTS
  The RT-BV system achieved a sufficient contrast-to-noise ratio to enable real-time monitoring of the LINAC beam at 20 fps with normal ambient lighting in the LINAC room. The RT-BV system successfully identified collimator movements with sub-millimeter resolution.
  
  
  CONCLUSIONS
  The RT-BV system is capable of localizing radiation therapy beams with sub-millimeter precision and tracking beam movement at video-rate exposure.
authors.affiliation: Department of Mechanical Engineering and Department of Radiation Oncology, Stanford University, Stanford, California 94305.
authors.forename: Cesare H
authors.initials: CH
authors.lastname: Jenkins
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California 94305.
authors.forename: Dominik J
authors.initials: DJ
authors.lastname: Naczynski
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California 94305.
authors.forename: Shu-Jung S
authors.initials: SJ
authors.lastname: Yu
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California 94305.
authors.forename: Lei
authors.initials: L
authors.lastname: Xing
mesh_terms: D000465:Algorithms; D006801:Humans; D007091:Image Processing, Computer-Assisted; D055096:Optical Devices; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation / Q000379:methods*; D012588:Scintillation Counting