title: Camera selection for real-time in vivo radiation treatment verification systems using Cherenkov imaging.
abstract: OBJECTIVE
  To identify achievable camera performance and hardware needs in a clinical Cherenkov imaging system for real-time, in vivo monitoring of the surface beam profile on patients, as novel visual information, documentation, and possible treatment verification for clinicians.
  
  
  METHODS
  Complementary metal-oxide-semiconductor (CMOS), charge-coupled device (CCD), intensified charge-coupled device (ICCD), and electron multiplying-intensified charge coupled device (EM-ICCD) cameras were investigated to determine Cherenkov imaging performance in a clinical radiotherapy setting, with one emphasis on the maximum supportable frame rate. Where possible, the image intensifier was synchronized using a pulse signal from the Linac in order to image with room lighting conditions comparable to patient treatment scenarios. A solid water phantom irradiated with a 6 MV photon beam was imaged by the cameras to evaluate the maximum frame rate for adequate Cherenkov detection. Adequate detection was defined as an average electron count in the background-subtracted Cherenkov image region of interest in excess of 0.5% (327 counts) of the 16-bit maximum electron count value. Additionally, an ICCD and an EM-ICCD were each used clinically to image two patients undergoing whole-breast radiotherapy to compare clinical advantages and limitations of each system.
  
  
  RESULTS
  Intensifier-coupled cameras were required for imaging Cherenkov emission on the phantom surface with ambient room lighting; standalone CMOS and CCD cameras were not viable. The EM-ICCD was able to collect images from a single Linac pulse delivering less than 0.05 cGy of dose at 30 frames/s (fps) and pixel resolution of 512 × 512, compared to an ICCD which was limited to 4.7 fps at 1024 × 1024 resolution. An intensifier with higher quantum efficiency at the entrance photocathode in the red wavelengths [30% quantum efficiency (QE) vs previous 19%] promises at least 8.6 fps at a resolution of 1024 × 1024 and lower monetary cost than the EM-ICCD.
  
  
  CONCLUSIONS
  The ICCD with an intensifier better optimized for red wavelengths was found to provide the best potential for real-time display (at least 8.6 fps) of radiation dose on the skin during treatment at a resolution of 1024 × 1024.
authors: Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755.
authors: Jacqueline M
authors: JM
authors: Andreozzi
authors: Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755.
authors: Rongxiao
authors: R
authors: Zhang
authors: Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755.
authors: Adam K
authors: AK
authors: Glaser
authors: Department of Medicine, Geisel School of Medicine and Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03766.
authors: Lesley A
authors: LA
authors: Jarvis
authors: Thayer School of Engineering and Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755.
authors: Brian W
authors: BW
authors: Pogue
authors: Department of Medicine, Geisel School of Medicine and Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03766.
authors: David J
authors: DJ
authors: Gladstone
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted; D061848:Optical Imaging / Q000295:instrumentation*; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation*; D012666:Semiconductors; D013997:Time Factors
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