title: On the use of a single-fiber multipoint plastic scintillation detector for 192Ir high-dose-rate brachytherapy.
abstract: OBJECTIVE
  The goal of this study was to prove the feasibility of using a single-fiber multipoint plastic scintillation detector (mPSD) as an in vivo verification tool during (192)Ir high-dose-rate brachytherapy treatments.
  
  
  METHODS
  A three-point detector was built and inserted inside a catheter-positioning template placed in a water phantom. A hyperspectral approach was implemented to discriminate the different optical signals composing the light output at the exit of the single collection optical fiber. The mPSD was tested with different source-to-detector positions, ranging from 1 to 5 cm radially and over 10.5 cm along the longitudinal axis of the detector, and with various integration times. Several strategies for improving the accuracy of the detector were investigated. The device's accuracy in detecting source position was also tested.
  
  
  RESULTS
  Good agreement with the expected doses was obtained for all of the scintillating elements, with average relative differences from the expected values of 3.4 ± 2.1%, 3.0 ± 0.7%, and 4.5 ± 1.0% for scintillating elements from the distal to the proximal. A dose threshold of 3 cGy improved the general accuracy of the detector. An integration time of 3 s offered a good trade-off between precision and temporal resolution. Finally, the mPSD measured the radioactive source positioning uncertainty to be no more than 0.32 ± 0.06 mm. The accuracy and precision of the detector were improved by a dose-weighted function combining the three measurement points and known details about the geometry of the detector construction.
  
  
  CONCLUSIONS
  The use of a mPSD for high-dose-rate brachytherapy dosimetry is feasible. This detector shows great promise for development of in vivo applications for real-time verification of treatment delivery.
authors.affiliation: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: François
authors.initials: F
authors.lastname: Therriault-Proulx
authors.forename: Sam
authors.initials: S
authors.lastname: Beddar
authors.forename: Luc
authors.initials: L
authors.lastname: Beaulieu
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D007496:Iridium Radioisotopes / Q000032:analysis* / Q000627:therapeutic use*; D010969:Plastics / Q000528:radiation effects*; D011879:Radiotherapy Dosage; D015203:Reproducibility of Results; D012588:Scintillation Counting / Q000295:instrumentation*; D012680:Sensitivity and Specificity
chemical_list: D007496:Iridium Radioisotopes; D010969:Plastics