title: Practical issues regarding angular and energy response in in vivo intraoperative electron radiotherapy dosimetry.
abstract: OBJECTIVE
  To estimate angular response deviation of MOSFETs in the realm of intraoperative electron radiotherapy (IOERT), review their energy dependence, and propose unambiguous names for detector rotations.
  
  
  BACKGROUND
  MOSFETs have been used in IOERT. Movement of the detector, namely rotations, can spoil results.
  
  
  METHODS
  We propose yaw, pitch, and roll to name the three possible rotations in space, as these unequivocally name aircraft rotations. Reinforced mobile MOSFETs (model TN-502RDM-H) and an Elekta Precise linear accelerator were used. Two detectors were placed in air for the angular response study and the whole set of five detectors was calibrated as usual to evaluate energy dependence.
  
  
  RESULTS
  The maximum readout was obtained with a roll of 90° and 4 MeV. With regard to pitch movement, a substantial drop in readout was achieved at 90°. Significant overresponse was measured at 315° with 4 MeV and at 45° with 15 MeV. Energy response is not different for the following groups of energies: 4, 6, and 9 MeV; and 12 MeV, 15 MeV, and 18 MeV.
  
  
  CONCLUSIONS
  Our proposal to name MOSFET rotations solves the problem of defining sensor orientations. Angular response could explain lower than expected results when the tip of the detector is lifted due to inadvertent movements. MOSFETs energy response is independent of several energies and differs by a maximum of 3.4% when dependent. This can limit dosimetry errors and makes it possible to calibrate the detectors only once for each group of energies, which saves time and optimizes lifespan of MOSFETs.
authors: Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Avda. Dr. Clará, 19, Castellón de la Plana 12002, Spain.
authors: Juan
authors: J
authors: López-Tarjuelo
authors: Servicio de Oncología Radioterápica, Consorcio Hospitalario Provincial de Castellón, Avda. Dr. Clará, 19, Castellón de la Plana 12002, Spain.
authors: Ana
authors: A
authors: Bouché-Babiloni
authors: Servicio de Oncología Radioterápica, Consorcio Hospitalario Provincial de Castellón, Avda. Dr. Clará, 19, Castellón de la Plana 12002, Spain.
authors: Virginia
authors: V
authors: Morillo-Macías
authors: Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Avda. Dr. Clará, 19, Castellón de la Plana 12002, Spain.
authors: Agustín
authors: A
authors: Santos-Serra
authors: Servicio de Oncología Radioterápica, Consorcio Hospitalario Provincial de Castellón, Avda. Dr. Clará, 19, Castellón de la Plana 12002, Spain.
authors: Carlos
authors: C
authors: Ferrer-Albiach
keywords: ANOVA, analysis of variance; Angular response; CF, calibration factor; Energy dependence; GH, Games–Howell test; IOERT; IOERT, intraoperative electron radiotherapy; MOSFET; MOSFET, metal oxide semiconductor field effect transistor; Rotations; T, Tukey's test