title: Application of failure mode and effects analysis to intraoperative radiation therapy using mobile electron linear accelerators.
abstract: OBJECTIVE
  Failure mode and effects analysis (FMEA) represents a prospective approach for risk assessment. A multidisciplinary working group of the Italian Association for Medical Physics applied FMEA to electron beam intraoperative radiation therapy (IORT) delivered using mobile linear accelerators, aiming at preventing accidental exposures to the patient.
  
  
  METHODS
  FMEA was applied to the IORT process, for the stages of the treatment delivery and verification, and consisted of three steps: 1) identification of the involved subprocesses; 2) identification and ranking of the potential failure modes, together with their causes and effects, using the risk probability number (RPN) scoring system, based on the product of three parameters (severity, frequency of occurrence and detectability, each ranging from 1 to 10); 3) identification of additional safety measures to be proposed for process quality and safety improvement. RPN upper threshold for little concern of risk was set at 125.
  
  
  RESULTS
  Twenty-four subprocesses were identified. Ten potential failure modes were found and scored, in terms of RPN, in the range of 42-216. The most critical failure modes consisted of internal shield misalignment, wrong Monitor Unit calculation and incorrect data entry at treatment console. Potential causes of failure included shield displacement, human errors, such as underestimation of CTV extension, mainly because of lack of adequate training and time pressures, failure in the communication between operators, and machine malfunctioning. The main effects of failure were represented by CTV underdose, wrong dose distribution and/or delivery, unintended normal tissue irradiation. As additional safety measures, the utilization of a dedicated staff for IORT, double-checking of MU calculation and data entry and finally implementation of in vivo dosimetry were suggested.
  
  
  CONCLUSIONS
  FMEA appeared as a useful tool for prospective evaluation of patient safety in radiotherapy. The application of this method to IORT lead to identify three safety measures for risk mitigation.
authors.affiliation: Unit of Medical Physics, Centro Nazionale di Adroterapia Oncologica Foundation, via Campeggi, 27100 Pavia, Italy. mario.ciocca@cnao.it
authors.forename: Mario
authors.initials: M
authors.lastname: Ciocca
authors.forename: Marie-Claire
authors.initials: MC
authors.lastname: Cantone
authors.forename: Ivan
authors.initials: I
authors.lastname: Veronese
authors.forename: Federica
authors.initials: F
authors.lastname: Cattani
authors.forename: Guido
authors.initials: G
authors.lastname: Pedroli
authors.forename: Silvia
authors.initials: S
authors.lastname: Molinelli
authors.forename: Viviana
authors.initials: V
authors.lastname: Vitolo
authors.forename: Roberto
authors.initials: R
authors.lastname: Orecchia
mesh_terms: D000465:Algorithms; D004583:Electrons / Q000009:adverse effects / Q000627:therapeutic use*; D019544:Equipment Failure Analysis / Q000379:methods*; D006283:Health Physics / Q000379:methods; D006801:Humans; D007432:Intraoperative Period; D007558:Italy; D009369:Neoplasms / Q000532:radiotherapy / Q000601:surgery; D010315:Particle Accelerators; D061214:Patient Safety; D011336:Probability; D011832:Radiation Injuries / Q000517:prevention & control*; D012308:Risk Management / Q000379:methods*