title: Evaluation of the Machine Performance Check application for TrueBeam Linac.
abstract: BACKGROUND
  Machine Performance Check (MPC) is an application to verify geometry and beam performances of TrueBeam Linacs, through automated checks based on their kV-MV imaging systems. In this study, preliminary tests with MPC were analyzed using all photon beam energies of our TrueBeam, comparing whenever possible with external independent checks.
  
  
  METHODS
  Data acquisition comprises a series of 39 images (12 with kV and 27 with MV detector) acquired at predefined positions without and with the IsoCal phantom in the beam, and with particular MLC pattern settings. MPC performs geometric and dosimetric checks. The geometric checks intend to test the treatment isocenter size and its coincidence with imaging devices, the positioning accuracy of the imaging systems, the collimator, the gantry, the jaws, the MLC leaves and the couch position. The dosimetric checks: refer to a reference MV image and give the beam output, uniformity and center change relative to the reference. MPC data were acquired during 10 repetitions on different consecutive days. Alternative independent checks were performed. Geometric: routine mechanical tests, Winston-Lutz test for treatment isocenter radius. Dosimetric: the 2D array StarCheck (PTW) was used just after the MPC data acquisition.
  
  
  RESULTS
  Results were analyzed for 6, 10, 15 MV flattened, and 6, 10 MV FFF beams. Geometric checks: treatment isocenter was between 0.31 ± 0.01 mm and 0.42 ± 0.02 mm with MPC, compared to 0.27 ± 0.01 mm averaged on all energies with the Winston-Lutz test. Coincidence of kV and MV imaging isocenters was within 0.36 ± 0.0 and 0.43 ± 0.06 mm, respectively (0.4 ± 0.1 mm with external tests). Positioning accuracy of MLC was within 0.5 mm; accuracy of jaws was 0.04 ± 0.02, 0.10 ± 0.05, -1.01 ± 0.03, 0.92 ± 0.04 mm for X1, X2, Y1, Y2 jaws, respectively, with MPC. Dosimetric tests: the output stability relative to the baseline was in average 0.15 ± 0.07% for MPC to compare with 0.3 ± 0.2% with the independent measurement.
  
  
  CONCLUSIONS
  MPC proved to be a reliable, fast and easy to use method for checking the machine performances on both geometric and dosimetric aspects.
authors.affiliation: IOSI, Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona, 6504, Switzerland. alessandro.clivio@eoc.ch.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Clivio
authors.affiliation: IOSI, Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona, 6504, Switzerland. eugenio.vanettidepalma@eoc.ch.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Vanetti
authors.affiliation: Varian Medical Systems Imaging Laboratory, Baden-Dättwil, Switzerland. steven.rose@varian.com.
authors.forename: Steven
authors.initials: S
authors.lastname: Rose
authors.affiliation: IOSI, Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona, 6504, Switzerland. giorgia.nicolini@eoc.ch.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Nicolini
authors.affiliation: IOSI, Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona, 6504, Switzerland. mariafrancesca.belosi@eoc.ch.
authors.forename: Maria F
authors.initials: MF
authors.lastname: Belosi
authors.affiliation: Radiotherapy and Radiosurgery Department, Humanitas Research Hospital, Milan-Rozzano, Italy. luca.cozzi@humanitas.it.
authors.forename: Luca
authors.initials: L
authors.lastname: Cozzi
authors.affiliation: Varian Medical Systems Imaging Laboratory, Baden-Dättwil, Switzerland. christof.baltes@varian.com.
authors.forename: Christof
authors.initials: C
authors.lastname: Baltes
authors.affiliation: Radiotherapy and Radiosurgery Department, Humanitas Research Hospital, Milan-Rozzano, Italy. antonella.fogliata@humanitas.it.
authors.forename: Antonella
authors.initials: A
authors.lastname: Fogliata
mesh_terms: D001331:Automation; D002138:Calibration; D004867:Equipment Design; D004868:Equipment Failure; D004869:Equipment Safety; D010315:Particle Accelerators / Q000295:instrumentation / Q000592:standards*; D019047:Phantoms, Imaging; D011785:Quality Assurance, Health Care; D011874:Radiometry / Q000379:methods; D012984:Software