title: Technical Note: Procedure for the calibration and validation of kilo-voltage cone-beam CT models.
abstract: OBJECTIVE
  The aim of this work is to propose a general and simple procedure for the calibration and validation of kilo-voltage cone-beam CT (kV CBCT) models against experimental data.
  
  
  METHODS
  The calibration and validation of the CT model is a two-step procedure: the source model then the detector model. The source is described by the direction dependent photon energy spectrum at each voltage while the detector is described by the pixel intensity value as a function of the direction and the energy of incident photons. The measurements for the source consist of a series of dose measurements in air performed at each voltage with varying filter thicknesses and materials in front of the x-ray tube. The measurements for the detector are acquisitions of projection images using the same filters and several tube voltages. The proposed procedure has been applied to calibrate and assess the accuracy of simple models of the source and the detector of three commercial kV CBCT units. If the CBCT system models had been calibrated differently, the current procedure would have been exclusively used to validate the models. Several high-purity attenuation filters of aluminum, copper, and silver combined with a dosimeter which is sensitive to the range of voltages of interest were used. A sensitivity analysis of the model has also been conducted for each parameter of the source and the detector models.
  
  
  RESULTS
  Average deviations between experimental and theoretical dose values are below 1.5% after calibration for the three x-ray sources. The predicted energy deposited in the detector agrees with experimental data within 4% for all imaging systems.
  
  
  CONCLUSIONS
  The authors developed and applied an experimental procedure to calibrate and validate any model of the source and the detector of a CBCT unit. The present protocol has been successfully applied to three x-ray imaging systems. The minimum requirements in terms of material and equipment would make its implementation suitable in most clinical environments.
authors: Université de Lyon, CREATIS, CNRS UMR5220, Inserm U1206, INSA-Lyon, Université Lyon 1, Centre Léon Bérard, Lyon 69373 Cedex 08, France.
authors: Gloria
authors: G
authors: Vilches-Freixas
authors: Université de Lyon, CREATIS, CNRS UMR5220, Inserm U1206, INSA-Lyon, Université Lyon 1, Centre Léon Bérard, Lyon 69373 Cedex 08, France.
authors: Jean Michel
authors: JM
authors: Létang
authors: Ion Beam Application, Louvain-la-Neuve 1348, Belgium.
authors: Sébastien
authors: S
authors: Brousmiche
authors: Université de Lyon, CREATIS, CNRS UMR5220, Inserm U1206, INSA-Lyon, Université Lyon 1, Centre Léon Bérard, Lyon 69373 Cedex 08, France and Ion Beam Application, Louvain-la-Neuve 1348, Belgium.
authors: Edward
authors: E
authors: Romero
authors: Université de Lyon, CREATIS, CNRS UMR5220, Inserm U1206, INSA-Lyon, Université Lyon 1, Centre Léon Bérard, Lyon 69373 Cedex 08, France and Ion Beam Application, Louvain-la-Neuve 1348, Belgium.
authors: Marc
authors: M
authors: Vila Oliva
authors: Institute for Research and Development on Advanced Radiation Technologies, Paracelsus Medical University, Salzburg 5020, Austria.
authors: Daniel
authors: D
authors: Kellner
authors: Institute for Research and Development on Advanced Radiation Technologies, Paracelsus Medical University, Salzburg 5020, Austria.
authors: Heinz
authors: H
authors: Deutschmann
authors: Institute for Research and Development on Advanced Radiation Technologies, Paracelsus Medical University, Salzburg 5020, Austria.
authors: Peter
authors: P
authors: Keuschnigg
authors: Institute for Research and Development on Advanced Radiation Technologies, Paracelsus Medical University, Salzburg 5020, Austria.
authors: Philipp
authors: P
authors: Steininger
authors: Université de Lyon, CREATIS, CNRS UMR5220, Inserm U1206, INSA-Lyon, Université Lyon 1, Centre Léon Bérard, Lyon 69373 Cedex 08, France.
authors: Simon
authors: S
authors: Rit
mesh_terms: D002138:Calibration; D054893:Cone-Beam Computed Tomography; D008962:Models, Theoretical