title: Monte Carlo comparison of x-ray and proton CT for range calculations of proton therapy beams.
abstract: Proton computed tomography (CT) has been described as a solution for imaging the proton stopping power of patient tissues, therefore reducing the uncertainty of the conversion of x-ray CT images to relative stopping power (RSP) maps and its associated margins. This study aimed to investigate this assertion under the assumption of ideal detection systems. We have developed a Monte Carlo framework to assess proton CT performances for the main steps of a proton therapy treatment planning, i.e. proton or x-ray CT imaging, conversion to RSP maps based on the calibration of a tissue phantom, and proton dose simulations. Irradiations of a computational phantom with pencil beams were simulated on various anatomical sites and the proton range was assessed on the reference, the proton CT-based and the x-ray CT-based material maps. Errors on the tissue's RSP reconstructed from proton CT were found to be significantly smaller and less dependent on the tissue distribution. The imaging dose was also found to be much more uniform and conformal to the primary beam. The mean absolute deviation for range calculations based on x-ray CT varies from 0.18 to 2.01 mm depending on the localization, while it is smaller than 0.1 mm for proton CT. Under the assumption of a perfect detection system, proton range predictions based on proton CT are therefore both more accurate and more uniform than those based on x-ray CT.
authors.affiliation: Institut de Physique Nucléaire de Lyon, CNRS/IN2P3 UMR5822, Université Lyon 1, 69622 Villeurbanne, France. Université de Lyon, CREATIS, CNRS UMR5220, Inserm U1044, INSA-Lyon, Université Lyon 1, Centre Léon Bérard, France.
authors.forename: N
authors.initials: N
authors.lastname: Arbor
authors.forename: D
authors.initials: D
authors.lastname: Dauvergne
authors.forename: G
authors.initials: G
authors.lastname: Dedes
authors.forename: J M
authors.initials: JM
authors.lastname: Létang
authors.forename: K
authors.initials: K
authors.lastname: Parodi
authors.forename: C T
authors.initials: CT
authors.lastname: Quiñones
authors.forename: E
authors.initials: E
authors.lastname: Testa
authors.forename: S
authors.initials: S
authors.lastname: Rit
mesh_terms: D002138:Calibration; D006801:Humans; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011522:Protons; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D011522:Protons