title: Real time evaluation of overranging in helical computed tomography.
abstract: Overranging or overscanning increases the dose delivered to patients undergoing helical Computed Tomography examinations. In order to reduce it, nowadays most of the multidetector tomographs close the X-ray beam aperture at the scan extremes. This technical innovation, usually referred to as dynamic or adaptive collimation, also influences the overranging assessment methods. In particular, the film free approach proposed in previous studies is not suitable for these modern tomographs. The present study aims to introduce a new method of estimating overranging with real time dosimetry, even suitable for tomographs equipped with adaptive collimation. The approach proposed is very easy to implement and time saving because only a pencil chamber is required. It is also equivalent in precision and in accuracy to the film based one, considered an absolute benchmark.
authors.affiliation: Department of Medical Physics, S. Chiara Hospital, APSS Trento, Italy. Electronic address: diego.trevisan@apss.tn.it.
authors.forename: Diego
authors.initials: D
authors.lastname: Trevisan
authors.affiliation: Department of Medical Physics, S. M. della Misericordia Hospital, Udine, Italy.
authors.forename: Faustino
authors.initials: F
authors.lastname: Bonutti
authors.affiliation: Department of Proton Therapy, S. Chiara Hospital, APSS Trento, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Ravanelli
authors.affiliation: Department of Medical Physics, S. Chiara Hospital, APSS Trento, Italy.
authors.forename: Aldo
authors.initials: A
authors.lastname: Valentini
mesh_terms: D000465:Algorithms; D001822:Body Burden; D003198:Computer Simulation; D006801:Humans; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation / Q000379:methods*; D012984:Software; D036542:Tomography, Spiral Computed / Q000295:instrumentation / Q000379:methods*; D014965:X-Rays
keywords: Computed tomography; Overranging; Overscanning