Monte Carlo simulation of a prototypical patient dosimetry system for fluoroscopic procedures. (17th July 2015)

• Record Type: Journal Article
• Authors: Goertz, Lukas; Tsiamas, Panagiotis; Karellas, Andrew; Sajo, Erno; Zygmanski, Piotr
• Is Part Of: Physics in medicine & biology. Volume 60:Number 15(2015:Aug.)
• Page Start: 5891
• Page End: 5909
• Publication Date: 2015-07-17
• Subjects: real-time dosimetry -- fluoroscopy -- thin-film detector arrays -- Monte Carlo -- peak skin dose -- entrance dose -- integral dose; Biophysics -- Periodicals; Medical physics -- Periodicals; 610.153
• DOI: 10.1088/0031-9155/60/15/5891
• Languages: English
• ISSNs: 0031-9155

Abstract

Abstract: The purpose of this study is to investigate feasibility of a novel real-time dosimetry method for fluoroscopically guided interventions utilizing thin-film detector arrays in several potential locations with respect to the patient and x-ray equipment. We employed Monte Carlo (MC) simulation to establish the fluoroscopic beam model to determine dosimetric quantities directly from measured doses in thin-film detector arrays at three positions: A—attached to the x-ray source, B—on the couch under the patient and C—attached to the fluoroscopic imager. Next, we developed a calibration method to determine skin dose at the entry of the beam ( ) as well as the dose distribution along each ray of the beam in a water-equivalent patient model. We utilized the concept of water-equivalent thickness to determine the dose inside the patient based on doses measured outside of the patient by the thin-film detector array layers: (a) A, (b) B, or (c) B and C. In the process of calibration we determined a correction factor that characterizes the material-specific response of the detector, backscatter factor and attenuation factor for slab water phantoms of various thicknesses. Application of this method to an anthropomorphic phantom showed accuracy of about 1% for and up to about 10% for integral dose along the beam path when compared to a direct simulation of dose by MC.