title: A phantom-based feasibility study for detection of gadolinium in bone in-vivo using X-ray fluorescence.
abstract: Gadolinium (Gd) based contrast agents have been commonly used over the past three decades to improve contrast in magnetic resonance imaging. These complexes, originally thought to be stable and clear from the body shortly after administration, have been shown to dissociate to a small extent and deposit in organs such as bone. A safe and non-invasive method for measuring Gd in bone is necessary for further exploring Gd retention in the body following the administration of a contrast agent. A feasibility study using a K x-ray fluorescence (K-XRF) system to measure Gd in human tibias was investigated. Bone phantoms mimicking human tibia were created with Gd concentrations ranging from 0 to 120ppm. The minimum detection limit (MDL) was calculated from 20-hour and 7-hour phantom measurements with a source activity of 0.11GBq. All MDL values were scaled to a more realistic measurement time of 30-minutes with a stronger source. Scaling arguments were based on activity ratio, measurement time, and system dead time. The MDL for a 1GBq source was estimated to be 3.60-3.64ppm, for an average range of tissue thicknesses overlaying a human tibia. For a stronger source of 5GBq and a four detector cloverleaf system, the MDL was estimated to be 1.49-1.52ppm. Determined and predicted MDLs are within the range of previous in-vitro Gd measurement data. The K-XRF system shows promising results for detecting Gd in bone and should be seriously considered for in-vivo measurements.
authors.affiliation: Department of Medical Physics and Radiation Science, McMaster University, Main St. W., Hamilton, Canada L8S 4L8. Electronic address: lordml@mcmaster.ca.
authors.forename: M L
authors.initials: ML
authors.lastname: Lord
authors.affiliation: Department of Medical Physics and Radiation Science, McMaster University, Main St. W., Hamilton, Canada L8S 4L8. Electronic address: fmcneill@mcmaster.ca.
authors.forename: F E
authors.initials: FE
authors.lastname: McNeill
authors.affiliation: Department of Physics, Ryerson University, Victoria St., Toronto, Canada M5B 2K3. Electronic address: james.grafe@ryerson.ca.
authors.forename: J L
authors.initials: JL
authors.lastname: Gräfe
authors.affiliation: Department of Medical Physics and Radiation Science, McMaster University, Main St. W., Hamilton, Canada L8S 4L8; McMaster School of Biomedical Engineering, McMaster University, Main St. W., Hamilton, Canada L8S 4L8; Imaging Research, St. Joseph's Healthcare, Charlton Ave. E., Hamilton, Canada L8N 4A6; Department of Radiology, McMaster University, Main St. W., Hamilton, Canada L8S 4L8; Department of Electrical and Computer Engineering, McMaster University, Main St. W., Hamilton, Canada L8S 4L8. Electronic address: nosewor@mcmaster.ca.
authors.forename: M D
authors.initials: MD
authors.lastname: Noseworthy
authors.affiliation: Department of Medical Physics and Radiation Science, McMaster University, Main St. W., Hamilton, Canada L8S 4L8. Electronic address: chettle@mcmaster.ca.
authors.forename: D R
authors.initials: DR
authors.lastname: Chettle
mesh_terms: D001842:Bone and Bones / Q000000981:diagnostic imaging* / Q000528:radiation effects; D003287:Contrast Media / Q000493:pharmacokinetics*; D005240:Feasibility Studies; D005682:Gadolinium / Q000493:pharmacokinetics*; D006801:Humans; D057230:Limit of Detection; D008279:Magnetic Resonance Imaging; D019047:Phantoms, Imaging; D011874:Radiometry; D013052:Spectrometry, X-Ray Emission / Q000379:methods*; D014018:Tissue Distribution
chemical_list: D003287:Contrast Media; D005682:Gadolinium
keywords: Gadolinium; MRI; Minimum detection limit; X-ray fluorescence (XRF)