title: A feasibility study to determine the potential of in vivo detection of gadolinium by x-ray fluorescence (XRF) following gadolinium-based contrast-enhanced MRI.
abstract: The feasibility of using a (109)Cd γ-ray induced K x-ray fluorescence (K-XRF) system for the in vivo detection of gadolinium (Gd) in bone has been investigated. The K-XRF bone measurement system employs an array of four detectors, and is normally used for the non-invasive study of bone lead levels. The system was used to measure bone simulating phantoms doped with varying levels of gadolinium and fixed amounts of sodium (Na), chlorine (Cl) and calcium (Ca). The detection limits for bare bone phantoms, using a source of activity 0.17 GBq, were determined to be 3.9 ppm and 6.5 ppm (µg Gd per gram phantom) for the Kα1 and Kα2 Gd x-ray peaks, respectively. This leads to an overall detection limit of 3.3 ppm (µg Gd per gram phantom). Layers of plastic were used to simulate overlying soft tissue and this permitted prediction of a detection limit, using the current strength of our radioisotope source, of 6.1 ppm to 8.6 ppm (µg Gd per gram phantom) for fingers with 2-4 mm of overlying tissue. With a new source of activity 5 GBq, we predict that this system could achieve a detection limit of 4-5.6 µg Gd g(-1) Ca. This is within the range of levels (2-30 µg Gd g(-1) Ca) previously found in the bone of patients receiving Gd based contrast imaging agents. The technique is promising and warrants further investigation.
authors.affiliation: Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, ON L8S 4K1, Canada.
authors.forename: F
authors.initials: F
authors.lastname: Mostafaei
authors.forename: F E
authors.initials: FE
authors.lastname: McNeill
authors.forename: D R
authors.initials: DR
authors.lastname: Chettle
authors.forename: M D
authors.initials: MD
authors.lastname: Noseworthy
mesh_terms: D001842:Bone and Bones / Q000737:chemistry*; D002106:Cadmium Radioisotopes; D002118:Calcium / Q000032:analysis; D002713:Chlorine / Q000032:analysis; D003287:Contrast Media; D004867:Equipment Design; D005240:Feasibility Studies; D005682:Gadolinium / Q000032:analysis*; D005720:Gamma Rays; D006801:Humans; D057230:Limit of Detection; D008279:Magnetic Resonance Imaging; D008954:Models, Biological; D019047:Phantoms, Imaging; D010969:Plastics; D012964:Sodium / Q000032:analysis; D013052:Spectrometry, X-Ray Emission
chemical_list: D002106:Cadmium Radioisotopes; D003287:Contrast Media; D010969:Plastics; D002713:Chlorine; D012964:Sodium; D005682:Gadolinium; D002118:Calcium