title: Quantitative and qualitative assessment of Yttrium-90 PET/CT imaging.
abstract: Yttrium-90 is known to have a low positron emission decay of 32 ppm that may allow for personalized dosimetry of liver cancer therapy with (90)Y labeled microspheres. The aim of this work was to image and quantify (90)Y so that accurate predictions of the absorbed dose can be made. The measurements were performed within the QUEST study (University of Sydney, and Sirtex Medical, Australia). A NEMA IEC body phantom containing 6 fillable spheres (10-37 mm ∅) was used to measure the 90Y distribution with a Biograph mCT PET/CT (Siemens, Erlangen, Germany) with time-of-flight (TOF) acquisition. A sphere to background ratio of 8:1, with a total (90)Y activity of 3 GBq was used. Measurements were performed for one week (0, 3, 5 and 7 d). he acquisition protocol consisted of 30 min-2 bed positions and 120 min-single bed position. Images were reconstructed with 3D ordered subset expectation maximization (OSEM) and point spread function (PSF) for iteration numbers of 1-12 with 21 (TOF) and 24 (non-TOF) subsets and CT based attenuation and scatter correction. Convergence of algorithms and activity recovery was assessed based on regions-of-interest (ROI) analysis of the background (100 voxels), spheres (4 voxels) and the central low density insert (25 voxels). For the largest sphere, the recovery coefficient (RC) values for the 30 min -2-bed position, 30 min-single bed and 120 min-single bed were 1.12 ± 0.20, 1.14 ± 0.13, 0.97 ± 0.07 respectively. For the smaller diameter spheres, the PSF algorithm with TOF and single bed acquisition provided a comparatively better activity recovery. Quantification of Y-90 using Biograph mCT PET/CT is possible with a reasonable accuracy, the limitations being the size of the lesion and the activity concentration present. At this stage, based on our study, it seems advantageous to use different protocols depending on the size of the lesion.
authors.affiliation: Medical Radiation Physics/Radiation Protection, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
authors.forename: Ali Asgar
authors.initials: AA
authors.lastname: Attarwala
authors.affiliation: Medical Radiation Physics/Radiation Protection, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
authors.forename: Flavia
authors.initials: F
authors.lastname: Molina-Duran
authors.affiliation: Institute of Clinical Radiology and Nuclear Medicine, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
authors.forename: Karen-Anett
authors.initials: KA
authors.lastname: Büsing
authors.affiliation: Institute of Clinical Radiology and Nuclear Medicine, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
authors.forename: Stefan O
authors.initials: SO
authors.lastname: Schönberg
authors.affiliation: Department of Nuclear Medicine, Royal North Shore Hospital, Sydney, Australia.
authors.forename: Dale L
authors.initials: DL
authors.lastname: Bailey
authors.affiliation: Institute of Medical Physics, School of Physics, University of Sydney, Sydney, NSW, Australia.
authors.forename: Kathy
authors.initials: K
authors.lastname: Willowson
authors.affiliation: Medical Radiation Physics/Radiation Protection, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Glatting
mesh_terms: D000465:Algorithms; D002138:Calibration; D006801:Humans; D021621:Imaging, Three-Dimensional; D008113:Liver Neoplasms / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography / Q000592:standards; D019275:Radiopharmaceuticals / Q000737:chemistry; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000592:standards; D015021:Yttrium Radioisotopes / Q000737:chemistry
chemical_list: D019275:Radiopharmaceuticals; D015021:Yttrium Radioisotopes