title: Utilizing High-Energy γ-Photons for High-Resolution 213Bi SPECT in Mice.
abstract: The combined α-, γ-, and x-ray emitter (213)Bi (half-life, 46 min) is promising for radionuclide therapy. SPECT imaging of (213)Bi is challenging, because most emitted photons have a much higher energy (440 keV) than common in SPECT. We assessed (213)Bi imaging capabilities of the Versatile Emission Computed Tomograph (VECTor) dedicated to (simultaneous) preclinical imaging of both SPECT and PET isotopes over a wide photon energy range of 25-600 keV.
  
  
  METHODS
  VECTor was equipped with a dedicated clustered pinhole collimator. Both the 79 keV x-rays and the 440 keV γ-rays emitted by (213)Bi could be imaged. Phantom experiments were performed to determine the maximum resolution, contrast-to-noise ratio, and activity recovery coefficient for different energy window settings. Additionally, imaging of [(213)Bi-DOTA,Tyr(3)]octreotate and (213)Bi-diethylene triamine pentaacetic acid (DTPA) in mouse models was performed.
  
  
  RESULTS
  Using 440 keV γ-rays instead of 79 keV x-rays in image reconstruction strongly improved the resolution (0.75 mm) and contrast-to-noise characteristics. Results obtained with a single 440 keV energy window setting were close to those with a combined 79 keV/440 keV window. We found a reliable activity recovery coefficient down to 0.240 MBq/mL with 30-min imaging time. In a tumor-bearing mouse injected with 3 MBq of [(213)Bi-DOTA,Tyr(3)]octreotate, tumor uptake could be visualized with a 1-h postmortem scan. Imaging a nontumor mouse at 5-min frames after injection of 7.4 MBq of (213)Bi-DTPA showed renal uptake and urinary clearance, visualizing the renal excretion pathway from cortex to ureter. Quantification of the uptake data allowed kinetic modeling and estimation of the absorbed dose to the kidneys.
  
  
  CONCLUSIONS
  It is feasible to image (213)Bi down to a 0.75-mm resolution using a SPECT system equipped with a dedicated collimator.
authors.affiliation: Department of Nuclear Medicine, Erasmus Medical Centre, Rotterdam, The Netherlands j.deswart@erasmusmc.nl.
authors.forename: Jan
authors.initials: J
authors.lastname: de Swart
authors.affiliation: Department of Nuclear Medicine, Erasmus Medical Centre, Rotterdam, The Netherlands.
authors.forename: Ho Sze
authors.initials: HS
authors.lastname: Chan
authors.affiliation: Section Radiation, Detection and Medical Imaging, Delft University of Technology, Delft, The Netherlands.
authors.forename: Marlies C
authors.initials: MC
authors.lastname: Goorden
authors.affiliation: European Commission, Joint Research Centre, Institute for Transuranium Elements (ITU), Karlsruhe, Germany.
authors.forename: Alfred
authors.initials: A
authors.lastname: Morgenstern
authors.affiliation: European Commission, Joint Research Centre, Institute for Transuranium Elements (ITU), Karlsruhe, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Bruchertseifer
authors.affiliation: Section Radiation, Detection and Medical Imaging, Delft University of Technology, Delft, The Netherlands MIlabs B.V., Utrecht, The Netherlands Department of Translational Neuroscience, Brain Center Rudolf Magnus, The Netherlands; and.
authors.forename: Freek J
authors.initials: FJ
authors.lastname: Beekman
authors.affiliation: Department of Nuclear Medicine, Erasmus Medical Centre, Rotterdam, The Netherlands Department of Radiology, Erasmus Medical Centre, Rotterdam, The Netherlands.
authors.forename: Marion
authors.initials: M
authors.lastname: de Jong
authors.affiliation: Department of Nuclear Medicine, Erasmus Medical Centre, Rotterdam, The Netherlands.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Konijnenberg
mesh_terms: D000465:Algorithms; D000818:Animals; D001729:Bismuth; D005260:Female; D005720:Gamma Rays; D006573:Heterocyclic Compounds, 1-Ring; D007091:Image Processing, Computer-Assisted; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000000981:diagnostic imaging; D015282:Octreotide / Q000031:analogs & derivatives; D009942:Organometallic Compounds; D019047:Phantoms, Imaging; D017785:Photons; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D059629:Signal-To-Noise Ratio; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: C580872:(213)Bi-DTPA-F3; C476041:DOTA-Tyr(1)-octreotate; D006573:Heterocyclic Compounds, 1-Ring; D009942:Organometallic Compounds; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D015282:Octreotide; D001729:Bismuth
keywords: 213Bi; SPECT; ultra-high-energy