Radiances of Cerenkov-Emitting Isotopes on the IVIS

Cerenkov (or Cherenkov) luminescence occurs when charged particles exceed the phase velocity of a given medium. Cerenkov has gained interest in preclinical space as well as in clinical trials for optical visualization of numerous radionuclides. However, Cerenkov intensity has to be inferred from alternative databases with energy emission spectra, or theoretical fluence estimates. Here we present the largest experimental dataset of Cerenkov emitting isotopes recorded using the IVIS optical imaging system. We report Cerenkov measurements spanning orders of magnitude normalized to the activity concentration for 21 Cerenkov emitting isotopes, covering electron, alpha, beta minus, and positron emissions. Isotopes measured include Carbon-11, Fluorine-18, Phosphorous-32, Scandium-47, Copper-64, Copper-67, Gallium-68, Arsenic-72, Bromine-76, Yttrium-86, Zirconium-89, Yttrium-90, Iodine-124, Iodine-131, Cerium-134, Lutetium-177, Lead-203, Lead-212, Radium-223, Actinium-225, and Thorium-227. We hope this updating resource will serve as a rank ordering for comparing isotopes for Cerenkov luminescence in the visible window and serve as a rule of thumb for comparing Cerenkov intensities in vitro and in vivo. MethodsAll Cerenkov emitting radionuclides were either produced at Memorial Sloan Kettering Cancer Center (Carbon-11, 11C; Fluorine-18, 18F; Iodine-124, 124I), from commercial sources such as Perkin Elmer (Phosphorous-32, 32P; Yttrium-90, 90Y), Bayer (Radium-223, 223Ra, Xofigo), 3D-Imaging (Zirconium-89, 89Zr), Nuclear Diagnostic Products (Iodine-131, 131I), or from academic collaborators at Washington University at St. Louis (Copper-64, 64Cu), University of Wisconsin (Bromine-76, 76Br), MD Anderson Cancer Center (Yttrium-86, 86Y), Brookhaven National Laboratory (Arsenic-72, 72As; Thorium-227, 227Th), or Oak Ridge National Laboratory (Cerium-134, 134Ce, Actinium-225, 225Ac), and Viewpoint Molecular Targeting (Lead-203, 203Pb; Lead 212, 212Pb). All isotopes were diluted in triplicate on a black bottomed corning 96 well plate to several activity concentrations ranging from 0.1-250 Ci in 100-200 L of Phosphate Buffered Saline. Cerenkov imaging was acquired on a single Perkin-Elmer Spectrum In-Vivo Imaging System (IVIS) at field of view c with exposures ranging up to 15 minutes or lower provided no part of the image intensity was saturated, or that the activity significantly changed during the exposure. Experimental radiances on the IVIS were calculated from regions of interest drown over each 96 well, and then normalized for the activity present in the well, and the volume the isotope was diluted into.