BioSpace Gamma Imager
Dynamic planar imaging (list mode) will be performed with the Biospace Gamma--Imager, which is available in the IVISR. This unit is capable of high resolution planar imaging utilizing its position sensitive photomultiplier tube. If the agent is radiolabeled with Tc-99m a low-energy high sensitivity collimator can be used; the energy window will be set at 127 – 171keV. If the agent is radiolabeled with In-111, a medium-energy high sensitivity collimator can be employed and a dual energy windows set at 145 – 195keV and 208 – 282keV. After an iv injection (0.5 mCi) of a known amount (mole) of agent list-mode data can be acquired for two hours, after which a plasma sample will be used to calibrate heart time-activity data to mole of radiopharmaceutical per liter of plasma. After euthanasia the tumors and other tissues can be excised and assayed for radioactivity. Using Biospace software the list-mode data can be reformatted into frames of any duration. The list mode acquisition will allow reanalysis of the data at a finer temporal resolution as deemed necessary based on the dynamics of the blood and tissue radiopharamcokinetics. After comparison to an injection standard the tumor and heart/lung time-activity data can be calibrated to absolute amount (mole) of radiopharmaceutical within the entire organ or tissue. The calibrated time-activity curves can be transferred for kinetic analysis.