U-SPECT-II: An Ultra-High-Resolution Device for Molecular Small-Animal Imaging

Abstract

We present a new rodent SPECT system (U-SPECT-II) that enables molecular imaging of murine organs down to resolutions of less than half a millimeter and high-resolution total-body imaging. Methods: The U-SPECT-II is based on a triangular stationary detector set-up, an XYZ stage that moves the animal during scanning, and interchangeable cylindric collimators (each containing 75 pinhole apertures) for both mouse and rat imaging. A novel graphical user interface incorporating preselection of the field of view with the aid of optical images of the animal focuses the pinholes to the area of interest, thereby maximizing sensitivity for the task at hand. Images are obtained from list-mode data using statistical reconstruction that takes system blurring into account to increase resolution. Results: For 99m Tc, resolutions determined with capillary phantoms were smaller than 0.35 and 0.45 mm using the mouse collimator with 0.35-and 0.6-mm pinholes, respectively, and less than 0.8 mm using the rat collimator with 1.0-mm pinholes. Peak geometric sensitivity is 0.07% and 0.18% for the mouse collimator with 0.35-and 0.6-mm pinholes, respectively, and 0.09% for the rat collimator. Resolution with 111 In, compared with that with 99m Tc, was barely degraded, and resolution with 125 I was degraded by about 10%, with some additional distortion. In vivo, kidney, tumor, and bone images illustrated that U-SPECT-II could be used for novel applications in the study of dynamic biologic systems and radiopharmaceuticals at the suborgan level. Conclusion: Images and movies obtained with U-SPECT-II provide high-resolution radiomolecule visualization in rodents. Discrimination of molecule concentrations between adjacent volumes of about 0.04 mL in mice and 0.5 mL in rats with U-SPECT-II is readily possible.

Tissue Distribution Studies of Protein Therapeutics Using Molecular Probes: Molecular Imaging

“…However, such low energy rays are highly attenuated by absorption and scattering in the body, making I-125 unsuitable for imaging in large animals or humans, but it can work well for small animal imaging (50) where appropriate detectors are more available.…”

Optical simulation of monolithic scintillator detectors using GATE/GEANT4

“…et al , Cherry 2004, Mitchell and Cherry 2009, Schramm et al 2003, Van der Have et al 2009 and/or developing hybrid imaging modalities such as PET/MRI (Catana et al 2009, Judenhofer et al 2008, Shao et al 1997.…”

An enhanced high-resolution EMCCD-based gamma camera using SiPM side detection

“…In the rejection method, which is based on the notion that the number of incident gammas in a small-animal pinhole geometry is expected to be less than one per frame (Beekman and Vastenhouw 2004, Rentmeester et al 2007and Van der Have et al 2009, those frames for which the SiPMs detect no events are simply discarded. In the more advanced counting method, the SiPM count is used to select the number of scintillation events that the scintillation detection algorithm detects in each frame.…”

“…small-animal) research. The application of pinhole geometries leads to unsurpassed imaging capabilities in small-animal SPECT (Schramm et al 2003, Van der Have et al 2009 and is also applied for human SPECT imaging of specific regions-of-interest, e.g. brain, chest and extremities (Rowe et al 1993, Funk et al 2006, Ostendorf et al 2006.…”