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


CONCLUSIONS
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 microL in mice and 0.5 microL in rats with U-SPECT-II is readily possible.
van der Have
Frans
F
Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
Vastenhouw
Brendan
B
Ramakers
Ruud M
RM
Branderhorst
Woutjan
W
Krah
Jens O
JO
Ji
Changguo
C
Staelens
Steven G
SG
Beekman
Freek J
FJ
D000818:Animals; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation*; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D023421:Models, Animal; D015336:Molecular Probe Techniques / Q000295:instrumentation* / Q000662:veterinary*; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation* / Q000662:veterinary*