VECTor: a preclinical imaging system for simultaneous submillimeter SPECT and PET.
Today, PET and SPECT tracers cannot be imaged simultaneously at high resolutions but require 2 separate imaging systems. This paper introduces a Versatile Emission Computed Tomography system (VECTor) for radionuclides that enables simultaneous submillimeter imaging of single-photon and positron-emitting radiolabeled molecules.


METHODS
γ-photons produced both by electron-positron annihilation and by single-photon emitters are projected onto the same detectors by means of a novel cylindric high-energy collimator containing 162 narrow pinholes that are grouped in clusters. This collimator is placed in an existing SPECT system (U-SPECT-II) with 3 large-field-of-view γ-detectors. From the acquired projections, PET and SPECT images are obtained using statistical image reconstruction that corrects for energy-dependent system blurring.


RESULTS
For PET tracers, the tomographic resolution obtained with a Jaszczak hot rod phantom was less than 0.8 mm, and 0.5-mm resolution images of SPECT tracers were acquired simultaneously. SPECT images were barely degraded by the simultaneous presence of a PET tracer, even when the activity concentration of the PET tracer exceeded that of the SPECT tracer by up to a factor of 2.5. Furthermore, we simultaneously acquired fully registered 3- and 4-dimensional multiple functional images from living mice that, in the past, could be obtained only sequentially.


CONCLUSIONS
High-resolution complementary information about tissue function contained in SPECT and PET tracer distributions can now be obtained simultaneously using a fully integrated imaging device. These combined unique capabilities pave the way for new perspectives in imaging the biologic systems of rodents.
Delft University of Technology, Delft, The Netherlands.
Marlies C
MC
Goorden
Frans
F
van der Have
Rob
R
Kreuger
Ruud M
RM
Ramakers
Brendan
B
Vastenhouw
J Peter H
JP
Burbach
Jan
J
Booij
Carla F M
CF
Molthoff
Freek J
FJ
Beekman
D000818:Animals; D002138:Calibration; D003198:Computer Simulation; D003201:Computers; D004867:Equipment Design; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D051379:Mice; D008810:Mice, Inbred C57BL; D019047:Phantoms, Imaging; D017785:Photons; D049268:Positron-Emission Tomography / Q000379:methods*; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D012984:Software; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*