High-resolution clustered pinhole (131)Iodine SPECT imaging in mice.
High-resolution pre-clinical (131)I SPECT can facilitate development of new radioiodine therapies for cancer. To this end, it is important to limit resolution-degrading effects of pinhole edge penetration by the high-energy γ-photons of iodine. Here we introduce, optimize and validate (131)I SPECT performed with a dedicated high-energy clustered multi-pinhole collimator.



A SPECT-CT system (VECTor/CT) with stationary gamma-detectors was equipped with a tungsten collimator with clustered pinholes. Images were reconstructed with pixel-based OSEM, using a dedicated (131)I system matrix that models the distance- and energy-dependent resolution and sensitivity of each pinhole, as well as the intrinsic detector blurring and variable depth of interaction in the detector. The system performance was characterized with phantoms and in vivo static and dynamic (131)I-NaI scans of mice.



Reconstructed image resolution reached 0.6mm, while quantitative accuracy measured with a (131)I filled syringe reaches an accuracy of +3.6±3.5% of the gold standard value. In vivo mice scans illustrated a clear shape of the thyroid and biodistribution of (131)I within the animal. Pharmacokinetics of (131)I was assessed with 15-s time frames from the sequence of dynamic images and time-activity curves of (131)I-NaI.



High-resolution quantitative and fast dynamic (131)I SPECT in mice is possible by means of a high-energy collimator and optimized system modeling. This enables analysis of (131)I uptake even within small organs in mice, which can be highly valuable for development and optimization of targeted cancer therapies.
Section Radiation, Detection and Medical Imaging, Delft University of Technology, Mekelweg 15, 2629 JB, Delft, The Netherlands; MIlabs B.V., Heidelberglaan 100 STR 4.105, 3584, CX, Utrecht, The Netherlands; Department for Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584, CG, Utrecht, The Netherlands.
Frans
F
van der Have
Section Radiation, Detection and Medical Imaging, Delft University of Technology, Mekelweg 15, 2629 JB, Delft, The Netherlands; MIlabs B.V., Heidelberglaan 100 STR 4.105, 3584, CX, Utrecht, The Netherlands; Department for Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584, CG, Utrecht, The Netherlands. Electronic address: O.Ivashchenko-1@tudelft.nl.
Oleksandra
O
Ivashchenko
Section Radiation, Detection and Medical Imaging, Delft University of Technology, Mekelweg 15, 2629 JB, Delft, The Netherlands.
Marlies C
MC
Goorden
Section Radiation, Detection and Medical Imaging, Delft University of Technology, Mekelweg 15, 2629 JB, Delft, The Netherlands; MIlabs B.V., Heidelberglaan 100 STR 4.105, 3584, CX, Utrecht, The Netherlands; Department for Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584, CG, Utrecht, The Netherlands.
Ruud M
RM
Ramakers
Section Radiation, Detection and Medical Imaging, Delft University of Technology, Mekelweg 15, 2629 JB, Delft, The Netherlands; MIlabs B.V., Heidelberglaan 100 STR 4.105, 3584, CX, Utrecht, The Netherlands; Department for Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584, CG, Utrecht, The Netherlands.
Freek J
FJ
Beekman
D000818:Animals; D007091:Image Processing, Computer-Assisted; D007457:Iodine Radioisotopes; D051379:Mice; D008810:Mice, Inbred C57BL; D019047:Phantoms, Imaging; D059629:Signal-To-Noise Ratio; D000072098:Single Photon Emission Computed Tomography Computed Tomography / Q000379:methods*; D012974:Sodium Iodide / Q000493:pharmacokinetics; D014018:Tissue Distribution
D007457:Iodine Radioisotopes; D012974:Sodium Iodide
Molecular imaging; Radioimmunotherapy; Radioiodine; SPECT