Joke Parthoens

Small-animal repetitive transcranial magnetic stimulation combined with [18F]-FDG microPET to quantify the neuromodulation effect in the rat brain

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive neurostimulation technique for the treatment of various neurological and psychiatric disorders. To investigate the working mechanism of this treatment approach, we designed a small-animal coil for dedicated use in rats and we combined this neurostimulation method with small-animal positron emission tomography (microPET or μPET) to quantify regional 2-deoxy-2-((18)F)fluoro-d-glucose ([(18)F]-FDG) uptake in the rat brain, elicited by a low- (1 Hz) and a high- (50 Hz) frequency paradigm. Rats (n=6) were injected with 1 mCi of [(18)F]-FDG 10 min after the start of 30 min of stimulation (1 Hz, 50 Hz or sham), followed by a 20-min μPET image acquisition. Voxel-based statistical parametric mapping (SPM) image analysis of 1-Hz and 50-Hz versus sham stimulation was performed. For both the 1-Hz and 50-Hz paradigms we found a large [(18)F]-FDG hypermetabolic cluster (2.208 mm(3) and 2.616 mm(3), resp.) (analysis of variance (ANOVA), p<0.05) located in the dentate gyrus complemented with an additional [(18)F]-FDG hypermetabolic cluster (ANOVA, p<0.05) located in the entorhinal cortex (2.216 mm(3)) for the 50-Hz stimulation. The effect on [(18)F]-FDG metabolism was 2.9 ± 0.8% at 1 Hz and 2.5 ± 0.8% at 50 Hz for the dentate gyrus clusters and 3.3 ± 0.5% for the additional cluster in the entorhinal cortex at 50 Hz. The maximal (4.19 vs. 2.58) and averaged (2.87 vs. 2.21) T-values are higher for 50 Hz versus 1 Hz. This experimental study demonstrates the feasibility to combine μPET imaging in rats stimulated with rTMS using a custom-made small-animal magnetic stimulation setup to quantify changes in the cerebral [(18)F]-FDG uptake as a measure for neuronal activity.

Performance Characterization of an Actively Cooled Repetitive Transcranial Magnetic Stimulation Coil for the Rat

This study characterizes and validates a recently developed dedicated circular rat coil for small animal repetitive Transcranial Magnetic Stimulation (rTMS).

Motion uncertainty deblurring in motion corrected reconstruction for μPET brain imaging of awake rats

The implementation and improvement of the spatial resolution of the reconstructions of a motion correction method for unconstrained and unanesthetized rats is presented for a small bore (16 cm diameter) Siemens Inveon microPET scanner. The motion scans are corrected using the LOR rebinning technique. After correction, the images still suffer from loss of spatial resolution compared to motion-free scans. We propose to improve the spatial resolution after motion correction by using a motion dependent and spatially variant kernel applied to the reconstruction using 3D deconvolution in the image space. The resolution kernel is calculated using the motion data. The method is applied in a microDerenzo phantom and an in vivo experiment. In the phantom experiment the resolution loss, compared to the motion-free scan that was observed in the motion corrected scan, was reduced by the proposed additional deconvolution. Moreover, the final image resolution was independent of the motion when using the motion dependent deconvolution..