Gamma-cube and X-cube: A New Scanner Generation for Benchtop Small Animal SPECT/CT (EANM, 2015)

Authors R. Van Holen, K. Deprez, B. Vandeghinste, S. Vandenberghe
Ghent University, Gent, BELGIUM.

Abstract: The first generation small animal imaging systems offer molecular 3D imaging at sub millimetre spatial resolution with SPECT and sensitivities in the order of several percents using PET. These systems often occupy a whole room because they are based on large to medium-size detector technology, borrowed from clinical scanners. The next generation systems aims at (i) improved image quality, (ii) at a much smaller footprint and (iii) at lower operational cost. Our group has been working on detector hardware and collimator designs to perform SPECT and CT imaging at a footprint of 1/4th of a square meter. Using additive manufacturing of tungsten, lofthole collimators and high-resolution detectors, we have designed and constructed a benchtop microSPECT system. On the other hand, using state-of-the-art CMOS X-ray detector technology, a micro-focal X-ray tube and iterative image reconstruction, we have designed and constructed a benchtop microCT system.
SPECT benchmarking has been performed using performance measurements previously used to objectively determine spatial resolution, sensitivity, uniformity and contrast-to-noise.
CT quality control has determined spatial resolution, low-contrast detectability and whole-body mouse imaging time.

Results show that SPECT spatial resolution is below 700um measured using a line source. Image reconstruction from a hot-rod resolution phantom separates all rods from 700 micron diameter and larger. Point source sensitivity is above 1200cps/MBq in a simultaneous cylindrical FOV of 3 cm diameter and 1 cm height. Differential uniformity is 23% while contrast to noise curves are in line with current commercial systems’ performance.
CT imaging at 80um is possible with a soft tissue contrast that outperforms current systems. Whole body imaging of a mouse is possible within 30 seconds, using compressive sensing for dose reduction.

All electronics and reconstruction servers are within a cube of 56x56x56cm3 system and the systems can be easily controlled using a tablet or a laptop. The small animal bed supports anesthesia, ECG, respiratory monitoring and heating. It can easily be transferred between both systems to obtain multi-modal SPECT-CT images.