Design and performance of SIAT aPET: a uniform high-resolution small animal PET scanner using dual-ended readout detectors

Abstract

In this work, a small animal PET scanner named SIAT aPET was developed using dual-ended readout depth encoding detectors to simultaneously achieve high spatial resolution and high sensitivity. The scanner consists of four detector rings with 12 detector modules per ring; the ring diameter is 111 mm and the axial field of view (FOV) is 105.6 mm. The images are reconstructed using an ordered subset expectation maximization (OSEM) algorithm. The spatial resolution of the scanner was measured by using a 22Na point source at the center axial FOV with different radial offsets. The sensitivity of the scanner was measured at center axis of the scanner with different axial positions. The count rate performance of the system was evaluated by scanning mouse-sized and rat-sized phantoms. An ultra-micro hot-rods phantom and two mice injected with 18F-NaF and 18F-FDG were scanned on the scanner. An average depth of interaction (DOI) resolution of 1.96 mm, energy resolution of 19.1% and timing resolution of 1.20 ns were obtained for the detector. Average spatial resolutions of 0.82 mm and 1.16 mm were obtained up to a distance of 30 mm radially from the center of the FOV when reconstructing a point source in 1% and 10% warm backgrounds, respectively, using OSEM reconstruction with 16 subsets and 10 iterations. Sensitivities of 16.0% and 11.9% were achieved at center of the scanner for energy windows of 250–750 keV and 350–750 keV respectively. Peak noise equivalent count rates (NECRs) of 324 kcps and 144 kcps were obtained at an activity of 26.4 MBq for the mouse-sized and rat-sized phantoms. Rods of 1.0 mm diameter can be visually resolved from the image of the ultra-micro hot-rods phantom. The capability of the scanner was demonstrated by high quality in-vivo mouse images.

Physical and imaging performance of SIAT aPET under different energy windows and timing windows

“…Compared to the sensitivity obtained with a narrow TW of 4 ns, the sensitivity increases by 18.8%, 24.0%, and 27.1%, respectively, as the TW changes to 8 ns, 12 ns, and 20 ns. The random count rates for a TW of 12 ns are about 9% and 15% of the prompt count rate at the peak NECR activity for the mouse‐sized and rat‐sized phantom 33 . The peak NECR of the mouse‐sized phantom increases by 19.8%, 24.7%, and 24.9%, respectively, as the TW changes from 4 to 8 ns, 12 ns, and 20 ns.…”

“…SIAT aPET is an abbreviation of Shenzhen Institute of Advanced Technology small animal PET scanner. The scanner was introduced in detail in our previous publication 33 and will be only introduced briefly in this paper. A photograph of the scanner and its detector geometry schematic are shown in Figure 1.…”

“…The system electronics are mainly comprised of 96 resistor network readout circuits, 12 singles processing units, one coincidence processing unit and one system clock board.A resistor network,as shown in our previous publications, 33,34 was used to read out the signals of an 8 × 8 SiPM array with a 64 to 4 multiplexing. In the resistor network readout circuit, first, signals of 8 SiPMs in a row were connected to a resistor chain, then both ends of the 8 resistor chains were connected to two column resistor chains, and finally 4 position encoding energy signals were generated.…”

Design and system evaluation of a dual-panel portable PET (DP-PET)

“…There have been a few initiatives to develop MR-compatible PET inserts [20][21][22][23], which show great potential for their future clinical adoption. A few successful prototypes have been developed for dedicated brain and small animal imaging applications using radiofrequency (RF)-shielding techniques and RF-penetrable technology [19,24,25]. However, all existing MR-compatible PET insert prototypes require cumbersome power supply systems and cooling systems, and hence, mobility and configurability of these systems remain limited.…”

Design and System Evaluation of a Dual-Panel Portable PET (DP-PET)

“…There have been a few initiatives to develop MR-compatible PET inserts [20][21][22], which show great potential for their future clinical adoption. A few successful prototypes have been developed for dedicated brain and small animals imaging applications using radiofrequency (RF)-shielding techniques and RF-penetrable technology [23][24][25]. However, all existing MR-compatible PET insert prototypes require cumbersome power supply systems and cooling systems, and hence mobility and configurability of these systems remain limited.…”