Performance evaluation of a very high resolution small animal PET imager using silicon scatter detectors

Abstract

A very high resolution positron emission tomography (PET) scanner for small animal imaging based on the idea of inserting a ring of high-granularity solid-state detectors into a conventional PET scanner is under investigation. A particularly interesting configuration of this concept, which takes the form of a degenerate Compton camera, is shown capable of providing sub-millimeter resolution with good sensitivity. We present a Compton PET system and estimate its performance using a proof-of-concept prototype. A prototype single-slice imaging instrument was constructed with two silicon detectors 1 mm thick, each having 512 1.4 mm x 1.4 mm pads arranged in a 32 x 16 array. The silicon detectors were located edgewise on opposite sides and flanked by two non-position sensitive BGO detectors. The scanner performance was measured for its sensitivity, energy, timing, spatial resolution and resolution uniformity. Using the experimental scanner, energy resolution for the silicon detectors is 1%. However, system energy resolution is dominated by the 23% FWHM BGO resolution. Timing resolution for silicon is 82.1 ns FWHM due to time-walk in trigger devices. Using the scattered photons, time resolution between the BGO detectors is 19.4 ns FWHM. Image resolution of 980 microm FWHM at the center of the field-of-view (FOV) is obtained from a 1D profile of a 0.254 mm diameter (18)F line source image reconstructed using the conventional 2D filtered back-projection (FBP). The 0.4 mm gap between two line sources is resolved in the image reconstructed with both FBP and the maximum likelihood expectation maximization (ML-EM) algorithm. The experimental instrument demonstrates sub-millimeter resolution. A prototype having sensitivity high enough for initial small animal images can be used for in vivo studies of small animal models of metabolism, molecular mechanism and the development of new radiotracers.

A new virtual ring-based system matrix generator for iterative image reconstruction in high resolution small volume PET systems

“…To provide sufficient DoI information and increase intrinsic spatial resolution, successive generations of PET scanners have tended to reduce the size of the scintillation crystals-or, in the extreme case, may eliminate the scintillator altogether, instead using direct gamma photon detection in pixellated semiconductor detector arrays (typically fabricated from relatively thick silicon or CZT) (Domenico et al 2007, Habte et al 2007, Park et al 2007, Li et al 2013. This geometry results in a very large number of potential LoRs, especially for 3D scanners with a multi-ring geometry.…”

Physical effects of mechanical design parameters on photon sensitivity and spatial resolution performance of a breast‐dedicated PET system

“…26͒ where one of the two photodetectors is placed right in front of the crystal face. Another example is a high resolution PET imager employing silicon scatter detectors 27 in which an inner detector ring ͑insert͒ is placed within the FoV of a conventional PET ring. We claim that the results presented in this study prove the importance of studying the aforementioned effects in any such system.…”

Design and performance evaluation of a high resolution IRI-microPET preclinical scanner

“…The pulse height spectra were measured by ADC, via an output amplifier. Energy resolutions were calculated as FWHM by fitting the full-energy peaks with Gaussians, in percentage [18,19].…”