Sub-millimetre DOI detector based on monolithic LYSO and digital SiPM for a dedicated small-animal PET system

Abstract

The mouse model is widely used in a vast range of biomedical and preclinical studies. Thanks to the ability to detect and quantify biological processes at the molecular level in vivo, PET has become a well-established tool in these investigations. However, the need to visualize and quantify radiopharmaceuticals in anatomic structures of millimetre or less requires good spatial resolution and sensitivity from small-animal PET imaging systems.In previous work we have presented a proof-of-concept of a dedicated high-resolution small-animal PET scanner based on thin monolithic scintillator crystals and Digital Photon Counter photosensor. The combination of thin monolithic crystals and MLE positioning algorithm resulted in an excellent spatial resolution of 0.7 mm uniform in the entire field of view (FOV). However, the limitation of the scanner was its low sensitivity due to small thickness of the lutetium-yttrium oxyorthosilicate (LYSO) crystals (2 mm).Here we present an improved detector design for a small-animal PET system that simultaneously achieves higher sensitivity and sustains a sub-millimetre spatial resolution. The proposed detector consists of a 5 mm thick monolithic LYSO crystal optically coupled to a Digital Photon Counter. Mean nearest neighbour (MNN) positioning combined with depth of interaction (DOI) decoding was employed to achieve sub-millimetre spatial resolution. To evaluate detector performance the intrinsic spatial resolution, energy resolution and coincidence resolving time (CRT) were measured. The average intrinsic spatial resolution of the detector was 0.60 mm full-width-at-half-maximum (FWHM). A DOI resolution of 1.66 mm was achieved. The energy resolution was 23% FWHM at 511 keV and CRT of 529 ps were measured. The improved detector design overcomes the sensitivity limitation of the previous design by increasing the nominal sensitivity of the detector block and retains an excellent intrinsic spatial resolution.

Computationally Efficient Hybrid Interpolation and Baseline Restoration of the Brain-PET Pulses

“…Each sensor is composed of a scintillator crystal matrix. The LYSO scintillators are used in this study [6,7]. The γ-rays interact with these crystals and turn their energies into photons of light.…”

“…These are released at about 180°relative angles at the same time. Crystal scintillators absorb energy from emitted γ-rays [6,7]. They are turning the energy into photons of light.…”

Characterization and Simulation of an Adaptable Fan-Beam Collimator for Fast Calibration of Radiation Detectors for PET

“…An alternative approach is dedicated setups shaping a gamma beam usually consisting of a material with high atomic mass (e.g., tungsten or lead). First, parallel hole collimators with precise drilling of known diameter ranging from 0.5 mm to 1.0 mm were employed for PET detector calibration [9], [24], [25], [27], [31]. The thickness of the shielding material and shape of the parallel hole determine the beam profile.…”

A depth encoding PET detector using four‐crystals‐to‐one‐SiPM coupling and light‐sharing window method

“…Moreover, their DOI capabilities are limited by the number of layers. Another method is to use the quasi-monolithic crystals [26][27][28][29] or the monolithic crystals [30][31][32][33] to construct the DOI detectors. That method is very attractive and promising because of the advantages in filling factor, cost, and the potential performance.…”