A mouse brain PET prototype with a staggered 3-layer DOI detector

Objectives: Development of a mouse brain PET prototype with a staggered 3-layer DOI detector using a 1 mm crystal pitch for realizing a 0.7 mm resolution.

Methods: The proposed mouse brain PET had a 53 mm inner diameter and 11 mm axial FOV. The PET scanner consisted of 16 DOI detectors each of which had a 3-layer staggered 3-layer LYSO crystal array. The LYSO crystal array had the pixel pitch of 1 mm and total thickness of 15 mm. The LYSO crystal array was optically coupled to a 4×4 SiPM (Hamamatsu, S14161-3050HS-04, Japan) array with a pixel pitch of 3.2 mm. The SiPM anode signals were multiplexed using a resistive network and then digitized by the Hamamatsu DAQ with an integration time of 250 ns. The performance of the PET scanner was evaluated by using a ²²Na point source (D=0.25 mm) and a resolution phantom. In vivo mouse brain and bone imaging studies were performed for 60 min with the FDG and ⁸⁹Zr-oxalate radiopharmaceuticals, respectively. Results: The measured spatial resolutions at the center and 15 mm radial offset were 0.67 mm, and 1.56 mm for filtered-back-projection (FBP), and 0.50 mm, and 1.16 mm for ordered-subset-expectation-maximization (OSEM), respectively. The peak absolute sensitivity was 0.76% with an energy window of 400-600 keV. The 0.8 mm rods were resolved clearly in the phantom study. The mouse brain structures such as cortex and thalamus were identified clearly with the FDG PET scan. The mouse skull structure can be delineated clearly with the ⁸⁹Zr PET scan. Conclusions: In conclusion, we developed a high-resolution and high-sensitivity mouse brain PET prototype with 3-layer DOI detectors. We plan to extend the axial FOV up to 50 mm to increase the sensitivity significantly.

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