Performance of detector modules designed for the NeuroSphere brain PET system

Area of Science:

• Medical Imaging
• Neuroscience
• Physics

Background:

• The Human Dynamic NeuroChemical Connectome (HDNCC) scanner combines a 7-T MRI with a dedicated brain PET insert (NeuroSphere PET).
• This integration allows simultaneous studies of neurochemical dynamics and functional MRI on comparable timescales.
• It aims for high spatio-temporal resolution in neurochemical imaging.

Purpose of the Study:

• To develop a novel PET module for high-resolution PET/MR applications.
• The module aims for unprecedented sensitivity using spherical geometry and novel detectors.
• Key requirements include time-of-flight (TOF) and depth-of-interaction (DOI) encoding without compromising performance.

Main Methods:

• A 10x10 array of LSO crystals (1.6-mm pitch) coupled to a 4x4 SiPM array was used.
• DOI encoding was achieved via light sharing with a top light guide.
• Time-to-digital converter (TDC) performance, nonlinearity correction, and DOI-based energy/timing corrections were evaluated.

Main Results:

• The TDC achieved 55-ps coincidence timing resolution (CTR) after nonlinearity correction.
• DOI resolution was 7.45 ± 2.02 mm FWHM.
• DOI-based correction improved energy resolution to 11.0% ± 1.8% FWHM and CTR to ~510 ps FWHM.

Conclusions:

• The NeuroSphere PET module demonstrates competitive energy resolution, DOI encoding, and TOF PET performance for brain imaging.
• A CTR of ~500 ps offers a signal-to-noise ratio (SNR) gain for neuroimaging.
• DOI-based corrections effectively improved energy resolution and CTR using a scalable calibration procedure.