Wavelength discrimination (WLD) TOF-PET detector with DOI information

Area of Science:

• Medical Imaging
• Nuclear Physics
• Detector Technology

Background:

• Depth-of-interaction (DOI) encoding improves spatial resolution uniformity and sensitivity in positron-emission-tomography (PET) scanners.
• Time-of-flight (TOF) PET scanners with DOI encoding offer enhanced spatial resolution, sensitivity, and overall image quality.
• Existing DOI detector configurations often require complex signal processing.

Purpose of the Study:

• To propose and evaluate a new DOI detector configuration for PET scanners.
• To utilize scintillator emission wavelengths and optical filters for DOI information acquisition.
• To assess the energy, timing, and DOI performance of the proposed detector.

Main Methods:

• Developed a two-layered phoswich-type detector using Ce:GAGG (top) and LYSO:Ce (bottom) scintillators with different emission spectra.
• Employed optical filters (short pass filter - SPF, or long pass filter - LPF) to differentiate light photons based on wavelength.
• Used a digital silicon photomultiplier (dSiPM) for photosensing and data acquisition, with one dSiPM pixel covered by an optical filter.

Main Results:

• With SPF: Energy resolutions of 16.2% (Ce:GAGG) and 11.8% (LYSO:Ce); Coincidence-Resolving Times (CRTs) of 338 ps (top) and 244 ps (bottom); DOI-separation Figure-of-Merit (FoM) of 1.9.
• With LPF: Energy resolutions of 12.0% (Ce:GAGG) and 12.9% (LYSO:Ce); CRTs of 314 ps (top) and 263 ps (bottom); DOI-separation FoM of 1.5.
• The proposed method achieved excellent discrete DOI positioning accuracy.

Conclusions:

• The novel DOI detector configuration effectively acquires DOI information at the detector level using simple optical filtering.
• The detector demonstrates high DOI positioning accuracy without compromising timing performance.
• This approach offers a promising advancement for improving PET scanner performance and image quality.