Depth-encoding using optical photon TOF in a prism-PET detector with tapered crystals

Area of Science:

• Medical Imaging
• Nuclear Physics
• Neuroscience

Background:

• High-resolution brain positron emission tomography (PET) scanners are crucial for neuroscience research and clinical diagnosis.
• Time-of-flight (TOF) and depth-of-interaction (DOI) information enhance PET imaging performance.
• Optical photon TOF (oTOF) from scintillation photons can provide DOI information, but light leak degrades resolution.

Purpose of the Study:

• To demonstrate the feasibility of oTOF-based depth encoding in Prism-PET detector modules.
• To mitigate light leak in detector modules using tapered crystals.
• To improve energy-based DOI and coincidence timing resolutions.

Main Methods:

• Developed tapered Prism-PET detector modules with lutetium yttrium oxyorthosilicate (LYSO) crystals.
• Tapered crystals reduced dimensions at the crystal-readout interface to minimize light leak.
• Experimentally evaluated performance metrics including energy resolution, DOI, and timing resolution; simulated scanner sensitivities using Geant4.

Main Results:

• Tapered modules achieved improved oTOF-based DOI resolution (5.42 mm vs. 13.87 mm) and energy-based DOI resolution (2.35 mm vs. 3.18 mm) compared to non-tapered.
• Timing resolution improved from 286 ps to 243 ps with tapered crystals.
• Simulated scanner sensitivities showed a slight decrease with tapered crystals (29.5 kcps/MBq vs. 30.9 kcps/MBq).

Conclusions:

• The tapered Prism-PET module enabled the first experimental oTOF-based depth encoding at the detector module level.
• Minimized light leak with tapered crystals improved energy-based DOI and timing resolutions.
• Enabled thinner inter-crystal spacing with barium sulfate reflector.