CHERENCUBE: concept definition and implementation challenges of a Cherenkov-based detector block for PET

Area of Science:

• Nuclear Instrumentation
• Medical Imaging Physics
• Detector Technology

Background:

• Time-of-flight Positron Emission Tomography (TOF-PET) systems benefit from depth-of-interaction (DOI) measurements for improved spatial resolution and image reconstruction.
• Current TOF-PET detectors often rely on scintillation light, which can limit DOI resolution and introduce timing uncertainties.

Purpose of the Study:

• To introduce and analyze the feasibility of the CHERENCUBE concept, a novel TOF-PET detector utilizing only Cherenkov photons for DOI capability.
• To theoretically and computationally evaluate the potential advantages of a Cherenkov-only detector for TOF-PET with DOI.
• To present an algorithm for DOI estimation and define requirements for practical implementation.

Main Methods:

• Monte Carlo simulations were performed using a cubic Cherenkov radiator (PbWO4) with position-sensitive photodetectors on each face.
• Simulations analyzed Cherenkov photons from 511 keV gamma-ray interactions across various crystal sizes (1x1x1 mm³ to 10x10x10 mm³).
• DOI determination was based on the spatial and temporal distribution of detected Cherenkov photons.

Main Results:

• Detection efficiency increased with crystal size, reaching 58.6% for a 10x10x10 mm³ cube, though thresholds reduced this.
• The detector demonstrated a DOI reconstruction accuracy of approximately 23% of the cube length (average 2.2 mm for 10x10x10 mm³).
• Photon detection timing windows were 30 ps (1x1x1 mm³) and 150 ps (10x10x10 mm³), indicating good time resolution for DOI.

Conclusions:

• The CHERENCUBE concept shows potential for DOI-capable TOF-PET using only Cherenkov photons, requiring high photodetection efficiency and precise timing.
• 3D DOI recognition relies on accurate time stamps and detection coordinates, not projected photon patterns.
• The material's refractive index can intrinsically reject scattered PET events, albeit with reduced sensitivity.