Ultra-dense lutetium oxide ceramic scintillators for positron emission tomography

Area of Science:

• Materials Science
• Nuclear Instrumentation
• Medical Imaging

Background:

• Lutetium oxide (Lu₂O₃) possesses high density, ideal for detecting 511 keV photons in positron emission tomography (PET).
• Challenges in crystal growth and slow decay times have limited Lu₂O₃'s PET applications.
• Advancements in ceramic processing and doping have enabled transparent Lu₂O₃ ceramics with improved luminescence.

Purpose of the Study:

• To evaluate the performance of Lu₂O₃:Yb and a novel (Lu,Y)₂O₃:La ceramic scintillator.
• To assess their suitability for positron emission tomography (PET) applications, particularly time-of-flight (TOF) PET.

Main Methods:

• Fabrication of ceramic disks and cutting into 3 × 3 × 5 mm³ samples.
• Assessment of decay time, energy resolution, and coincidence timing resolution (CTR) using photomultiplier tubes (PMT) and silicon photomultipliers (SiPM).
• Irradiation with 511 keV photons from a ²²Na source and coincidence measurements against a reference LYSO detector.

Main Results:

• (Lu,Y)₂O₃:La samples showed a triple exponential decay, dominated by a slow component (1379.3–1515.6 ns), with the best energy resolution (15.4%) and CTR (237.9 ps FWHM).
• Lu₂O₃:Yb samples exhibited a fast decay (1.6 ns) and CTR values from 237.9 ps to 261.4 ps FWHM, but with difficult-to-distinguish photopeaks.
• Despite slower decay, (Lu,Y)₂O₃:La achieved comparable CTR to Lu₂O₃:Yb due to higher light yield, offsetting the decay time disadvantage.

Conclusions:

• The (Lu,Y)₂O₃:La ceramic scintillators demonstrate significant potential for PET imaging.
• These materials are particularly promising for advancing time-of-flight (TOF) PET technology.