Image blurring due to light-sharing in PET block detectors

Area of Science:

• Medical Imaging
• Nuclear Physics
• Detector Technology

Background:

• Positron Emission Tomography (PET) spatial resolution is limited compared to CT or MRI.
• Block detectors in PET scanners contribute to image blurring due to mispositioned photons.
• The "block effect" is a primary cause of reduced spatial resolution in PET imaging.

Purpose of the Study:

• To quantify the "block effect" in two clinical PET scanners (CTI HR+ and GE Advance).
• To investigate the influence of gamma-ray interaction depth on the block effect.
• To identify factors contributing to inaccurate event positioning in PET detectors.

Main Methods:

• Measured the block effect in CTI HR+ and GE Advance PET scanner detectors.
• Studied the impact of varying the depth of first gamma-ray interaction within scintillation crystals.
• Calculated the percentage of inaccurately positioned events for each detector type.

Main Results:

• The block effect was 1.2 +/- 0.5 mm (central) and negligible (edge) in CTI HR+.
• The block effect was 0.9 +/- 0.3 mm (central) and 0.7 +/- 0.3 mm (edge) in GE Advance.
• CTI HR+ showed depth dependence; GE Advance showed consistent positioning regardless of depth. Up to 16% (CTI HR+) and 13% (GE Advance) of events were inaccurately positioned.

Conclusions:

• Depth of interaction significantly impacts the block effect in pseudodiscrete crystal detectors (CTI HR+).
• The block effect is less influenced by interaction depth in discrete crystal detectors with light sharing (GE Advance).
• Understanding interaction depth effects can improve PET detector design and reduce image blurring.