Effects of Detector Thickness on Geometric Sensitivity and Event Positioning Errors in the Rectangular PET/X Scanner

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Positron Emission Tomography (PET)

Background:

• Quantitative assessment of breast cancers using PET requires optimizing scanner sensitivity and spatial resolution.
• Crystal thickness is a key parameter influencing PET scanner performance.

Purpose of the Study:

• To investigate the impact of crystal thickness on sensitivity and spatial resolution in a rectangular PET scanner designed for breast cancer imaging.
• To evaluate the role of Depth-of-Interaction (DOI) resolution in PET performance.

Main Methods:

• Simulations were used to model a PET scanner with varying crystal thicknesses and detector configurations.
• Spatial resolution was assessed using a surrogate metric (d_FWHM) derived from list-mode data.
• The effect of DOI information on spatial resolution was analyzed for different crystal thicknesses.

Main Results:

• Increasing crystal thickness from 5 to 40 mm increased d_FWHM from 0.72 to 1.6 mm without DOI.
• DOI information improved d_FWHM by 12-44%, with greater improvement for thicker crystals.
• Increasing thickness on smaller detectors enhanced sensitivity by 24% with only a minor degradation in resolution.

Conclusions:

• Optimizing crystal thickness on specific detectors can significantly increase PET scanner sensitivity for breast cancer imaging.
• Depth-of-Interaction (DOI) measurement is crucial for improving spatial resolution, particularly with thicker crystals.
• The trade-offs between sensitivity and resolution must be considered for clinical tasks like assessing small lesion tracer uptake.