Experimental determination of PET modulation transfer functions incorporating positron range effects using an...

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Physics

Background:

• Spatial resolution is key for Positron Emission Tomography (PET) performance.
• Standardized air-based measurements do not account for positron transport in tissue.
• Improving PET systems necessitate considering positron range effects for accurate resolution assessment.

Purpose of the Study:

• Develop and validate an experimental method for PET spatial resolution.
• Incorporate positron-range effects directly into measurements.
• Avoid reliance on Monte Carlo simulations or parametric modeling.

Main Methods:

• Utilized a modular PMMA phantom with a thin linear source (18F or 68Ga) for full positron absorption.
• Implemented an oversampling strategy by inclining the source.
• Derived sub-pixel sampled point spread function (PSF) and modulation transfer function (MTF) via Fourier transformation.

Main Results:

• The oversampling strategy achieved low statistical uncertainty in PSF and MTF.
• Negligible radionuclide differences were found in an older PET/CT system.
• Modern PET/CT systems showed measurable differences, with 68Ga exhibiting broader PSF and lower MTF than 18F.

Conclusions:

• The proposed methodology offers an efficient experimental framework for PET spatial resolution characterization.
• Enables quantitative assessment of positron-range effects under realistic conditions.
• Complements standard measurements, especially for high-resolution PET systems.