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Updated: May 24, 2026
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Whole-body PET/MRI of Pediatric Patients: The Details That Matter
Published on: December 19, 2017
Magnetic field effects on positron range and image quality in PET/MR
Mario Alberto González-Ramírez1, Héctor Alva-Sánchez1
1Instituto de Física, Universidad Nacional Autónoma de México, A. P. 20-364, 01000 Mexico City, Mexico.
Biomedical Physics & Engineering Express
|May 22, 2026
Summary
Strong magnetic fields in PET/MR imaging reduce positron range effects, improving image quality and quantification. Ultra-high fields (9 T) significantly mitigate positron range dependence on tissue density.
Area of Science:
- Medical Physics
- Nuclear Medicine
- Imaging Science
Background:
- Positron emission tomography/magnetic resonance (PET/MR) combines functional and anatomical imaging.
- Strong magnetic fields in PET/MR may influence positron transport and image quality.
- Understanding these effects is crucial for optimizing PET/MR performance.
Purpose of the Study:
- To investigate the impact of strong magnetic fields (0-9 T) on positron transport from 18F and 68Ga.
- To evaluate how magnetic fields affect image quality metrics in PET/MR imaging.
- To assess the influence of positron range and tissue density on quantitative accuracy.
Main Methods:
- Monte Carlo simulations using PENELOPE 2018.
- Tracking positrons in uniform magnetic fields (0, 3, 9 T).
- Simulations in tissue-equivalent phantoms and NEMA-like image quality phantoms.
Main Results:
- Positron range significantly impacts recovery coefficients and spill-over ratios, especially for 68Ga in lung.
- Magnetic fields reduce positron range effects perpendicular to field lines, enhancing spatial resolution and accuracy.
- At 9 T, the dependence of positron range on tissue density is substantially reduced.
Conclusions:
- Positron range establishes fundamental limits on PET/MR image quality in magnetic fields.
- Magnetic fields offer potential benefits for spatial resolution and quantitative accuracy in PET/MR.
- Findings support the development of positron-range correction methods and highlight ultra-high-field PET/MR potential.
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