Experimental studies of the effect of the magnetic field in PET/MR on positron range

Positron range is a factor that influences image quality of positron emission tomography (PET) studies. In this work, the effect of the magnetic field of a PET/MR Siemens Biograph mMR 3T on the quality of PET images was studied. Experimental measurements were carried out using
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F and
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Ga-filled phantoms to quantify image uniformity, recovery coefficients (RC), and spill-over ratios (SOR). In addition, tissue-equivalent phantoms that mimic lung (inhale and exhale), adipose, water, bone tissue (trabecular and cortical), were used together with a thin line-source to experimentally quantify the impact of the magnetic field on the reconstructed PET images. To evaluate the influence of the magnetic field, a comparison was made with images acquired with a Siemens Biograph Vision 600 PET/CT system, using the same radionuclides and phantoms. The results show an evident improvement in image quality, particularly in phantoms filled with
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Ga when using a PET/MR system compared to those acquired in PET/CT due to the presence of the magnetic field.