Performance evaluation for 68Ga and 18F of the ARGUS small-animal PET scanner based on the NEMA NU-4 standard

⁶⁸Ga is one of the non-conventional nuclides that are being used in preclinical imaging. One disadvantage of ⁶⁸Ga versus ¹⁸F is its larger positron range, which deteriorates the effective spatial resolution and the overall image quality. In this work we present a performance evaluation of the ARGUS small-animal positron emission tomography (PET) scanner for two positron emitters, ⁶⁸Ga and ¹⁸F. These experiments followed the procedure based on the National Electrical Manufacturers Association (NEMA) NU 4-2008 standard. We show how the use of ⁶⁸Ga may affect the NEMA performance of the system in terms of image quality and spatial resolution. The recovery coefficients (RC) measured in the image-quality phantom ranged from 0.17 to 0.72 for ⁶⁸Ga and from 0.28 to 0.92 for ¹⁸F, using iterative image reconstruction methods and applying all corrections. Under the same conditions the image noise (%STD) in a uniform region was 17.0% for ⁶⁸Ga and 15.1% for ¹⁸F. The respective spillover ratios (SOR) were 0.13 and 0.09 in air, and 0.21 and 0.12 in water. Attenuation correction yielded an improvement of the SOR close to 50% for both radionuclides in the air-filled region. This work evaluates the image reconstruction methods and corrections available in the ARGUS PET for ⁶⁸Ga and ¹⁸F to assess the influence of their physical properties on the NEMA parameters.