Investigation of acquisition time for harmonization of image quality between PET/CT and PET/MRI systems: A phantom study

Abstract

The positron emission tomography (PET) system has technological differences between PET/computed tomography (CT) and PET/magnetic resonance imaging (MRI). It is important to compare image quality on acquisition time for equal diagnostic performance. Therefore, the aim of study was to investigate acquisition time as a factor for harmonizing the image quality. NEMA image quality phantom experiments were performed using Siemens Biograph PET/CT and PET/MRI. The phantom was filled with 18F-solution at a 10:1 of sphere-to-background ratio and scanned in the list-mode. PET images were reconstructed with increasing time frames of 1 min. To compare image quality and measure difference, the contrast recovery (CR), background variability (BV), and measure root mean square error (RMSE) of BVs were used. PET/CT and PET/MRI showed similar CR for spheres regardless of acquisition time, whereas the BV was higher with PET/MRI than with PET/CT at the same acquisition time. The BV decreased with increasing acquisition time. The difference of BV by RMSE showed small values at an acquisition time delay of 2 min for PET/MRI. The PET images on visual analysis were also comparable at the lowest RMSE values. In conclusion, the image quality between PET/CT and PET/MRI was harmonized at a PET/MRI acquisition time of PET/CT acquisition time plus 2 min