Performance of the Iterative OSEM and HYPER Algorithm for Total-body PET at SUVmax with a Low 18F-FDG Activity, a Short Acquisition Time and Small Lesions

Objective:The primary objective of this comparative investigation was to examine the qualitative attributes of image reconstructions utilizing two distinctalgorithms, namely OSEM and HYPER Iterative, in total-body 18F- FDG PET/CT under various acquisition durations and injection activities. Methods:An initial assessment was executed using a NEMA phantom to compare image quality engendered by OSEM and HYPER Iterative algorithms.Parameters such as BV, COV, and CRC were meticulously evaluated. Subsequently, a prospective cohort study was conducted on 50 patients,employing both reconstruction algorithms. The study was compartmentalized into distinct acquisition time and dosage groups. Lesions werefurther categorized into three size-based groups. Quantifiable metrics including SD of noise, SUVmax, SNR, and TBR were computed. Additionally,the differences in values, namely Delta SUVmax, Delta TBR, %Delta SUVmax, %Delta SD, and %Delta SNR, between OSEM and HYPER Iterative algorithms were alsocalculated. Results:The HYPER Iterative algorithm showed reduced BV and COV compared to OSEM in the phantom study, with constant acquisition time. In theclinical study, lesion SUVmax, TBR, and SNR were significantly elevated in images reconstructed using the HYPER Iterative algorithm incomparison to those generated by OSEM (p < 0.001). Furthermore, an amplified increase in SUVmax was predominantly discernible in lesions withdimensions less than 10 mm. Metrics such as %Delta SNR and %Delta SD in HYPER Iterative exhibited improvements correlating with reducedacquisition times and dosages, wherein a more pronounced degree of enhancement was observable in both Delta SUVmax and Delta TBR. Conclusion:The HYPER Iterative algorithm significantly improves SUVmax and reduces noise level, with particular efficacy in lesions measuring <= 10 mm andunder conditions of abbreviated acquisition times and lower dosages.