Reduction of [68Ga]Ga-DOTA-TATE injected activity for digital PET/MR in comparison with analogue PET/CT

• Published in: EJNMMI physics 2024-03, Vol.11 (1), p.27-17, Article 27
• Main Authors: Cox, Christina P. W., Brabander, Tessa, Vegt, Erik, de Lussanet de la Sablonière, Quido G., Graven, Laura H., Verburg, Frederik A., Segbers, Marcel
• Format: Article
• Language: English
• Subjects: Algorithms; Applied and Technical Physics; Block-sequential regularized expectation maximization; BSREM; Computational Mathematics and Numerical Analysis; Computed tomography; Digital imaging; Engineering; Gallium Ga 68 dotatate; Image quality; Image reconstruction; Imaging; Lesions; Magnetic resonance; Medical imaging; Medicine; Medicine & Public Health; Nuclear Medicine; Original Research; PET/MRI; Positron emission; Positron emission tomography; Positron emission tomography computed tomography; Quantitative analysis; Radiology; Reduction; Tomography
• ISSN: 2197-7364; 2197-7364
• DOI: 10.1186/s40658-024-00629-z

Background New digital detectors and block-sequential regularized expectation maximization (BSREM) reconstruction algorithm improve positron emission tomography (PET)/magnetic resonance (MR) image quality. The impact on image quality may differ from analogue PET/computed tomography (CT) protocol. The aim of this study is to determine the potential reduction of injected [ 68 Ga]Ga-DOTA-TATE activity for digital PET/MR with BSREM reconstruction while maintaining at least equal image quality compared to the current analogue PET/CT protocol. Methods NEMA IQ phantom data and 25 patients scheduled for a diagnostic PET/MR were included. According to our current protocol, 1.5 MBq [ 68 Ga]Ga-DOTA-TATE per kilogram (kg) was injected. After 60 min, scans were acquired with 3 (≤ 70 kg) or 4 (> 70 kg) minutes per bedposition. PET/MR scans were reconstructed using BSREM and factors β 150, 300, 450 and 600. List mode data with reduced counts were reconstructed to simulate scans with 17%, 33%, 50% and 67% activity reduction. Image quality was measured quantitatively for PET/CT and PET/MR phantom and patient data. Experienced nuclear medicine physicians performed visual image quality scoring and lesion counting in the PET/MR patient data. Results Phantom analysis resulted in a possible injected activity reduction of 50% with factor β  = 600. Quantitative analysis of patient images revealed a possible injected activity reduction of 67% with factor β  = 600. Both with equal or improved image quality as compared to PET/CT. However, based on visual scoring a maximum activity reduction of 33% with factor β  = 450 was acceptable, which was further limited by lesion detectability analysis to an injected activity reduction of 17% with factor β  = 450. Conclusion A digital [ 68 Ga]Ga-DOTA-TATE PET/MR together with BSREM using factor β  = 450 result in 17% injected activity reduction with quantitative values at least similar to analogue PET/CT, without compromising on PET/MR visual image quality and lesion detectability.