Impact of scan duration and scatter correction on quantitative accuracy in Yttrium-90 PET/CT imaging using LAFOV and...

This study compared quantitative accuracy and image quality of post-radioembolization selective internal radiation therapy (SIRT) ⁹⁰Y PET/CT using a long axial field-of-view (LAFOV) and standard axial field-of-view (SAFOV) system, focusing on absolute (ABS) versus relative (RS) scatter correction. Additionally, variance modeling and logistic regression were performed to define injected-activity thresholds ensuring reliable quantification at different acquisition durations.

Phantom experiments were conducted on Biograph Vision Quadra (LAFOV) and Vision 600 (SAFOV) PET/CT scanners using NEMA IQ phantoms filled with ⁹⁰Y activity. Reconstructions employed OSEM + TOF + PSF with ABS and RS scatter correction at 50 min (both scanners) and 10- and 1-minute (only for LAFOV). Metrics included NEMA recovery coefficients (RC) and background variability (BV). 44 post-SIRT patients (median age 70 y) were analyzed for image-based quantification of injected activity using whole-liver VOIs, across multiple durations (20, 15, 10, 5, 1 min). Metrics included Bland-Altman analysis, equivalence testing (± 10%), and Lin's concordance correlation coefficient (CCC). Variance-activity relationships and logistic regression quantified thresholds for 80%, 90% and 95% success probability.

LAFOV achieved higher RCs and ~ 3× lower BV than SAFOV. ABS yielded significantly improved accuracy and stability versus RS, particularly at short scans. Patient data acquired on the LAFOV system showed ABS quantification equivalent to injected activity within ± 10% for ≥ 5 min (CCC ≥ 0.99), whereas RS required ≥ 10 min. Variance followed a power-law decay (γ ≈ 1.5 at 5 min), and logistic regression identified an activity threshold of ~ 1.6 GBq for 90% accuracy at 5 min. At ≥ 10 min, quantification became independent of activity.

Compared with a SAFOV 50-minute clinical routine acquisition, LAFOV PET enabled a similar BV performance at 7-times accelerated scanning duration. LAFOV PET/CT with absolute scatter correction enables accurate ⁹⁰Y quantification and dosimetry with acquisition times as short as 10 min regardless of the administered ⁹⁰Y activity, supporting efficient clinical post-SIRT imaging workflows.