Clinical performance of long axial field of view PET/CT: a head-to-head intra-individual comparison of the Biograph Vision Quadra with the Biograph Vision PET/CT

Abstract

Purpose: To investigate the performance of the new long axial field-of-view (LAFOV) Biograph Vision Quadra PET/CT and a standard axial field-of-view (SAFOV) Biograph Vision 600 PET/CT (both: Siemens Healthineers) system using an intra-patient comparison.

Methods: Forty-four patients undergoing routine oncological PET/CT were prospectively included and underwent a same-day dual-scanning protocol following a single administration of either ¹⁸F-FDG (n = 20), ¹⁸F-PSMA-1007 (n = 16) or ⁶⁸Ga-DOTA-TOC (n = 8). Half the patients first received a clinically routine examination on the SAFOV (FOV_axial 26.3 cm) in continuous bed motion and then immediately afterwards on the LAFOV system (10-min acquisition in list mode, FOV_axial 106 cm); the second half underwent scanning in the reverse order. Comparisons between the LAFOV at different emulated scan times (by rebinning list mode data) and the SAFOV were made for target lesion integral activity, signal to noise (SNR), target lesion to background ratio (TBR) and visual image quality.

Results: Equivalent target lesion integral activity to the SAFOV acquisitions (16-min duration for a 106 cm FOV) were obtained on the LAFOV in 1.63 ± 0.19 min (mean ± standard error). Equivalent SNR was obtained by 1.82 ± 1.00 min LAFOV acquisitions. No statistically significant differences (p > 0.05) in TBR were observed even for 0.5 min LAFOV examinations. Subjective image quality rated by two physicians confirmed the 10 min LAFOV to be of the highest quality, with equivalence between the LAFOV and the SAFOV at 1.8 ± 0.85 min. By analogy, if the LAFOV scans were maintained at 10 min, proportional reductions in applied radiopharmaceutical could obtain equivalent lesion integral activity for activities under 40 MBq and equivalent doses for the PET component of <1 mSv.

Conclusion: Improved image quality, lesion quantification and SNR resulting from higher sensitivity were demonstrated for an LAFOV system in a head-to-head comparison under clinical conditions. The LAFOV system could deliver images of comparable quality and lesion quantification in under 2 min, compared to routine SAFOV acquisition (16 min for equivalent FOV coverage). Alternatively, the LAFOV system could allow for low-dose examination protocols. Shorter LAFOV acquisitions (0.5 min), while of lower visual quality and SNR, were of adequate quality with respect to target lesion identification, suggesting that ultra-fast or low-dose acquisitions can be acceptable in selected settings.

Keywords: Digital PET; PET/CT; Positron-emission-tomography; Total-body; Ultra-long FOV PET; Whole-body.

Fig. 1

Study flowchart showing patient recruitment, total patients included and excluded

Fig. 2

Scan times (min) for the LAFOV delivering equivalent lesion integral activity to the SAFOV standard examination (16.06 min). In the inset tile, a zoomed graph showing only LAFOV data is available to aid comparison. Error bars show the standard error

Fig. 3

Violin plots showing lesion integral activity (all radiotracers) for the SAFOV (blue) and for various scan times (0.5 to 10 min) on the LAFOV (red). The measured integral activity on the SAFOV scanner was equivalent to between 1- and 2-min scans obtained on the LAFOV. The violin plots represent data density and distribution

Fig. 4

Boxplots showing signal-to-noise ratio (SNR) for the liver background, which is the reciprocal of the coefficient of variation. The measured SNR for SAFOV scanner (blue) was equivalent to between 1- and 2-min scans obtained on the LAFOV (red)

Fig. 5

Tumour-to-background ratios (TBR) for the SAFOV (left, blue) and LAFOV (right, red). No statistically significant differences were observed between the SAFOV and LAFOV acquisitions, even at short (0.5 min) scan times

Fig. 6

Example maximum intensity projection (MIP, top row) and axial PET images (bottom row) images for a 57-year-old female with non-small cell lung cancer, presented are images for the regular SAFOV acquisitions on the left (blue margin) and the LAFOV for 10-, 4-, 2-, 1- and 0.5-min acquisitions (right, red margin). For reference, the PET window is set to 0 to 8.5 SUV