Shortened duration whole body 18 F-FDG PET Patlak imaging on the Biograph Vision Quadra PET/CT using a population-averaged input function.

Background: Excellent performance characteristics of the Vision Quadra PET/CT, e.g. a substantial increase in sensitivity, allow for precise measurements of image-derived input functions (IDIF) and tissue time activity curves. Previously we have proposed a method for a reduced 30 min (as opposed to 60 min) whole body ¹⁸ F-FDG Patlak PET imaging procedure using a previously published population-averaged input function (PIF) scaled to IDIF values at 30-60 min post-injection (p.i.). The aim of the present study was to apply this method using the Vision Quadra PET/CT, including the use of a PIF to allow for shortened scan durations.
Methods: Twelve patients with suspected lung malignancy were included and received a weight-based injection of ¹⁸ F-FDG. Patients underwent a 65-min dynamic PET acquisition which were reconstructed using European Association of Nuclear Medicine Research Ltd. (EARL) standards 2 reconstruction settings. A volume of interest (VOI) was placed in the ascending aorta (AA) to obtain the IDIF. An external PIF was scaled to IDIF values at 30-60, 40-60, and 50-60 min p.i., respectively, and parametric ¹⁸ F-FDG influx rate constant (K _i ) images were generated using a t* of 30, 40 or 50 min, respectively. Herein, tumour lesions as well as healthy tissues, i.e. liver, muscle tissue, spleen and grey matter, were segmented.
Results: Good agreement between the IDIF and corresponding PIF scaled to 30-60 min p.i. and 40-60 min p.i. was obtained with 7.38% deviation in K _i . Bland-Altman plots showed excellent agreement in K _i obtained using the PIF scaled to the IDIF at 30-60 min p.i. and at 40-60 min p.i. as all data points were within the limits of agreement (LOA) (- 0.004-0.002, bias: - 0.001); for the 50-60 min p.i. K _i , all except one data point fell in between the LOA (- 0.021-0.012, bias: - 0.005).
Conclusions: Parametric whole body ¹⁸ F-FDG Patlak K _i images can be generated non-invasively on a Vision Quadra PET/CT system. In addition, using a scaled PIF allows for a substantial (factor 2 to 3) reduction in scan time without substantial loss of accuracy (7.38% bias) and precision (image quality and noise interference).
(© 2022. The Author(s).)