Setup and characterisation according to NEMA NU 4 of the phenoPET scanner, a PET system dedicated for plant sciences

Abstract

Objective. The phenoPET system is a plant dedicated positron emission tomography (PET) scanner consisting of fully digital photo multipliers with lutetium–yttrium oxyorthosilicate crystals and located inside a custom climate chamber. Here, we present the setup of phenoPET, its data processing and image reconstruction together with its performance. Approach. The performance characterization follows the national electrical manufacturers association (NEMA) standard for small animal PET systems with a number of adoptions due to the vertical oriented bore of a PET for plant sciences. In addition temperature stability and spatial resolution with a hot rod phantom are addressed. Main results. The spatial resolution for a 22Na point source at a radial distance of 5 mm to the center of the field-of-view (FOV) is 1.45 mm, 0.82 mm and 1.88 mm with filtered back projection in radial, tangential and axial direction, respectively. A hot rod phantom with 18F gives a spatial resolution of up to 1.6 mm. The peak noise-equivalent count rates are 550 kcps @ 35.08 MBq, 308 kcps @ 33 MBq and 45 kcps @ 40.60 MBq for the mouse, rat and monkey size scatter phantoms, respectively. The scatter fractions for these phantoms are 12.63%, 22.64% and 55.90%. We observe a peak sensitivity of up to 3.6% and a total sensitivity of up to S A,tot = 2.17%. For the NEMA image quality phantom we observe a uniformity of %STD = 4.22% with ordinary Poisson maximum likelihood expectation-maximization with 52 iterations. Here, recovery coefficients of 0.12, 0.64, 0.89, 0.93 and 0.91 for 1 mm, 2 mm, 3 mm, 4 mm and 5 mm rods are obtained and spill-over ratios of 0.08 and 0.14 for the water-filled and air-filled inserts, respectively. Significance. The phenoPET and its laboratory are now in routine operation for the administration of [11C]CO2 and non-invasive measurement of transport and allocation of 11C-labelled photoassimilates in plants.