Guide to Plant-PET Imaging Using 11CO2

Abstract

Due to its high sensitivity and specificity for tumor detection, positron emission tomography (PET) has become a standard and widely used molecular imaging technique. Given the popularity of PET, both clinically and preclinically, its use has been extended to study plants. However, only a limited number of research groups worldwide report PET-based studies, while we believe that this technique has much more potential and could contribute extensively to plant science. The limited application of PET may be related to the complexity of putting together methodological developments from multiple disciplines, such as radio-pharmacology, physics, mathematics and engineering, which may form an obstacle for some research groups. By means of this manuscript, we want to encourage researchers to study plants using PET. The main goal is to provide a clear description on how to design and execute PET scans, process the resulting data and fully explore its potential by quantification via compartmental modeling. The different steps that need to be taken will be discussed as well as the related challenges. Hereby, the main focus will be on, although not limited to, tracing 11CO2 to study plant carbon dynamics.

Design Study of a Novel Positron Emission Tomography System for Plant Imaging

“…As recently noticed, Plant Positron Emission Tomography is an emerging field of research, which requires a strong cross-disciplinary interplay between physics, engineering, mathematics, biology, and agronomy (Mincke et al, 2021 ). A first result of this study is to determine the method of communication between these disciplines during the design and optimization of a plant PET system, on the basis of a standard assessment strategy.…”

“…Although in current plant investigations imaging techniques are commonly used for functional analysis, like fluorescence microscopy (Toyota et al, 2018 ) and Nuclear Magnetic Resonance (Kuchenbrod et al, 1998 ), they carry important drawbacks in terms of sample disruption during long term observations (Dixit and Cyr, 2003 ) and poor sensitivity (Chatham and Blackband, 2001 ). Positron Emission Tomography (PET) proposes a solution to the problem, being a high-sensitive digital imaging technique able to provide a non-invasive 3D visualization of the dynamic flow of nutrients and water within plants (Galieni et al, 2021 ), that is essential in early stress assessment (Keutgen et al, 2005 ; Converse et al, 2013 ; Schmidt et al, 2020 ; Mincke et al, 2021 ). Thanks to the easy availability of molecular probes, it has been used to assess changes in the functional mechanisms of plants under different conditions.…”

Kinetically Consistent Data Assimilation for Plant PET Sparse Time Activity Curve Signals

“…The extraction of quantitative plant transport parameters from the sparse time activity curve (TAC) signals measured with positron emission tomography (PET) techniques represents one of the frontiers of plant digital imaging (Hubeau and Steppe, 2015;Galieni et al, 2021;Mincke et al, 2021a;Antonecchia et al, 2022), with a strong impact in early stress assessment (Tsukamoto et al, 2008;Yoshihara et al, 2014;Partelová et al, 2017), yield improvement (Yamazaki et al, 2015;Hubeau et al, 2019b;Mincke et al, 2020a), sustainable agriculture (Karve et al, 2015;Kuritaa et al, 2020) and climate change studies (Hubeau et al, 2019a).…”

“…Therefore, voxels are grouped in larger regions of interest (ROI). For instance, a typical ROI structure along the stem of a plant is illustrated in Figure 1E (Mincke et al, 2021a). ROIs with a minimal thickness of one voxel are displaced adjacent to each other.…”

“…To mitigate this intrinsic limitation of TAC signals, datadriven model-free techniques consider only physical parameters with already known validity ranges (Keutgen et al, 2002(Keutgen et al, , 2005Minchin and Thorpe, 2003;Matsuhashi et al, 2010;Ferrieri et al, 2012) and compartmental modeling estimates only quantities averaged in space and time (Bühler et al, 2011;Hubeau et al, 2018;Mincke et al, 2021a). These approaches cannot be extended to a complete estimation of the FD processes occurring inside the plant vascular system, which remain largely unexplored (Jensen et al, 2012).…”