## 8 Conclusions  
A computational model of the Siemens ECAT \"EXACT3D\" HR++ PET scanner was constructed in GATE to explore the ability of PEPT measurements at PEPT Cape Town to track flow behaviour in multiphase applications such as mineral froth flotation. The model was validated for PEPT research by measuring the coincidence rate over a range of activity radiolabelled on the tracer particle and by comparing tracer locations calculated from the GATE simulation to values acquired from experiments with stationary and two moving sources at varying speeds.  
The model was then used to explore two extended scenarios that were used to investigate the tracking of turbulent fluctuations. Using simulations of a path with non-sinuoidal oscillation in 1D, the location data from PEPT measurements at a typical location rate of 1 kHz were able to track high-speed, linear motion but unable to track the turning points in the motion. Following a tracer on a simulated spiral path, the uncertainty in the location increased as the size of the spiral decreased. Above a radius of 2.0 mm, the PEPT measurement tracked the path of the spiral to an uncertainty less than the size of the tracer particle, \(\approx\)300 \(\upmu\)m, and below a 2.0 mm radius of the spiral. The location uncertainty increased beyond this threshold due to the high acceleration along the helical path.  
In conclusion, for the benefit of the host facility for this research, PEPT Cape Town at the University of Cape Town, the validated GATE model presented can be used to explore more complicated flow situations, providing realistic data to aid in experimental design, and to better understand the limitations of the HR++ detector. Future applications for the HR++ model that are currently underway include: optimising measurement parameters at iThemba LABS by being able to initially run an experiment virtually; advancing tracer development by looking at an extensive range of materials, shapes, and sizes to determine the best combination for a given situation, even possibly providing custom tracers; and extending the work to include investigations into dynamic sampling with field-of-view attenuation to improve the tracking of turbulent, multiphase flows.  
Conceptualization, R.P., K.C., S.W.P, J.S. and P.R.B.-P.; methodology, R.P., K.C., J.S. and S.W.P.; software, R.P., S.W.P. and K.C.; validation, K.C., S.W.P, J.S. and P.R.B.-P.; formal analysis, R.P.; investigation, R.P., K.C., M.R.v.H., Y.-Y.L. and J.Z.; resources, K.C., S.W.P, A.B., M.R.v.H. and P.R.B.-P.; data curation, A.B., K.C., S.W.P., P.R.B.-P. and M.R.v.H.; writing--original draft preparation, R.P., K.C. and S.W.P.; writing--review and editing, R.P., K.C., S.W.P., J.S., P.R.B.-P., A.B., Y.-Y.L., J.Z. and M.R.v.H.; visualization, R.P.; supervision, K.C., S.W.P. and J.S.; project administration, S.W.P. and K.C.; funding acquisition, K.C., R.P., S.W.P. and P.R.B.-P. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the University Research Council at the University of Cape Town (1551680) and the National Research Foundation (NRF) through their DSI-NRF First Time Doctoral Scholarships (PMDS22060920524).  
The data and simulations presented in this study are available on request from the corresponding author.  
The authors declare no conflict of interest.