Non-Intrusive Visualization of Optically Inaccessible Flow Fields Utilizing Positron Emission Tomography

Abstract

A technology gap persists in the visualization of optically inaccessible flow fields such as those in integrated systems. Advances in positron emission tomography (PET) technology are enabling its use in the engineering field to address this technology gap. This paper discusses a numerical study performed to characterize a modern PET system’s ability to reconstruct a three-dimensional mapping of the optically inaccessible flow field downstream of an orifice. A method was devised to simulate a ring detector response to a flourine-18 radioisotope/water solution injected into the flow through a standard thickness pipe with orifice. A commercial computational fluid dynamics code and the GEANT4 Applications for the Tomographic Emission Monte Carlo simulation physics package were used to carry out the simulations. Results indicate that geometrical features, such as the pipe internal diameter, can be resolved to within a few millimeters with specific activity levels of 155 Bq/Voxel (91.2 Bq/mm3), and acquisition times as low as 15 s. Results also suggest that flow features, such as the radial extent of the shear layer between the primary and secondary recirculating flow can be resolved to within 5 mm with the same activity level, but with acquisition times of 45 s.

Using Gaussian process for velocity reconstruction after coronary stenosis applicable in positron emission particle tracking: An in-silico study

“…This tendency is particularly exacerbated when areas of flow recirculation occur after a stenosis and cause negative velocity near the wall, which the kriging algorithm is unable to detect, resulting in large e RMS . Negative velocity in regions with the recirculating flow is due to the pulsatile nature of blood and the occlusion, which is consistent with the report from [ 42 ] that used simulated PET results to reconstruct the flow field in a jet flow and found a larger error in the recirculation region; however, the retrograde velocity in our study was always underestimated by the kriging and particle tracking. It is important to note that data from the radioisotope particles trapped in the recirculation region could result in errors due to the inability to differentiate the core flow and the recirculation flow.…”

“…Assuming the surface forces between the particles, the effect of the blood rheology, and the interaction between the particles and the blood cells are negligible, the low Stokes number reported by [ 33 ] implies the path of the particles in the flow is only governed by the velocity field of the flow, not the particle inertia, meaning the effect of the particles on the flow is negligible. Bruggemann and co-workers [ 42 ] used the Monte Carlo technique implemented in the package GEANT4 Applications for Tomographic Emission (GATE) [ 11 ] to reconstruct the flow downstream of an orifice to find the required acquisition duration to resolve the flow features of interest for a given activity and the Reynolds number for simulated PET data. GATE was also used to assess the ability of PEPT to track particles in turbulent flows [ 43 ] and to model a PET scanner to for the for the development of new PEPT algorithms [ 44 ].…”

Hook Fabric Electroencephalography Electrode for Brain Activity Measurement without Shaving the Head

“… Brain activity measurement approaches: ( a ) Functional Magnetic Resonance Imaging (fMRI) [ 2 ], under CC by 4.0; ( b ) Magnetoencephalography (MEG) [ 3 ], under CC by 3.0; ( c ) Electroencephalography (EEG) [ 4 ], under CC by 4.0; ( d ) Positron Emission Tomography (PET) [ 5 ], under CC by 4.0. …”

“…The associated problems with wet Ag/AgCl and gold cups (Figure 3a) led to the development of dry electrodes made of a conductive substance that mechanically interfaces with the skin, avoiding the skin preparation procedure and the use of conductive paste [11]. They can work without any physical contact on pure capacitive coupling (Figure 3b) [2], under CC by 4.0; (b) Magnetoencephalography (MEG) [3], under CC by 3.0; (c) Electroencephalography (EEG) [4], under CC by 4.0; (d) Positron Emission Tomography (PET) [5], under CC by 4.0.…”

FBP‐CNN: A Direct PET Image Reconstruction Network for Flow Visualization

“…[ 3 ] The National Aeronautics and Space Administration (NASA) has studied the response of modern PET systems to the flow of an 18 F radioisotope solution through a steel pope with a cylindrical orifice. [ 4 ] This shows that PET has good potential for flow visualization inside opaque devices.…”