Abstract
To study the flow of objects in opaque flow processes, the PEPT (positron emission particle tracking) technique may be utilized. The PEPT technique is based on the same principle of positron emission tomography (PET). Both techniques detect the characteristic back-to-back gamma pairs caused by positron-electron annihilation. PEPT allows tracking of β+ - activated objects (tracers) with high spatial (microns) and temporal resolutions (milliseconds). This makes the technique promising in a number of medical applications that require observation of fast transient phenomena e.g. heart and brain hemodynamics, the aerodynamics of respiratory tract etc. However, a majority of PEPT-tracers used nowadays are tailored for industrial applications and are based on solid particles of a micrometric size, which are hardly suitable for in-vivo tests. In this contribution, we propose new bio-compatible tracers. The tracers are based on frozen radioactive solutions rather than activated solids. We produced a number of millimetre-sized ice tracers dispersing the droplets of radioactive solution in oil at negative temperatures. In this preliminary study, we demonstrate how the tracers behave in a settling column and in an agitated vessel. The PEPT-tracks are presented together with a supplementary numerical analysis that was conducted in order to estimate the freezing time of the droplets.
Highlights
Positron-emitting isotopes such as 18F, 68Ga, 13N, and 11C have been utilized to activate tracers for positron emission tomography (PET) via chemical bonding
The positron emission particle tracking (PEPT) technique is based on the same principle of positron emission tomography (PET)
Conventional PET scanners consist of position-sensitive gamma detectors or gamma detector matrices for identifying the gamma pairs if they are detected within a short time window and within a predefined energy range
Summary
Positron-emitting isotopes such as 18F, 68Ga, 13N, and 11C have been utilized to activate tracers for positron emission tomography (PET) via chemical bonding. To address the limitations of the temporal and spatial resolutions of the conventional PET in medical applications, in this work we proposed to further develop the positron emission particle tracking (PEPT) technique as well as to develop bio-compatible PEPT tracers. The PEPT technique is based on the same principle of PET in terms of detecting the characteristic back-to-back gamma pairs originated from positron-electron annihilation. In order to achieve tracking of tracers with spatial and temporal resolutions higher than PET, the data processing algorithms have to be redesigned and developed separately. For investigating flow in process equipment using PEPT, the biological toxicity of the tracer particles are not of concern, and materials such as ion exchange resins have been employed in order to optimise radionuclide absorption and be able to represent the flow of studied subjects [3,8]. We explored the possibility of using frozen droplets (i.e. ice particles) as PEPT tracers, in the expectation that frozen droplets of bio-compatible liquids as tracers will further open up the potential of applying PEPT as a diagnostic and even a theranostic tool
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