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Dual-ended Readout Innovative Method for Positron Emission Tomography

Positron Emission Tomography is among the best examples of the contribution of medical imaging systems to clinical research. The development of PET systems adequate for small animal imaging has been an active area of research in the last two decades, with important applications in drug development and imaging of gene expression. This allowed a better understanding of human diseases and the development of more effective ways for disease diagnosis and treatment, through the translation of pre-clinical molecular imaging discoveries in small animals, to medical practice. In the case of research-dedicated PET scanners for small animal imaging, size adequacy is essential. In fact, for instance, a rat’s heart is more than 100 times smaller than the human heart.
This work aims at developing a small PET scanner with improved spatial resolution using depth-of-interaction (DOI) information. The system combines scintillator-photodetector cells with a new DOI determination method, based on light guides (optical fibres) with silicon photomultiplier readout (SiPM).
The method requires a small number of components to obtain DOI; therefore, it allows producing a high-performance PET system at acceptable cost, presenting state-of-the-art characteristics.
The foreseen system comprises one ring of 128 1.5 x 1.5 x 20 mm3 LYSO crystals radially distributed. Each single LYSO crystal is read out on both ends by silicon photomultipliers (SiPMs), but using wavelength-shifting (WLS) fibers/bars and a reduced number of SiPMs on one end. The DRIM-PET can be modulated for axial capability by using several rings modules placed side-by-side.
Two different signal readout systems will be considered. A simpler one that uses only a few readout channels for readout of the entire 128 detector cells, being the position determination obtained by a resistive chain method. The more complex one, with improved capabilities in terms of reduction of false coincidences, sensitivity and position resolution, will use individual channels for each cell.
Experimental and simulation studies will be performed in order to optimize the system’s parameters the aim of building and characterizing a prototype for its interest as new PET scanner for pre-clinical research.
Dedicated image reconstruction methods and imaging software will be developed taking into account the characteristics of the system and in order to optimize the image quality as a function of produced signals.
Prototype characterization, using beta+ emitters, will be done, first with 22-Na calibration sources and after with phantoms filled with 18-F. Finally, in order to demonstrate the potential of the developed PET scanner, small animals with different pathologies of interest (e.g. oncologic) and radio-tracers will be used as final evaluation task.
Principal Investigator: João Veloso (UA)