Su Jung An

FPGA-based multichannel data acquisition system for prototype in-beam PET

In-beam positron emission tomography (PET) is a clinically proven imaging technique for the online investigation of position emitters induced by hadron irradiation. Because the PET involves the use of many photodetectors, the data acquisition (DAQ) system of the PET system requires many elements and a high processing speed to handle many input signals and complex data sets simultaneously. To create a fast and compact DAQ system for a prototype in-beam PET system, we used an FPGA-based multichannel analysis board and developed a firmware program that was geared to acquire the prototype in-beam PET data. As a result, a flood map of the detector block with 22Na 10μCi sources was acquired, and all pixels were well separated. 18F-FDG (4-mm diameter, 3 mCi), which was located in the center of a PET ring, was explored to acquire preliminary results from the prototype in-beam PET system. We produced an energy histogram with an energy resolution of 26% at 511 keV and a reconstructed point image. The measured maximum count rate on the host PC using the developed DAQ system was 120,000 cps. Although there were many improvements in terms of the count rate, the calculation of the pulse timing and correction methods can still be improved, and we were able to assess the feasibility of the prototype in-beam PET system from the achieved preliminary results.

Design and Simulation of Depth-Encoding PET Detector using Wavelength-Shifting (WLS) Fiber Readout

We propose a new concept for a depth of interaction (DOI) positron emission tomography (PET) detector based on dual-ended-scintillator (DES) readout for small animal imaging. The detector consists of lutetium yttrium orthosilicate (LYSO) arrays coupled with orthogonal wavelength-shifting (WLS) fibre placed on the top and bottom of the arrays. On every other line, crystals that are 2 mm shorter are arranged to create grooves. WLS fibre is inserted into these grooves. This paper describes the design and performance evaluation of this PET detector using Monte Carlo simulations. To investigate sensitivity by crystal size, five types of PET detectors were simulated. Because the proposed detector is composed of crystals with three different lengths, degradation in sensitivity across the field of view was also explored by simulation. In addition, the effect of DOI resolution on image quality was demonstrated. The simulation results proved that the devised PET detector with excellent DOI resolution is helpful for reducing the channels of sensors/electronics and minimizing gamma ray attenuation and scattering while maintaining good detector performance.