Design of a Real Time FPGA-Based Three Dimensional Positioning Algorithm

Abstract

We report on the implementation and hardware platform of a real time Statistics-Based Positioning (SBP) method with depth of interaction processing for a positron emission tomography detector. The processing method works in conjunction with continuous miniature crystal element (cMiCE) detectors using a sensor on the entrance surface design. Our group previously reported on a Field Programmable Gate Array (FPGA) SBP implementation that provided a two dimensional (2D) detector positioning solution [1]. This new implementation extends that work to take advantage of three dimensional (3D) look up tables to provide a 3D positioning solution that improves intrinsic spatial resolution. Resolution is most improved along the edges of the crystal, an area where the 2D algorithm's performance suffers. The algorithm allows an intrinsic spatial resolution of 0.90 mm FWHM in X and Y and a resolution of 1.90 mm FWHM in Z (i.e., the depth of the crystal) based upon DETECT2000 simulation results that include the effects of Compton scatter in the crystal. A pipelined FPGA implementation is able to process events in excess of 220 K events per second, which is greater than the maximum expected coincidence rate for an individual detector. In contrast to all detectors being processed at a centralized host (as in the current system) a separate FPGA is available at each detector, thus dividing the computational load. A prototype design has been implemented and tested on an Altera Stratix II FPGA using a reduced word size due to memory limitations of our commercial prototyping board.Index Terms-Data acquisition, field programmable gate array, maximum likelihood estimation.

Resolution Properties of a Prototype Continuous Miniature Crystal Element (cMiCE) Scanner

“…To address both of these issues we are currently designing a high-throughput data acquisition electronics board [30]. We have implemented both 2D and 3D SBP algorithms in our FPGA [31,32]. The 2D SBP implementation runs at over 360 KHz and the 3D SBP implementation runs at over 220 KHz.…”

An 8×8 row-column summing readout electronics for preclinical positron emission tomography scanners

“…We will also integrate this readout electronics to the acquisition board under development in our lab [11,12]. …”

Improved statistics based positioning scheme for continuous thick crystal PET detectors

“…3D SBP not only provides the DOl information but also improves the 2D positioning performance as well, especially at the edge and comer areas [8] [9]. Meanwhile, the real-time realization of the 3D positioning algorithm on FPGA was also carried out and reported [9]. All of these research efforts have shown that the SBP algorithm has a very good application prospect for continuous crystal based PET detectors.…”

“…By creating a 2D-LUT for different DOl (depth of interaction) region, for example, 15 DOl regions in [8], a 3D-LUT is built to directly estimate 3D coordinates in the detector. 3D SBP not only provides the DOl information but also improves the 2D positioning performance as well, especially at the edge and comer areas [8] [9]. Meanwhile, the real-time realization of the 3D positioning algorithm on FPGA was also carried out and reported [9].…”

“…According to the most recent work on extending 2D SBP to 3D SBP [8] [9], the most significant improvements are that 3D SBP produces greatly improved results at the edge of the crystal, and corrects the "multiple peaking." In this paper, we investigate why the 2D SBP has a poor performance, and propose to adapt the current 2D SBP as ISBP (Improved Statistics Based Positioning scheme).…”