Real time digital signal processing implementation for an APD-based PET scanner with phoswich detectors

In small-animal Positron Emission Tomography (PET), spatial resolution improvements rely on detector minimization in size and often come at the expense of lowering the detector photoelectric fraction. As a result, Inter-Crystal Scatter (ICS) occurrences are increased and affect the overall PET detection efficiency. To reclaim some lost efficiency, previous work used an artificial neural network (ANN) to identify the true line of response (LOR) for the simplest multiple event detection case, three coincident singles known as triplets. Despite promising results, this method is limited to an offline processing which is impractical when a limited data bandwidth is present between the scanner and the PC. This paper demonstrates the capability of processing triplets in real time using an ANN implemented in the field-programmable gate array (FPGA). The ANN pipelined architecture can process over 1 million triplets/second using less than 6000 FPGA slices. Real time processing on the LabPET I scanner yielded an overall 39.7% increase in detection efficiency relative to traditional high resolution settings with a 360-660 keV energy window along with a slight Contrast-to-Noise Ratio ( ) degradation. Although improvements are still possible, the proposed FPGA implementation proves the usability of an ANN in real time PET applications in conditions where spare computational resources are limited and the data rate to be processed is high.Index Terms-Artificial neural network (ANN), detection efficiency, field programmable gate array (FPGA), inter-crystal scatter (ICS), line-of-response (LOR), multiple coincidences, positron emission tomography (PET).

Section: A Coincidence Enginementioning

confidence: 99%

Real Time Artificial Neural Network FPGA Implementation for Triple Coincidences Recovery in PET

Geoffroy

Michaud

Tetrault

et al. 2015

“…Sophisticated data acquisition systems for PET, which store singles events [22], or make use of sampled detector waveforms for timing [23], have been shown possible for an entire scanner, and similar approaches will be considered for this proposed system. Using non-photopeak events will be essential with a CdTe scanner given the lower photopeak fraction as compared to typical inorganic scintillator materials.…”

Section: Pet System Designmentioning

confidence: 99%

CdTe Strip Detector Characterization for High Resolution Small Animal PET

Mitchell

Sinha

Stickel

et al. 2008

Excellent spatial resolution is a requirement for preclinical PET imaging. In order to achieve spatial resolution of significantly better than one millimeter, an appealing possibility is to employ direct detector materials, such as cadmium telluride (CdTe). Prototype thin orthogonal strip detectors have been developed for testing. They have dimensions of 20 mm by 20 mm and are 0.5 mm thick, and have strips of 0.5 mm pitch on one side and 2.5 mm pitch on the other. Results are presented for the energy resolution (3% at 511 keV), intrinsic position resolution (equal to the 0.5 mm strip pitch), and timing resolution (3 ns FWHM in coincidence with an LSO detector, 8 ns FWHM for coincidence of two CdTe detectors) of the detectors. A PET scanner design is proposed using blocks made of the CdTe strip detectors, oriented in the blocks with their thin edges toward the center of the scanner. Simulation results suggest that this scanner, using a threshold of 250 keV, would have a sensitivity of 3.4% for a point source at its center.Index Terms-Cadmium telluride (CdTe), positron emission tomography (PET), small animal imaging.

“…Despite its simplicity, this approach has proven to be accurate enough for the computation of the time stamp with LSO pulses shaped for 75 ns rise time and sampled at 40 MHz [12] and for LSO/LGSO integrated signals sampled at 45 MHz [13].…”

Section: Linear Interpolationmentioning

confidence: 99%

Real-Time Digital Timing in Positron Emission Tomography

Guerra¹,

Ortuño

Kontaxakis

et al. 2008

Abstract-Positron emission tomography (PET) requires accurate timing of scintillation events to properly discriminate between coincident and noncoincident pairs. The traditional solution to timing is based on custom application specific integrated circuits (ASIC) designs, whose cost may not be justified in the design of experimental small animal PET scanners. The new generation of PET scanners introduces the idea of continuous sampling of the detected scintillation pulse, replacing event-triggered acquisition front-ends. This approach enables new options to the timing procedure based on digital processing of the sampled pulse signal. This work proposes a time stamping algorithm based on the optically matched filter and compares the potential performance benefits of this approach versus other FIR-based timing algorithms, some of which have been already implemented by different authors. Results show that the coincidence timing resolution may be as low as 1.5 ns without the need of expensive high-speed converters when the proper signal processing is applied.