Data acquisition electronics for gamma ray emission tomography using width-modulated leading-edge discriminators

Abstract

We present a new high-performance and low-cost approach for implementing radiation detection acquisition systems. The basic elements used are chargeintegrating ADCs and a set of components encapsulated in an HDL (hardware definition language) library which makes it possible to implement several acquisition tasks such as time pickoff and coincidence detection using a new and simple trigger technique that we name WMLET (width-modulated leading-edge timing). As proof of concept, a 32-channel hybrid PET/SPECT acquisition system based on these elements was developed and tested. This demonstrator consists of a master module responsible for the generation and distribution of trigger signals, 2 × 16-channel ADC cards (12-bit resolution) for data digitization and a 32-bit digital I/O PCI card for handling data transmission to a personal computer. System characteristics such as linearity, maximum transmission rates or timing resolution in coincidence mode were evaluated with test and real detector signals. Imaging capabilities of the prototype were also evaluated using different detector configurations. The performance tests showed that this implementation is able to handle data rates in excess of 600k events s −1 when acquiring simultaneously 32 channels (96-byte events). ADC channel linearity is >98.5% in energy quantification. Time resolution in PET mode for the tested configurations ranges from 3.64 ns FWHM to 7.88 ns FWHM when signals from LYSO-based detectors are used. The measured energy resolution matched the expected values for the detectors evaluated and single elements of crystal matrices can be neatly separated in the acquired flood histograms.

Improvement on Timing Accuracy of Lidar for Remote Sensing

“…Additionally, the experimental accuracy of proposed method has compared with the accuracy of other methods of LED (Table 2), and the walk error decreases over 60%. Minimum walk error (ps) Gupta (2005) 1 1320 Lage (2010) 1 90 Kurtti (2012) 4 2200 Our method 11 4.63 Table 2. The comparison of experimental accuracy for other timing discrimination with LED…”

“…Gupta (2005) designed a simple circuit to convert the output signal of PMT to digital pulse, which can achieve a timing error of 90 ps under in the actual environment. Lage (2010) proposed and evaluated a hybrid analog/digital scheme that achieves a timing accuracy of 1.32 ns at a rise time of 1.5 ns, 6 ns width and 800 mV amplitude. Kurtti (2012) measured the length of the received pulse based on multi-channel time digital conversion circuit (TDC), and used the known relationship to compensate for the walk error (Kurtti, 2009); the minimum error was 2.2 ns.…”

Sistemas tomográficos multimodalidad para animales de laboratorio

“…A su vez en este apartado se explican los detalles básicos del prototipo de sistema de adquisición de datos realizado para demostrar la viabilidad de uso de esta técnica. Este capítulo está basado en (Lage et al, 2009a;Lage et al, 2009b).…”