Fast circuit topology for spatial signal distribution analysis

Abstract

We present a novel active and analog readout and preprocessing topology for position sensitive photodetectors (PSPD) that allows to readout a large variety of PSPD devices with different pixel numbers. Additionally, the topology was designed to allow for a significant reduction of analog-to-digital conversion channels. The circuit topology replaces the common passive charge divider and consists of N input stages, N x M weighting stages and M analog adder stages, where N is the number of the input channels, i.e. the number of photodetector pixels and M is the number of outputs. The circuit performs the multiplication of a matrix (the weights) with a vector (signals). For this, the input stage makes M copies of each of the N input signals, the weighting stage multiplies these signal copies with N x M different weights and the output stage adds all weighted copies with the same copy index. For high flexibility, the weights are programmable and the topology allows to interconnect several identical circuits for larger N. As application for the circuit, we present a Neural Network based positioning scheme for γ-ray imaging detectors with thick, monolithic scintillation crystals. We used Monte Carlo simulation for training and evaluation of the method and found that the spatial resolution of the γ-ray imaging detectors was significantly enhanced. The strong border artifacts of the center of gravity positioning scheme in monolithic scintillation crystals could be corrected to a large extent.

Evaluation of a Modular PET System Architecture with Synchronization over Data Links

“…AMIC can thus be used as a replacement for a resistor network used as a charge division circuit for Anger-like logic [30], [31], benefiting from a higher bandwidth due to integrated preamplifiers, and the capability for automatic correction of photodetector channel gain mismatch by fine adjustment of weighted sum coefficients [32]. Additionally, it can be used to obtain the first few statistical moments of the light distribution in a continuous scintillator [33], from which 3D event position can be extracted. In particular, the second moment contains information on depth of interaction within the crystal [34].…”

AMIC: an expandable integrated analog front-end for light distribution moments analysis

“…Though benefits in data acquisition were described in [5], the main drawback of the presented ASIC was its closed structure that made expandability impossible without a circuit redesign, so that one of the main goals while designing a new prototype was to allow expandability of the front-end. As it was presented in [7], light distribution moments analysis can be used to improve front-end performances. Since the whole light distribution is needed, the use of a pixellated scintillator is unfeasible.…”

Estudio e implementación de algoritmos digitales para la mejora de la resolución temporal en sistemas de tomografía por emisión de positrones

“…Para la etapa integrada, el grupo de investigación en el que se ha desarrollado este trabajo ha propuesto dos aproximaciones distintas dando lugar a dos circuitos integrados diferentes: PESIC [56], [57] y AMIC [58], [59], [60]. Las dos tecnologías se encargan de reducir el número de señales analógicas de los 64ánodos de corriente que proporciona el PMT.…”