Novel method for hit-position reconstruction using voltage signals in plastic scintillators and its application to Positron Emission Tomography

TL;DR

This paper introduces a new hit-position reconstruction method using voltage signal sampling in plastic scintillators, demonstrating a spatial resolution of 1 cm and timing resolution of 80 ps for PET applications.

Contribution

It presents a novel waveform sampling technique and statistical analysis for accurate hit-position reconstruction in plastic scintillators for PET imaging.

Findings

Achieved approximately 1 cm spatial resolution.

Demonstrated about 80 ps timing resolution.

Validated the normal distribution assumption for sampled signals.

Abstract

Currently inorganic scintillator detectors are used in all commercial Time of Flight Positron Emission Tomograph (TOF-PET) devices. The J-PET collaboration investigates a possibility of construction of a PET scanner from plastic scintillators which would allow for single bed imaging of the whole human body. This paper describes a novel method of hit-position reconstruction based on sampled signals and an example of an application of the method for a single module with a 30 cm long plastic strip, read out on both ends by Hamamatsu R4998 photomultipliers. The sampling scheme to generate a vector with samples of a PET event waveform with respect to four user-defined amplitudes is introduced. The experimental setup provides irradiation of a chosen position in the plastic scintillator strip with an annihilation gamma quanta of energy 511~keV. The statistical test for a multivariate normal (MVN) distribution of measured vectors at a given position is developed, and it is shown that signals sampled at four thresholds in a voltage domain are approximately normally distributed variables. With the presented method of a vector analysis made out of waveform samples acquired with four thresholds, we obtain a spatial resolution of about 1 cm and a timing resolution of about 80 ps