PESIC: An Integrated Front-End for PET Applications

Research areas:
Authors:
Herrero-Bosch, V.; Colom, R. J.; Gadea, R.; Espinosa, J.; Monzo, J. M.; Esteve, R.; Sebastia, A.; Lerche, C. W.; Benlloch, J. M.
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ISSN:
2008
Article
IEEE Trans. Nucl. Sci.
55
1
27-33
February
0018-9499
Keywords:
ASIC , PET , depth of interaction , front-end , pile-up

 Abstract:

An ASIC front-end has been developed for multianode photomultiplier based nuclear imaging devices. Its architecture has been designed to improve resolution and decrease pile-up probability in positron emission tomography systems which employ continuous scintillator crystals. Analog computation elements are isolated from the photomultiplier by means of a current sensitive preamplifier stage. This allows digitally programmable adjustment of every anode gain, also providing better resolution in gamma event position calculation and a shorter front-end deadtime. The preamplifier stage also offers the possibility of using other types of photomultiplier devices such as SiPM. The ASIC architecture includes measurement of the depth of interaction of the gamma event based on the width of the light distribution in order to reduce parallax error and increase spatial resolution during image reconstruction stage. An output stage of transresistance amplifiers offer voltage output signals which may be introduced in the A/D conversion stage with no further processing.

Online version

Improved Digital Pulse Height Estimation for PET Detectors Using LMS Adaptive Filters

Research areas:
Authors:
Monzó, J. M.; Martínez, J. D.; Toledo, J.; Esteve, R.; Herrero, V.; Sebastiá, A.; Mora, F. J.; Benlloch, J. M.; Lerche, C. W.; Sánchez, F.
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2008
Article
IEEE Trans. Nucl. Sci.
55
48-53
February
0018-9499

Keywords:

Adaptive signal processing , FIR digital filters , biomedical nuclear imaging , least mean square methods , positron emission tomography

Abstract:
Digital positron emission tomography (PET) systems enable us to implement sophisticated algorithms for real time signal processing. Usually, energy and position are encoded on the amplitude of the digitized signals. Although a lot of work has been made for spectroscopy applications, digital pulse height estimation in PET detectors presents important challenges mainly due to the fast response of state-of-the-art detectors. In this paper we propose a digital filtering technique for improving amplitude estimation in order to achieve high spatial and energy resolution with moderate conversion rates (80 MSPS). Our approach is based on the trapezoidal shaping of the incoming pulses by using adaptive filtering based on Least-Mean-Squares (LMS) algorithm for modelling detector and front-end electronics response. Thus, the filtered signals are well suited both for pile-up recovery and accurate pulse height computation. The filter can be easily implemented on programmable logic devices and integrated on the data acquisition chain for real-time applications.

Online version

Accurate simulation testbench for nuclear imaging systems

Research areas:
Authors:
Monzó, J. M.; Aliaga, R. J.; Herrero, V.; Martínez, J. D.; Mateo, F.; Sebastià, A.; Mora, F. J.; Benlloch, J. M.; Pavón, N.
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2008
Article
IEEE Transactions on Nuclear Science
55
1
421-428

Abstract:
Current testbenches for nuclear imaging devices aim to simulate only a single stage of the system at a time. This approach is useful in early design stages where accuracy is not necessary. However, it would be desirable that different tools could be combined to achieve more detailed simulations. In this work, we present a high precision testbench that has been developed to test nuclear imaging systems. Its accuracy lies in the possibility of linking different simulation tools using the right one for each part of the system. High energy events are simulated using Geant4 (High Energy Simulator). Analog and digital electronics are verified using Cadence Spectre and ModelSim. This testbench structure allows testing any physical topology, scintillation crystals, photomultiplier tubes (PMTs), avalanche photodiodes (APDs), with any kind of ASIC, discrete analog and digital electronics, thus reducing the prototyping and design time. New system developments can be easily verified using behavioral and circuital description models for analog and digital electronics. Finally, a dual-head continuous LSO scintillation crystal positron emission tomography (PET) system has been used as an example for evaluation of the testbench.

Online version