Design of a high resolution small animal octagonal PET scanner: preliminary studies

[Abstract] AMI International Conference 2003, September 21 - 27, Madrid, Spain: "High Resolution Molecular Imaging: from Basic Science to Clinical Applications"We present a preliminary study on the design of a high resolution small animal octagonal positron emission tomography (PET) scanner, based on Monte Carlo simulations. The purpose of this study is to evaluate the impact of several critical design parameters on the reconstructed image quality, as well as the calculation of the system matrix for iterative image reconstruction based on statistical modelsPublicad

Efficient methodology for 3D statistical reconstruction of high resolution coplanar PET/CT scanner

Proceeding of: 2008 IEEE Nuclear Science Symposium Conference Record (NSS '08), Dresden, Germany, 19-25 Oct. 2008A fully 3D statistical image reconstruction algorithm has been developed for a high-resolution coplanar PETtCT scanner based on rotating planar PET detectors. The system matrix has been modeled with custom Monte Carlo techniques optimized for the specific scanner architecture. The system model includes positron range, non-colinearity of gamma rays and crystal interaction modelling with attenuation and Compton scattering effects. Only 0.21 % of the system matrix columns are modeled in detail, obtaining the rest of the values with axial and transaxial voxel-driven symmetries. The iterative algorithm is a fully 3D approach, regularized with the anatomical registered image using a novel version of the minimum cross entropy (MXE) scheme, and accelerated employing ordered subsets. The proposed method has been shown to produce images with superior quality than 3D hybrid (FORE+2D-OSEM) algorithms applied on synthetic GATE data, as well as on real small animal acquisitionsThis work has been partly funded by the CDTEAM project and CENIT programme (Spanish Ministry of Industry), EMIL (ED Network of Excellence), CIBER CB07/09/0031 and RETIC-RECAVA (Spanish Ministry of Health) and TEC2007-64731/TCM(Spanish Ministry of Education and Science

Modeling the acquisition front-end in high resolution gamma-ray imaging

The availability of synthetic realistic data eases design optimization, algorithm evaluation and verification of any digital system where a significant amount of digital signal processing is performed. The evolution of positron emission tomography cameras towards continuous sampling of individual position-sensitive photomultiplier anodes with processing algorithms implemented on digital programmable logic devices creates a new framework where new approaches to the γ-event detection are possible. We have developed a system model of the acquisition chain, including multi-layer phoswich, photomultiplier, front-end analog electronics, data acquisition and digital processing. This processing includes estimation algorithms for the most relevant event parameters: energy, layer-of-interaction, time picking-off and event location. The selected simulation platform couples gently to digital hardware simulation tools, in such a way that implemented models may generate real-like stimuli for the digital system under development. The modeling of the whole front-end electronics enables deeper understanding and tuning of different system trade-offs and provides a rapid and soft transition between specification and hardware developmentPublicad

Preliminary results of the small animal rotational positron emisson tomography scanner

[Abstract] AMI Annual Conference 2004, March 27-31, Orlando, FloridaThis contribution reports preliminary results of a high-resolution small animal positron emission tomography (PET) based on pairs of opposed scintillation rotating detectors working in time coincidencePublicad

Modeling the acquisition front-end in high resolution gamma-ray imaging

Proceeding of: 2004 IEEE Nuclear Science Symposium Conference Record, Rome, Italy, 16-22 October 2004The availability of synthetic realistic data enables design optimization, algorithm evaluation and verification of any digital system where a significant amount of digital signal processing is performed. The evolution of positron emission tomography cameras towards continuous sampling of individual position-sensitive photomultiplier anodes with processing algorithms implemented on digital programmable logic devices creates a new framework where new approaches to the γ-event detection are possible. We have developed a system model of the acquisition chain, including multi-layer phoswich, photomultiplier, front-end analog electronics, data acquisition and data processing. This processing includes estimation algorithms for the most relevant event parameters: energy, layerof- interaction, time picking-off and event location. The selected simulation platform couples gently to digital hardware simulation tools, in such a way that implemented models may generate reallike stimuli for the digital system under development. The modeling of the whole front-end electronics enables deeper understanding and tuning of different system trade-offs and provides a rapid and soft transition between specification and hardware development

Digital timing in positron emission tomography

Proceeding of: 2006 IEEE Nuclear Science Symposium Conference Record, San Diego, CA, Oct. 29 - Nov. 1, 2006Positron emission tomography (PET) requires accurate timing of events in order to properly discriminate between coincident and non-coincident events. The traditional solution to timing is based on custom ASIC designs, whose cost may not be justified in the design of an experimental small animal PET scanner. The new generation of PET scanners introduces the idea of continuous sampling of the detected scintillation pulse, in substitution of the event triggered acquisition systems. This approach enables new options to timing 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 filter designs, some of which have been already implemented by different authors. Results show that time resolution of the timestamp may be as 1 ns without the need of expensive high-speed converters when the proper processing is applied.This work has been partially funded by the Spanish Ministry of Culture and Science through the FPU grant program as well as projects TEC2004-07052-C02-02 and PI052204.

Multipurpose Monte Carlo simulator for photon transport in turbid media

Proceeding of: 2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC), Orlando, Florida, 25-31 October 2009Monte Carlo methods provide a flexible and rigorous solution to the problem of light transport in turbid media, which enable approaching complex geometries for a closed analytical solution is not feasible. The simulator implements local rules of propagation in the form of probability density functions that depend on the local optical properties of the tissue. This work presents a flexible simulator that can be applied in multiple applications related to optical tomography. In particular, unlike previous codes, the simulator explicitly supports fluorescent-tissues and variance reduction and code parallelization techniques are implemented in order to speed up the execution with fluorochrome-labelled agents. The simulator is validated with simple geometries for which an analytical solution exists, as well as with an experimental polyester resin based optical phantom.This work was supported in part by the Ministry of Science and Innovation under projects TEC2008-06715 and TEC2007-64731/TCM and by the EU’s 7th Frame Programme under contract HEALTH-F5-2008-20179

New embedded digital front-end for high resolution PET scanner

This work describes a new digital front-end for a high-resolution low-cost animal PET scanner which is currently under development. The advances in flexibility and size of modern FPGAs together with the release of new tools enable the integration of most of the front-end electronics in a single FPGA. The implemented system includes a small 32-bit RISC processor, several peripherals attached to the internal buses and a special DSP unit closely attached to the processor which is dedicated to the detection of the gamma events. On top of these, a small footprint real time operating system abstracts the underlying hardware, providing the mechanisms to combine on-chip slow control and data streamingThis work was supported in part by the FPU Research Grant from the Spanish Education and Science Ministry, by the Spanish Thematic Network IM3 (PI052204) and project TEC2004-07052-C02-02Publicad

Real-Time Digital Timing in Positron Emission Tomography

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 appliedIEEE Nuclear and Plasma Sciences SocietyPublicad

Preliminary studies on the design and simulation of high resolution small animal PET scanners with octagonal geometry

Proceding of: 2003 IEEE Nuclear Science Symposium Conference Record, Portland, Oregon, USA, 19-25 October, 2003We present a preliminary study on the design of a small animal positron emission tomograph with octagonal geometry. The main goal is to evaluate the impact of critical design parameters on the quality of the reconstructed images. Monte Carlo simulations take into account the depth of interaction in individual crystals. The activity sources are simulated as parametric distributions within the field of view and images are reconstructed with iterative algorithms based on the estimation of maximum likelihood and Bayesian regularization. The probability system matrix used by these algorithms is also calculated based on statistical models and Monte Carlo simulation. 2D and 3D techniques have been employed.This work has been partly founded by the Spanish Ministry of Science & Technology, (TIC 2001-0175-C03) and by Red Temática IM3 from Spanish Health Ministry (G03/185).Publicad