Corrección de atenuación de imágenes PET usando datos de TAC en el escáner para animales pequeños Argus PET/CT

Actas de: XXVIII Congreso Anual de la Sociedad Española de Ingeniería Biomédica (CASEIB 2010). Madrid, 24-26 de noviembre de 2010.Existen diversos efectos físicos que degradan la calidad de la imagen PET, como por ejemplo la atenuación que sufren los fotones al atravesar el cuerpo en estudio. Este efecto reduce el número de fotones detectados, pero puede corregirse si se dispone de información anatómica del objeto. En este trabajo se describe la corrección de atenuación basada en una imagen TAC para el escáner de animales pequeños Argus PET/CT con imágenes PET reconstruidas con el algoritmo iterativo 3DOSEM.Este trabajo ha sido financiado en parte por el MEC (FPA2007-62216), la UCM (Grupos UCM, 910059), el CPAN (Consolider-Ingenio 2010, CSPD-2007-00042), la red RECAVA-RETIC el proyecto ARTEMIS (S2009/DPI-1802, Fondo Europeo de Desarrollo Regional), el proyecto ENTEPRASE (PSE-300000-2009-5, MICINN. España), por los proyectos del Ministerio de Ciencia e Innovación, TEC2007-64731, TEC 2008-06715-C02-1, la RETIC-RECAVA del Ministerio de Sanidad y Consumo, y el proyecto EU FP7 FMT-XCT-201792.Publicad

Frequency selective signal extrapolation for compensation of missing data in sinograms

Proceeding of: 2008 IEEE Nuclear Science Symposium Conference Record (NSS '08), Dresden, Germany, 19-25 Oct. 2008We present a method to compensate for missing projection data in positron emission tomography (PET), which may result from gaps between adjacent detectors or from malfunctioning detectors. To prevent artifacts in the reconstruction when using Fourier rebinning (FORE) or analytical reconstruction algorithms, filling the data gaps is required. This new approach for sinogram data interpolation prior to reconstruction is based on a simple iterative freq uency selective signal extrapolation method initially proposed and successfully applied for error concealment in image and video communication. In this work the method has been improved taking advantage of well known restrictions in the allowed region of frequencies of the sinograms. We compare quantitatively the results of this technique with previously proposed gap filling procedures in both the sinograms and in their reconstructed images. The proposed technique outperforms those methods without requiring too much computational time.This work was supported in part by the MEC (FPA2007-07393), CDTEAM (CENIT-Ingenio 2010) Ministerio de Industria, Spain, CPAN (Consolider-Ingenio 2010) CSPD-2007-00042 projects, and the RECAVA-RETIC network. Vicente acknowledges support from a CSIC-JAE predoctoral fellowship

Nonlinear effect of pile-up in the quantification of a small animal PET scanner

Proceeding of: 2008 IEEE Nuclear Science Symposium Conference Record (NSS '08), Dresden, Germany, 19-25 Oct. 2008Accurate and reliable quantitative analysis of PET images are necessary for pre-clinical studies. To derive quantitative information from PET images, determination of the calibration curve, that is, the relationship between the pixel values in the reconstructed image and radiotracer concentrations is required. In a typical PET acquisition, several effects, such as random counts and pile-up contributions make this relationship nonlinear. We find that for PET detectors based upon relatively large PMTs like the Hamamatsu H8500, pile up may become the dominant nonlinear effect, with random contributions playing a minor role. We confirm this by means of detailed simulations of small and large cylinders in the rPET small animal scanner as well as with real acquisitions. The simulations allow us to study the impact of pile-up as a source of nonlinearity in the calibration curve of this commercially available small animal PET scanner. We compare the results obtained from images for both real and simulated data. The results show that for the activities considered in this study the quantitative results can be affected by pile-up by more than 20%. We find that pile-up, which shifts counts to the center of the FOV and attenuation, which removes activity from the center of the FOV, may cancel each other for moderate activity values. This would cause quantification errors if attenuation corrections were attempted for acquisitions without pile-up corrections. The pile-up correction software improves the linearity of the calibration curve, extending the range of activity values for which a linear calibration curve can be reliably applied.This work was supported in part by the MEC (FPA2007-07393), CDTEAM (CENIT-Ingenio 2010) Ministerio de Industria, Spain, CPAN (Consolider-Ingenio 2010) CSPD-2007-00042 projects, and the RECAVA-RETIC network. E. Vicente acknowledges support from a CSIC-JAE predoctoral fellowship

Real-time 3D PET image with pseudoinverse reconstruction

Real-time positron emission tomography (PET) may provide information from first-shot images, enable PET-guided biopsies, and allow awake animal studies. Fully-3D iterative reconstructions yield the best images in PET, but they are too slow for real-time imaging. Analytical methods such as Fourier back projection (FBP) are very fast, but yield images of poor quality with artifacts due to noise or data incompleteness. In this work, an image reconstruction based on the pseudoinverse of the system response matrix (SRM) is presented. w. To implement the pseudoinverse method, the reconstruction problem is separated into two stages. First, the axial part of the SRM is pseudo-inverted (PINV) to rebin the 3D data into 2D datasets. Then, the resulting 2D slices can be reconstructed with analytical methods or by applying the pseudoinverse algorithm again. The proposed two-step PINV reconstruction yielded good-quality images at a rate of several frames per second, compatible with real time applications. Furthermore, extremely fast direct PINV reconstruction of projections of the 3D image collapsed along specific directions can be implemented.Part of the calculations in this work were performed in the “Clúster de Cálculo para Técnicas Físicas” funded in part by UCM and in part by UE Regional Funds. We acknowledge the support from the Spanish Government (FPA2015-65035-P, RTC-2015-3772-2, and RTI2018-095800-A-I00), Comunidad de Madrid (S2013/MIT-3024 TOPUS-CM, B2017/BMD-3888 PRONTO-CM), and European Regional Funds. This work was also supported by the EU’s H2020 under MediNet, a Networking Activity of ENSAR-2 (grant agreement 654002), and by a NIH R01 CA215700-2 grant. The CNIC is supported by the Ministerio de Ciencia, Innovación y Universidades and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505)

Producción ecológica en los cultivos de lavanda en Cuenca (España). Estudio del rendimiento y calidad de sus aceites esenciales

In the present paper, we present a description of the ecological agriculture of different lavenders in Cuenca province (Spain). We focused on the important aromatic crops of Lavandula angustifolia (lavender) and on three varieties of Lavandula × intermedia (lavandin) called name abrial, rosso and super. A description of yield production and essential oil qualities obtained in our experimental fields are presented. Lavandin var. super showed the best essential oil quality with good yield production as well. The current market of Fragrant and Medicinal Plants claims raw materials with confirmed quality, with good practices of harvesting, transformation and manufacture by means of ecological production.En este trabajo presentamos una descripción del cultivo ecológico de diferentes lavandas en la provincia de Cuenca (España), concretamente de los cultivos de Lavandula angustifolia (lavanda) y de tres variedades de Lavandula × intermedia denominadas abrial, grosso y super. Se presenta una descripción de los rendimientos de estos cultivos y de las calidades obtenidas de la destilación de sus aceites esenciales. Con la variedad super de lavandin se obtuvieron las mejores producciones y calidades. El mercado actual de plantas aromáticas y medicinales reclama materias primas de calidad contrastada, con trazabilidad óptima de los productos, buenas prácticas de recolección, transformación y manufactura mediante producción ecológica

Nuclear astrophysics with radioactive ions at FAIR

The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process beta-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes

PeneloPET v3.0, an improved multiplatform PET Simulator

PeneloPET is a Monte Carlo simulation tool for positron emission tomography based on PENELOPE. It was developed by the Nuclear Physics Group at University Complutense of Madrid and its initial version was released in 2009. In this work, we present PeneloPET v3.0, which is now available precompiled for Microsoft Windows, MacOS and Linux OS. This new release includes improved simulations of the positron range in different materials and an accurate description of the decay cascades for many radioactive nuclei including the most common non-pure positron emitters used in PET. This enables the simulation of PET acquisitions with positron-gamma emitters. This release also includes many different fully-working examples, of both clinical and preclinical scanners, as well as several numerical phantoms. Due to the simplicity of the input the output files, and the installation process, PeneloPET v3.0 can be perfectly used not only for research, but also as an educational tool in class

Iterative determination of clinical beam phase space from dose measurements

Monte Carlo (MC) method can accurately compute the dose produced by medical linear accelerators. However, these calculations require a reliable description of the electron and/or photon beams delivering the dose, the phase space (PHSP), which is not usually available. A method to derive a phase space model from reference measurements that does not heavily rely on a detailed model of the accelerator head is presented. The iterative optimization process extracts the characteristics of the particle beams which best explains the reference dose measurements in water and air, given a set of constrain

Feasibility assessment of the interactive use of a Monte Carlo algorithm in treatment planning for intraoperative electron radiation therapy

This work analysed the feasibility of using a fast, customized Monte Carlo (MC) method to perform accurate computation of dose distributions during pre- and intraplanning of intraoperative electron radiation therapy (IOERT) procedures. The MC method that was implemented, which has been integrated into a specific innovative simulation and planning tool, is able to simulate the fate of thousands of particles per second, and it was the aim of this work to determine the level of interactivity that could be achieved. The planning workflow enabled calibration of the imaging and treatment equipment, as well as manipulation of the surgical frame and insertion of the protection shields around the organs at risk and other beam modifiers. In this way, the multidisciplinary team involved in IOERT has all the tools necessary to perform complex MC dosage simulations adapted to their equipment in an efficient and transparent way. To assess the accuracy and reliability of this MC technique, dose distributions for a monoenergetic source were compared with those obtained using a general-purpose software package used widely in medical physics applications. Once accuracy of the underlying simulator was confirmed, a clinical accelerator was modelled and experimental measurements in water were conducted. A comparison was made with the output from the simulator to identify the conditions under which accurate dose estimations could be obtained in less than 3 min, which is the threshold imposed to allow for interactive use of the tool in treatment planning. Finally, a clinically relevant scenario, namely early-stage breast cancer treatment, was simulated with pre- and intraoperative volumes to verify that it was feasible to use the MC tool intraoperatively and to adjust dose delivery based on the simulation output, without compromising accuracy. The workflow provided a satisfactory model of the treatment head and the imaging system, enabling proper configuration of the treatment planning system and providing good accuracy in the dosage simulation

Desarrollo de un libro electrónico mejorado sobre aplicaciones de la Física Nuclear a la Medicina

Proyecto de innovación docente con el objetivo de desarrollar una herramienta que facilite el aprendizaje de las aplicaciones a la Medicina de la Física Nuclear. Se ha creado el sitio web https://fisnucmed.wordpress.com/. Se abordan, entre otros contenidos, las radiaciones ionizantes y los fundamentos de la interacción de la radiación con la materia, nociones de detección de radiación e instrumentación nuclear , diagnóstico por imagen, y las modalidades de imagen PET, SPECT, CT, resonancia magnética nuclear, ultrasonidos, así como la radioterapia y en particular la hadronterapia