Impact of PET acquisition durations on image quality and lesion detectability in whole-body 68Ga-PSMA PET-MRI

Lesion detectabilities for different acquisition durations and PET reconstructions. (ODS 13 kb

Truncation artifact correction for micro-CT scanners

The work included in this project is framed on one of the lines of research carried out at the Laboratorio de Imagen Médica de la Unidad de Medicina y Cirugía Experimental (UMCE) of Hospital General Universitario Gregorio Marañón and the Bioengineering and Aerospace Department of Universidad Carlos III de Madrid. Its goal is to design, develop and evaluate new data acquisition systems, processing and reconstruction of multimodal images for application in preclinical research. Inside this research line, an x-ray computed tomography (micro-CT add on) system of high resolution has been designed for small animal. Nowadays, computed tomography (CT) is one of the techniques most widely used to obtain anatomical information from living subjects. Different artifacts from different nature usually degrade the qualitative and quantitative analysis of these images. This creates the urgent need of developing algorithms to compensate and/or reduce these artifacts. The general objective of the present thesis is to implement a method for compensating truncation artifact in the micro-CT add-on scanner for small animal developed at Hospital Universitario Gregorio Marañón. This artifact appears due to the acquisition of incomplete x-ray projections when part of the sample, especially obese rats, lies outside the field of view. As a result of these data inconsistencies, bright shading artifacts and quantification errors in the images may appear after the reconstruction process. First of all, truncation artifact in the high resolution micro-CT add-on scanner was studied. Then, after a review of the proposed methods in the literature, the optimal approach for the micro-CT add-on was selected, based on a sinogram extrapolation technique developed by Ohnesorge et al [1]. This method consists on a symmetric mirroring extrapolation of the truncated projections that guarantees continuity at the truncation point. It includes a sine shaping effect that ensures a smooth attenuation signal drop. Truncation artifact correction method has been validated in simulated and real studies. Results show an overall significant reduction of truncation artifact. This algorithm has been adapted and implemented in the reconstruction interface of the preclinical high-resolution micro-CT scanner, which is manufactured by SEDECAL S.L. and commercialized worldwide.El trabajo de este proyecto se encuadra dentro de una línea de investigación que se desarrolla en el Laboratorio de Imagen Médica de la Unidad de Medicina y Cirugía Experimental (UMCE) del Hospital General Universitario Gregorio Marañón y el Departamento de Bioingeniería e Ingeniería Aeroespacial de la Universidad Carlos III de Madrid. Su objetivo es diseñar, desarrollar y evaluar nuevos sistemas de adquisición de datos, procesamiento y reconstrucción de imágenes multi-modales para aplicaciones en investigación preclínica. Dentro de esta línea de investigación se ha desarrollado un tomógrafo de rayos X de alta resolución para pequeños animales (micro-TAC add-on). Actualmente, la tomografía axial computarizada es una de las técnicas más ampliamente utilizadas para la obtención de información anatómica in vivo. Existe una serie de artefactos de distinta naturaleza en este tipo de imágenes que generalmente degradan y dificultan el análisis cualitativo y cuantitativo de las imágenes, dando lugar a una necesidad imperante de desarrollar algoritmos de corrección y/o reducción de estos artefactos. El objetivo general del presente proyecto es la implementación de un algoritmo para la corrección del artefacto de truncamiento en el escáner micro-TAC add-on desarrollado en el Hospital Universitario Gregorio Marañón. Este artefacto aparece debido a la adquisición de proyecciones incompletas cuando parte de la muestra, especialmente ratas obesas, se extiende fuera del campo de visión. Estas inconsistencias en los datos obtenidos pueden dar lugar a la aparición de bandas brillantes y errores en la cuantificación de las imágenes después del proceso de reconstrucción. En primer lugar, se ha estudiado el artefacto de truncamiento en el escáner micro-TAC add-on de alta resolución. Seguidamente, se ha llevado a cabo una revisión de los métodos propuestos en la bibliografía, seleccionando una estrategia óptima para el micro-TAC add-on bajo estudio: una técnica de extrapolación del sinograma publicado por Ohnesorge et al [1]. Este método consiste en una extrapolación de espejo simétrico de las proyecciones truncadas que garantiza la continuidad en el punto de truncamiento. Incluye el modelado de una sinusoide que asegura una caída de señal en los valores de atenuación suave. Este método ha sido validado en estudios simulados y reales. Los resultados muestran una clara reducción del artefacto de truncamiento. El resultado de este proyecto ha sido incorporado en la interfaz de reconstrucción del escáner pre-clínico micro-TAC add-on de alta resolución fabricado por SEDECAL S.A. y comercializado por todo el mundo.Ingeniería Biomédic

Automatic correction of dental artifacts in PET/MRI

A challenge when using current magnetic resonance (MR)-based attenuation correction in positron emission tomography/MR imaging (PET/MRI) is that the MRIs can have a signal void around the dental fillings that is segmented as artificial air-regions in the attenuation map. For artifacts connected to the background, we propose an extension to an existing active contour algorithm to delineate the outer contour using the nonattenuation corrected PET image and the original attenuation map. We propose a combination of two different methods for differentiating the artifacts within the body from the anatomical air-regions by first using a template of artifact regions, and second, representing the artifact regions with a combination of active shape models and k-nearest-neighbors. The accuracy of the combined method has been evaluated using 25 [Formula: see text]-fluorodeoxyglucose PET/MR patients. Results showed that the approach was able to correct an average of [Formula: see text] of the artifact areas

Hybrid cardiac imaging using PET/MRI:A joint position statement by the European Society of Cardiovascular Radiology (ESCR) and the European Association of Nuclear Medicine (EANM)

Positron emission tomography (PET) and magnetic resonance imaging (MRI) have both been used for decades in cardiovascular imaging. Since 2010, hybrid PET/MRI using sequential and integrated scanner platforms has been available, with hybrid cardiac PET/MR imaging protocols increasingly incorporated into clinical workflows. Given the range of complementary information provided by each method, the use of hybrid PET/MRI may be justified and beneficial in particular clinical settings for the evaluation of different disease entities. In the present joint position statement, we critically review the role and value of integrated PET/MRI in cardiovascular imaging, provide a technical overview of cardiac PET/MRI and practical advice related to the cardiac PET/MRI workflow, identify cardiovascular applications that can potentially benefit from hybrid PET/MRI, and describe the needs for future development and research. In order to encourage its wide dissemination, this article is freely accessible on the European Radiology and European Journal of Hybrid Imaging web sites.Key Points center dot Studies and case-reports indicate that PET/MRI is a feasible and robust technology.center dot Promising fields of application include a variety of cardiac conditions.center dot Larger studies are required to demonstrate its incremental and cost-effective value.center dot The translation of novel radiopharmaceuticals and MR-sequences will provide exciting new opportunities.</p