Optimization of 2-DEOXY-2-[18F] FLUORO-D-GLUCOSE positron emission tomography thorax imaging of laboratory small animals

[Abstract] AMI Annual Conference 2005, March 18-23, Orlando, FloridaThe search of oncologic lesions in thorax may be hindered by the high uptake of organs such as the heart or back muscles that prevent the proper visualization of neighbor organs. The aim of this study is to analyze to what extent glucose metabolism can be modulated to obtain an optimal thorax image in micePublicad

FDG-PET studies of the effect of MDMA in rat brain

[Abstract] The 10th International Conference on Functional Mapping of the Human Brain, June 13-17, 2004, Budapest, HungaryAlterations of the human brain due to MDMA use are a focus of ongoing research. MDMA abuse produces both short and long-term effects on brain; MDMA-induced functional alterations of the serotonergic system are reported to alter local energy metabolism of cortical and subcortical structures. Presently, there are no FDG-PET experimental studies reported in animals. The aim of this study is to assess these brain glucose metabolism changes after a single dose of MDMA in rats by using FDG-PETPublicad

Detection of small murine lung tumours by FDG-PET

[Abstract] AMI International Conference 2003, September 21 - 27, Madrid, Spain: "High Resolution Molecular Imaging: from Basic Science to Clinical Applications"The functional information provided by 2-deoxy-2- [18F]fluoro-D-Glucose (FDG) positron emission tomography (PET) is commonly used to detect primary tumours and metastases in clinical studies. The aim of this work is to assess the possibilities of FDG-PET studies to detect small lung tumour lesions in mice, using a dedicated small animal PET scannerPublicad

A new algorithm for ring artifact reduction in cone-beam computed tomography: preliminary results

[Abstract] 22nd International Congress and Exhibition, Barcelona, Spain, June 25-28, 2008In this work we present a new method for ring artifact compensation, suitable for cone beam data. Starting from the idea of Sijbers et al., we have developed an improved procedure that operates on the projection data before the reconstruction and does not require interpolations, thus avoiding image degradation and reducing the computational burden. Results on phantoms and rodent studies are presentedPublicad

Imagen de alta resolución en pequeños animales de laboratorio

La posibilidad de visualizar y cuantificar la función de un determinado órgano en animales de laboratorio es una herramienta científica de gran importancia en el estudio de modelos de enfermedades humanas, en el descubrimiento y desarrollo de nuevos medicamentos y en la caracterización del fenotipo de animales transgénicos y noqueados. La tomografía por emisión de positrones (PET) y la imagen proyectiva de radiofármacos marcados con emisores de positrones proporcionan una herramienta genérica y no invasiva para la investigación científica en los casos anteriormente expuestos. En este trabajo se describe un sistema mutimodal PET/CT basado en cámaras de coincidencia y detectores de estado sólido para los rayos X, diseñado para adquirir tanto imágenes tomográficas como de proyección con alta resolución temporal, con capacidad para visualizar ratas y ratones, estos últimos en cuerpo completo en un solo campo de visión.Publicad

Reduction of respiratory blurring in small-animal CT scans based on a fast retrospective gating method

[Abstract] The 22nd International Congress and Exhibition, Barcelona, Spain, June 25-28, 2008The purpose of the present work was to develop a fast retrospective method to extract the respiratory signal from the CT projections in cone beam geometry and to obtain dynamic breathing studies in small animal scans. The whole process had to be software-based and automatic, avoiding the use of any additional respiratory gating instrumentsPublicad

Validation of SPM analysis of visual activation in rat brain pet studies

[Abstract] AMI Annual Conference 2004, March 27-31, Orlando, FloridaStatistical parametric mapping (SPM) is used to detect subtle activity changes in brain not requiring a priori assumptions about the expected activations. We adapt the methodology for analyzing rat brain positron emission tomography (PET) scansPublicad

Sinogram bow-tie filtering in FBP PET reconstruction

Low-pass filtering of sinograms in the radial direction is the most common practice to limit noise amplification in filtered back projection FBP reconstruction of positron emission tomography studies. Other filtering strategies have been proposed to prevent the loss in resolution due to low-pass radial filters, although results have been diverse. Using the well-known properties of the Fourier transform of a sinogram, the authors defined a binary mask that matches the expected shape of the support region in the Fourier domain of the sinogram “bow tie”. This mask was smoothed by a convolution with a ten-point Gaussian kernel which not only avoids ringing but also introduces a pre-emphasis at low frequencies. A new filtering scheme for FBP is proposed, comprising this smoothed bow-tie filter combined with a standard radial filter and an axial filter. The authors compared the performance of the bow-tie filtering scheme with that of other previously reported methods: Standard radial filtering, angular filtering, and stackgram-domain filtering. All the quantitative data in the comparisons refer to a baseline reconstruction using a ramp filter only. When using the smallest size of the Gaussian kernel in the stackgram domain, the authors achieved a noise reduction of 33% at the cost of degrading radial and tangential resolutions 14.5% and 16%, respectively, for cubic interpolation . To reduce the noise by 30%, the angular filter produced a larger degradation of contrast 3% and tangential resolution 46% at 10 mm from the center of the field of view and showed noticeable artifacts in the form of circular blurring dependent on the distance to the center of the field of view. For a similar noise reduction 33%, the proposed bow-tie filtering scheme yielded optimum results in resolution (gain in radial resolution of 10%) and contrast (1% increase) when compared with any of the other filters alone. Experiments with rodent images showed noticeable image quality enhancement when using the proposed bow-tie filtering schemeThis work was partially funded by projects CD-TEAM CENIT program, Ministerio de Industria, CIBERsam CB07/09/0031 Ministerio de Sanidad y Consumo, TEC2004-07052-C02 Ministerio de Educación y Ciencia, and GR/SAL/024104 Comunidad de MadridPublicad

Multimodal assessment of myocardial infarction in rats: comparison of late gadolinium enhanced MRI and PET

[Poster] 4th European Molecular Imaging Meeting, Barcelona, Spain, May 27 - 30, 2009Myocardial infarction (Mi) size in rats has been assessed using Mri and nuclear imaging, but little information is available on the suitability and assessment of the information provided by each technique. We are running a study to compare results on the infarct size as assessed by each modality 30 days after an induced Mi in ratsThis work is supported by the reCaVa-reTiC network, Ministerio de Ciencia e innovación (TeC2008-06715-C02-01 and TeC2007-64731/TCM) and Ministerio de industria (CdTeaM, Programa CeniT)Publicad

Validation of a restrospective respiratory gating method for small-animal CT scanners

Proceeding of: 2008 IEEE Nuclear Science Symposium Conference Record (NSS '08), Dresden, Germany, 19-25 October 2008We propose a retrospective respiratory gating algorithm to generate dynamic CT studies. To this end, we compared three different methods of extracting the respiratory signal from the projections of small-animal cone-beam computed tomography (CBCT) scanners. Given a set of frames acquired from a certain axial angle, subtraction of their average image from each individual frame produces a set of difference images. The respiratory signals were extracted by analyzing the shape of the histogram of these difference images: we calculated the first four central and non-central moments. However, only odd-order moments produced the desired breathing signal, as the even-order moments lacked information about the phase. Each of these curves was compared to a reference signal recorded by means of a pneumatic pillow. Given the similar correlation coefficients yielded by all of them, we selected the mean to implement our retrospective protocol. Respiratory phase bins were separated, reconstructed independently and included in a dynamic sequence, suitable for cine playback. We validated our method in 5 adult rat studies by comparing profiles drawn across the diaphragm dome, with and without retrospective respiratory gating. Results showed a sharper transition in the gated reconstruction, with an average slope improvement of 60.7%.This project was supported by the CENIT Programme (Ministerio de Industria), CIBER CB07/09/0031 and RETICRECAVA (Ministerio de Sanidad y Consumo), and TEC2007-64731 TCM (Ministerio de Educaci6n y Ciencia)