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Publications (4)0.76 Total impact

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    ABSTRACT: Quantitative analysis of positron emission tomography (PET) dynamic images allows to estimate physiological parameters such as glucose metabolic rate (GMR), perfusion, and cardiac output (CO). However, several physical effects such as photon attenuation, scatter and partial volume can reduce the accuracy of parameter estimation. The main goal of this work was to improve small animal PET image quality by introducing system point spread function (PSF) in the reconstruction scheme and to evaluate the effect of partial volume correction (PVC) on physiological parameter estimation. Images reconstructed respectively using constant and spatially variant (SV) PSFs and no PSF modeling was compared. The proposed algorithms were tested on simulated and real phantoms and mice images. Results show that the SV-PSF-based reconstruction method provides a significant contrast improvement of small animals PET cardiac images and, thus, the effects of PVC on physiological parameters were evaluated using such algorithm. Simulations show that the proposed PVC method reduces errors with respect to the true values for parametric images of GMR and perfusion. A reduction of CO percentage error with respect to the original value was also obtained using the SF-PSF approach. In conclusion, SV-PSF reconstruction method provides a more accurate estimation of several physiological parameters obtained from a dynamic PET scan.
    Journal of Mechanics in Medicine and Biology 04/2012; 10(01). · 0.76 Impact Factor
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    ABSTRACT: Physiologic parameters such as glucose metabolic rate (GMR), perfusion and cardiac output (CO) can be estimated by performing quantitative analysis using PET dynamic images. The measurement of the image derived arterial input function (IF) and the tissue time activity curve (TAC) can be affected by partial volume effect (PVE). Because of partial volume, the estimate of different physiological parameters can be severely biased. The main goal of this work was to evaluate the effects of an image reconstruction based partial volume correction (PVC) method of small animal PET images on metabolic rate and perfusion on a pixel-based analysis and on cardiac output. The proposed PVC method is based on Point Spread Function (PSF) modeling in the reconstruction scheme. Dynamic mouse heart images were created using the Moby phantom. IF and TAC were simulated for one and two compartmental models and different radiotracers in order to take into account the different positron range. Images were simulated using different sets of rate constants and different noise levels. In order to obtain an estimate of the probability distribution of each kinetic parameter from each pixel value, bootstrap resampling with replacement was applied. The coefficient of variation and the bias of the mean of the distribution with respect to the theoretical value were estimated. Pre and post-correction parametric images of GMR and perfusion and the relative errors show that the image reconstruction PVC reduces errors with respect to the theoretical values in each pixel. The percentage error of CO from uncorrected and corrected images with respect to the theoretical value was 13.5% and 2.3%, respectively, for <sup>18</sup>F-FDG study. Regarding images acquired using <sup>82</sup>Rb, CO estimate was equal to 34.6 % and 23.2 % for non PVC and PVC images, respectively. In conclusion, pixel based PVC allows to obtain a better measure of the radiotracer concentration in the heart and a more accurate estimation- - of the phisiological parameters.
    Nuclear Science Symposium Conference Record, 2008. NSS '08. IEEE; 11/2008
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    ABSTRACT: Small animal positron emission tomography (PET) image quantitation is severely affected by partial volume effect (PVE) caused by the spatial resolution of PET tomographs. The aim of this work was to reduce the PVE using a modified iterative expectation maximization (EM) reconstruction algorithm. The goal of the method was to increase the accuracy of tracer concentration values in order to obtain an in vivo better estimate of physiological parameters. The performance of the proposed correction method was evaluated by calculating left ventricle and myocardium mean value using simulated cardiac fluorodeoxyglucose (FDG) dynamic images.
    Computers in Cardiology, 2008; 10/2008
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    ABSTRACT: The goal of this work was to improve the image quality of small animal PET images by introducing in the reconstruction process the true system point spread function (PSF) and an anatomical image prior. Simulations were performed using a mouse heart phantom (myocardium and ventricles) and a comparison between standard EM reconstruction and EM with PSF modelling and anatomical prior was performed. The system PSF was assumed to be a Gaussian function and its Full Width Half Maximum (FWHM) was modelled to be spatially variant in order to simulate the different spatial resolution inside the scanner field of view. A visual comparison of the images reconstructed with the standard EM and with the proposed image reconstruction method showed that the reconstructed images look much sharper and are very close to the true ones when using EM with PSF modelling and anatomical prior.
    Computers in Cardiology, 2008; 01/2008