Time filter

Source Type

Barcelona, Spain

Aguiar P.,Fundacion Ramon Dominguez | Aguiar P.,French National Center for Scientific Research | Pino F.,University of Barcelona | Pino F.,Institute Catala dOncologia | And 7 more authors.
Medical Physics

Purpose: To assess the performance of two approaches to the system response matrix (SRM) calculation in pinhole single photon emission computed tomography (SPECT) reconstruction. Methods: Evaluation was performed using experimental data from a low magnification pinhole SPECT system that consisted of a rotating flat detector with a monolithic scintillator crystal. The SRM was computed following two approaches, which were based on Monte Carlo simulations (MC-SRM) and analytical techniques in combination with an experimental characterization (AE-SRM). The spatial response of the system, obtained by using the two approaches, was compared with experimental data. The effect of the MC-SRM and AE-SRM approaches on the reconstructed image was assessed in terms of image contrast, signal-to-noise ratio, image quality, and spatial resolution. To this end, acquisitions were carried out using a hot cylinder phantom (consisting of five fillable rods with diameters of 5, 4, 3, 2, and 1 mm and a uniform cylindrical chamber) and a custom-made Derenzo phantom, with center-to-center distances between adjacent rods of 1.5, 2.0, and 3.0 mm. Results: Good agreement was found for the spatial response of the system between measured data and results derived from MC-SRM and AE-SRM. Only minor differences for point sources at distances smaller than the radius of rotation and large incidence angles were found. Assessment of the effect on the reconstructed image showed a similar contrast for both approaches, with values higher than 0.9 for rod diameters greater than 1 mm and higher than 0.8 for rod diameter of 1 mm. The comparison in terms of image quality showed that all rods in the different sections of a custom-made Derenzo phantom could be distinguished. The spatial resolution (FWHM) was 0.7 mm at iteration 100 using both approaches. The SNR was lower for reconstructed images using MC-SRM than for those reconstructed using AE-SRM, indicating that AE-SRM deals better with the projection noise than MC-SRM. Conclusions: The authors' findings show that both approaches provide good solutions to the problem of calculating the SRM in pinhole SPECT reconstruction. The AE-SRM was faster to create and handle the projection noise better than MC-SRM. Nevertheless, the AE-SRM required a tedious experimental characterization of the intrinsic detector response. Creation of the MC-SRM required longer computation time and handled the projection noise worse than the AE-SRM. Nevertheless, the MC-SRM inherently incorporates extensive modeling of the system and therefore experimental characterization was not required. © 2014 Author(s). Source

Ninerola-Baizan A.,University of Barcelona | Ninerola-Baizan A.,Research Center Biomedica En Red Of Bioingenieria | Rojas S.,Thrombotargets Europe S.L. | Bonastre M.,Institute dInvestigacions Biomediques August Pi i Sunyer | And 11 more authors.
Contrast Media and Molecular Imaging

The 6-hydroxydopamine (6-OHDA) rodent model of Parkinson's disease (PD) has been used to evaluate the nigrostriatal pathway. The aim of this work was to explore the relationship between the degree of 6-OHDA-induced dopaminergic degeneration and [123I]FP-CIT binding using single photon emission computed tomography (SPECT). Fourteen rats received a 6-OHDA injection (4 or 8μg) into the left medial forebrain bundle. After 3weeks, magnetic resonance imaging and scans with a small-animal SPECT system were performed. Finally, the nigrostriatal lesion was assessed by immunohistochemical analysis. Immunohistochemical analysis confirmed two levels of dopaminergic degeneration. Lesions induced by 6-OHDA diminished the ipsilateral [123I]FP-CIT binding by 61 and 76%, respectively. The decrease in tracer uptake between control and lesioned animals was statistically significant, as was the difference between the two 6-OHDA lesioned groups. Results concluded that [123I]FP-CIT SPECT is a useful technique to discriminate the degree of dopaminergic degeneration in a rat model of PD. © 2014 John Wiley & Sons, Ltd. Source

Roe-Vellve N.,University of Barcelona | Roe-Vellve N.,CIBER ISCIII | Cot A.,University of Barcelona | Cot A.,CIBER ISCIII | And 6 more authors.
IEEE Nuclear Science Symposium Conference Record

Small-animal molecular imaging is a prominent field of research, and SPECT plays an important role within it. Evaluation of imaging systems and reconstruction algorithms in SPECT imaging often involves Monte Carlo simulations, and SimSET is a widely used code for emission tomography simulation. 123I is a frequently used radionuclide in human and small animal studies. It emits a main yield of 159 keV photons, which are used for imaging, but it also has a low contribution of higher energy photons, which generate non-negligible noise in SPECT studies. The aim of this work was to implement experiment-based high- and low-energy response functions for a small animal SPECT system, to incorporate them into SimSET and to carry out a preliminary validation of the simulator obtained for 123I labeled radiotracers. Experimental measurements with 99mTc were carried out to characterize 159 keV detection of 123I. Since most of the relevant high-energy (HE) lines of 123I are close to 511 keV, the detector response to HE photons was characterized with the 511 keV photons from positron-electron annihilation subsequent to 18F decay. Once the obtained response functions were incorporated into SimSET, experimental and simulated images of capillaries and small spheres containing 123I were generated at various distances. Efficiency and spatial resolution were estimated from these images. The values from simulated images are close to the experimental ones, with deviations of under 10% in efficiency and under 6% in spatial resolution. © 2011 IEEE. Source

Ninerola-Baizan A.,CIBER ISCIII | Ninerola-Baizan A.,University of Barcelona | Rojas S.,Institute DAlta Tecnologia | Roe-Vellve N.,University of Barcelona | And 9 more authors.
Nuclear Medicine and Biology

Introduction: Rodent models are extensively used to assess the biochemical and physiological changes associated with aging. They play a major role in the development of therapies for age-related pathologies such as Parkinson's disease. To validate the usefulness of these animal models in aging or age-related disease research, the consistency of cerebral aging processes across species must be evaluated. The dopaminergic system seems particularly susceptible to the aging process. One of the results of this susceptibility is a decline in striatal dopamine transporter (DAT) availability. Methods: We sought to ascertain whether similar age changes could be detected in-vivo in rats, using molecular imaging techniques such as single photon emission computed tomography (SPECT) with [123I]FP-CIT. Results: A significant decrease of 17.21% in the striatal specific uptake ratio was observed in the aged rats with respect to the young control group. Conclusions: Our findings suggest that age-related degeneration in the nigrostriatal track is similar in humans and rats, which supports the use of this animal in models to evaluate the effect of aging on the dopaminergic system. Advances in Knowledge and Implications for patient Care: Our findings indicate that age-related degeneration in the nigrostriatal track is similar in humans and rats and that these changes can be monitored in vivo using small animal SPECT with [123I]FP-CIT, which could facilitate the translational research in rat models of age related disorders of dopaminergic system. © 2015 Elsevier Inc. Source

Cipollini M.,University of Pisa | Pastor S.,Autonomous University of Barcelona | Pastor S.,CIBER ISCIII | Gemignani F.,University of Pisa | And 13 more authors.
International Journal of Cancer

Thyroid cancer risk involves the interaction of genetic and environmental factors. The thyroperoxidase (TPO) has a key role in the iodine metabolism, being essential for the thyroid function. Mutations in the TPO gene are common in congenital hypothyroidism, and there are also signs of the implication of TPO in thyroid cancer. We performed a case-control association study of genetic variants in TPO and differentiated thyroid carcinoma (DTC) in 1,586 DTC patients and 1,769 controls including two European populations (Italy: 1,190 DTC and 1,290 controls; Spain: 396 DTC and 479 controls). Multivariate logistic regression analyses were performed separately for each population and each single-nucleotide polymorphism (SNP). From the three studied polymorphisms, significant associations were detected between DTC and rs2048722 and rs732609 in both populations (p < 0.05). In the Italian population, both SNPs showed a negative association (rs2048722, odds ratio [OR] = 0.79, 95% confidence interval [CI] = 0.63-1.00, p = 0.045; rs732609, OR = 0.72, 95% CI = 0.55-0.94, p = 0.016), whereas in the Spanish population, these SNPs showed a positive association (rs2048722, OR = 1.39, 95% CI = 1.03-1.89, p = 0.033; rs732609, OR = 1.41, 95% CI = 1.06-1.87, p = 0.018). The corresponding associations for papillary or follicular thyroid cancer were similar to those for all DTC, within population. No association was detected for the third TPO polymorphism in the Italian and the Spanish populations. Our results, for the first time, point to TPO as a gene involved in the risk of DTC, and suggest the importance of interactions between TPO variants and other unidentified population-specific factors in determining thyroid cancer risk. © 2013 UICC. Source

Discover hidden collaborations