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Publicaciones científicas más recientes (desde 2010)

Autores: Prieto, Elena; Garcia-Velloso, Maria Jose; Rodríguez-Fraile, M; et al.
Revista: PHYSICA MEDICA
ISSN 1120-1797  Vol. 46  2018  págs. 134-139
A significant radiation dose reduction of 28.7% was reached. Despite a slight reduction in image quality, the new regime was successfully implemented with readers reporting unchanged clinical confidence
Autores: Marti-Climent, JM; Morán, Verónica; Mota, M. L.; et al.
Revista: EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN 1619-7070  Vol. 45  2018  págs. S733
Autores: Prieto, Elena; Aguilar Redondo, P. B.; Morán, Verónica; et al.
Revista: EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN 1619-7070  Vol. 45  Nº Supl. 1  2018  págs. S312 - S313
Autores: Guillen Valderrama, E; Perez-Grijalba, V.; Prieto, Elena; et al.
Revista: EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN 1619-7070  Vol. 45  Nº Supl. 1  2018  págs. S227 - S228
Autores: Marti-Climent, JM; Prieto, Elena; Morán, Verónica; et al.
Revista: EJNMMI RESEARCH
ISSN 2191-219X  Vol. 7  Nº 1  2017  págs. 37
The mean ED for body and brain PET/CT protocols with different radiopharmaceuticals ranged between 4.6 and 20.0 mSv. The major contributor to total ED for body protocols is CT, whereas for brain studies, it is the PET radiopharmaceutical.
Autores: T Monserrat; Prieto, Elena; Barbes, B; et al.
Revista: ACTA RADIOLOGICA
ISSN 0284-1851  Vol. 59  Nº 6  2017  págs. 649-56
CDMAM phantom images were acquired for various PMMA thicknesses and inverse Image Quality Figure (IQFinv) was calculated. Values of incident entrance surface air kerma (ESAK) and average glandular dose (AGD) were obtained from the DICOM header for a total of 1088 pairs of clinical cases. Two experienced radiologists compared subjectively the image quality of a total of 149 pairs of clinical cases. Results CNR values were higher and doses were lower in PRIME mode for all thicknesses. IQFinv values in PRIME mode were lower for all thicknesses except for 40¿mm of PMMA equivalent, in which IQFinv was slightly greater in PRIME mode. A mean reduction of 10% in ESAK and 12% in AGD in PRIME mode with respect to standard mode was obtained. The clinical image quality in PRIME and standard acquisitions resulted to be similar in most of the cases (84% for the first radiologist and 67% for the second one). Conclusion The use of PRIME software reduces, in average, the dose of radiation to the breast without affecting image quality. This reduction is greater for thinner and denser breasts
Autores: Collantes M; Pelacho, Beatriz; Garcia-Velloso, Maria Jose; et al.
Revista: JOURNAL OF TRANSLATIONAL MEDICINE
ISSN 1479-5876  Vol. 15  Nº 1  2017  págs. 56
PET/CT imaging of 18F-FDG-labeled CSC allows quantifying biodistribution and acute retention of implanted cells in a clinically relevant pig model of chronic myocardial infarction. Similar levels of acute retention are achieved when cells are IM or IC administered. However, acute cell retention does not correlate with cell engraftment, which is improved by IM injection.
Autores: Garcia-Velloso, Maria Jose; Rodríguez-Fraile, M; et al.
Revista: EUROPEAN RADIOLOGY
ISSN 0938-7994  Vol. 27  Nº 8  2017  págs. 3190-3198
Our aim was to evaluate the diagnostic accuracy of magnetic resonance imaging (MRI) fused with prone 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) in primary tumour staging of patients with breast cancer. METHODS: This retrospective study evaluated 45 women with 49 pathologically proven breast carcinomas. MRI and prone PET-CT scans with time-of-flight and point-spread-function reconstruction were performed with the same dedicated breast coil. The studies were assessed by a radiologist and a nuclear medicine physician, and evaluation of fused images was made by consensus. The final diagnosis was based on pathology (90 lesions) or follow-up¿¿¿24 months (17 lesions). RESULTS: The study assessed 72 malignant and 35 benign lesions with a median size of 1.8 cm (range 0.3-8.4 cm): 31 focal, nine multifocal and nine multicentric cases. In lesion-by-lesion analysis, sensitivity, specificity, positive and negative predictive values were 97%, 80%, 91% and 93% for MRI, 96%, 71%, 87%, and 89% for prone PET, and 97%. 94%, 97% and 94% for MRI fused with PET. Areas under the curve (AUC) were 0.953, 0.850, and 0.983, respectively (p¿<¿0.01). CONCLUSIONS: MRI fused with FDG-PET is more accurate than FDG-PET in primary tumour staging of breast cancer patients and increases the specificity of MRI.
Autores: Morán, Verónica; Prieto, Elena; García, Berta; et al.
Revista: REVISTA ESPAÑOLA DE MEDICINA NUCLEAR E IMAGEN MOLECULAR
ISSN 2253-654X  Vol. 35  Nº 3  2016  págs. 175-85
It is recommended to increase the distance between the patients during the radiopharmaceutical incorporation and to distribute them according to the diagnostic procedure. Patients should be encouraged to use private instead of public transport. Depending on the number of nuclear medicine outpatients per year attended by a physician, it could be necessary to apply restrictions
Autores: Morán, Verónica; Prieto, Elena; García, Berta; et al.
Revista: REVISTA ESPANOLA DE MEDICINA NUCLEAR E IMAGEN MOLECULAR
ISSN 2253-654X  Vol. 35  Nº 3  2016  págs. 175 - 185
Objectives: The aim of this study was to assess the dose received by members of the public due to close contact with patients undergoing nuclear medicine procedures during radiopharmaceutical incorporation, and comparing it with the emitted radiation dose when the test was complete, in order to establish recommendations. Material and methods: A prospective study was conducted on 194 patients. H*(10) dose rates were measured at 0.1, 0.5, and 1.0 m after the radiopharmaceutical administration, before the image acquisition, and at the end of the nuclear medicine procedure. Effective dose for different close contact scenarios were calculated, according to 95th percentile value (bone scans) and the maximum value (remaining tests). Results: During the radiopharmaceutical incorporation, a person who stays with another injected patient in the same waiting room may receive up to 0.59 mSv. If the patient had a medical appointment, or went to a restaurant or a coffee shop, members of the public could receive 23, 43, and 22 mu Sv, respectively. After finishing the procedure, these doses are reduced by a factor 3. In most of the studies, the use of private instead of public transport may reduce the dose by more than a factor 6. Conclusion: It is recommended to increase the distance between the patients during the radiopharmaceutical incorporation and to distribute them according to the diagnostic procedure. Patients should be encouraged to use private instead of public transport. Depending on the number of nuclear medicine outpatients per year attended by a physician, it could be necessary to apply restrictions.
Autores: Collantes M; Benito, M.; Delgado, M.; et al.
Revista: HUMAN MOLECULAR GENETICS
ISSN 0964-6906  Vol. 25  Nº 7  2016  págs. 1318 - 1327
Porphobilinogen deaminase (PBGD) haploinsufficiency (acute intermittent porphyria, AIP) is characterized by neurovisceral attacks when hepatic heme synthesis is activated by endogenous or environmental factors including fasting. While the molecular mechanisms underlying the nutritional regulation of hepatic heme synthesis have been described, glucose homeostasis during fasting is poorly understood in porphyria. Our study aimed to analyse glucose homeostasis and hepatic carbohydrate metabolism during fasting in PBGD-deficient mice. To determine the contribution of hepatic PBGD deficiency to carbohydrate metabolism, AIP mice injected with a PBGD-liver gene delivery vector were included. After a 14 h fasting period, serum and liver metabolomics analyses showed that wild-type mice stimulated hepatic glycogen degradation to maintain glucose homeostasis while AIP livers activated gluconeogenesis and ketogenesis due to their inability to use stored glycogen. The serum of fasted AIP mice showed increased concentrations of insulin and reduced glucagon levels. Specific over-expression of the PBGD protein in the liver tended to normalize circulating insulin and glucagon levels, stimulated hepatic glycogen catabolism and blocked ketone body production. Reduced glucose uptake was observed in the primary somatosensorial brain cortex of fasted AIP mice, which could be reversed by PBGD-liver gene delivery. In conclusion, AIP mice showed a different response to fasting as measured by altered carbohydrate metabolism in the liver and modified glucose consumption in the brain cortex. Glucose homeostasis in fasted AIP mice was efficiently normalized after restoration of PBGD gene expression in the liver.
Autores: Arbizu, Javier Ignacio; Danilenko, A.; Guillen Valderrama, E; et al.
Revista: EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN 1619-7070  Vol. 43  Nº Supl.1  2016  págs. S118 - S118
Autores: Sancho, Lidia; Rodríguez-Fraile, M; Prieto, Elena; et al.
Revista: EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN 1619-7070  Vol. 43  Nº Suppl. 1  2016  págs. S12 - S12
Autores: Prieto, Elena; Morán, Verónica; García, Berta; et al.
Revista: EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN 1619-7070  Vol. 43  Nº Supl.1  2016  págs. S528 - S528
Autores: Morán, Verónica; Prieto, Elena; Zubiria, A.; et al.
Revista: EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN 1619-7070  Vol. 43  Nº Supl 1  2016  págs. S410
Autores: Prieto, Elena; Marti-Climent, JM; Morán, Verónica; et al.
Revista: PHYSICA MEDICA
ISSN 1120-1797  Vol. 31  Nº 8  2015  págs. 948-955
Optimization of reconstruction algorithm and parameters has been performed to take particular advantage of the last generation PET scanner, recommending specific settings for different brain PET radiotracers.
Autores: Marti-Climent, JM; Collantes M; Jauregui-Osoro M; et al.
Revista: EJNMMI RESEARCH
ISSN 2191-219X  Vol. 15  Nº 1  2015  págs. 70
(18)F]-tetrafluoroborate is a very useful radiotracer for PET thyroid imaging in primates, with a characteristic biodistribution in organs expressing NIS. It delivers an effective dose slightly higher than the dose produced by (99m)Tc-pertechnetate but much lower than that produced by radioiodine in the form of (131)INa, (123)INa, or (124)INa.
Autores: Cardier, M; Zulueta-Santos, Cristina; Manrique, Raquel; et al.
Revista: AUDIOLOGY AND NEURO-OTOLOGY
ISSN 1420-3030  Vol. 20  Nº Supl 1  2015  págs. 48 - 52
This article presents an analysis of the impact of functional neuroimaging studies (positron emission tomography, PET) in asymmetric hearing loss based on the clinical expertise obtained from a group of 21 patients. In these patients, PET studies are performed at rest and after auditory stimulation in order to measure the increase in brain activity in the ipsi- and contralateral cortex, providing supporting evidence to recommend a specific treatment and the side to implant. In conclusion, PET is a useful tool for selected cases in which information on the metabolic status of the auditory pathway can drive the decision regarding the treatment of the most appropriate ear. However, in view of our small sample, further research is needed to confirm our results in this topic
Autores: Barbes, B; Azcona, Juan Diego; Prieto, Elena; et al.
Revista: JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS
ISSN 1526-9914  Vol. 16  Nº 5  2015  págs. 306-321
Autores: Gago, B.; Quiroga-Varela, A.; Juri, C.; et al.
Revista: NEUROBIOLOGY OF DISEASE
ISSN 0969-9961  Vol. 77  2015  págs. 165 - 172
Carbon-11 labeled dihydrotetrabenazine (11C-DTBZ) binds to the vesicular monoamine transporter 2 and has been used to assess nigro-striatal integrity in animal models and patients with Parkinson's disease. Here, we applied 11C-DTBZ positron emission tomography (PET) to obtain longitudinally in-vivo assessment of striatal dopaminergic loss in the classic unilateral and in a novel bilateral 6-hydroxydopamine (6-OHDA) lesion rat model. Forty-four Sprague-Dawley rats were divided into 3 sub-groups: 1. 6-OHDA-induced unilateral lesion in the medial forebrain bundle, 2. bilateral lesion by injection of 6-OHDA in the third ventricle, and 3. vehicle injection in either site. 11C-DTBZ PET studies were investigated in the same animals successively at baseline, 1, 3 and 6weeks after lesion using an anatomically standardized volumes-of-interest approach. Additionally, 12 rats had PET and Magnetic Resonance Imaging to construct a new 11C-DTBZ PET template. Behavior was characterized by rotational, catalepsy and limb-use asymmetry tests and dopaminergic striatal denervation was validated post-mortem by immunostaining of the dopamine transporter (DAT). 11C-DTBZ PET showed a significant decrease of striatal binding (SB) values one week after the unilateral lesion. At this point, there was a 60% reduction in SB in the affected hemisphere compared with baseline values in 6-OHDA unilaterally lesioned animals. A 46% symmetric reduction over baseline SB values was found in bilaterally lesioned rats at the first week after lesion. SB values remained constant in unilaterally lesioned rats whereas animals with bilateral lesions showed a modest (22%) increase in binding values at the 3rd and 6th weeks post-lesion. The degree of striatal dopaminergic denervation was corroborated histologically by DAT immunostaining. Statistical analysis revealed a high correlation between 11C-DTBZ PET SB and striatal DAT immunostaining values (r=0.95, p<0.001). The data presented here indicate that 11C-DTBZ PET may be used to ascertain changes occurring in-vivo throughout the evolution of nigro-striatal dopaminergic neurodegeneration, mainly in the unilateral 6-OHDA lesion rat.
Autores: Prieto, Elena; Riverol, M.; et al.
Revista: EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN 1619-7070  Vol. 42  Nº 10  2015  págs. 1522-9
Patients with a prion disease exhibit a characteristic pattern of brain metabolism presentation in FDG PET imaging. Consequently, in patients with rapidly progressive cognitive impairment, the detection of these patterns in the FDG PET study could orient the diagnosis to a prion disease.
Autores: Marti-Climent, JM; Collantes M; Prieto, Elena; et al.
Revista: RADIOPROTECCION
ISSN 1133-1747  Vol. 79  2014  págs. 26 - 36
Autores: Marti-Climent, JM; Prieto, Elena; Elosúa C; et al.
Revista: MEDICAL PHYSICS
ISSN 0094-2405  Vol. 41  Nº 9  2014  págs. 092503
Qualitative and quantitative 90Y PET imaging improved with the introduction of TOF in a PET/CT scanner, thereby allowing the visualization of microsphere deposition in lesions not visible in non-TOF images. This technique accurately quantifies the total activity delivered to the liver during radioembolization with (90)Y-microspheres and allows dose estimation.
Autores: Prieto, Elena; Marti-Climent, JM; Marisol Gómez Fernández; et al.
Revista: INTERNATIONAL JOURNAL OF OPHTHALMOLOGY
ISSN 2222-3959  Vol. 33  Nº 2  2014  págs. 79 - 86
Objetivo Diseñar una técnica novedosa de adquisición ex-vivo para establecer un marco común de validación de diferentes técnicas de segmentación para imágenes PET oncológicas. Evaluar sobre estas imágenes el funcionamiento de varios algoritmos de segmentación automática. Material y métodos En 15 pacientes oncológicos se realizaron estudios PET ex-vivo de las piezas quirúrgicas extraídas durante la cirugía, previa inyección de 18F-FDG, adquiriéndose imágenes en 2 tomógrafos: un PET/CT clínico y un tomógrafo PET de alta resolución. Se determinó el volumen tumoral real en cada paciente, generándose una imagen de referencia para la segmentación de cada tumor. Las imágenes se segmentaron con 12 algoritmos automáticos y con un método estándar para PET (umbral relativo del 42%) y se evaluaron los resultados mediante parámetros cuantitativos. Resultados La segmentación de imágenes PET de piezas quirúrgicas ha demostrado que para imágenes PET de alta resolución 8 de las 12 técnicas de segmentación evaluadas superan al método estándar del 42%. Sin embargo, ninguno de los algoritmos superó al método estándar en las imágenes procedentes del PET/CT clínico. Debido al gran interés de este conjunto de imágenes PET, todos los estudios se han publicado a través de Internet con el fin de servir de marco común de validación y comparación de diferentes técnicas de segmentación. Conclusiones Se ha propuesto una técnica novedosa para validar técnicas de segmentación para imágenes PET oncológicas, adquiriéndose estudios ex-vivo de piezas quirúrgicas. Se ha demostrado la utilidad de este conjunto de imágenes PET mediante la evaluación de varios algoritmos automáticos.
Autores: Arbizu, Javier Ignacio; Prieto, Elena; et al.
Revista: EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN 1619-7070  Vol. 10  Nº 9  2013  págs. 1394 - 1405
To introduce, evaluate and validate a voxel-based analysis method of F-18-FDG PET imaging for determining the probability of Alzheimer's disease (AD) in a particular individual. The subject groups for model derivation comprised 80 healthy subjects (HS), 36 patients with mild cognitive impairment (MCI) who converted to AD dementia within 18 months, 85 non-converter MCI patients who did not convert within 24 months, and 67 AD dementia patients with baseline FDG PET scan were recruited from the AD Neuroimaging Initiative (ADNI) database. Additionally, baseline FDG PET scans from 20 HS, 27 MCI and 21 AD dementia patients from our institutional cohort were included for model validation. The analysis technique was designed on the basis of the AD-related hypometabolic convergence index adapted for our laboratory-specific context (AD-PET index), and combined in a multivariable model with age and gender for AD dementia detection (AD score). A logistic regression analysis of different cortical PET indexes and clinical variables was applied to search for relevant predictive factors to include in the multivariable model for the prediction of MCI conversion to AD dementia (AD-Conv score). The resultant scores were stratified into sixtiles for probabilistic diagnosis. The area under the receiver operating characteristic curve (AUC) for the AD score detecting AD dementia in the ADNI database was 0.879, and the observed probability of AD dementia in the six defined groups ranged from 8 % to 100 % in a monotonic trend. For predicting MCI conversion to AD dementia, only the posterior cingulate index, Mini-Mental State Examination (MMSE) score and apolipoprotein E4 genotype (ApoE4) exhibited significant independent effects in the univariable and multivariable models. When only the latter two clinical variables were included in the model, the AUC was 0.742 (95 % CI 0.646 - 0.838), but this increased to 0.804 (95 % CI 0.714 - 0.894, bootstrap p = 0.027) with the addition of the posterior cingulate index (AD-Conv score). Baseline clinical diagnosis of MCI showed 29.7 % of converters after 18 months. The observed probability of conversion in relation to baseline AD-Conv score was 75 % in the high probability group (sixtile 6), 34 % in the medium probability group (merged sixtiles 4 and 5), 20 % in the low probability group (sixtile 3) and 7.5 % in the very low probability group (merged sixtiles 1 and 2). In the validation population, the AD score reached an AUC of 0.948 (95 % CI 0.625 - 0.969) and the AD-Conv score reached 0.968 (95 % CI 0.908 - 1.000), with AD patients and MCI converters included in the highest probability categories. Posterior cingulate hypometabolism, when combined in a multivariable model with age and gender as well as MMSE score and ApoE4 data, improved the determination of the likelihood of patients with MCI converting to AD dementia compared with clinical variables alone. The probabilistic model described here provides a new tool that may aid in the clinical diagnosis of AD and MCI conversion.
Autores: Prieto, Elena; Garcia-Velloso, Maria Jose; et al.
Revista: CLINICAL NUCLEAR MEDICINE
ISSN 0363-9762  Vol. 38  Nº 2  2013  págs. 103-109
Background: Accuracy in the quantification of the SUV is a critical point in PET because proper quantification of tumor uptake is essential for therapy monitoring and prognosis evaluation. Recent advances such as time-of-flight (TOF) and point-spread-function (PSF) reconstructions have dramatically improved detectability. However, first experiences with these techniques have shown a consistent tendency to measure markedly high SUV values, bewildering nuclear medicine physicians and referring clinicians. Purpose: We investigated different reconstruction and quantification procedures to determine the optimum protocol for an accurate SUV quantification in last generation PET scanners. Methods: Both phantom and patient images were evaluated. A complete set of experiments was performed using a body phantom containing 6 spheres with different background levels and contrasts. Whole-body FDG PET/CT of 20 patients with breast and lung cancer was evaluated. One hundred five foci were identified by 2 experienced nuclear medicine physicians. Each acquisition was reconstructed both with classical and advanced (TOF, PSF) reconstruction techniques. Each sphere and each in vivo lesion was quantified with different parameters as follows: SUVmax, SUVmean, and SUV50 (mean within a 50% isocontour). Results: This study has confirmed that quantification with SUVmax produces important overestimation of metabolism in new generation PET scanners. This is a relevant result because, currently, SUVmax is the standard parameter for quantification. SUV50 has been shown as the best alternative, especially when applied to images reconstructed with PSF + TOF. Conclusions: SUV50 provides accurate quantification and should replace SUVmax in PET tomographs incorporating advanced reconstruction techniques. PSF + TOF reconstruction is the optimum for both detection and accurate quantification.
Autores: Marti-Climent, JM; Prieto, Elena; et al.
Revista: REVISTA ESPAÑOLA DE MEDICINA NUCLEAR
ISSN 0212-6982  Vol. 32  Nº 1  2013  págs. 13 - 21
Objective: To characterize the performance of the Biograph mCT PET/CT TrueV scanner with time of flight (TOF) and point spread function (PSF) modeling. Material and methods: The PET/CT scanner combines a 64-slice CT and PET scanner that incorporates in the reconstruction the TOF and PSF information. PET operating characteristics were evaluated according to the standard NEMA NU 2-2007, expanding some tests. In addition, different reconstruction algorithms were included, and the intrinsic radiation and tomographic uniformity were also evaluated. Results: The spatial resolution (FWHM) at 1 and 10 cm was 4.4 and 5.3 mm, improving to 2.6 and 2.5 mm when PSF is introduced. Sensitivity was 10.9 and 10.2 Kcps/MBq at 0 and 10 cm from the axis. Scatter fraction was less than 34% at low concentrations and the noise equivalent count rate (NECR) was maximal at 27.8 kBq/mL with 182 Kcps, the intrinsic radiation produced a rate of 4.42 true coincidences per second. Coefficient of variation of the volume and system uniformity were 4.7 and 0.8% respectively. The image quality test showed better results when PSF and TOF were included together. PSF improved the hot spheres contrast and background variability, while TOF improved the cold spheres contrast. Conclusions: The Biograph mCT TrueV scanner has good performance characteristics. The image quality improves when the information from the PSF and the TOF is incorporated in the reconstruction.
Autores: Arbizu, Javier Ignacio; Tejada, Sonia; Marti-Climent, JM; et al.
Revista: EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN 1619-7070  Vol. 39  Nº 5  2012  págs. 771 - 781
PURPOSE: The aim of the study was to evaluate the volumetric integration patterns of standard MRI and (11)C-methionine positron emission tomography (PET) images in the surgery planning of gliomas and their relationship to the histological grade. METHODS: We studied 23 patients with suspected or previously treated glioma who underwent preoperative (11)C-methionine PET because MRI was imprecise in defining the surgical target contour. Images were transferred to the treatment planning system, coregistered and fused (BrainLAB). Tumour delineation was performed by (11)C-methionine PET thresholding (vPET) and manual segmentation over MRI (vMRI). A 3-D volumetric study was conducted to evaluate the contribution of each modality to tumour target volume. All cases were surgically treated and histological classification was performed according to WHO grades. Additionally, several biopsy samples were taken according to the results derived either from PET or from MRI and analysed separately. RESULTS: Fifteen patients had high-grade tumours [ten glioblastoma multiforme (GBM) and five anaplastic), whereas eight patients had low-grade tumours. Biopsies from areas with high (11)C-methionine uptake without correspondence in MRI showed tumour proliferation, including infiltrative zones, distinguishing them from dysplasia and radionecrosis. Two main PET/MRI integration patterns emerged after analysis of volumetric data: pattern vMRI-in-vPET (11/23) and pattern vPET-in-vMRI (9/23). Besides, a possible third pattern with differences in both directions (vMRI-diff-vPET) could also be observed (3/23). There was a statistically significant association between the tumour classification and integration patterns described above (p¿<¿0.001, ¿¿=¿0.72). GBM was associated with pattern vMRI-in-vPET (9/10), low-grade with pattern vPET-in-vMRI (7/8) and anaplastic with pattern vMRI-diff-vPET (3/5). CONCLUSION: The metabolically active tumour volume observed in (11)C-methionine PET differs from the volume of MRI by showing areas of infiltrative tumour and distinguishing from non-tumour lesions. Differences in (11)C-methionine PET/MRI integration patterns can be assigned to tumour grades according to the WHO classification. This finding may improve tumour delineation and therapy planning for gliomas.
Autores: Prieto, Elena; Pagola, M.; et al.
Revista: PHYSICS IN MEDICINE AND BIOLOGY
ISSN 0031-9155  Vol. 57  Nº 12  2012  págs. 3963-80
Tumor volume delineation over positron emission tomography (PET) images is of great interest for proper diagnosis and therapy planning. However, standard segmentation techniques (manual or semi-automated) are operator dependent and time consuming while fully automated procedures are cumbersome or require complex mathematical development. The aim of this study was to segment PET images in a fully automated way by implementing a set of 12 automated thresholding algorithms, classical in the fields of optical character recognition, tissue engineering or non-destructive testing images in high-tech structures. Automated thresholding algorithms select a specific threshold for each image without any a priori spatial information of the segmented object or any special calibration of the tomograph, as opposed to usual thresholding methods for PET. Spherical (18)F-filled objects of different volumes were acquired on clinical PET/CT and on a small animal PET scanner, with three different signal-to-background ratios. Images were segmented with 12 automatic thresholding algorithms and results were compared with the standard segmentation reference, a threshold at 42% of the maximum uptake. Ridler and Ramesh thresholding algorithms based on clustering and histogram-shape information, respectively, provided better results that the classical 42%-based threshold (p < 0.05). We have herein demonstrated that fully automated thresholding algorithms can provide better results than classical PET segmentation tools
Autores: Prieto, Elena; Arbizu, Javier Ignacio; et al.
Revista: BRAIN
ISSN 0006-8950  Vol. 135  2012  págs. 2817-25
Neuronal loss in Alzheimer's disease, a better correlate of cognitive impairment than amyloid deposition, is currently gauged by the degree of regional atrophy. However, functional markers, such as GABA(A) receptor density, a marker of neuronal integrity, could be more sensitive. In post-mortem hippocampus, GABA(A) messenger RNA expression is reduced even in mild cognitive impairment. We measured whole-brain GABA(A) binding potential in vivo using [(11)C]-flumazenil positron emission tomography and compared GABA(A) binding with metabolic and volumetric measurements. For this purpose, we studied 12 subjects, six patients with early Alzheimer's disease and six healthy controls, with [(11)C]-flumazenil and [(18)F]-fluorodeoxyglucose positron emission tomography, as well as with high-resolution magnetic resonance imaging. Data were evaluated with both voxel-based parametric methods and volume of interest methods. We found that in early Alzheimer's disease, with voxel-based analysis, [(11)C]-flumazenil binding was decreased in infero-medial temporal cortex, retrosplenial cortex and posterior perisylvian regions. Inter-group differences reached corrected significance when using an arterial input function. Metabolism measured with positron emission tomography and volumetric measurements obtained with magnetic resonance imaging showed changes in regions affected in early Alzheimer's disease, but, unlike with [(11)C]-flumazenil binding and probably due to sample size, the voxel-based findings failed to reach corrected significance in any region of the brain. With volume of interest analysis, hippocampi and posterior cingulate gyrus showed decreased [(11)C]-flumazenil binding. In addition, [(11)C]-flumazenil hippocampal binding correlated with memory performance. Remarkably, [(11)C]-flumazenil binding was decreased precisely in the regions showing the greatest degree of neuronal loss in post-mortem studies of early Alzheimer's disease. From these data, we conclude that [(11)C]-flumazenil binding could be a useful marker of neuronal loss in early Alzheimer's disease
Autores: Marti-Climent, JM; Prieto, Elena; Collantes M; et al.
Revista: Radiation Measurements
ISSN 1350-4487  Vol. 46  Nº 11  2011  págs. 1307 - 1309
This study focuses on the occupational doses of technologists working at an Animal Research Unit using PET radiotracers and on the environmental dose rates produced by the animals (mice, rats and monkeys). In particular, whole body and extremity monitoring is reported and related with the workload. The study shows that doses not only depend on the amount of activity injected but also on the type of animals and radiotracers managed. The extremities, with a great variability of the doses received, are the limiting organs as far as regulatory dose limits for workers are concerned. Mean H¿(10) rates in contact and at 20 cm from the animals, when they are handled by the technologist, range from around 1 mSv/h to 20 ¿Sv/h, respectively.
Autores: Prieto, Elena; et al.
Revista: REVISTA ESPAÑOLA DE MEDICINA NUCLEAR
ISSN 0212-6982  Vol. 30  Nº 2  2011  págs. 88 - 93
(18)F-FDOPA is an amino acid analogue used to evaluate presynaptic dopaminergic activity, which has aroused great interest in neuro-oncology. We have evaluated five (18)F-FDOPA PET studies of patients referred for study of parkinsonian syndrome. Two subjects had previously treated high-grade brain tumors, one nonspecific brain injury, and 2 subjects presented unexpected tumoral lesions. For all lesions SUVmax, time to SUVmax and tumor-to-normal grey matter SUVmax rate (T/N) were calculated, and 90 minutes (18)F-FDOPA kinetics were analyzed. Tumor lesions corresponded to three malignant neurocytomas, one meningioma, one pineocytoma and one intrasinusal hemangioma. Both malignant and benign tumors exhibited high uptake of (18)F-FDOPA well above the normal cortex. However, the analysis of the curve uptake displayed characteristic patterns that facilitate the characterization of tumor lesions. A dual phase maximum uptake was observed, with an early 10 minutes uptake in malignant lesions, and a late 60 to 90 minutes uptake in benign or low grade lesions.
Autores: Prieto, Elena; Collantes M; Delgado, M; et al.
Revista: European Journal of Nuclear Medicine & Molecular Imaging
ISSN 1619-7070  Vol. 38  Nº 12  2011  págs. 2228 - 2237
This study demonstrates that any difference detected with SPM analysis of MOSAIC PET images of rat brain is detected also by the gold standard autoradiographic technique, confirming that this methodology provides reliable results, although partial volume effects might make it difficult to detect slight differences in small regions.
Autores: Prieto, Elena; Marti-Climent, JM; et al.
Revista: JOURNAL OF NUCLEAR MEDICINE
ISSN 0161-5505  Vol. 52  Nº 6  2011  págs. 865-72
Compared with standard (18)F-FDG PET studies, quantitative dual-time-point (18)F-FDG PET can improve sensitivity for the identification and volume delineation of high-grade brain tumors.
Autores: Prieto, Elena; Marti-Climent, JM; Arbizu, Javier Ignacio; et al.
Revista: Computers in Biology and Medicine
ISSN 0010-4825  Vol. 40  Nº 1  2010  págs. 75 - 80
Autores: Marti-Climent, JM; Prieto, Elena; López Lafuente, J; et al.
Revista: REVISTA ESPAÑOLA DE MEDICINA NUCLEAR
ISSN 0212-6982  Vol. 29  Nº 4  2010  págs. 189-210
Autores: Juri, Carlos Andrés; Collantes M; Peñuelas, Iván; et al.
Revista: Neurobiology of Disease
ISSN 0969-9961  Vol. 38  Nº 3  2010  págs. 456 - 463
Autores: Prieto, Elena; Arbizu, Javier Ignacio; et al.
Revista: STROKE
ISSN 0039-2499  Vol. 41  Nº 12  2010  págs. 2889-93
The anatomy of metabolic abnormalities in vascular disease with dementia suggests that, at least in some cases, dementia with vascular disease may be independent of AD. The metabolic abnormality involves the thalamus, caudate, and frontal lobe, a pattern concordant with the neuropsychological findings of impaired executive function characteristic of vascular dementia.
Autores: Marti-Climent, JM; Prieto, Elena; et al.
Libro:  Medicina Nuclear en la práctica clínica
2012  págs. 29-37