Nuestros investigadores

Josep María Marti Climent

Publicaciones científicas más recientes (desde 2010)

Autores: Reynes-Llompart, G. ; Sabate-Llobera, A. ; Llinares-Tello, E.; et al.
Revista: SCIENTIFIC REPORTS
ISSN 2045-2322  Vol. 9  2019  págs. 10640
The present work investigates the influence of different biological and physical parameters on image quality (IQ) perception of the abdominal area in a modern PET scanner, using new reconstruction algorithms and testing the utility of a radiomics approach. Scans of 112 patients were retrospectively included. Images were reconstructed using both OSEM + PSF and BSRM methods, and IQ of the abdominal region was subjectively evaluated. First, 22 IQ related parameters were obtained (including count rate and biological or mixed parameters) and compared to the subjective IQ scores by means of correlations and logistic regression. Second, an additional set of radiomics features was extracted, and a model was constructed by means of an elastic-net regression. For the OSEM + PSF and especially for the BSRM reconstructions, IQ parameters presented only at best moderated correlations with the subjective IQ. None of the studied parameters presented a good predictive power for IQ, while a simple radiomics model increased the performance of the IQ prediction. These results suggest the necessity of changing the standard parameters to evaluate IQ, particularly when a BSRM algorithm is involved. Furthermore, it seems that a simple radiomics model can outperform the use of any single parameter to assess IQ.
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: Reynes-Llompart, G.; Martin-Vaello, R.; Notta, P. ; et al.
Revista: EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN 1619-7070  Vol. 45  Nº Supl. 1  2018  págs. S706 - S707
Autores: Vaello, R. M.; Reynes-Llompart, G.; Mateo-Navarro, D.; et al.
Revista: RADIOTHERAPY AND ONCOLOGY
ISSN 0167-8140  Vol. 127  Nº Supl.1  2018  págs. S1217 - S1218
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: Aznárez-Sanado, Maite; Sierrasesúmaga, Luis; et al.
Revista: ANALES DEL SISTEMA SANITARIO DE NAVARRA
ISSN 1137-6627  Vol. 40  Nº 1  2017  págs. 85 - 92
Background. Osteosarcoma paediatric patients are usually treated with intra-arterial chemotherapy (QTia) which is administered directly to the tumour. This procedure exposes patients to ionizing radiation. Paediatric patients are especially sensitive to this exposure. Methods. The total amount of ionizing radiation received from QTia administration was quantified in a group of 16 osteosarcoma paediatric patients from the Clinica Universidad de Navarra. Results. The median of the total radiation received per patient was 33.4 Gy.cm(2) (IQR: 43.33 Gy.cm(2)), and the median number of procedures performed per subject was 10 (IQR: 6.5). Conclusions. The study highlights the importance of quantifying the radiation received by a group of children and adolescents affected by osteosarcoma during treatment with QTia. Long-term side effects of this radiation should be considered in paediatric patients. Currently, there are no previous studies that provide data of the amount of ionizing radiation received through this procedure.
Autores: Collantes M; Quincoces, Gemma; et al.
Revista: THE QUARTERLY JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN 1824-4785  Vol. 61  Nº 4  2017  págs. 447 - 455
Background: The feasibility of beta cell mass (BCM) imaging and quantification with positron emission tomography (PET) in the pancreas is controversial. In an effort to shed some light on this topic, we have used a xenograft model of rat insulinoma (RIN) in mice, mimicking an intramuscular islet transplantation situation. Methods: A total of 105 RIN cells were subcutaneously implanted in nude mice (N.=8). Tumor size and glycaemia levels were determined daily. Rat C-peptide was measured to demonstrate rat insulin production. PET imaging with 11C-(+)-¿-dihydrotetrabenazine (11C-DTBZ) was done at 3 and 4 weeks and compared with 18F-FDG and 18F-DOPA studies in the same mice. Ex-vivo autoradiography with 11C-DTBZ was carried out in frozen sections of tumors. VMAT2 expression was measured by Western-blot and immunohistochemistry in tumors and RIN cells. Results: Functional rat insulin production in mice was demonstrated by substantial decrease in glycaemia (<50 mg/dL by week 4) and rat C-peptide levels (7.2±2.6 ng/mL) similar to those measured in control rats. PET studies showed that tumor imaging with 11C-DTBZ at four (N.=8) and five (N.=5) weeks was negative; only bigger tumors could be seen with 18F-DOPA. In explanted tumors 11C-DTBZ autoradiography was negative, albeit VMAT2 expression measured by Western-blot and immunohistochemistry was lower than in cultured RIN cells. Conclusions: Although insulinomas are fully functional it does not seem feasible to use 11C-DTBZ for in-vivo measuring of BCM. This might either be due to inherent technical limitations of PET, decrease in VMAT2 expression in the tumors due to unknown reasons, or other biological limiting facts.
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: 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: 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: Reynes-Llompart, G. ; Montes, E.; Saldana, P.; et al.
Revista: EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN 1619-7070  Vol. 43  Nº Supl 1  2016  págs. S523 - S523
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: Sancho, Lidia; Morán, Verónica; et al.
Revista: REVISTA ESPAÑOLA DE MEDICINA NUCLEAR E IMAGEN MOLECULAR
ISSN 2253-8070  Vol. 34  Nº Supl. 1  2015  págs. 59
La evaluación clínica del PET de amiloide con 18 F-florbetapir no se afecta por el tipo de equipo, aunque los de nueva generación reducen el número de casos dudosos. Para el seguimiento, los estudios deben ser adquiridos en un tiempo de adquisición similar. Estos hallazgos son relevantes para los ensayos de posibles nuevos fármacos anti-amiloid
Autores: Marti-Climent, JM; Collantes M; Prieto, Elena; et al.
Revista: RADIOPROTECCION
ISSN 1133-1747  Vol. 79  2014  págs. 26 - 36
Autores: Pérez Azorin,JF; Marti-Climent, JM;
Revista: MEDICAL PHYSICS
ISSN 0094-2405  Vol. 41  Nº 6  2014  págs. 062101
The improved multichannel dosimetric method is able to remove many of the common disturbances usually present in radiochromic films and improves the gamma analysis results compared with the other three methods.
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: Barbes, B; Azcona, Juan Diego; Burguete, Javier; et al.
Revista: MEDICAL PHYSICS
ISSN 0094-2405  Vol. 41  Nº 1  2014  págs. 12102-11
Autores: Marti-Climent, JM; Garcia-Velloso, Maria Jose; et al.
Revista: INTERNATIONAL JOURNAL OF OPHTHALMOLOGY
ISSN 2222-3959  Vol. 33  Nº 5  2014  págs. 280-285
Objectives: To investigate quantitative methods of tumor proliferation using 3'-[F-18]fluoro-3'-deoxythymidine ([F-18]FLT) PET in patients with breast cancer (BC), studied before and after one bevacizumab administration, and to correlate the [F-18]FLT-PET uptake with the Ki67 index. Material and methods: Thirty patients with newly diagnosed, untreated BC underwent a [F-18]FLT-PET before and 14 days after bevacizumab treatment. A dynamic scan centered over the tumor began simultaneously with the injection of [F-18]FLT (385 +/- 56 MBq). Image derived input functions were obtained using regions of interest drawn on the left ventricle (LV) and descending aorta (DA). Metabolite corrected blood curves were used as input functions to obtain the kinetic Ki constant using the Patlak graphical analysis (time interval 10-60 min after injection). Maximum SUV values were derived for the intervals 40-60 min (SUV40) and 50-60 min (SUV50). PET parameters were correlated with the Ki67 index obtained staining tumor biopsies. Results: [F-18]FLT uptake parameters decreased significantly (p < 0.001) after treatment: SUV50 = 3.09 +/- 1.21 vs 2.22 +/- 0.96; SUV40 = 3.00 +/- 1.18 vs 2.14 +/- 0.95, Ki_LV(10-3) = 52[22-116] vs 38[13-80] and Ki_DA(10-3) = 49[15-129] vs 33[11-98]. Consistency interclass correlation coefficients within SUV and within Ki were high. Changes of SUV50 and Ki_DA between baseline PET and after one bevacizumab dose PET correlated with changes in Ki67 index (r-Pearson = 0.35
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: Peñuelas, Iván; Garcia-Velloso, Maria Jose; et al.
Revista: JOURNAL OF ONCOLOGY
ISSN 1687-8450  Vol. 12  Nº 7  2012  págs. 710561
Molecular imaging of breast cancer has undoubtedly permitted a substantial development of the overall diagnostic accuracy of this malignancy in the last years. Accurate tumour staging, design of individually suited therapies, response evaluation, early detection of recurrence and distant lesions have also evolved in parallel with the development of novel molecular imaging approaches. In this context, positron emission tomography (PET) can be probably seen as the most interesting molecular imaging technology with straightforward clinical application for such purposes. Dozens of radiotracers for PET imaging of breast cancer have been tested in laboratory animals. However, in this review we shall focus mainly in the smaller group of PET radiopharmaceuticals that have lead through into the clinical setting. PET imaging can be used to target general metabolic phenomena related to tumoural transformation, including glucose metabolism and cell proliferation, but can also be directed to specific hormone receptors that are characteristic of the breast cancer cell. Many other receptors and transport molecules present in the tumour cells could also be of interest for imaging. Furthermore, molecules related with the tumour microenvironment, tumour induced angiogenesis or even hypoxia could also be used as molecular biomarkers for breast cancer imaging.
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; 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: Richter, José Ángel; Rodríguez-Fraile, M; et al.
Revista: Molecular Imaging and Biology
ISSN 1536-1632  Vol. 12  Nº 2  2010  págs. 210 - 217
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: Arbizu, Javier Ignacio; Rodríguez-Fraile, M; Marti-Climent, JM; et al.
Libro:  Liver radioembolization with 90Y microspheres
2014  págs. 63-75
Autores: Marti-Climent, JM; Prieto, Elena; et al.
Libro:  Medicina Nuclear en la práctica clínica
2012  págs. 29-37
Autores: Garcia-Velloso, Maria Jose; Coma, María Isabel; Peñuelas, Iván; et al.
Libro:  Medicina Nuclear en la práctica clínica
2012  págs. 295-305
Autores: Marti-Climent, JM; Puchal, R;
Libro:  Tomografía por emisión de positrones y CT. Instrumentación y aplicaciones
2011  págs. 81-102

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