Revistas
Revista:
SCIENTIFIC REPORTS
ISSN:
2045-2322
Año:
2022
Vol.:
12
N°:
1
Págs.:
18161
The aim was to study the performance of the U-SPECT6/CT E-class system for preclinical imaging, to later demonstrate the viability of simultaneous multi-animal and multi-isotope imaging with reliable quantitative accuracy. The performance of the SPECT was evaluated for two collimators dedicated for mouse (UHS-M) and rat imaging (UHR-RM) in terms of sensitivity, energy resolution, uniformity and spatial resolution. Point sources, hot-rod and uniform phantoms were scanned, and additional tests were carried out to evaluate singular settings such as simultaneous multi-isotope acquisition and imaging with a multi-bed system. For in-vivo evaluation, simultaneous triple-isotope and multi-animal studies were performed on mice. Sensitivity for Tc-99m was 2370 cps/MBq for the UHS-M collimator and 493 cps/MBq for the UHR-RM. Rods of 0.6 mm and 0.9 mm were discernible with the UHS-M and UHR-RM collimators respectively, with optimized reconstruction. Uniformity in low counting conditions has proven to be poor (> 75%). Multi-isotope and multi-bed phantom acquisitions demonstrated accurate quantification. In mice, simultaneous multi-isotope imaging provided the separate distribution of 3 tracers and image quality of the multi-mouse bone scan was adequate. The U-SPECT6/CT E-class has shown good sensitivity and spatial resolution. This system provides quantitative images with suitable image quality for multi-mouse and multi-isotope acquisitions.
Autores:
López-Vega, J. M.; Álvarez, I.; Antón, A.; et al.
Revista:
CANCERS
ISSN:
2072-6694
Año:
2021
Vol.:
13
N°:
14
Págs.:
3511
Simple Summary New blood vessel formation (angiogenesis) has a crucial role in tumour growth and spread. Bevacizumab is an anticancer therapy that targets angiogenesis by inhibiting the vascular endothelial growth factor (VEGF) and is approved for the treatment of metastatic breast cancer. However, there are no validated methods for predicting which patients will respond to bevacizumab, although some have investigated whether a response can be predicted by using scanning (imaging) techniques that study tumour blood vessels or by using the levels of VEGF markers before treatment. In this study, we used a combination of imaging techniques and VEGF marker levels to show that bevacizumab caused structural and functional changes in the blood vessels of breast tumours and substantially slowed tumour growth. The increasing availability and refinement of imaging technology can help to identify biomarkers that will be able to predict which patients with breast cancer are most likely to respond to bevacizumab. This prospective, phase II study evaluated novel biomarkers as predictors of response to bevacizumab in patients with breast cancer (BC), using serial imaging methods and gene expression analysis. Patients with primary stage II/III BC received bevacizumab 15 mg/kg (cycle 1; C1), then four cycles of neoadjuvant docetaxel doxorubicin, and bevacizumab every 3 weeks (C2-C5). Tumour proliferation and hypoxic status were evaluated using F-18-fluoro-3 '-deoxy-3 '-L-fluorothymidine (FLT)- and F-18-fluoromisonidazole (FMISO)-positron emission tomography (PET) at baseline, and during C1 and C5. Pre- and post-bevacizumab vascular changes were evaluated using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Molecular biomarkers were assessed using microarray analysis. A total of 70 patients were assessed for treatment efficacy. Significant decreases from baseline in tumour proliferation (FLT-PET), vascularity, and perfusion (DCE-MRI) were observed during C1 (p <= 0.001), independent of tumour subtype. Bevacizumab treatment did not affect hypoxic tumour status (FMISO-PET). Significant changes in the expression of 28 genes were observed after C1. Changes in vascular endothelial growth factor receptor (VEGFR)-2p levels were observed in 65 patients, with a > 20% decrease in VEGFR-2p observed in 13/65. Serial imaging techniques and molecular gene profiling identified several potentially predictive biomarkers that may predict response to neoadjuvant bevacizumab therapy in BC patients.
Revista:
PHYSICA MEDICA
ISSN:
1120-1797
Año:
2021
Vol.:
84
Págs.:
1 - 9
Purpose: To investigate within phantoms the minimum CT dose allowed for accurate attenuation correction of PET data and to quantify the effective dose reduction when a CT for this purpose is incorporated in the clinical setting.
Methods: The NEMA image quality phantom was scanned within a large parallelepiped container. Twenty-one different CT images were acquired to correct attenuation of PET raw data. Radiation dose and image quality were evaluated. Thirty-one patients with proven multiple myeloma who underwent a dual tracer PET/CT scan were retrospectively reviewed. 18F-fluorodeoxyglucose PET/CT included a diagnostic whole-body low dose CT (WBLDCT: 120 kV-80mAs) and 11C-Methionine PET/CT included a whole-body ultra-low dose CT (WBULDCT) for attenuation correction (100 kV-40mAs). Effective dose and image quality were analysed.
Results: Only the two lowest radiation dose conditions (80 kV-20mAs and 80 kV-10mAs) produced artifacts in CT images that degraded corrected PET images. For all the other conditions (CTDIvol ¿ 0.43 mGy), PET contrast recovery coefficients varied less than ± 1.2%. Patients received a median dose of 6.4 mSv from diagnostic CT and 2.1 mSv from the attenuation correction CT. Despite the worse image quality of this CT, 94.8% of bone lesions were identifiable.
Conclusion: Phantom experiments showed that an ultra-low dose CT can be implemented in PET/CT procedures without any noticeable degradation in the attenuation corrected PET scan. The replacement of the standard CT for this ultra-low dose CT in clinical PET/CT scans involves a significant radiation dose reduction.
Revista:
NUCLEAR ESPAÑA
ISSN:
2660-8715
Año:
2020
Vol.:
Mayo
Págs.:
2 - 8
Revista:
REVISTA ESPAÑOLA DE MEDICINA NUCLEAR E IMAGEN MOLECULAR
ISSN:
2253-654X
Año:
2020
Vol.:
39
N°:
3
Págs.:
135 - 137
Revista:
EJNMMI PHYSICS
ISSN:
2197-7364
Año:
2020
Vol.:
7
N°:
1
Págs.:
72
Background Prior radioembolization, a simulation using Tc-99m-macroaggregated albumin as Y-90-microspheres surrogate is performed. Gamma scintigraphy images (planar, SPECT, or SPECT-CT) are acquired to evaluate intrahepatic Y-90-microspheres distribution and detect possible extrahepatic and lung shunting. These images may be used for pre-treatment dosimetry evaluation to calculate the Y-90 activity that would get an optimal tumor response while sparing healthy tissues. Several dosimetry methods are available, but there is still no consensus on the best methodology to calculate absorbed doses. The goal of this study was to retrospectively evaluate the impact of using different dosimetry approaches on the resulting Y-90-radioembolization pre-treatment absorbed dose evaluation based on Tc-99m-MAA images. Methods Absorbed doses within volumes of interest resulting from partition model (PM) and 3D voxel dosimetry methods (3D-VDM) (dose-point kernel convolution and local deposition method) were evaluated. Additionally, a new "Multi-tumor Partition Model" (MTPM) was developed. The differences among dosimetry approaches were evaluated in terms of mean absorbed dose and dose volume histograms within the volumes of interest. Results Differences in mean absorbed dose among dosimetry methods are higher in tumor volumes than in non-tumoral ones. The differences between MTPM and both 3D-VDM were substantially lower than those observed between PM and any 3D-VDM. A poor correlation and concordance were found between PM and the other studied dosimetry approaches. DVH obtained from either 3D-VDM are pretty similar in both healthy liver and individual tumors. Although no relevant global differences, in terms of absorbed dose in Gy, between both 3D-VDM were found, important voxel-by-voxel differences have been observed. Conclusions Significant differences among the studied dosimetry approaches for Y-90-radioembolization treatments exist. Differences do not yield a substantial impact in treatment planning for healthy tissue but they do for tumoral liver. An individual segmentation and evaluation of the tumors is essential. In patients with multiple tumors, the application of PM is not optimal and the 3D-VDM or the new MTPM are suggested instead. If a 3D-VDM method is not available, MTPM is the best option. Furthermore, both 3D-VDM approaches may be indistinctly used.
Autores:
Reynes-Llompart, G. ; Sabate-Llobera, A. ; Llinares-Tello, E.; et al.
Revista:
SCIENTIFIC REPORTS
ISSN:
2045-2322
Año:
2019
Vol.:
9
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.
Revista:
REVISTA DE FÍSICA MÉDICA
ISSN:
1576-6632
Año:
2019
Vol.:
20
N°:
1
Págs.:
31 - 53
Autores:
Reynés-Llompart, G.; Gámez-Cenzano, C.; Vercher-Conejero, J. L.; et al.
Revista:
MEDICAL PHYSICS
ISSN:
0094-2405
Año:
2018
Vol.:
45
N°:
7
Págs.:
3214 - 3222
Introduction: The aim of this study was to evaluate the behavior of a penalized-likelihood image reconstruction method (Q.Clear) under different count statistics and lesion-to-background ratios (LBR) on a BGO scanner, in order to obtain an optimum penalization factor (ß value) to study and optimize for different acquisition protocols and clinical goals.
Methods: Both phantom and patient images were evaluated. Data from an image quality phantom were acquired using different Lesion-to-Background ratios and acquisition times. Then, each series of the phantom was reconstructed using ß values between 50 and 500, at intervals of 50. Hot and cold contrasts were obtained, as well as background variability and contrast-to-noise ratio (CNR). Fifteen 18 F-FDG patients (five brain scans and 10 torso acquisitions) were acquired and reconstructed using the same ß values as in the phantom reconstructions. From each lesion in the torso acquisition, noise, contrast, and signal-to-noise ratio (SNR) were computed. Image quality was assessed by two different nuclear medicine physicians. Additionally, the behaviors of 12 different textural indices were studied over 20 different lesions.
Results: Q.Clear quantification and optimization in patient studies depends on the activity concentration as well as on the lesion size. In the studied range, an increase on ß is translated in a decrease in lesion contrast and noise. The net product is an overall increase in the SNR, presenting a tendency to a steady value similar to the CNR in phantom data. As the activity concentration or the sphere size increase the optimal ß increases, similar results are obtained from clinical data. From the subjective quality assessment, the optimal ß value for torso scans is in a range between 300 and 400, and from 100 to 200 for brain scans. For the recommended torso ß values, texture indices present coefficients of variation below 10%.
Conclusions: Our phantom and patients demonstrate that improvement of CNR and SNR of Q.Clear algorithm which depends on the studied conditions and the penalization factor. Using the Q.Clear reconstruction algorithm in a BGO scanner, a ß value of 350 and 200 appears to be the optimal value for 18F-FDG oncology and brain PET/CT, respectively.
Revista:
PHYSICA MEDICA
ISSN:
1120-1797
Año:
2018
Vol.:
46
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
Revista:
EJNMMI RESEARCH
ISSN:
2191-219X
Año:
2017
Vol.:
7
N°:
1
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.
Revista:
ANALES DEL SISTEMA SANITARIO DE NAVARRA
ISSN:
1137-6627
Año:
2017
Vol.:
40
N°:
1
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.
Revista:
THE QUARTERLY JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN:
1824-4785
Año:
2017
Vol.:
61
N°:
4
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:
Reynés-Llompart, G.; Gámez-Cenzano, C.; Romero-Zayas, I.; et al.
Revista:
JOURNAL OF NUCLEAR MEDICINE
ISSN:
0161-5505
Año:
2017
Vol.:
58
N°:
7
Págs.:
1155 - 1161
The aim of this study was to assess the physical performance of a new PET/CT system, the Discovery IQ with 5-ring detector blocks. Methods: Performance was measured using the National Electrical Manufacturers Association NU2-2012 methodology. Image quality was extended by accounting for different acquisition parameters (lesion-to-background ratios [8:1, 4:1, and 2:1] and acquisition times) and reconstruction algorithms (VUE-point HD [VPHD], VPHD with point-spread-function modeling [VPHD-S], and Q.Clear). Tomographic reconstruction was also assessed using a Jaszczak phantom. Additionally, 30 patient lesions were analyzed to account for differences in lesion volume and SUV quantification between reconstruction algorithms. Results: Spatial resolution ranged from 4.2 mm at 1 cm to 8.5 mm at 20 cm. Sensitivity measured at the center and at 10 cm was 22.8 and 20.4 kps/kBq, respectively. The noise-equivalent counting rate peak was 124 kcps at 9.1 kBq/cm(3). The scatter fraction was 36.2%. The accuracy of correction for count losses and randoms was 3.9%. In the image quality test, contrast recovery for VPHD, VPHD-S, and Q.Clear ranged from 18%, 18%, and 13%, respectively (hot contrast; 10-mm sphere diameter; ratio, 2:1), to 68%, 67%, and 81%, respectively (cold contrast; 37-mm sphere diameter; ratio, 8:1). Background variability ranged from 3.4%, 3.0%, and 2.1%, respectively (ratio, 2: 1), to 5.5%, 4.8%, and 3.7%, respectively (ratio, 8: 1). On Q.Clear reconstruction, the decrease in the penalty term (b) increased the contrast recovery coefficients and background variability. With the Jaszczak phantom, image quality increased overall when a reconstruction algorithm modeling the point-spread function was used, and use of Q.Clear increased the signal-to-noise ratio. Lesions nalyzed using VPHD-S and Q.Clear had an SUVmean of 6.5 +/- 3 and 7 6 3, respectively (P<0.01), and an SUVmax of 11 +/- 4.8 and 12 +/- 4, respectively (P<0.01). No significant difference in mean lesion volume was found between algorithms. Conclusion: Among the various Discovery bismuth germanium oxide-based PET/CT scanners, the IQ with 5-ring detector blocks has the highest overall performance, with improved sensitivity and counting rate performance. Q.Clear reconstruction improves the PET image quality, with higher recovery coefficients and lower background variability.
Autores:
Barquero-Sanz, R.; Ferrer-García, N.; Simón, J. L.; et al.
Revista:
REVISTA DE FÍSICA MÉDICA
ISSN:
1576-6632
Año:
2017
Vol.:
18
N°:
2
Págs.:
143 - 176
Revista:
REVISTA ESPAÑOLA DE MEDICINA NUCLEAR E IMAGEN MOLECULAR
ISSN:
2253-654X
Año:
2016
Vol.:
35
N°:
3
Págs.:
175 - 185
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
Revista:
PHYSICA MEDICA
ISSN:
1120-1797
Año:
2015
Vol.:
31
N°:
8
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.
Revista:
EJNMMI RESEARCH
ISSN:
2191-219X
Año:
2015
Vol.:
15
N°:
1
Págs.:
70
Background: [F-18]-tetrafluoroborate is a PET radiotracer taken up by the sodium/iodide symporter (NIS). Albeit the in vivo behavior in rodents is similar to the (99)mTc-pertechnetate, no studies exist in primates or in humans. The aims of this study were to evaluate the biodistribution of [F-18]-tetrafluoroborate in non-human primates with PET and to estimate the absorbed dose in organs.
Methods: Whole-body PET imaging was done in a Siemens ECAT HR+ scanner in two male Macaca fascicularis monkeys. After an i.v. injection of 24.93 +/- 0.05 MBq/kg of [F-18]-tetrafluoroborate, prepared by isotopic exchange of sodium tetrafluoroborate with [F-18]-fluoride under acidic conditions, eight sequential images from the head to the thigh (five beds) were collected for a total duration of 132 min. The whole-body emission scan was reconstructed applying attenuation and scatter corrections. After image reconstruction, three-dimensional volumes of interest (VOIs) were hand-drawn on the PET transaxial or coronal slices of the frame where the organ was most conspicuous. Time-activity curves for each VOI were obtained, and the organ residence times were calculated by integration of the time-activity curves. Human absorbed doses were estimated using the OLINDA/EXM software and the standard human model.
Results: [F-18]-tetrafluoroborate was able to discriminate clearly the thyroid gland with an excellent signal-to-noise ratio. Most of the radiotracers (residence time) are localised in the orga
Revista:
MEDICAL PHYSICS
ISSN:
0094-2405
Año:
2014
Vol.:
41
N°:
6
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.
Revista:
MEDICAL PHYSICS
ISSN:
0094-2405
Año:
2014
Vol.:
41
N°:
1
Págs.:
12102-11
Revista:
MEDICAL PHYSICS
ISSN:
0094-2405
Año:
2014
Vol.:
41
N°:
9
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.
Revista:
RADIOPROTECCION
ISSN:
1133-1747
Año:
2014
Vol.:
79
Págs.:
26 - 36
La imagen preclínica engloba distintas técnicas de imagen molecular que utilizan radiaciones ionizantes, destacando la tomografía por emisión de fotón único (SPECT), la tomografía de emisión de positrones (PET) y la imagen autorradiográfica. Cada una de ellas utiliza distintas sondas que permiten obtener imágenes de una gran variedad de procesos metabólicos. En ocasiones se emplean junto a equipos de rayos X que permiten obtener imágenes anatómicas. En consecuencia, la investigación en las instalaciones de imagen molecular preclínica deberá realizarse en un contexto en el que se aplique la protección radiológica. De entre los riesgos radiológicos del personal que opera este tipo de instalaciones destaca la irradiación de las manos producida tanto por la administración de los radiotrazadores a los animales como por la manipulación de los mismos, siendo importante el entrenamiento y el uso de los blindajes. El diseño de la instalación radiactiva estará determinado por la actividad que en ella se realice. En particular dependerá tanto de las distintas técnicas de imagen molecular preclínica que se desarrollen como de la relación funcional que la instalación tenga con el resto del centro en el que se encuentre, en particular con el animalario y la unidad de radiofarmacia.
Revista:
REVISTA ESPAÑOLA DE MEDICINA NUCLEAR E IMAGEN MOLECULAR
ISSN:
2253-8089
Año:
2014
Vol.:
33
N°:
2
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.
Revista:
REVISTA ESPAÑOLA DE MEDICINA NUCLEAR E IMAGEN MOLECULAR
ISSN:
2253-8089
Año:
2014
Vol.:
33
N°:
5
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
Revista:
EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN:
1619-7070
Año:
2013
Vol.:
10
N°:
9
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.
Revista:
REVISTA ESPAÑOLA DE MEDICINA NUCLEAR
ISSN:
0212-6982
Año:
2013
Vol.:
32
N°:
1
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.
Revista:
CLINICAL NUCLEAR MEDICINE
ISSN:
0363-9762
Año:
2013
Vol.:
38
N°:
2
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.
Revista:
BRAIN
ISSN:
0006-8950
Año:
2012
Vol.:
135
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
Revista:
EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
ISSN:
1619-7070
Año:
2012
Vol.:
39
N°:
5
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.
Revista:
PHYSICS IN MEDICINE AND BIOLOGY
ISSN:
0031-9155
Año:
2012
Vol.:
57
N°:
12
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
Revista:
Radiation Measurements
ISSN:
1350-4487
Año:
2011
Vol.:
46
N°:
11
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.
Revista:
European Journal of Nuclear Medicine & Molecular Imaging
ISSN:
1619-7070
Año:
2011
Vol.:
38
N°:
12
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.
Revista:
JOURNAL OF NUCLEAR MEDICINE
ISSN:
0161-5505
Año:
2011
Vol.:
52
N°:
6
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.
Revista:
STROKE
ISSN:
0039-2499
Año:
2010
Vol.:
41
N°:
12
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.
Revista:
Molecular Imaging and Biology
ISSN:
1536-1632
Año:
2010
Vol.:
12
N°:
2
Págs.:
210 - 217
Revista:
Computers in Biology and Medicine
ISSN:
0010-4825
Año:
2010
Vol.:
40
N°:
1
Págs.:
75 - 80
Revista:
REVISTA ESPAÑOLA DE MEDICINA NUCLEAR
ISSN:
0212-6982
Año:
2010
Vol.:
29
N°:
4
Págs.:
189 - 210
Neuroimaging using both functional and structural examinations like positron emission tomography (PET), single photon emission tomography (SPECT), computed tomography (CT) and magnetic nuclear imaging (MRI) provide supportive information of great importance for the diagnosis and treatment of patients with central nervous system disorders. Therefore, they have become commonplace in clinical practice and basic biomedical research. In recent years we have seen the development of multimodality equipment that enables PET or SPECT to be combined with a CT structural image. Moreover, experimental equipment combining PET and MRI has now been developed. Additionally, methodological features that provide a higher image quality, and analysis tools for objective quantification and interpretation have been refined. This article reviews the technical aspects of those imaging methods, highlighting the most significant and recent advances in the development of neuroimaging.
Revista:
Neurobiology of Disease
ISSN:
0969-9961
Año:
2010
Vol.:
38
N°:
3
Págs.:
456 - 463