Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 13 de 13
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
J Magn Reson Imaging ; 51(1): 183-194, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31044459

RESUMO

BACKGROUND: H2 15 O-positron emission tomography (PET) is considered the reference standard for absolute cerebral blood flow (CBF). However, this technique requires an arterial input function measured through continuous sampling of arterial blood, which is invasive and has limitations with tracer delay and dispersion. PURPOSE: To demonstrate a new noninvasive method to quantify absolute CBF with a PET/MRI hybrid scanner. This blood-free approach, called PC-PET, takes the spatial CBF distribution from a static H2 15 O-PET scan, and scales it to the whole-brain average CBF value measured by simultaneous phase-contrast MRI. STUDY TYPE: Observational. SUBJECTS: Twelve healthy controls (HC) and 13 patients with Moyamoya disease (MM) as a model of chronic ischemic disease. FIELD STRENGTH/SEQUENCES: 3T/2D cardiac-gated phase-contrast MRI and H2 15 O-PET. ASSESSMENT: PC-PET CBF values from whole brain (WB), gray matter (GM), and white matter (WM) in HCs were compared with literature values since 2000. CBF and cerebrovascular reactivity (CVR), which is defined as the percent CBF change between baseline and post-acetazolamide (vasodilator) scans, were measured by PC-PET in MM patients and HCs within cortical regions corresponding to major vascular territories. Statistical Tests: Linear, mixed effects models were created to compare CBF and CVR, respectively, between patients and controls, and between different degrees of stenosis. RESULTS: The mean CBF values in WB, GM, and WM in HC were 42 ± 7 ml/100 g/min, 50 ± 7 ml/100 g/min, and 23 ± 3 ml/100 g/min, respectively, which agree well with literature values. Compared with normal regions (57 ± 23%), patients showed significantly decreased CVR in areas with mild/moderate stenosis (47 ± 17%, P = 0.011) and in severe/occluded areas (40 ± 16%, P = 0.016). Data Conclusion: PC-PET identifies differences in cerebrovascular reactivity between healthy controls and cerebrovascular patients. PC-PET is suitable for CBF measurement when arterial blood sampling is not accessible, and warrants comparison to fully quantitative H2 15 O-PET in future studies. LEVEL OF EVIDENCE: 3 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019. J. Magn. Reson. Imaging 2020;51:183-194.

3.
Stroke ; 50(2): 373-380, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30636572

RESUMO

Background and Purpose- Noninvasive imaging of brain perfusion has the potential to elucidate pathophysiological mechanisms underlying Moyamoya disease and enable clinical imaging of cerebral blood flow (CBF) to select revascularization therapies for patients. We used hybrid positron emission tomography (PET)/magnetic resonance imaging (MRI) technology to characterize the distribution of hypoperfusion in Moyamoya disease and its relationship to vessel stenosis severity, through comparisons with a normative perfusion database of healthy controls. Methods- To image CBF, we acquired [15O]-water PET as a reference and simultaneously acquired arterial spin labeling (ASL) MRI scans in 20 Moyamoya patients and 15 age-matched, healthy controls on a PET/MRI scanner. The ASL MRI scans included a standard single-delay ASL scan with postlabel delay of 2.0 s and a multidelay scan with 5 postlabel delays (0.7-3.0s) to estimate and account for arterial transit time in CBF quantification. The percent volume of hypoperfusion in patients (determined as the fifth percentile of CBF values in the healthy control database) was the outcome measure in a logistic regression model that included stenosis grade and location. Results- Logistic regression showed that anterior ( P<0.0001) and middle cerebral artery territory regions ( P=0.003) in Moyamoya patients were susceptible to hypoperfusion, whereas posterior regions were not. Cortical regions supplied by arteries with stenosis on MR angiography showed more hypoperfusion than normal arteries ( P=0.001), but the extent of hypoperfusion was not different between mild-moderate versus severe stenosis. Multidelay ASL did not perform differently from [15O]-water PET in detecting perfusion abnormalities, but standard ASL overestimated the extent of hypoperfusion in patients ( P=0.003). Conclusions- This simultaneous PET/MRI study supports the use of multidelay ASL MRI in clinical evaluation of Moyamoya disease in settings where nuclear medicine imaging is not available and application of a normative perfusion database to automatically identify abnormal CBF in patients.


Assuntos
Bases de Dados Factuais , Imagem por Ressonância Magnética , Artéria Cerebral Média , Doença de Moyamoya , Tomografia por Emissão de Pósitrons , Adolescente , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Artéria Cerebral Média/diagnóstico por imagem , Artéria Cerebral Média/fisiopatologia , Doença de Moyamoya/diagnóstico por imagem , Doença de Moyamoya/fisiopatologia , Marcadores de Spin
6.
Artigo em Inglês | MEDLINE | ID: mdl-31186825

RESUMO

Purpose of Review: Ischemic heart disease is caused by atherosclerosis, the build-up of plaque in the coronary arteries, which can lead to the development of heart attacks and heart muscle damage. Despite the advent of medical and surgical therapy to prevent and treat atherosclerosis and its adverse clinical effects, ischemic heart disease remains a leading cause of morbidity and mortality. Recent studies have suggested that the immune system may play a greater role in the development of plaque rupture and adverse left ventricular remodeling after myocardial infarction. Understanding the molecular processes by which inflammation contributes to the pathophysiology of ischemic heart disease is, therefore, worthwhile. This review focuses on new molecular imaging techniques to visualize immune cells to study their contribution to ischemic heart disease. Recent Findings: A common technique applied to imaging inflammation in ischemic heart disease is targeting the up-regulation and trafficking of immune cells, which may contribute to the adverse consequences associated with atherosclerosis. In the past five years, advances in cell labeling for imaging with PET and MRI, including radioisotopes and nanoparticles, have confirmed that inflammatory cells can be visualized in vivo and in greater abundance in unstable cardiovascular disease and in areas of ischemic damage. The major criticisms of these studies to date include their small sample size, lack of histological correlation, limited association with long-term outcomes, and bias toward macrophage imaging. Summary: While much progress has been made in imaging inflammation in ischemic heart disease over the past five years, additional studies in larger cohorts with histological validation and outcome correlation are needed. Nevertheless, imaging inflammation using PET or MRI has the potential to become an important adjunct tool to improve the diagnosis, risk stratification, and therapeutic monitoring of patients with ischemic heart disease.

7.
J Nucl Med ; 58(10): 1679-1684, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28490473

RESUMO

6″-18F-fluoromaltotriose is a PET tracer that can potentially be used to image and localize most bacterial infections, much like 18F-FDG has been used to image and localize most cancers. However, unlike 18F-FDG, 6″-18F-fluoromaltotriose is not taken up by inflammatory lesions and appears to be specific to bacterial infections by targeting the maltodextrin transporter that is expressed in gram-positive and gram-negative strains of bacteria. Methods: 6″-18F-fluoromaltotriose was synthesized with high radiochemical purity and evaluated in several clinically relevant bacterial strains in cultures and in living mice. Results: 6″-18F-fluoromaltotriose was taken up in both gram-positive and gram-negative bacterial strains. 6″-18F-fluoromaltotriose was also able to detect Pseudomonas aeruginosa in a clinically relevant mouse model of wound infection. The utility of 6″-18F-fluoromaltotriose to help monitor antibiotic therapies was also evaluated in rats. Conclusion: 6″-18F-fluoromaltotriose is a promising new tracer that has significant diagnostic utility, with the potential to change the clinical management of patients with infectious diseases of bacterial origin.


Assuntos
Infecções Bacterianas/diagnóstico por imagem , Infecções Bacterianas/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Polissacarídeos/metabolismo , Tomografia por Emissão de Pósitrons/métodos , Trissacarídeos , Animais , Transporte Biológico , Camundongos , Camundongos Nus , Traçadores Radioativos , Infecção dos Ferimentos/diagnóstico por imagem , Infecção dos Ferimentos/metabolismo
8.
PLoS One ; 9(8): e103745, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25111700

RESUMO

Head movement during a dynamic brain PET/CT imaging results in mismatch between CT and dynamic PET images. It can cause artifacts in CT-based attenuation corrected PET images, thus affecting both the qualitative and quantitative aspects of the dynamic PET images and the derived parametric images. In this study, we developed an automated retrospective image-based movement correction (MC) procedure. The MC method first registered the CT image to each dynamic PET frames, then re-reconstructed the PET frames with CT-based attenuation correction, and finally re-aligned all the PET frames to the same position. We evaluated the MC method's performance on the Hoffman phantom and dynamic FDDNP and FDG PET/CT images of patients with neurodegenerative disease or with poor compliance. Dynamic FDDNP PET/CT images (65 min) were obtained from 12 patients and dynamic FDG PET/CT images (60 min) were obtained from 6 patients. Logan analysis with cerebellum as the reference region was used to generate regional distribution volume ratio (DVR) for FDDNP scan before and after MC. For FDG studies, the image derived input function was used to generate parametric image of FDG uptake constant (Ki) before and after MC. Phantom study showed high accuracy of registration between PET and CT and improved PET images after MC. In patient study, head movement was observed in all subjects, especially in late PET frames with an average displacement of 6.92 mm. The z-direction translation (average maximum = 5.32 mm) and x-axis rotation (average maximum = 5.19 degrees) occurred most frequently. Image artifacts were significantly diminished after MC. There were significant differences (P<0.05) in the FDDNP DVR and FDG Ki values in the parietal and temporal regions after MC. In conclusion, MC applied to dynamic brain FDDNP and FDG PET/CT scans could improve the qualitative and quantitative aspects of images of both tracers.


Assuntos
Movimentos da Cabeça , Processamento de Imagem Assistida por Computador/instrumentação , Imagens de Fantasmas , Tomografia por Emissão de Pósitrons , Tomografia Computadorizada por Raios X , Automação , Fluordesoxiglucose F18 , Humanos , Nitrilos , Estudos Retrospectivos
9.
Eur J Nucl Med Mol Imaging ; 41(6): 1199-209, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24604590

RESUMO

PURPOSE: In this study, kinetic parameters of the cellular proliferation tracer (18)F-3'-deoxy-3'-fluoro-L-thymidine (FLT) and the amino acid probe 3,4-dihydroxy-6-(18)F-fluoro-L-phenylalanine (FDOPA) were measured before and early after the start of therapy, and were used to predict the overall survival (OS) of patients with recurrent malignant glioma using multiple linear regression (MLR) analysis. METHODS: High-grade recurrent brain tumors in 21 patients (11 men and 10 women, age range 26 - 76 years) were investigated. Each patient had three dynamic PET studies with each probe: at baseline and after 2 and 6 weeks from the start of treatment. Treatment consisted of biweekly cycles of bevacizumab (an angiogenesis inhibitor) and irinotecan (a chemotherapeutic agent). For each study, about 3.5 mCi of FLT (or FDOPA) was administered intravenously and dynamic PET images were acquired for 1 h (or 35 min for FDOPA). A total of 126 PET scans were analyzed. A three-compartment, two-tissue model was applied to estimate tumor FLT and FDOPA kinetic rate constants using a metabolite- and partial volume-corrected input function. MLR analysis was used to model OS as a function of FLT and FDOPA kinetic parameters for each of the three studies as well as their relative changes between studies. An exhaustive search of MLR models using three or fewer predictor variables was performed to find the best models. RESULTS: Kinetic parameters from FLT were more predictive of OS than those from FDOPA. The three-predictor MLR model derived using information from both probes (adjusted R(2) = 0.83) fitted the OS data better than that derived using information from FDOPA alone (adjusted R(2) = 0.41), but was only marginally different from that derived using information from FLT alone (adjusted R(2) = 0.82). Standardized uptake values (either from FLT alone, FDOPA alone, or both together) gave inferior predictive results (best adjusted R(2) = 0.25). CONCLUSION: For recurrent malignant glioma treated with bevacizumab and irinotecan, FLT kinetic parameters obtained early after the start of treatment (absolute values and their associated changes) can provide sufficient information to predict OS with reasonable confidence using MLR. The slight increase in accuracy for predicting OS with a combination of FLT and FDOPA PET information may not warrant the additional acquisition of FDOPA PET for therapy monitoring in patients with recurrent glioma.


Assuntos
Neoplasias Encefálicas/diagnóstico por imagem , Didesoxinucleosídeos/farmacocinética , Di-Hidroxifenilalanina/análogos & derivados , Glioma/diagnóstico por imagem , Adulto , Idoso , Inibidores da Angiogênese/uso terapêutico , Anticorpos Monoclonais Humanizados/uso terapêutico , Bevacizumab , Neoplasias Encefálicas/tratamento farmacológico , Camptotecina/análogos & derivados , Camptotecina/uso terapêutico , Interpretação Estatística de Dados , Di-Hidroxifenilalanina/farmacocinética , Feminino , Glioma/tratamento farmacológico , Humanos , Irinotecano , Cinética , Masculino , Pessoa de Meia-Idade , Modelos Biológicos , Tomografia por Emissão de Pósitrons , Compostos Radiofarmacêuticos/farmacocinética , Recidiva , Distribuição Tecidual
10.
Int J Alzheimers Dis ; 2012: 512069, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22482071

RESUMO

We evaluate an automated approach to the cortical surface mapping (CSM) method of VOI analysis in PET. Although CSM has been previously shown to be successful, the process can be long and tedious. Here, we present an approach that removes these difficulties through the use of 3D image warping to a common space. We test this automated method using studies of FDDNP PET in Alzheimer's disease and mild cognitive impairment. For each subject, VOIs were created, through CSM, to extract regional PET data. After warping to the common space, a single set of CSM-generated VOIs was used to extract PET data from all subjects. The data extracted using a single set of VOIs outperformed the manual approach in classifying AD patients from MCIs and controls. This suggests that this automated method can remove variance in measurements of PET data and can facilitate accurate, high-throughput image analysis.

11.
Clin Cancer Res ; 17(20): 6553-62, 2011 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-21868765

RESUMO

PURPOSE: The primary objective of this study was to investigate whether changes in 3'-deoxy-3'-[¹8F]fluorothymidine (¹8F-FLT) kinetic parameters, taken early after the start of therapy, could predict overall survival (OS) and progression-free survival (PFS) in patients with recurrent malignant glioma undergoing treatment with bevacizumab and irinotecan. EXPERIMENTAL DESIGN: High-grade recurrent brain tumors were investigated in 18 patients (8 male and 10 female), ages 26 to 76 years. Each had 3 dynamic positron emission tomography (PET) studies as follows: at baseline and after 2 and 6 weeks from the start of treatment, ¹8F-FLT (2.0 MBq/kg) was injected intravenously, and dynamic PET images were acquired for 1 hour. Factor analysis generated factor images from which blood and tumor uptake curves were derived. A three-compartment, two-tissue model was applied to estimate tumor ¹8F-FLT kinetic rate constants using a metabolite- and partial volume-corrected input function. Different combinations of predictor variables were exhaustively searched in a discriminant function to accurately classify patients into their known OS and PFS groups. A leave-one-out cross-validation technique was used to assess the generalizability of the model predictions. RESULTS: In this study population, changes in single parameters such as standardized uptake value or influx rate constant did not accurately classify patients into their respective OS groups (<1 and ≥ 1 year; hit ratios ≤ 78%). However, changes in a set of ¹8F-FLT kinetic parameters could perfectly separate these two groups of patients (hit ratio = 100%) and were also able to correctly classify patients into their respective PFS groups (<100 and ≥ 100 days; hit ratio = 88%). CONCLUSIONS: Discriminant analysis using changes in ¹8F-FLT kinetic parameters early during treatment seems to be a powerful method for evaluating the efficacy of therapeutic regimens.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Neoplasias Encefálicas/diagnóstico por imagem , Didesoxinucleosídeos , Glioma/diagnóstico por imagem , Adulto , Idoso , Anticorpos Monoclonais Humanizados/administração & dosagem , Bevacizumab , Neoplasias Encefálicas/tratamento farmacológico , Neoplasias Encefálicas/mortalidade , Camptotecina/administração & dosagem , Camptotecina/análogos & derivados , Análise Discriminante , Intervalo Livre de Doença , Feminino , Glioma/tratamento farmacológico , Glioma/mortalidade , Humanos , Irinotecano , Masculino , Pessoa de Meia-Idade , Prognóstico , Cintilografia
12.
J Nucl Med ; 51(2): 210-8, 2010 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-20080894

RESUMO

UNLABELLED: Head movement during a PET scan (especially a dynamic scan) can affect both the qualitative and the quantitative aspects of an image, making it difficult to accurately interpret the results. The primary objective of this study was to develop a retrospective image-based movement correction (MC) method and evaluate its implementation on dynamic 2-(1-{6-[(2-(18)F-fluoroethyl)(methyl)amino]-2-naphthyl}ethylidene)malononitrile ((18)F-FDDNP) PET images of cognitively intact controls and patients with Alzheimer's disease (AD). METHODS: Dynamic (18)F-FDDNP PET images, used for in vivo imaging of beta-amyloid plaques and neurofibrillary tangles, were obtained from 12 AD patients and 9 age-matched controls. For each study, a transmission scan was first acquired for attenuation correction. An accurate retrospective MC method that corrected for transmission-emission and emission-emission misalignments was applied to all studies. No restriction was assumed for zero movement between the transmission scan and the first emission scan. Logan analysis, with the cerebellum as the reference region, was used to estimate various regional distribution volume ratio (DVR) values in the brain before and after MC. Discriminant analysis was used to build a predictive model for group membership, using data with and without MC. RESULTS: MC improved the image quality and quantitative values in (18)F-FDDNP PET images. In this subject population, no significant difference in DVR value was observed in the medial temporal (MTL) region of controls and patients with AD before MC. However, after MC, significant differences in DVR values in the frontal, parietal, posterior cingulate, MTL, lateral temporal (LTL), and global regions were seen between the 2 groups (P < 0.05). In controls and patients with AD, the variability of regional DVR values (as measured by the coefficient of variation) decreased on average by more than 18% after MC. Mean DVR separation between controls and patients with AD was higher in frontal, MTL, LTL, and global regions after MC. Group classification by discriminant analysis based on (18)F-FDDNP DVR values was markedly improved after MC. CONCLUSION: The streamlined and easy-to-use MC method presented in this work significantly improves the image quality and the measured tracer kinetics of (18)F-FDDNP PET images. The proposed MC method has the potential to be applied to PET studies on patients having other disorders (e.g., Down syndrome and Parkinson's disease) and to brain PET scans with other molecular imaging probes.


Assuntos
Encéfalo/diagnóstico por imagem , Tomografia por Emissão de Pósitrons/estatística & dados numéricos , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/diagnóstico por imagem , Estudos de Casos e Controles , Feminino , Radioisótopos de Flúor , Movimentos da Cabeça , Humanos , Processamento de Imagem Assistida por Computador/estatística & dados numéricos , Masculino , Pessoa de Meia-Idade , Nitrilos , Compostos Radiofarmacêuticos , Estudos Retrospectivos
13.
Eur J Nucl Med Mol Imaging ; 37(3): 575-88, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19882153

RESUMO

PURPOSE: Subcortical white matter is known to be relatively unaffected by amyloid deposition in Alzheimer's disease (AD). We investigated the use of subcortical white matter as a reference region to quantify [(18)F]FDDNP binding in the human brain. METHODS: Dynamic [(18)F]FDDNP PET studies were performed on 7 control subjects and 12 AD patients. Population efflux rate constants (k(')(2)) from subcortical white matter (centrum semiovale) and cerebellar cortex were derived by a simplified reference tissue modeling approach incorporating physiological constraints. Regional distribution volume ratio (DVR) estimates were derived using Logan and simplified reference tissue approaches, with either subcortical white matter or cerebellum as reference input. Discriminant analysis with cross-validation was performed to classify control subjects and AD patients. RESULTS: The population estimates of k(')(2) in subcortical white matter did not differ significantly between control subjects and AD patients but the variability of individual estimates of k(')(2) determined in white matter was lower than that in cerebellum. Logan DVR showed dependence on the efflux rate constant in white matter. The DVR estimates in the frontal, parietal, posterior cingulate, and temporal cortices were significantly higher in the AD group (p<0.01). Incorporating all these regional DVR estimates as predictor variables in discriminant analysis yielded accurate classification of control subjects and AD patients with high sensitivity and specificity, and the results agreed well with those using the cerebellum as the reference region. CONCLUSION: Subcortical white matter can be used as a reference region for quantitative analysis of [(18)F]FDDNP with the Logan method which allows more accurate and less biased binding estimates, but a population efflux rate constant has to be determined a priori.


Assuntos
Encéfalo/metabolismo , Nitrilos , Tomografia por Emissão de Pósitrons , Idoso , Doença de Alzheimer/metabolismo , Doença de Alzheimer/fisiopatologia , Doença de Alzheimer/psicologia , Amiloide/metabolismo , Transporte Biológico , Encéfalo/irrigação sanguínea , Estudos de Casos e Controles , Cerebelo/metabolismo , Cognição , Análise Discriminante , Feminino , Humanos , Cinética , Masculino , Nitrilos/metabolismo , Valores de Referência , Células Receptoras Sensoriais/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA