RESUMO
BACKGROUND: In acute stroke, the magnetic resonance (MR) imaging-based mismatch concept is used to select patients with tissue at risk of infarction for reperfusion therapies. There is however a controversy if non-deconvolved or deconvolved perfusion weighted (PW) parameter maps perform better in tissue at risk prediction and which parameters and thresholds should be used to guide treatment decisions. METHODS: In a group of 22 acute stroke patients with consecutive MR and quantitative positron emission tomography (PET) imaging, non-deconvolved parameters were validated with the gold standard for penumbral-flow (PF) detection 15O-water PET. Performance of PW parameters was assessed by a receiver operating characteristic curve analysis to identify the accuracy of each PWI map to detect the -upper PF threshold as defined by PET cerebral blood flow <20 mL/100 g/min. RESULTS: Among normalized non-deconvolved parameters, PW-first moment without delay correction (FM without DC) > 3.6 s (area under the curve [AUC] = 0.89, interquartile range [IQR] 0.85-0.94), PW-maximum of the concentration curve (Cmax) < 0.66 (AUC = 0.92, IQR 0.84-0.96) and PW-time to peak (TTP) > 4.0 s (AUC = 0.92, IQR 0.87-0.94) perform significantly better than other non-deconvolved parameters to detect the PF threshold as defined by PET. CONCLUSIONS: Non-deconvolved parameters FM without DC, Cmax and TTP are an observer-independent alternative to established deconvolved parameters (e.g., Tmax) to guide treatment decisions in acute stroke.
Assuntos
Circulação Cerebrovascular , Imageamento por Ressonância Magnética , Radioisótopos de Oxigênio/administração & dosagem , Imagem de Perfusão/métodos , Tomografia por Emissão de Pósitrons , Compostos Radiofarmacêuticos/administração & dosagem , Acidente Vascular Cerebral/diagnóstico por imagem , Tomada de Decisão Clínica , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Variações Dependentes do Observador , Valor Preditivo dos Testes , Prognóstico , Reprodutibilidade dos Testes , Acidente Vascular Cerebral/fisiopatologia , Acidente Vascular Cerebral/terapiaRESUMO
BACKGROUND AND PURPOSE: Adult patients with symptomatically ischemic moyamoya disease (MMD) initially undergo medical treatment alone including antiplatelet drugs when symptomatic cerebral hemispheres do not exhibit hemodynamic compromise. The purpose of the present study subanalyzing the same patient cohort used in a previous study was to determine which antiplatelet drug, clopidogrel or cilostazol, provides better improvement of cerebral perfusion in such patients. METHODS: All patients without cerebral misery perfusion on 15O gas positron emission tomography (PET) did not undergo revascularization surgery and were treated with medication alone, including antiplatelet therapy. Patients ≥50years and <50years initially received clopidogrel and cilostazol, respectively. When a patient suffered side effects of an antiplatelet drug, they were switched to the other antiplatelet drug. Cerebral blood flow (CBF) in the symptomatic hemisphere was measured at inclusion and at 2years after inclusion using 15O gas PET. RESULTS: Of 68 patients, 31 and 38 were treated with clopidogrel and cilostazol, respectively, for 2years after inclusion. For patients treated with clopidogrel, CBF did not differ between first and second PET. For patients treated with cilostazol, CBF was significantly greater in the second PET than in the first PET. On multivariate analysis, cilostazol administration was an independent predictor of CBF improvement in the symptomatic hemisphere (95% confidence interval, 1.34-139.20; P =.0271). CONCLUSIONS: Cilostazol improves cerebral perfusion better than clopidogrel in adult patients with symptomatically ischemic MMD not accompanied by misery perfusion.
Assuntos
Isquemia Encefálica/tratamento farmacológico , Circulação Cerebrovascular/efeitos dos fármacos , Doença de Moyamoya/tratamento farmacológico , Inibidores da Agregação Plaquetária/uso terapêutico , Tetrazóis/uso terapêutico , Ticlopidina/análogos & derivados , Adulto , Velocidade do Fluxo Sanguíneo , Isquemia Encefálica/diagnóstico por imagem , Isquemia Encefálica/fisiopatologia , Cilostazol , Clopidogrel , Substituição de Medicamentos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Doença de Moyamoya/diagnóstico por imagem , Doença de Moyamoya/fisiopatologia , Análise Multivariada , Radioisótopos de Oxigênio/administração & dosagem , Imagem de Perfusão/métodos , Inibidores da Agregação Plaquetária/efeitos adversos , Tomografia por Emissão de Pósitrons , Estudos Prospectivos , Compostos Radiofarmacêuticos/administração & dosagem , Tetrazóis/efeitos adversos , Ticlopidina/efeitos adversos , Ticlopidina/uso terapêutico , Fatores de Tempo , Resultado do TratamentoRESUMO
Understanding cerebral oxygen metabolism is of great importance in both clinical diagnosis and animal experiments because oxygen is a fundamental source of brain energy and supports brain functional activities. Since small animals such as rats are widely used to study various diseases including cerebral ischemia, cerebrovascular diseases, and neurodegenerative diseases, the development of a noninvasive in vivo measurement method of cerebral oxygen metabolic parameters such as oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO2) as well as cerebral blood flow (CBF) and cerebral blood volume (CBV) has been a priority. Although positron emission tomography (PET) with (15)O labeled gas tracers has been recognized as a powerful way to evaluate cerebral oxygen metabolism in humans, this method could not be applied to rats due to technical problems and there were no reports of PET measurement of cerebral oxygen metabolism in rats until an (15)O-O2 injection method was developed a decade ago. Herein, we introduce an intravenous administration method using two types of injectable (15)O-O2 and an (15)O-O2 gas inhalation method through an airway placed in the trachea, which enables oxygen metabolism measurements in rats.
Assuntos
Córtex Cerebral/metabolismo , Consumo de Oxigênio , Oxigênio/metabolismo , Tomografia por Emissão de Pósitrons , Administração por Inalação , Animais , Encéfalo/irrigação sanguínea , Encéfalo/metabolismo , Encéfalo/patologia , Infarto Encefálico/metabolismo , Infarto Encefálico/patologia , Córtex Cerebral/irrigação sanguínea , Córtex Cerebral/patologia , Circulação Cerebrovascular , Masculino , Oxigênio/administração & dosagem , Radioisótopos de Oxigênio/administração & dosagem , RatosRESUMO
Quantitative [15O]H2O positron emission tomography (PET) is the accepted reference method for regional cerebral blood flow (rCBF) quantification. To perform reliable quantitative [15O]H2O-PET studies in PET/MRI scanners, MRI-based attenuation-correction (MRAC) is required. Our aim was to compare two MRAC methods (RESOLUTE and DeepUTE) based on ultrashort echo-time with computed tomography-based reference standard AC (CTAC) in dynamic and static [15O]H2O-PET. We compared rCBF from quantitative perfusion maps and activity concentration distribution from static images between AC methods in 25 resting [15O]H2O-PET scans from 14 healthy men at whole-brain, regions of interest and voxel-wise levels. Average whole-brain CBF was 39.9 ± 6.0, 39.0 ± 5.8 and 40.0 ± 5.6 ml/100 g/min for CTAC, RESOLUTE and DeepUTE corrected studies respectively. RESOLUTE underestimated whole-brain CBF by 2.1 ± 1.50% and rCBF in all regions of interest (range -2.4%- -1%) compared to CTAC. DeepUTE showed significant rCBF overestimation only in the occipital lobe (0.6 ± 1.1%). Both MRAC methods showed excellent correlation on rCBF and activity concentration with CTAC, with slopes of linear regression lines between 0.97 and 1.01 and R2 over 0.99. In conclusion, RESOLUTE and DeepUTE provide AC information comparable to CTAC in dynamic [15O]H2O-PET but RESOLUTE is associated with a small but systematic underestimation.
Assuntos
Encéfalo , Circulação Cerebrovascular , Aprendizado Profundo , Imageamento por Ressonância Magnética , Radioisótopos de Oxigênio/administração & dosagem , Tomografia por Emissão de Pósitrons , Compostos Radiofarmacêuticos/administração & dosagem , Água/administração & dosagem , Adulto , Encéfalo/irrigação sanguínea , Encéfalo/diagnóstico por imagem , Humanos , MasculinoRESUMO
PURPOSE: Astronauts traveling beyond low-Earth orbit will be exposed to high linear-energy transfer charged particles. Because there is concern about the adverse effects of space radiation on the cardiovascular system, this study assessed cardiac function and structure and immune cell infiltration in a mouse model of charged-particle irradiation. MATERIALS AND METHODS: Male C57BL/6â¯J mice were exposed to oxygen ions (16O, 600 MeV/n at 0.25-0.26â¯Gy/min to a total dose of 0, 0.05, 0.1, 0.25, or 1â¯Gy), protons (150 MeV, 0.35-0.55â¯Gy/min to 0, 0.5, or 1â¯Gy), or protons (150 MeV, 0.5â¯Gy) followed by 16O (600 MeV/n, 0.1â¯Gy). Separate groups of mice received 137Cs γ-rays (1â¯Gy/min to 0, 0.5, 1, or 3â¯Gy) as a reference. Cardiac function and blood velocity were measured with ultrasonography at 3, 5, 7, and 9 months after irradiation. At 2 weeks, 3 months, and 9 months, cardiac tissue was collected to assess apoptosis, tissue remodeling, and markers of immune cells. RESULTS: Ejection fraction and fractional shortening decreased at 3 and 7 months after 16O. These parameters did not change in mice exposed to γ-rays, protons, or protons followed by 16O. Each of the radiation exposures caused only small increases in cleaved caspase-3 and numbers of apoptotic nuclei. Changes in the levels of α-smooth muscle cell actin and a 75-kDa peptide of collagen type III in the left ventricle suggested tissue remodeling, but there was no significant change in total collagen deposition at 2 weeks, 3 months, and 9 months. Increases in protein amounts of cluster of differentiation (CD)2, CD68, and CD45 as measured with immunoblots at 2 weeks, 3 months, and 9 months after exposure to protons or 16O alone suggested immune cell infiltration. For type III collagen, CD2 and CD68, the efficacy in inducing protein abundance of CD2, CD68, and CD45 was 16O > protons > γ-rays > protons followed by 16O. CONCLUSIONS: Low-dose, high-energy charged-particle irradiation caused mild changes in cardiac function and tissue remodeling in the mouse.
Assuntos
Biomarcadores/análise , Coração/fisiopatologia , Radioisótopos de Oxigênio/administração & dosagem , Prótons , Exposição à Radiação/análise , Animais , Apoptose , Coração/efeitos da radiação , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Doses de Radiação , Voo EspacialRESUMO
Phase-contrast mapping (PCM) magnetic resonance imaging (MRI) provides easy-access non-invasive quantification of global cerebral blood flow (gCBF) but its accuracy in altered perfusion states is not established. We aimed to compare paired PCM MRI and 15O-H2O positron emission tomography (PET) measurements of gCBF in different perfusion states in a single scanning session. Duplicate combined gCBF PCM-MRI and 15O-H2O PET measurements were performed in the resting condition, during hyperventilation and after acetazolamide administration (post-ACZ) using a 3T hybrid PET/MR system. A total of 62 paired gCBF measurements were acquired in 14 healthy young male volunteers. Average gCBF in resting state measured by PCM-MRI and 15O-H2O PET were 58.5 ± 10.7 and 38.6 ± 5.7 mL/100 g/min, respectively, during hyperventilation 33 ± 8.6 and 24.7 ± 5.8 mL/100 g/min, respectively, and post-ACZ 89.6 ± 27.1 and 57.3 ± 9.6 mL/100 g/min, respectively. On average, gCBF measured by PCM-MRI was 49% higher compared to 15O-H2O PET. A strong correlation between the two methods across all states was observed (R2 = 0.72, p < 0.001). Bland-Altman analysis suggested a perfusion dependent relative bias resulting in higher relative difference at higher CBF values. In conclusion, measurements of gCBF by PCM-MRI in healthy volunteers show a strong correlation with 15O-H2O PET, but are associated with a large and non-linear perfusion-dependent difference.
Assuntos
Encéfalo , Circulação Cerebrovascular/fisiologia , Angiografia por Ressonância Magnética , Radioisótopos de Oxigênio/administração & dosagem , Tomografia por Emissão de Pósitrons , Adolescente , Adulto , Velocidade do Fluxo Sanguíneo , Encéfalo/irrigação sanguínea , Encéfalo/diagnóstico por imagem , Humanos , Masculino , Radioisótopos de Oxigênio/farmacocinéticaRESUMO
UNLABELLED: (15)O-Gas PET is useful for evaluating hemodynamic status in patients with ischemic cerebrovascular disease. To reduce examination time and exposure to radioactive gas, we assessed a count-based method with shorter continuous (15)O(2) gas inhalation. METHODS: Twenty-five patients (66 +/- 13 [mean +/- SD] y old) with unilateral cerebrovascular stenoocclusive disease were examined by use of measurements of asymmetric oxygen extraction fraction (OEF) elevation. Dynamic PET scans of 1 min per frame were obtained starting 2 min after the beginning of (15)O(2) inhalation at a constant flow rate (740 MBq/min). Each subject also underwent C(15)O and H(2)(15)O PET with the bolus administration method. To evaluate the effects of different scan start times and durations during (15)O(2) inhalation, we extracted and summed individual (15)O(2) PET data from the dynamic (15)O(2) dataset. Count-based OEF (cbOEF) images were calculated from (15)O(2) and H(2)(15)O PET images. The asymmetric indices (AI) of cbOEF (cbOEF-AI) were obtained from regions of interest drawn on territories of the bilateral middle cerebral artery. These AI were compared with the AI of quantitative OEF (qOEF-AI). RESULTS: The slopes of the regression lines and the coefficients of correlation between qOEF-AI and cbOEF-AI were close to 1.00 and greater than 0.79, respectively, regardless of different scan start times and durations. The cbOEF-AI obtained with a longer scan duration were closer to the qOEF-AI than those obtained with a shorter scan duration. Longer scan durations also provided better coefficients of correlation between cbOEF-AI and qOEF-AI regardless of scan start times. The coefficients of correlation between cbOEF-AI and qOEF-AI were greater than 0.90, except for cbOEF-AI obtained from (15)O(2) images at 2-3 min after (15)O(2) inhalation. CONCLUSION: The cbOEF obtained by (15)O(2) imaging from 4 min after (15)O(2) inhalation to 7 min or longer can correctly diagnose misery perfusion. The less invasive count-based PET method used in this study will be able to reduce examination time, exposure time, and stress for patients with ischemic cerebrovascular disease.
Assuntos
Encéfalo/diagnóstico por imagem , Transtornos Cerebrovasculares/diagnóstico por imagem , Radioisótopos de Oxigênio/administração & dosagem , Tomografia por Emissão de Pósitrons/métodos , Administração por Inalação , Idoso , Encéfalo/irrigação sanguínea , Feminino , Humanos , Masculino , Compostos Radiofarmacêuticos/administração & dosagem , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
OBJECTIVE: Regional cerebral blood flow (CBF), cerebral blood volume, oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO2) can be estimated from C15O, H(2)15O, and 15O2 tracers and positron emission tomography (PET) using an autoradiographic (ARG) method. Our objective in this study was to optimize the scan time for 15O2 gas study for accurate estimation of OEF and CMRO2. METHODS: We evaluated statistical noise in OEF by varying the scan time and error caused by the tissue heterogeneity in estimated OEF and CMRO2 using computer simulations. The characteristics of statistical noise were investigated by signal-to-noise (S/N) ratio from repeated tissue time activity curves with noise, which were generated using measured averaged arterial input function and assuming CBF=20, 50, and 80 (ml/100 g per minute). Error caused by tissue heterogeneity was also investigated by estimated OEF and CMRO2 from tissue time activity curve with mixture of gray and white matter varying fraction of mixture. In the simulations, three conditions were assumed (i) CBF in gray and white matter (CBFg and CBFw) was 80 and 20, OEF in gray and white matter (Eg and Ew) was 0.4 and 0.3, (ii) CBFg and CBFw decreased by 50%, and Eg and Ew increased by 50% when compared with conditions (i) and (iii). CBFg and CBFw decreased by 80%, and Eg and Ew increased by 50% when compared with condition (i). RESULTS: The longer scan time produced the better S/N ratio of estimated OEF value from three CBF values (20, 50, and 80). Errors of estimated OEF for three conditions owing to tissue heterogeneity decreased, as scan time took longer. Meanwhile in the case of CMRO2, 3 min of scan time was desirable. CONCLUSIONS: The optimal scan time of 15O2 inhalation study with the ARG method was concluded to be 3 min from taking into account for maintaining the S/N ratio and the quantification of accurate OEF and CMRO2.
Assuntos
Autorradiografia/métodos , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Modelos Neurológicos , Radioisótopos de Oxigênio/farmacocinética , Oxigênio/metabolismo , Administração por Inalação , Simulação por Computador , Humanos , Aumento da Imagem/métodos , Taxa de Depuração Metabólica , Consumo de Oxigênio/fisiologia , Radioisótopos de Oxigênio/administração & dosagem , Cintilografia , Compostos Radiofarmacêuticos/administração & dosagem , Compostos Radiofarmacêuticos/farmacocinética , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Fatores de TempoRESUMO
OBJECTIVE: High levels of radioactivity inside a facemask cause scatter correction (SC) errors that appear as photopenic artifacts on quantitative oxygen-15 (O) gas-inhalation positron emission tomography (PET) images. The present study aimed to validate the ability of scatter limitation correction (SLC) to eliminate SC errors in O gas-inhalation PET images acquired from patients and a phantom. MATERIALS AND METHODS: We analyzed the SC errors in phantom images and calculated parametric images of the cerebral blood flow (CBF), cerebral blood volume, oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO2). Phantoms comprised a cylinder and paper with radioactivity to simulate a facemask during (O)O2 gas inhalation. Parametric images were calculated from O gas-inhalation PET images of ten participants. All PET data were reconstructed using conventional SC as model-based SC and SLC. Images acquired from the phantoms and parametric images were assessed visually and quantitatively in the presence and absence of SC error. RESULTS: SC error was evident in images derived from the paper phantom and at the slice level of the cerebellum in CBF, OEF, and CMRO2 images. The radioactivity concentration in the cylindrical phantom with the paper phantom significantly improved with SLC. The SLC also increased the quantitative indices of CBF, OEF, and CMRO2 by 23.8, 42.2, and 44.4%, respectively. CONCLUSION: SLC visually eliminated the SC error and increased the quantitative parameters on O gas-inhalation images derived from a phantom and from patients.
Assuntos
Processamento de Imagem Assistida por Computador/métodos , Radioisótopos de Oxigênio/administração & dosagem , Tomografia por Emissão de Pósitrons/métodos , Espalhamento de Radiação , Administração por Inalação , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Imagens de FantasmasRESUMO
BACKGROUND: X-ray angiography perfusion (XAP) is a perfusion imaging technique based on conventional DSA. OBJECTIVE: In this study, we aimed to validate parameters derived from XAP by comparing them with 15O-gas/water positron emission tomography (PET), using data from patients with chronic ischemic cerebrovascular disease. METHODS: 18 consecutive patients were included. XAP was performed with intra-arterial infusion of contrast media, and a time-density curve was constructed for each cerebral hemisphere. From the curves, the relative values of mean transit time (rMTT) and wash-in rate (rWiR) were obtained by dividing the values of the right hemisphere by those of the left hemisphere. These were then compared with the relative values of cerebral blood flow (rCBF) and rMTT calculated from the PET data. RESULTS: XAP rWiR correlated strongly with PET rCBF (r=0.86, P<0.0001). rMTT measurements from the two modalities were also strongly correlated (r=0.85, P<0.0001). Bland-Altman analysis revealed a bias of 0.14±0.18 (95% limits of agreement -0.22 to 0.51) for PET rCBF versus XAP rWiR, and 0.016±0.093 (95% limits of agreement -0.17 to 0.20) for rMTT between the two modalities. CONCLUSIONS: The relative values obtained from XAP were validated across a population of patients with chronic ischemic cerebrovascular disease.
Assuntos
Angiografia Cerebral/métodos , Transtornos Cerebrovasculares/diagnóstico por imagem , Injeções Intra-Arteriais/métodos , Radioisótopos de Oxigênio , Imagem de Perfusão/métodos , Tomografia por Emissão de Pósitrons/métodos , Idoso , Idoso de 80 Anos ou mais , Circulação Cerebrovascular/fisiologia , Transtornos Cerebrovasculares/terapia , Meios de Contraste/administração & dosagem , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Radioisótopos de Oxigênio/administração & dosagem , Água/administração & dosagemRESUMO
OBJECTIVES: This study sought to compare Doppler flow velocity reserve (CFRDoppl) and thermodilution-derived coronary flow reserve (CFRthermo) head-to-head with the gold standard for quantification of myocardial perfusion, [15O]H2O positron emission tomography (PET). BACKGROUND: Coronary flow reserve (CFR) is an important parameter for assessing coronary vascular function. To date, 2 techniques are available for invasive assessment of CFR: Doppler flow velocity and thermodilution. Although these techniques have been compared with each other, neither has been compared with [15O]H2O PET perfusion imaging. METHODS: CFR was assessed in 98 vessels of 40 consecutive stable patients with suspected coronary artery disease. Patients underwent [15O]H2O PET, followed by invasive angiography in conjunction with simultaneous measurements of fractional flow reserve, CFRDoppl, and CFRthermo. Both normal and obstructed arteries were included. RESULTS: The quality of Doppler flow velocity traces was significantly lower than that of thermodilution curves (p < 0.001). A moderate correlation was observed between CFRDoppl and CFRthermo (r = 0.59; p < 0.001). CFRDoppl correlated well with PET-derived CFR (CFRPET) (r = 0.82; p < 0.001). In contrast, the correlation between CFRthermo and CFRPET was only modest (r = 0.55; p < 0.001). This difference in correlation with CFRPET was significant (t = 4.9; df = 95; p < 0.001). Bland-Altman analysis revealed a tendency of CFRthermo to overestimate flow reserve at higher values. CONCLUSIONS: Coronary flow reserve, determined using Doppler flow velocity, has superior agreement with [15O]H2O PET in comparison with CFRthermo.
Assuntos
Doença da Artéria Coronariana/diagnóstico por imagem , Estenose Coronária/diagnóstico por imagem , Ecocardiografia Doppler , Reserva Fracionada de Fluxo Miocárdico , Imagem de Perfusão do Miocárdio/métodos , Radioisótopos de Oxigênio/administração & dosagem , Tomografia por Emissão de Pósitrons , Compostos Radiofarmacêuticos/administração & dosagem , Idoso , Velocidade do Fluxo Sanguíneo , Doença da Artéria Coronariana/fisiopatologia , Estenose Coronária/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Variações Dependentes do Observador , Valor Preditivo dos Testes , Estudos Prospectivos , Reprodutibilidade dos Testes , Índice de Gravidade de Doença , TermodiluiçãoRESUMO
Combined myocardial flow reserve (MFR) by PET and CT coronary angiography (CTA) is a promising tool for assessment of coronary artery disease. Prior analyses of MFR/CTA has been performed as side-by-side interpretation, not as volume rendered, full hybrid analysis, with fused MFR/CTA. We aimed to: (i) establish a method for full hybrid analysis of MFR/CTA, (ii) validate the inter- and intra-observer reproducibility of MFR values, and (iii) determine the diagnostic value of side-by-side versus full hybrid MFR/CTA with 15-O-water PET. Forty-four outpatients scheduled for invasive coronary angiography (ICA) were enrolled prospectively. All underwent rest/stress 15-O-water PET/CTA with ICA as reference. Within two observers of different experience, the Pearson r at global and territorial level exceeded 0.953 for rest, stress, and MFR values, as determined by Carimas software. Within and between observers, the mean differences between rest, stress, and MFR values were close to zero and the confidence intervals for 95% limits of agreement were narrow. The diagnostic performance of full hybrid PET/CTA did not outperform the side-by-side approach, but performed better than MFR without CTA at vessel level: specificity 93% (95% confidence limits: 89-97%) versus 76% (64-88%), p = 0.0004; positive predictive value 71% (55-86%) versus 51% (37-65%), p = 0.0001; accuracy 90% (84-95%) versus 77% (69-84%), p = 0.0009. MFR showed high reproducibility within and between observers of different experience. The full hybrid model was not superior to side-by-side interpretation of MFR/CTA, but proved better than MFR alone at vessel level with regard to specificity, positive predictive value, and accuracy.
Assuntos
Angiografia por Tomografia Computadorizada/métodos , Angiografia Coronária/métodos , Doença da Artéria Coronariana/diagnóstico por imagem , Vasos Coronários/diagnóstico por imagem , Tomografia Computadorizada Multidetectores/métodos , Imagem de Perfusão do Miocárdio/métodos , Radioisótopos de Oxigênio/administração & dosagem , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Doença da Artéria Coronariana/fisiopatologia , Circulação Coronária , Vasos Coronários/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Variações Dependentes do Observador , Valor Preditivo dos Testes , Estudos Prospectivos , Reprodutibilidade dos TestesRESUMO
BACKGROUND: The main goal of coronary revascularization is to restore myocardial perfusion in case of ischemia, causing coronary artery disease. Yet, little is known on the effect of revascularization on absolute myocardial blood flow (MBF). Therefore, the present prospective study assesses the impact of coronary revascularization on absolute MBF as measured by [15O]H2O positron emission tomography and fractional flow reserve (FFR) in patients with stable coronary artery disease. METHODS AND RESULTS: Fifty-three patients (87% men, mean age 58.7±9.0 years) with suspected coronary artery disease were included prospectively. All patients underwent serial [15O]H2O positron emission tomography perfusion imaging at baseline and after revascularization by either percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery. FFR was routinely measured at baseline and directly post-PCI. After revascularization, regional rest and stress MBF improved from 0.77±0.16 to 0.86±0.25 mL/min/g and from 1.57±0.59 to 2.48±0.91 mL/min/g, respectively, yielding an increase in coronary flow reserve from 2.02±0.69 to 2.94±0.94 (P<0.01 for all). Mean FFR at baseline improved post-PCI from 0.61±0.17 to 0.89±0.08 (P<0.01). After PCI, an increase in FFR paralleled improvement in absolute myocardial perfusion as reflected by stress MBF and coronary flow reserve (r = 0.74 and r = 0.71, respectively, P<0.01 for both). PCI demonstrated a greater improvement of regional stress MBF as compared with coronary artery bypass graft surgery (1.14±1.11 versus 0.66±0.69 mL/min/g, respectively, P=0.02). However, patients undergoing bypass grafting had a more advanced stage of coronary artery disease and more incomplete revascularizations. CONCLUSION: Successful coronary revascularization has a significant and positive impact on absolute myocardial perfusion as assessed by serial quantitative [15O]H2O positron emission tomography. Notably, improvement of FFR after PCI was directly related to the increase in hyperemic MBF.
Assuntos
Cateterismo Cardíaco , Ponte de Artéria Coronária , Doença da Artéria Coronariana/cirurgia , Vasos Coronários/cirurgia , Reserva Fracionada de Fluxo Miocárdico , Imagem de Perfusão do Miocárdio/métodos , Radioisótopos de Oxigênio/administração & dosagem , Intervenção Coronária Percutânea , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada , Compostos Radiofarmacêuticos/administração & dosagem , Idoso , Angiografia Coronária , Doença da Artéria Coronariana/diagnóstico por imagem , Doença da Artéria Coronariana/fisiopatologia , Vasos Coronários/diagnóstico por imagem , Vasos Coronários/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Estudos Prospectivos , Recuperação de Função Fisiológica , Resultado do TratamentoRESUMO
OBJECTIVE: The quantitative measurement of cerebral metabolic rate of oxygen (CMRO(2)) for rats using positron emission tomography (PET) has been technically difficult. The present study was performed to provide a technique to measure CMRO(2) for rats using a dedicated animal PET technique. METHODS: CMRO(2) in the rat brain was quantitatively measured under alpha-chloralose anaesthesia (30 mg . kg(-1) . h(-1), intravenous infusion) using a PET imaging technique. In our experiment, the (15)O-labelled gas tracer (O(15)O) was administered by a bolus insufflation into the lung through a surgically placed cannula in the trachea. The tracer distribution was then dynamically imaged using the microPET. Unlike other conventional PET methods in which a series of arterial blood samples need to be withdrawn for the measurement of an arterial input function, no arterial blood sampling was employed. Instead, the heart was scanned in dynamic mode at the same time of imaging the brain, and the region of interest drawn over the heart was analysed to obtain an arterial input function. RESULTS: The CMRO(2) value (micromol . 100 g(-1) . min(-1)) from 10 rats was 208 +/- 15 (mean +/- SD). CONCLUSIONS: Our results suggest that the microPET-based CMRO(2) measurement in the rat brain combined with a non-invasive measurement of arterial input function is promising, especially for many applications involving small animals in which repeated measurements of absolute CMRO(2) need to be performed.
Assuntos
Mapeamento Encefálico/métodos , Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Interpretação de Imagem Assistida por Computador/métodos , Radioisótopos de Oxigênio , Oxigênio/metabolismo , Tomografia por Emissão de Pósitrons/métodos , Administração por Inalação , Animais , Gases/administração & dosagem , Masculino , Taxa de Depuração Metabólica , Consumo de Oxigênio/fisiologia , Radioisótopos de Oxigênio/administração & dosagem , Tomografia por Emissão de Pósitrons/veterinária , Compostos Radiofarmacêuticos , Ratos , Ratos Endogâmicos F344RESUMO
PURPOSE: Positron emission tomography (PET), the blood flow response in the primary visual cortex (V1) to two visual stimuli, low temporal frequency (6 Hz) to activate the parvocellular system, and high temporal frequency (25 Hz) to activate the magnocellular system were used to investigate pathophysiologic mechanism of amblyopia. METHODS: Five women and one man who were aged between 26 and 60 years, who were ophthalmologically normal except for amblyopia, and who had corrected visual acuity in the amblyopic eye of 0.6 or worse were examined. An intravenous injection of the H(2)(15)O was given, and the regional cerebral blood flow was measured by PET during full-field stimulation with either 6 Hz or 25 Hz flicker to the amblyopic or the sound eye. RESULT: The activation of blood flow in the contra-lateral area V1 by the 6-Hz stimulation of the sound eye was greater than that during the stimulation of the amblyopic eye (P<0.05, small volume correction, n=6). With 25-Hz stimulation of the sound and amblyopic eyes, the blood flow in the contra-lateral and ipsi-lateral areas V1 was not significantly different. CONCLUSION: The decreased activation of blood flow in the contra-lateral V1 by low temporal frequency stimuli supports the hypothesis that the parvocellular pathway in amblyopic eyes is depressed.
Assuntos
Ambliopia/diagnóstico por imagem , Encéfalo/irrigação sanguínea , Circulação Cerebrovascular/fisiologia , Fluxo Sanguíneo Regional/fisiologia , Adulto , Ambliopia/fisiopatologia , Autorradiografia/métodos , Progressão da Doença , Eletroculografia , Movimentos Oculares , Feminino , Humanos , Injeções Intravenosas , Masculino , Pessoa de Meia-Idade , Radioisótopos de Oxigênio/administração & dosagem , Tomografia por Emissão de Pósitrons/métodos , Reprodutibilidade dos Testes , Estimulação Química , Acuidade Visual , Água/administração & dosagemRESUMO
We measured the rate of washout of 15O-labeled water generated from labeled oxygen accumulated in brain after bolus [15O]O2 inhalation, and compared the washout with that of labeled water measured with H215O. Contrary to the original expectation, the radioactive water generated from labeled oxygen failed to leave the brain tissue at the rate predicted by exogenous water. Therefore, the use of a separately measured value for exogenous water clearance led to an error in the calculation of oxygen consumption. A new method presented in this paper eliminated the error by yielding oxygen consumption in a single oxygen study. We used time-weighted integration to estimate three parameters, including the unidirectional clearance from blood to brain (KO2(1)), the fractional clearance of the distribution volume in brain (kO2(2)), and the vascular volume correction (VO). We showed that the clearance of oxygen from blood to brain can be estimated with acceptable precision by this new approach, and that the new method yields a reliable measure of oxygen consumption.
Assuntos
Encéfalo/metabolismo , Consumo de Oxigênio , Tomografia Computadorizada de Emissão , Administração por Inalação , Barreira Hematoencefálica , Humanos , Cinética , Matemática , Modelos Biológicos , Radioisótopos de Oxigênio/administração & dosagem , Análise de RegressãoRESUMO
The present study was undertaken to determine the apparent value for the volume of distribution of water to be used in the dynamic/integral technique for generating functional CBF images. A value of 0.86 resulted in only a minor loss of accuracy compared to the more accurate (but time-consuming) dynamic only analysis, which incorporated the regionally fitted estimates of the volume of distribution of water. In contrast to the traditionally used in vitro value of 0.95, the value of 0.86 allows for the inclusion of a significant part of the washout phase in the integral analysis, thereby producing statistically improved CBF images.
Assuntos
Água Corporal/fisiologia , Encéfalo/fisiologia , Circulação Cerebrovascular , Administração por Inalação , Adulto , Velocidade do Fluxo Sanguíneo , Encéfalo/irrigação sanguínea , Humanos , Masculino , Pessoa de Meia-Idade , Radioisótopos de Oxigênio/administração & dosagem , Tomografia Computadorizada de Emissão/métodosRESUMO
The authors tested the hypothesis that the oxygen content of brain tissue is negligible by injecting an intracarotid bolus of 15O-labeled tracer into rats. Under the hypothesis, the clearance rates of 15O radioactivity from the brain after injections of both 15O-labeled water (H(2)15O) and 15O-labeled oxyhemoglobin (HbO15O) should be identical. However, the logarithmic slope of the 15O radioactivity curve after HbO15O injection (0.494 +/- 0.071 min-1) was steeper than that after H(2)15O injection (0.406 +/- 0.038 min-1) (P<0.001, n = 13), where the time range used in the comparison was between 60 and 120 seconds after the injection. A possible interpretation of this result is that nonmetabolized O15O may dwell in the brain tissue for a finite period of time before it is eventually metabolized or returned to the blood stream unaltered. These findings contradict assumptions made by models currently used to measure cerebral oxygen metabolism.
Assuntos
Artérias Carótidas/metabolismo , Radioisótopos de Oxigênio/administração & dosagem , Radioisótopos de Oxigênio/metabolismo , Oxiemoglobinas/metabolismo , Água/química , Animais , Encéfalo/metabolismo , Circulação Cerebrovascular , Masculino , Radioisótopos de Oxigênio/química , Oxiemoglobinas/química , Ratos , Ratos Sprague-Dawley , Fatores de TempoRESUMO
To test the hypothesis that brain oxidative metabolism is significantly increased upon adequate stimulation, we varied the presentation of a visual stimulus to determine the frequency at which the metabolic response would be at maximum. The authors measured regional CMR(O2) in 12 healthy normal volunteers with the ECAT EXACT HR+ (CTI/Siemens, Knoxville, TN, U.S.A.) three-dimensional whole-body positron emission tomograph (PET). In seven successive activating conditions, subjects viewed a yellow-blue annular checkerboard reversing its contrast at frequencies of 0, 1, 4, 8, 16, 32, and 50 Hz. Stimulation began 4 minutes before and continued throughout the 3-minute dynamic scan. In the baseline condition, the subjects began fixating a cross hair 30 seconds before the scan and continued to do so for the duration of the 3-minute scan. At the start of each scan, the subjects inhaled 20 mCi of (15)O-O2 in a single breath. The CMR(O2) value was calculated using a two-compartment, weighted integration method. Normalized PET images were averaged across subjects and coregistered with the subjects' magnetic resonance imaging in stereotaxic space. Mean subtracted image volumes (activation minus baseline) of CMR(O2) then were obtained and converted to z statistic volumes. The authors found a statistically significant focal change of CMR(O2) in the striate cortex (x = 9; y = -89; z = -1) that reached a maximum at 4 Hz and dropped off sharply at higher stimulus frequencies.
Assuntos
Encéfalo/metabolismo , Consumo de Oxigênio , Córtex Visual/fisiologia , Administração por Inalação , Adulto , Feminino , Humanos , Cinética , Imageamento por Ressonância Magnética , Masculino , Oxigênio/administração & dosagem , Radioisótopos de Oxigênio/administração & dosagem , Estimulação Física , Tomografia Computadorizada de Emissão , Visão OcularRESUMO
In positron emission tomography studies using bolus injection of [15O]water, activation responses reflect underlying CBF changes during a short time (15 to 20 seconds) after arrival of the bolus in the brain. This CBF sensitivity window may be too short for complex activation paradigms, however, particularly those of longer duration. To perform such paradigms, we used a slow infusion method of tracer administration to lengthen the CBF sensitivity window. The present study was designed to determine if this slow infusion technique yields similar results to a bolus injection with a short activation task involving memory for faces. When analyzed using statistical parametric mapping, scanning durations of either 90 or 120 seconds and a 90-second slow infusion schedule produced very similar results to a standard 60-second scan collected after bolus injection, indicating that statistically similar brain activation maps can be produced with the two infusion techniques. This slow infusion approach allows for increased flexibility in designing future studies in which a short CBF sensitivity window is a limiting factor.