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1.
Neuroimage ; 220: 117136, 2020 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-32634594

RESUMO

Oxygen extraction fraction (OEF) and the cerebral metabolic rate of oxygen (CMRO2) are key cerebral physiological parameters to identify at-risk cerebrovascular patients and understand brain health and function. PET imaging with [15O]-oxygen tracers, either through continuous or bolus inhalation, provides non-invasive assessment of OEF and CMRO2. Numerous tracer delivery, PET acquisition, and kinetic modeling approaches have been adopted to map brain oxygenation. The purpose of this technical review is to critically evaluate different methods for [15O]-gas PET and its impact on the accuracy and reproducibility of OEF and CMRO2 measurements. We perform a meta-analysis of brain oxygenation PET studies in healthy volunteers and compare between continuous and bolus inhalation techniques. We also describe OEF metrics that have been used to detect hemodynamic impairment in cerebrovascular disease. For these patients, advanced techniques to accelerate the PET scans and potential synthesis with MRI to avoid arterial blood sampling would facilitate broader use of [15O]-oxygen PET for brain physiological assessment.

2.
IEEE Trans Biomed Circuits Syst ; 14(3): 583-594, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32406843

RESUMO

This paper presents an ultrasonically powered microsystem for deep tissue optogenetic stimulation. All the phases in developing the prototype starting from modelling the piezoelectric crystal used for energy harvesting, design, simulation and measurement of the chip, and finally testing the whole system in a mimicking setup are explained. The developed system is composed of a piezoelectric harvesting cube, a rectifier chip, and a micro-scale custom-designed light-emitting-diode (LED), and envisioned to be used for freely moving animal studies. The proposed rectifier chip with a silicon area of [Formula: see text] is implemented in standard TSMC [Formula: see text] CMOS technology, for interfacing the piezoelectric cube and the microLED. Experimental results show that the proposed microsystem produces an available electrical power of  [Formula: see text] while loaded by a microLED, out of an acoustic intensity of [Formula: see text] using a [Formula: see text] crystal as the receiver. The whole system including the tested rectifier chip, a piezoelectric cube with the dimensions of [Formula: see text], and a µLED of [Formula: see text] have been integrated on a [Formula: see text] glass substrate, encapsulated inside a bio-compatible PDMS layer and tested successfully for final prototyping. The total volume of the fully-packaged device is estimated around [Formula: see text].

3.
Artigo em Inglês | MEDLINE | ID: mdl-32296882

RESUMO

PURPOSE: The purpose of this study was to investigate the prognostic value of whole-body metabolic tumor volume (MTV) and other metabolic tumor parameters, obtained from baseline and first restaging 18F-FDG PET/CT scans in melanoma patients treated with immune checkpoint inhibitors (ICIs). METHODS: Eighty-five consecutive melanoma patients (M, 57; F, 28) treated with ICIs who underwent PET/CT scans before and approximately 3 months after the start of immunotherapy were retrospectively enrolled. Metabolic tumor parameters including MTV for all melanoma lesions were measured on each scan. A Cox proportional hazards model was used for univariate and multivariate analyses of metabolic parameters combined with known clinical prognostic factors associated with overall survival (OS). Kaplan-Meier curves for patients dichotomized based on median values of imaging parameters were generated. RESULTS: The median OS time in all patients was 45 months (95% CI 24-45 months). Univariate analysis demonstrated that MTV obtained from first restaging PET/CT scans (MTVpost) was the strongest prognostic factor for OS among PET/CT parameters (P < 0.0001). The median OS in patients with high MTVpost (≥ 23.44) was 16 months (95% CI 12-32 months) as compared with more than 60 months in patients with low MTVpost (< 23.44) (P = 0.0003). A multivariate model including PET/CT parameters and known clinical prognostic factors revealed that MTVpost and the presence of central nervous system lesions were independent prognostic factors for OS (P = 0.0004, 0.0167, respectively). One pseudoprogression case (1.2%) was seen in this population and classified into the high MTVpost group. CONCLUSION: Whole-body metabolic tumor volume from PET scan acquired approximately 3 months following initiation of immunotherapy (MTVpost) is a strong prognostic indicator of OS in melanoma patients. Although the possibility of pseudoprogression must be considered whenever evaluating first restaging PET imaging, it only occurred in 1 patient in our cohort.

4.
Curr Treat Options Oncol ; 21(4): 25, 2020 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-32172368

RESUMO

OPINION STATEMENT: Neuroendocrine tumors (NETs) are a heterogenous group of neoplasms characterized by varied biological hallmarks and behavior, ranging from indolent to aggressive. For many decades, somatostatin analogues and few targeted therapies were available for NETs and these therapies had minimal response rates. However, there have been a number of recent treatment advances. Peptide receptor radionuclide therapy (PRRT) is a novel approach to treatment of NETs and has changed the landscape of treatment for NETs. It is a form of targeted therapy in which a radiolabeled somatostatin analogue delivers radiation specifically to tumor cells expressing the somatostatin receptor.

5.
IEEE Trans Biomed Circuits Syst ; 14(2): 343-358, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-31944987

RESUMO

Implantable neural interfacing devices have added significantly to neural engineering by introducing the low-frequency oscillations of small populations of neurons known as local field potential as well as high-frequency action potentials of individual neurons. Regardless of the astounding progression as of late, conventional neural modulating system is still incapable to achieve the desired chronic in vivo implantation. The real constraint emerges from mechanical and physical differences between implants and brain tissue that initiates an inflammatory reaction and glial scar formation that reduces the recording and stimulation quality. Furthermore, traditional strategies consisting of rigid and tethered neural devices cause substantial tissue damage and impede the natural behavior of an animal, thus hindering chronic in vivo measurements. Therefore, enabling fully implantable neural devices requires biocompatibility, wireless power/data capability, biointegration using thin and flexible electronics, and chronic recording properties. This article reviews biocompatibility and design approaches for developing biointegrated and wirelessly powered implantable neural devices in animals aimed at long-term neural interfacing and outlines current challenges toward developing the next generation of implantable neural devices.

6.
J Nucl Med ; 61(4): 533-539, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31562226

RESUMO

PET using radiolabeled prostate-specific membrane antigen (PSMA) is now being more widely adopted as a valuable tool to evaluate patients with prostate cancer (PC). Recently, 3 different criteria for interpretation of PSMA PET were published: the European Association of Nuclear Medicine (EANM) criteria, the Prostate Cancer Molecular Imaging Standardized Evaluation criteria, and the PSMA Reporting and Data System. We compared these 3 criteria in terms of interreader, intrareader, and intercriteria agreement. Methods: Data from 104 patients prospectively enrolled in research protocols at our institution were retrospectively reviewed. The cohort consisted of 2 groups: 47 patients (mean age, 64.2 y old) who underwent Glu-NH-CO-NH-Lys-(Ahx)-[68Ga(HBED-CC)] (68Ga-PSMA11) PET/MRI for initial staging of biopsy-proven intermediate- or high-risk PC, and 57 patients (mean age, 70.5 y old) who underwent 68Ga-PSMA11 PET/CT because of biochemically recurrent PC. Three nuclear medicine physicians independently evaluated all 68Ga-PSMA11 PET/MRI and PET/CT studies according to the 3 interpretation criteria. Two of them reevaluated all studies 6 mo later in the same manner and masked to the initial reading. The Gwet agreement coefficient was calculated to evaluate interreader, intrareader, and intercriteria agreement based on the following sites: local lesion (primary tumor or prostate bed after radical prostatectomy), lymph node metastases, and other metastases. Results: In the PET/MRI group, interreader, intrareader, and intercriteria agreement ranged from substantial to almost perfect for any site according to all 3 criteria. In the PET/CT group, interreader agreement ranged from substantial to almost perfect except for judgment of distant metastases based on the PSMA Reporting and Data System (Gwet agreement coefficient, 0.57; moderate agreement), in which the most frequent cause of disagreement was lung nodules. Intrareader agreement ranged from substantial to almost perfect for any site according to all 3 criteria. Intercriteria agreement for each site was also substantial to almost perfect. Conclusion: Although the 3 published criteria have good interreader and intrareader reproducibility in evaluating 68Ga-PSMA11 PET, there are some factors causing interreader disagreement. Further work is needed to address this issue.

7.
J Nucl Med ; 61(4): 546-551, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31628216

RESUMO

18F-DCFPyL (2-(3-{1-carboxy-5-[(6-18F-fluoropyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid) is a promising PET radiopharmaceutical targeting prostate-specific membrane antigen (PSMA). We present our experience with this single-academic-center prospective study evaluating the positivity rate of 18F-DCFPyL PET/CT in patients with biochemical recurrence (BCR) of prostate cancer (PC). Methods: We prospectively enrolled 72 men (52-91 y old; mean ± SD, 71.5 ± 7.2) with BCR after primary definitive treatment with prostatectomy (n = 42) or radiotherapy (n = 30). The presence of lesions compatible with PC was evaluated by 2 independent readers. Fifty-nine patients had scans concurrent with at least one other conventional scan: bone scanning (24), CT (21), MR (20), 18F-fluciclovine PET/CT (18), or 18F-NaF PET (14). Findings from 18F-DCFPyL PET/CT were compared with those from other modalities. Impact on patient management based on 18F-DCFPyL PET/CT was recorded from clinical chart review. Results: 18F-DCFPyL PET/CT had an overall positivity rate of 85%, which increased with higher prostate-specific antigen (PSA) levels (ng/mL): 50% (PSA < 0.5), 69% (0.5 ≤ PSA < 1), 100% (1 ≤ PSA < 2), 91% (2 ≤ PSA < 5), and 96% (PSA ≥ 5). 18F-DCFPyL PET detected more lesions than conventional imaging. For anatomic imaging, 20 of 41 (49%) CT or MRI scans had findings congruent with 18F-DCFPyL, whereas 18F-DCFPyL PET was positive in 17 of 41 (41%) cases with negative CT or MRI findings. For bone imaging, 26 of 38 (68%) bone or 18F-NaF PET scans were congruent with 18F-DCFPyL PET, whereas 18F-DCFPyL PET localized bone lesions in 8 of 38 (21%) patients with negative results on bone or 18F-NaF PET scans. In 8 of 18 (44%) patients, 18F-fluciclovine PET had located the same lesions as did 18F-DCFPyL PET, whereas 5 of 18 (28%) patients with negative 18F-fluciclovine findings had positive 18F-DCFPyL PET findings and 1 of 18 (6%) patients with negative 18F-DCFPyL findings had uptake in the prostate bed on 18F-fluciclovine PET. In the remaining 4 of 18 (22%) patients, 18F-DCFPyL and 18F-fluciclovine scans showed different lesions. Lastly, 43 of 72 (60%) patients had treatment changes after 18F-DCFPyL PET and, most noticeably, 17 of these patients (24% total) had lesion localization only on 18F-DCFPyL PET, despite negative results on conventional imaging. Conclusion: 18F-DCFPyL PET/CT is a promising diagnostic tool in the work-up of biochemically recurrent PC, given the high positivity rate as compared with Food and Drug Administration-approved currently available imaging modalities and its impact on clinical management in 60% of patients.

8.
Am J Nucl Med Mol Imaging ; 9(5): 243-247, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31772822

RESUMO

Standardized uptake values (SUVs) of 18F-fluorodeoxyglucose positron emission tomography (FDG PET) are widely used to help characterize pulmonary nodules. The purpose of this study is to assess the accuracy of the SUV corrected by blood glucose levels (SUVgluc), compared to four other commonly used semi-quantitative methods: maximal SUV normalized to body weight (SUVmax), ratio of SUV of nodule to cerebellum (SUVcer), SUV normalized to body surface area (SUVbsa) and SUV normalized to body mass index (SUVbmi). 52 patients with lung nodules had FDG PET scans, consecutively imaged between 7/1/2015 and 6/7/2016. Histopathologic result of the nodules, obtained within two months after the FDG PET scan, demonstrated 10 benign and 42 malignant lung nodules. The SUVgluc was defined as SUVmax × blood glucose level/100. The average SUVmax was 2.8 for benign nodules and 7.7 for malignant nodules. No significant difference in the receiver operating characteristic (ROC) area under the curves (AUCs) were found between the SUVmax (0.84) and the SUVcer (0.87) or SUVbsa (0.86), or SUVbmi (0.86) with p-values greater than 0.05; however, the ROC AUC for the SUVgluc (0.90) was larger than that for the SUVmax with p-value of 0.03. These results suggest that SUVgluc may assist in more accurately representing the glucose metabolism of malignant lung nodules by accounting for the patient's blood glucose level (BGL). The simplicity of the SUVgluc method avoids an additional reference ROI, uses preexisting clinical data, i.e. pre-injection blood glucose level, and retains the familiar SUV reference values.

9.
IEEE Trans Biomed Circuits Syst ; 13(6): 1362-1371, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31647446

RESUMO

This paper presents a novel micro-scale ultrasonically powered optogenetic microstimulator with the vision of treating Parkinson's Disease. This system features a power-efficient active rectifier benefiting from a novel powering approach for its comparators. The main basis of the idea is to lower the Rail-to-Rail supply voltage of the comparators, thereby lowering their propagation delays. This technique improves the power conversion efficiency of the active rectifiers in two ways. First by decreasing the propagation delay of the comparators, and second by reusing the consumed power by the active diodes. The proposed system including the active rectifier, a novel double-pass regulator, a current reference, and a burst detection circuit is designed, simulated and fabricated in TSMC [Formula: see text]m CMOS technology with a total silicon area of [Formula: see text]. Based on the experimental results, the proposed active rectifier exhibits a voltage conversion ratio of [Formula: see text]% for input voltages of around 3 V, and a power conversion efficiency of up to [Formula: see text]% for a load of [Formula: see text] and over the frequency range of [Formula: see text]. A proof-of-concept system including the fabricated chip, a [Formula: see text]-sized lead zirconate titanate (PZT-4) piezoelectric receiver, and a custom-designed [Formula: see text] blue µ LED is designed and measured in a Water tank. For an acoustic intensity of [Formula: see text], the available electrical power at the crystal terminals, the output DC power, and the output light intensity were measured equal to [Formula: see text], [Formula: see text], and [Formula: see text], respectively. The quiescent current of the chip in absence of power bursts is measured equal to [Formula: see text]A.


Assuntos
Fontes de Energia Elétrica , Optogenética/instrumentação , Ultrassom , Desenho de Equipamento , Humanos , Luz , Neurônios/fisiologia , Optogenética/métodos , Próteses e Implantes , Semicondutores , Tecnologia sem Fio
10.
IEEE Trans Biomed Circuits Syst ; 13(6): 1437-1450, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31443053

RESUMO

This paper presents a low-power high-input-impedance analog-front-end (AFE) design including an instrumentational-amplifier (IA) and a neural-signal-specific ADC (NSS-ADC) for continuous acquisition of electroencephalography (EEG) signals. In the proposed AFE, low-voltage low-power design techniques are used to reduce the power consumption of the whole system. Furthermore, by utilizing the proposed NSS-ADC, high-amplitude EEG spikes, which convey more important information, are converted with higher resolutions, while the background-noise (B-Noise) of the EEG signal is converted with the lowest resolution. Hence, when the NSS-ADC enters the inactive region, the resolution- and DAC- controlling-units (RCU and DCU) set the analog and digital components of the NSS-ADC into off mode, which leads to power reduction. Based on measurement results, the AFE consumes a power of 3.7 µW under the sampling rate of 20 KS/s. In the proposed AFE, to avoid signal attenuation, active-electrodes (AEs) are utilized to enhance the input impedance of the AFE up to 102 GΩ and 5.2 GΩ at 1 Hz and 20 Hz, respectively. In addition, by using circuit-design techniques the input-referred-noise is reduced as low as 1.5 µVrms over 0.5-1.2 kHz. Finally, by using a transconductance-driven-right-leg (TDRL) and a common-mode-feedback (CMFB) blocks, a common-mode-rejection-ratio (CMRR) of 108 dB is achieved.


Assuntos
Eletroencefalografia/instrumentação , Amplificadores Eletrônicos , Impedância Elétrica , Eletrodos , Eletroencefalografia/métodos , Desenho de Equipamento , Humanos , Razão Sinal-Ruído , Dispositivos Eletrônicos Vestíveis
11.
Radiographics ; 39(1): 169-185, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30620694

RESUMO

Chronic thromboembolic pulmonary hypertension (CTEPH) is a life-threatening complication of acute pulmonary embolism (PE). Because the treatment of CTEPH is markedly different from that of other types of pulmonary hypertension, lung ventilation-perfusion (V/Q) scintigraphy is recommended for the workup of patients with unexplained pulmonary hypertension. Lung V/Q scintigraphy is superior to CT pulmonary angiography for detecting CTEPH. Perfusion defect findings of CTEPH can be different from those of acute PE. Familiarity with the patterns of perfusion defects seen during the initial workup of CTEPH and the expected posttreatment changes seen at follow-up imaging is essential for accurate interpretation of V/Q scintigraphy findings. ©RSNA, 2019.


Assuntos
Hipertensão Pulmonar/diagnóstico por imagem , Pulmão/diagnóstico por imagem , Embolia Pulmonar/diagnóstico por imagem , Doença Crônica , Angiografia por Tomografia Computadorizada , Diagnóstico Diferencial , Endarterectomia , Feminino , Humanos , Hipertensão Pulmonar/etiologia , Hipertensão Pulmonar/cirurgia , Masculino , Imagem de Perfusão/métodos , Embolia Pulmonar/complicações
12.
Conf Proc IEEE Eng Med Biol Soc ; 2019: 4354-4358, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31946832

RESUMO

This paper presents a novel overvoltage protection technique for ultrasonically powered microsystems. The proposed idea benefits from voltage-current characteristics of the piezoelectric harvesters, and limits the amplitude of the harvested signal by regulating the current consumption of the system. For this purpose, a low-area low-power overvoltage regulator is proposed, analyzed and simulated in transistor level in standard TSMC 0.18µm CMOS technology occupying a silicon area of 285µm2. Furthermore, to avoid unnecessary power consumption of the overvoltage regulator, it is proposed to take advantage of an ultrasonic burst detection block to deactivate the regulator in the absence of ultrasonic waves. According to our simulation results, the quiescent power consumption of the proposed circuit in the presence and absence of ultrasonic waves are 37 and 3µW respectively, and the minimum phase margin of the negative feedback loop is 68 degree.


Assuntos
Próteses e Implantes , Retroalimentação , Ultrassom
13.
Conf Proc IEEE Eng Med Biol Soc ; 2019: 3827-3830, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31946708

RESUMO

This paper presents a novel ultrasonic transmitter with the ability of focusing ultrasonic waves for maximum power transmission at different depths for brain neurostimula-tor implants. The most important advantages of the proposed multi-ring ultrasonic transducer (MRUT) is its simplicity and no requirement of any lens or air cavity for focusing the ultrasonic waves. Furthermore, adjusting the focal point compared to the conventional transducers is significantly easier, especially as the location of implants may vary due to, for example, head movement or the need of using these implants at different depths. By the use of multiple rings on a single piezoelectric disk in our transducer, not only more focused ultrasound beams can be achieved, but also the side lobes can be diminished by exciting each rings with different electrical signal. The proposed transmitter is envisioned to be used for optogenetic stimulation of neurons in freely-moving animals.


Assuntos
Próteses e Implantes , Transdutores , Ondas Ultrassônicas , Animais
14.
Nucl Med Commun ; 37(9): 975-82, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27111100

RESUMO

PURPOSE: Extraskeletal findings detected on whole-body low-dose unenhanced computed tomography (CT) as a part of F-NaF PET/CT scans can be numerous and present challenges for further management. Here, we investigate the frequency and clinical significance of extraskeletal findings among 130 consecutive patients undergoing F-NaF PET/CT for osseous metastatic disease. METHODS: F-NaF PET/CT performed on 130 patients (101 men and 29 women; mean age: 61.4 years) with biopsy-proven malignancies were reviewed independently. Incidental soft tissue findings detected on unenhanced low-dose CT portions of the scans were compiled and categorized by clinical significance. RESULTS: A total of 275 incidental extraskeletal CT findings were observed in 114 out of 130 patients (87.7%). Seven patients (5.4%) showed clinically significant findings. One patient developed new lung nodules that were resected and proven to be metastases. Two patients showed new hypodense hepatic lesions that were highly suspicious for liver metastases. One patient with prostate cancer was found to have previously unknown retroperitoneal lymphadenopathy. Three patients showed indeterminate renal and adrenal lesions that necessitated further correlative imaging. CONCLUSION: Although CT indicated a large number of incidental extraskeletal lesions in the majority of patients undergoing F-NaF PET/CT, clinically significant incidental findings requiring further evaluation were relatively infrequently observed in 5.4% of patients. Thus, the low-dose unenhanced CT in F-NaF PET/CT performed for oncologic evaluation may indicate unexpected soft tissue lesions that can impact patient management and therefore should be interpreted by physicians skilled in CT reading, with correlation to available imaging, and familiar with established guidelines for work-up of incidental findings.


Assuntos
Neoplasias Ósseas/diagnóstico por imagem , Neoplasias Ósseas/secundário , Tomografia Computadorizada com Tomografia por Emissão de Pósitrons/métodos , Neoplasias de Tecidos Moles/diagnóstico por imagem , Neoplasias de Tecidos Moles/secundário , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Radioisótopos de Flúor , Humanos , Achados Incidentais , Masculino , Pessoa de Meia-Idade , Compostos Radiofarmacêuticos , Estudos Retrospectivos , Fluoreto de Sódio , Imagem Corporal Total/métodos , Adulto Jovem
15.
Conf Proc IEEE Eng Med Biol Soc ; 2016: 419-422, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-28268362

RESUMO

In this paper a new method for continuous pain detection is proposed. One approach to detect the presence of pain is by processing images taken from the face. It has been reported that expression of pain from the face can be detected utilizing Action Units (AUs). In this manner, each action units must be detected separately and then combined together through a linear expression. Also, pain detection can be directly done from a painful face. There are different methods to extract features of both shape and appearance. Shape and appearance features must be extracted separately, and then used to train a classifier. Here, a hierarchical unsupervised feature learning approach is proposed in order to extract the features needed for pain detection from facial images. In this work, features are extracted using convolutional deep belief network (CDBN). The extracted features include different properties of painful images such as head movements, shape and appearance information. The proposed model was tested on the publicly available UNBC MacMaster Shoulder Pain Archive Database and we achieved near 95% for the area under ROC curve metric that is prominent with respect to the other reported results.


Assuntos
Face/anormalidades , Processamento de Imagem Assistida por Computador , Dor/diagnóstico , Algoritmos , Humanos , Modelos Lineares , Modelos Teóricos , Curva ROC , Aprendizado de Máquina não Supervisionado
16.
Clin Nucl Med ; 41(6): e281-7, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-26673240

RESUMO

PURPOSE: To analyze the biodistribution of Ga-DOTA-TATE in the normal tissues and uptake in benign, indeterminate, and malignant lesions in a population of patients with known neuroendocrine tumors (NET) using semiquantitative standardized uptake values (SUV) measurements. METHODS: One hundred four consecutively scanned patients (51 men and 53 women; mean age, 56.4 years) with confirmed diagnosis of NET underwent PET/CT 1 hour after administration of Ga-DOTA-TATE. SUVmean, and SUVmax were measured in 37 normal anatomical structures for each patient. Abnormal uptake was divided into benign, indeterminate, and malignant categories based on imaging characteristic, clinical follow-up, and pathology. RESULTS: High physiologic uptake (SUVmax > 7) was observed in spleen, renal parenchyma, adrenal glands, pituitary gland, stomach, and liver (in decreasing order). Moderate uptake (3.5-7) was present in the prostate, jejunum, pancreas, ileum, and salivary glands. Mild uptake (2-3.5) was present in the uterus, colon, thyroid, rectum, and skeleton. A total of 678 lesions (limited to 5 lesions with highest uptake per organ) were included in the analysis, including 127 benign and 54 indeterminate lesions. Uptake was significantly higher in malignant lesions than in benign lesions, but an overlap was noted between the groups. CONCLUSIONS: Ga-DOTA TATE uptake in normal and abnormal structures is highly variable in patients with NET. SUV is a useful measure for characterizing benign versus malignant lesions. Anatomical and clinical correlation may be necessary to characterize foci of intermediate uptake.


Assuntos
Tumores Neuroendócrinos/metabolismo , Compostos Organometálicos/farmacocinética , Adulto , Idoso , Idoso de 80 Anos ou mais , Transporte Biológico , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Tumores Neuroendócrinos/diagnóstico por imagem , Tumores Neuroendócrinos/patologia , Tomografia Computadorizada com Tomografia por Emissão de Pósitrons , Distribuição Tecidual
17.
Front Neurosci ; 8: 139, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24966808

RESUMO

Recent studies from our group and others using quantitative fMRI methods have found that variations of the coupling ratio of blood flow (CBF) and oxygen metabolism (CMRO2) responses to a stimulus have a strong effect on the BOLD response. Across a number of studies an empirical pattern is emerging in the way CBF and CMRO2 changes are coupled to neural activation: if the stimulus is modulated to create a stronger response (e.g., increasing stimulus contrast), CBF is modulated more than CMRO2; on the other hand, if the brain state is altered such that the response to the same stimulus is increased (e.g., modulating attention, adaptation, or excitability), CMRO2 is modulated more than CBF. Because CBF and CMRO2 changes conflict in producing BOLD signal changes, this finding has an important implication for conventional BOLD-fMRI studies: the BOLD response exaggerates the effects of stimulus variation but is only weakly sensitive to modulations of the brain state that alter the response to a standard stimulus. A speculative hypothesis is that variability of the coupling ratio of the CBF and CMRO2 responses reflects different proportions of inhibitory and excitatory evoked activity, potentially providing a new window on neural activity in the human brain.

18.
Neuroimage ; 82: 182-9, 2013 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-23732885

RESUMO

Prolonged visual stimulation results in neurophysiologic and hemodynamic adaptation. However, the hemodynamic adaptation appears to be small compared to neural adaptation. It is not clear how the cerebral metabolic rate of oxygen (CMRO2) is affected by adaptation. We measured cerebral blood flow (CBF) and CMRO2 change in responses to peripheral stimulation either continuously, or intermittently (on/off cycles). A linear system's response to the continuous input should be equal to the sum of the original response to the intermittent input and a version of that response shifted by half a cycle. The CMRO2 response showed a large non-linearity consistent with adaptation, the CBF response adapted to a lesser degree, and the blood oxygenation level dependent (BOLD) response was nearly linear. The metabolic response was coupled with a larger flow in the continuous condition than in the intermittent condition. Our results suggest that contrast adaptation improves energy economy of visual processing. However BOLD modulations may not accurately represent the underlying metabolic nonlinearity due to modulation of the coupling of blood flow and oxygen metabolism changes.


Assuntos
Adaptação Fisiológica/fisiologia , Circulação Cerebrovascular/fisiologia , Córtex Visual/irrigação sanguínea , Córtex Visual/metabolismo , Percepção Visual/fisiologia , Adulto , Mapeamento Encefálico , Feminino , Hemodinâmica/fisiologia , Humanos , Processamento de Imagem Assistida por Computador , Imagem por Ressonância Magnética , Masculino , Oxigênio/metabolismo , Consumo de Oxigênio/fisiologia , Estimulação Luminosa
19.
Orthodontics (Chic.) ; 14(1): e76-81, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23646341

RESUMO

AIM: The purpose of this study was to investigate the salivary concentration of nickel and chromium of patients undergoing orthodontic treatment. METHODS: In this study 32 patients who presented to the orthodontic clinic were selected. The salivary samples were taken from the patients in four stages: before appliance placement and 20 days, 3 months, and 6 months following appliance placement. The salivary samples were collected in a plastic tube and were stored in the freezer before analysis. The samples were then transferred to the laboratory, and the amounts of metals were determined by graphite furnace atomic absorption spectrometry with an autosampler. Each sample was analyzed three times, and the average was reported. RESULTS: It was found that the average amount of nickel in the saliva 20 days after appliance placement was 0.8 µg/L more than before placement. Also, the amount of salivary nickel 20 days after the appliance placement was more than at the other stages, but the differences were not significant. The average amount of chromium in the saliva was found to be between 2.6 and 3.6 µg/L. The amount of chromium at all stages after appliance placement was more than before, but the differences between the chromium levels of saliva at all stages were not significant. CONCLUSION: There was no significant difference in the average amount of salivary nickel and chromium of patients at various stages of orthodontic appliance placement.


Assuntos
Cromo/análise , Níquel/análise , Braquetes Ortodônticos , Saliva/química , Adolescente , Criança , Estudos de Coortes , Ligas Dentárias/química , Seguimentos , Humanos , Níquel/química , Desenho de Aparelho Ortodôntico , Fios Ortodônticos , Espectrofotometria Atômica/métodos , Aço Inoxidável/química , Titânio/química , Adulto Jovem
20.
Orthodontics (Chic.) ; 14(1): e82-7, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23646342

RESUMO

AIM: The purpose of the present study was to evaluate the shear bond strength of orthodontic brackets bonded to porcelain following etching with erbium-doped yttrium aluminum garnet (Er:YAG) laser compared with 9.6% hydrofluoric acid (HF). METHODS: A total of 100 porcelain disk samples were divided into four groups, and after removing their glazed layer, the first group was etched with 9.6% HF, and the other three groups were etched with Er:YAG lasers of 1.6, 2, and 3.2 W, respectively. After application of silane on the disk surfaces, central incisor brackets were bonded with composite on the disks. The disks were mounted on an acrylic stand for measuring the shear bond strengths. The shear bond strengths were measured by a testing machine. RESULTS: The mean shear bond strength in the laser group with power of 1.6 W (7.88 MPa) was more than that of the HF (7.4MPa), 2-W power (7.52 MPa), and 3.2-W power (7.45 MPa) groups, but this difference was not statistically significant. Examination with an electron microscope showed different patterns of etching by HF and laser. Also, etching by laser and HF had not resulted in cracks on the porcelain surface. CONCLUSION: Er:YAG laser can be a suitable method for bonding of orthodontic brackets to porcelain surfaces.


Assuntos
Condicionamento Ácido do Dente/métodos , Colagem Dentária , Corrosão Dentária/métodos , Porcelana Dentária/química , Ácido Fluorídrico/química , Lasers de Estado Sólido , Braquetes Ortodônticos , Silicatos de Alumínio/química , Silicatos de Alumínio/efeitos da radiação , Ligas de Cromo/química , Resinas Compostas/química , Luzes de Cura Dentária , Porcelana Dentária/efeitos da radiação , Análise do Estresse Dentário/instrumentação , Humanos , Teste de Materiais , Ligas Metalo-Cerâmicas/química , Microscopia Eletrônica de Varredura , Compostos de Potássio/química , Compostos de Potássio/efeitos da radiação , Doses de Radiação , Cimentos de Resina/química , Resistência ao Cisalhamento , Silanos/química , Estresse Mecânico , Propriedades de Superfície , Temperatura , Fatores de Tempo , Água/química
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