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1.
J Nucl Cardiol ; 28(6): 2647-2656, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-32133601

RESUMO

BACKGROUND: Despite growing interest in coronary microvascular disease (CMVD), there is a dearth of mechanistic understanding. Mouse models offer opportunities to understand molecular processes in CMVD. We have sought to develop quantitative mouse imaging to assess coronary microvascular function. METHODS: We used 99mTc-sestamibi to measure myocardial blood flow in mice with MILabs U-SPECT+ system. We determined recovery and crosstalk coefficients, the influx rate constant from blood to myocardium (K1), and, using microsphere perfusion, constraints on the extraction fraction curve. We used 99mTc and stannous pyrophosphate for red blood cell imaging to measure intramyocardial blood volume (IMBV) as an alternate measure of microvascular function. RESULTS: The recovery coefficients for myocardial tissue (RT) and left ventricular arterial blood (RA) were 0.81 ± 0.16 and 1.07 ± 0.12, respectively. The assumption RT = 1 - FBV (fraction blood volume) does not hold in mice. Using a complete mixing matrix to fit a one-compartment model, we measured K1 of 0.57 ± 0.08 min-1. Constraints on the extraction fraction curve for 99mTc-sestamibi in mice for best-fit Renkin-Crone parameters were α = 0.99 and ß = 0.39. Additionally, we found that wild-type mice increase their IMBV by 22.9 ± 3.3% under hyperemic conditions. CONCLUSIONS: We have developed a framework for measuring K1 and change in IMBV in mice, demonstrating non-invasive µSPECT-based quantitative imaging of mouse microvascular function.


Assuntos
Técnicas de Imagem Cardíaca , Circulação Coronária , Vasos Coronários/diagnóstico por imagem , Microvasos/diagnóstico por imagem , Compostos Radiofarmacêuticos , Tecnécio Tc 99m Sestamibi , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Animais , Estudos de Viabilidade , Camundongos
2.
Psychol Med ; 46(5): 1069-78, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26671170

RESUMO

BACKGROUND: The attenuated positive symptoms syndrome (APSS) is considered an at-risk indicator for psychosis. However, the characteristics and developmental aspects of the combined or enriched risk criteria of APSS and basic symptom (BS) criteria, including self-experienced cognitive disturbances (COGDIS) remain under-researched. METHOD: Based on the Structured Interview of Prodromal Syndromes (SIPS), the prevalence of APSS in 13- to 35-year-old individuals seeking help in an early recognition program for schizophrenia and bipolar-spectrum disorders was examined. BS criteria and COGDIS were rated using the Schizophrenia Proneness Instrument for Adults/Children and Youth. Participants meeting APSS criteria were compared with participants meeting only BS criteria across multiple characteristics. Co-occurrence (APSS+/BS+, APSS+/COGDIS+) was compared across 13-17, 18-22 and 23-35 years age groups. RESULTS: Of 175 individuals (age = 20.6 ± 5.8, female = 38.3%), 94 (53.7%) met APSS criteria. Compared to BS, APSS status was associated with suicidality, higher illness severity, lower functioning, higher SIPS positive, negative, disorganized and general symptoms scores, depression scores and younger age (18.3 ± 5.0 v. 23.2 ± 5.6 years, p < 0.0001) with age-related differences in the prevalence of APSS (ranging from 80.3% in 13- to 17-year-olds to 33.3% in 23- to 35-year-olds (odds ratio 0.21, 95% confidence interval 0.11-0.37). Within APSS+ individuals, fewer adolescents fulfilled combined risk criteria of APSS+/BS+ or APSS+/COGDIS+ compared to the older age groups. CONCLUSIONS: APSS status was associated with greater suicidality and illness/psychophathology severity in this help-seeking cohort, emphasizing the need for clinical care. The age-related differences in the prevalence of APSS and the increasing proportion of APSS+/COGDIS+ may point to a higher proportion of non-specific/transient, rather than risk-specific attenuated positive symptoms in adolescents.


Assuntos
Antipsicóticos/uso terapêutico , Sintomas Prodrômicos , Transtornos Psicóticos/tratamento farmacológico , Transtornos Psicóticos/epidemiologia , Suicídio/estatística & dados numéricos , Adolescente , Adulto , Fatores Etários , Feminino , Humanos , Modelos Logísticos , Masculino , Escalas de Graduação Psiquiátrica , Transtornos Psicóticos/classificação , Fatores de Risco , Índice de Gravidade de Doença , Suíça/epidemiologia , Adulto Jovem
3.
Psychol Med ; 45(10): 2123-34, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25640248

RESUMO

BACKGROUND: Neurocognitive deficits are important aspects of schizophrenic disorder because they have a strong impact on social and vocational outcomes. Previously it was assumed that cognitive abilities progressively deteriorate with illness onset. However, recent research results have contradicted this with observations of continuous or even improved performance in individuals at risk for psychosis or manifest schizophrenia. The objective of our longitudinal study was to examine neurocognitive functioning in help-seeking individuals meeting basic symptoms or ultra-high-risk criteria for schizophrenic psychosis (HRSchiz) or risk criteria for affective psychosis (HRBip). The progression of cognitive functioning in individuals converting to psychosis was compared with that of at-risk individuals who did not convert during the follow-up period. METHOD: Data were available from 86 study participants who completed neurocognitive and clinical assessments at baseline and, on average, 12.8 (s.d. = 1.5) months later. Neurocognitive measures were grouped according to their load in factor analysis to five cognitive domains: speed, attention, fluency, learning and memory, and working memory. RESULTS: Neurocognitive functioning in HRSchiz and HRBip individuals generally improved over time. Subjects converting to manifest psychosis displayed a stable neurocognitive profile from baseline to follow-up. Compared with non-converters, they had already demonstrated a significantly lower level of performance during their baseline examinations. CONCLUSIONS: Our data provide no evidence for a progressive cognitive decline in individuals at risk of psychosis. In line with the neurodevelopmental model, our findings suggest that cognitive deficits are already present very early, before or during the prodromal stage of the illness.


Assuntos
Transtorno Bipolar/psicologia , Transtornos Neurocognitivos/psicologia , Adolescente , Adulto , Análise de Variância , Antipsicóticos/uso terapêutico , Transtorno Bipolar/diagnóstico , Transtorno Bipolar/tratamento farmacológico , Cognição , Feminino , Humanos , Estudos Longitudinais , Masculino , Testes Neuropsicológicos , Sintomas Prodrômicos , Escalas de Graduação Psiquiátrica , Esquizofrenia/diagnóstico , Esquizofrenia/tratamento farmacológico , Psicologia do Esquizofrênico , Suíça , Adulto Jovem
4.
Psychol Med ; 44(16): 3543-55, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25066246

RESUMO

BACKGROUND: Neurocognitive deficits are important aspects of the schizophrenic disorders because they have a strong impact on social and vocational outcomes. We expanded on previous research by focusing on the neurocognitive profiles of persons at high risk (HR) or ultra-high risk (UHR) for schizophrenic and affective psychoses. Our main aim was to determine whether neurocognitive measures are sufficiently sensitive to predict a group affiliation based on deficits in functional domains. METHOD: This study included 207 help-seeking individuals identified as HR (n = 75), UHR (n = 102) or at high risk for bipolar disorder (HRBip; n = 30), who were compared with persons comprising a matched, healthy control group (CG; n = 50). Neuropsychological variables were sorted according to their load in a factor analysis and were compared among groups. In addition, the likelihood of group membership was estimated using logistic regression analyses. RESULTS: The performance of HR and HRBip participants was comparable, and intermediate between the controls and UHR. The domain of processing speed was most sensitive in discriminating HR and UHR [odds ratio (OR) 0.48, 95% confidence interval (CI) 0.28-0.78, p = 0.004] whereas learning and memory deficits predicted a conversion to schizophrenic psychosis (OR 0.47, 95% CI 0.25-0.87, p = 0.01). CONCLUSIONS: Performances on neurocognitive tests differed among our three at-risk groups and may therefore be useful in predicting psychosis. Overall, cognition had a profound effect on the extent of general functioning and satisfaction with life for subjects at risk of psychosis. Thus, this factor should become a treatment target in itself.


Assuntos
Transtorno Bipolar/diagnóstico , Testes Neuropsicológicos/estatística & dados numéricos , Aceitação pelo Paciente de Cuidados de Saúde/psicologia , Esquizofrenia/diagnóstico , Adulto , Transtorno Bipolar/psicologia , Análise Fatorial , Feminino , Humanos , Masculino , Aceitação pelo Paciente de Cuidados de Saúde/estatística & dados numéricos , Risco , Medição de Risco/métodos , Medição de Risco/estatística & dados numéricos , Esquizofrenia/fisiopatologia , Psicologia do Esquizofrênico , Adulto Jovem
5.
Phys Med Biol ; 69(12)2024 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-38815617

RESUMO

Objective. Peripheral Vascular Disease (PVD) affects more than 230 million people worldwide and is one of the leading causes of disability among people over age 60. Nowadays, PVD remains largely underdiagnosed and undertreated, and requires the development of tailored diagnostic approaches. We present the full design of the Dynamic Extremity SPECT (DE-SPECT) system, the first organ-dedicated SPECT system for lower extremity imaging, based on 1 cm thick Cadmium Zinc Telluride (CZT) spectrometers and a dynamic dual field-of-view (FOV) synthetic compound-eye (SCE) collimator.Approach. The proposed DE-SPECT detection system consists of 48 1 cm thick 3D-position-sensitive CZT spectrometers arranged in a partial ring of 59 cm in diameter in a checkerboard pattern. The detection system is coupled with a compact dynamic SCE collimator that allows the user to select between two different FOVs at any time during an imaging study: a wide-FOV (28 cm diameter) configuration for dual-leg or scout imaging or a high-resolution and high-sensitivity (HR-HS) FOV (16 cm diameter) for single-leg or focused imaging.Main results.The preliminary experimental data show that the CZT spectrometer achieves a 3D intrinsic spatial resolution of <0.75 mm FWHM and an excellent energy resolution over a broad energy range (2.6 keV FWHM at 218, 3.3 keV at 440 keV). From simulations, the wide-FOV configuration offers a 0.034% averaged sensitivity at 140 keV and <8 mm spatial resolution, whereas the HR-HS configuration presents a peak central sensitivity of 0.07% at 140 keV and a ∼5 mm spatial resolution. The dynamic SCE collimator enables the capability to perform joint reconstructions that would ensure an overall improvement in imaging performance.Significance. The DE-SPECT system is a stationary and high-performance SPECT system that offers an excellent spectroscopic performance with a unique computer-controlled dual-FOV imaging capability, and a relatively high sensitivity for multi-tracer and multi-functional SPECT imaging of the extremities.


Assuntos
Desenho de Equipamento , Doenças Vasculares Periféricas , Tomografia Computadorizada de Emissão de Fóton Único , Tomografia Computadorizada de Emissão de Fóton Único/instrumentação , Humanos , Doenças Vasculares Periféricas/diagnóstico por imagem , Telúrio , Zinco , Imagens de Fantasmas , Processamento de Imagem Assistida por Computador/métodos , Cádmio
6.
Soc Psychiatry Psychiatr Epidemiol ; 48(12): 1993-2005, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23443272

RESUMO

PURPOSE: This study aimed at exploring the relationship between intelligence quotient (IQ) and alcohol consumption in a large sample of young males. This study explored whether IQ influences alcohol drinking and which pathways might be involved. We further hypothesized that IQ differences between lifetime abstainers and former drinkers exist, and that they primarily result from different group characteristics. METHOD: Within a psychiatric-epidemiological survey using a cross-sectional design IQ-tests were administered to approximately 50,000 Swiss conscripts at age of about 20 years. The sample was divided into four alcohol consumption categories (rare, occasional, moderate and daily drinking) and two non-drinker categories (former drinking and lifetime abstinence). Probabilities for different levels of consumption or former drinking against lifetime abstention in relation to IQ were estimated using multinomial logistic regression. Models were adjusted for education, disability pension, tobacco/cannabis use, migration, parental alcohol disorders, and mental health. RESULTS: After adjusting for confounders full-scale IQ displayed positive associations with being a rare (OR 1.13; CI 95 % 1.07-1.19), occasional (OR 1.41; CI 95 % 1.33-1.48), and moderate drinker (OR 1.53; CI 95 % 1.45-1.62), and negative associations with being a former drinker (OR 0.85; CI 95 % 0.79-0.93). Daily drinking was positively associated only with the performance subscale IQ (OR 1.12; CI 95 % 1.02-1.22). Confounders contributed significantly to the IQ-alcohol association and, therefore, highlight the distinction of non-drinkers into lifetime abstainers and former drinkers. CONCLUSIONS: Our data confirmed the positive link between IQ and moderate drinking. Lower IQ in non-drinkers, however, seems to be related to earlier consumption and the presence of other risk factors.


Assuntos
Consumo de Bebidas Alcoólicas/psicologia , Testes de Inteligência/estatística & dados numéricos , Inteligência , Adolescente , Consumo de Bebidas Alcoólicas/epidemiologia , Fatores de Confusão Epidemiológicos , Estudos Transversais , Feminino , Humanos , Modelos Logísticos , Masculino , Vigilância da População , Fatores de Risco , Fatores Socioeconômicos , Suíça/epidemiologia , Adulto Jovem
7.
Phys Med Biol ; 68(20)2023 10 04.
Artigo em Inglês | MEDLINE | ID: mdl-37348483

RESUMO

Objective. There is great interest in better understanding coronary microvascular disease using mouse models. Typical quantification requires dynamic imaging to estimate the rate constantK1of the tracer moving from the blood into the myocardium. In addition toK1, it is also desirable to determine blood volume fractionV, which if known allows for more accurate fitting ofK1. Our previously published kinetic modeling software did not consider the effect ofV. To ensure a better fit of experimental data to the model for myocardialµSPECT imaging, in this work we updated our kinetic modeling software to include a blood volume fractionV, which adds a fraction of the arterial activity concentration into the tissue concentration.Approach. The tissue and blood time-activity curves (TACs) used for fit input were generated using ideal equations with known values in MATLAB. This allowed post-fit results to be compared to known values to determine fit errors. Parameters that were varied in generating the TACs included blood volume fraction (0, 0.05, 0.1, 0.2 and 0.3),K1(0.5, 1.5, 2.5 ml min-1g-1), frame length (1, 2, 5, 10, 15, 20 s), FWHM of the input Gaussian (10, 20, 40 s), and time of the injection peak relative to frame duration. Blood volume-fraction results have low error when blood volume is lowest, but results worsen as frame length andK1increase.Main results. We demonstrated that blood volume can be accurately determined, and also show how fit accuracy varies across TACs with different input properties.Significance. This information allows for robust use of the fitting algorithm and aids in understanding fit performance when used in animal studies.


Assuntos
Coração , Tomografia por Emissão de Pósitrons , Camundongos , Animais , Tomografia por Emissão de Pósitrons/métodos , Coração/diagnóstico por imagem , Miocárdio , Simulação por Computador , Volume Sanguíneo
8.
Psychopathology ; 44(3): 201-4, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21412034

RESUMO

A 21-year-old female with Fabry's disease (FD) presented acute psychotic symptoms such as delusions, auditory hallucinations and formal thought disorders. Since the age of 14, she had suffered from various psychiatric symptoms increasing in frequency and intensity. We considered the differential diagnoses of prodromal symptoms of schizophrenia and organic schizophrenia-like disorder. Routine examinations including cognitive testing, electroencephalography and structural magnetic resonance imaging revealed no pathological findings. Additional structural and functional imaging demonstrated a minor CNS involvement of FD, yet without functional limitations. In summary our examination results support the thesis that in the case of our patient a mere coincidence of FD and psychotic symptoms is more likely than a causal connection.


Assuntos
Doença de Fabry/complicações , Transtornos Psicóticos/complicações , Feminino , Humanos , Imageamento por Ressonância Magnética , Transtornos Psicóticos/diagnóstico , Adulto Jovem
9.
Phys Med Biol ; 54(2): 207-25, 2009 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-19088387

RESUMO

We have designed a multi-pinhole collimator for a dual-headed, stationary SPECT system that incorporates high-resolution silicon double-sided strip detectors. The compact camera design of our system enables imaging at source-collimator distances between 20 and 30 mm. Our analytical calculations show that using knife-edge pinholes with small-opening angles or cylindrically shaped pinholes in a focused, multi-pinhole configuration in combination with this camera geometry can generate narrow sensitivity profiles across the field of view that can be useful for imaging small objects at high sensitivity and resolution. The current prototype system uses two collimators each containing 127 cylindrically shaped pinholes that are focused toward a target volume. Our goal is imaging objects such as a mouse brain, which could find potential applications in molecular imaging.


Assuntos
Tomografia Computadorizada de Emissão de Fóton Único/instrumentação , Animais , Fenômenos Biofísicos , Encéfalo/anatomia & histologia , Encéfalo/diagnóstico por imagem , Desenho de Equipamento , Imageamento Tridimensional , Camundongos , Modelos Teóricos , Imagens de Fantasmas , Espalhamento de Radiação , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Tomografia Computadorizada de Emissão de Fóton Único/estatística & dados numéricos
10.
Phys Med Biol ; 53(4): 953-66, 2008 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-18263951

RESUMO

Single photon emission computed tomography (SPECT) can be performed with various collimator types, which have an inherent tradeoff between the properties of sensitivity, resolution, field of view and complete sampling. Slit-slat collimation, which has seen recent interest in the literature, combines a slit parallel to the axis of rotation of a gamma camera with a set of septa perpendicular to the slit. This collimator geometry exhibits properties that may enhance some SPECT imaging applications, specifically imaging of the breast, limbs and medium-sized animals. However, a complete description of its system response is critical for a comparison to other collimator types and for accurate reconstruction of projection data. Herein, experimental and Monte Carlo methods are used to determine the sensitivity and transaxial and axial resolutions as a function of the incidence angle theta, which is the angle formed by the line from the photon source to the center of the slit and the plane of the slit, to compare to theoretical expectations. Four configurations are investigated by varying the slit width, septal spacing and septal height. Monte Carlo sensitivity data not modeling penetration and scatter exhibit a sin(3)theta dependence. Experimental and Monte Carlo-derived sensitivity data modeling scatter and penetration are consistent with each other and have a sin(x)theta dependence, where x is greater than 3. Transaxial resolution data show a small dependence on theta, and axial resolution data are consistent with no angular dependence.


Assuntos
Tomografia Computadorizada de Emissão de Fóton Único/métodos , Modelos Químicos , Método de Monte Carlo , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
11.
Phys Med Biol ; 51(21): 5675-96, 2006 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-17047277

RESUMO

The expressions for the sensitivity of converging collimators found in the literature diverge at points near the focal locus of the collimator. In this paper, an analytical formula that does not diverge is derived and compared to that available in the literature. An analysis is provided to predict the cases in which use of the new formula is advisable. Since the first expression derived is rather complex, approximations were made to reach simpler formulae. The formulae derived can be used to define and extend the realm of applicability of the literature expression in the cases identified in their derivation.


Assuntos
Processamento de Imagem Assistida por Computador/métodos , Tomografia Computadorizada de Emissão de Fóton Único/instrumentação , Simulação por Computador , Desenho de Equipamento , Modelos Estatísticos , Modelos Teóricos , Método de Monte Carlo , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Tomografia Computadorizada de Emissão de Fóton Único/métodos
12.
Phys Med Biol ; 51(21): 5697-705, 2006 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-17047278

RESUMO

The previous paper presented the derivation of an analytical formula for the sensitivity of converging collimators that does not diverge at the focal locus of the collimator. Its predictions, those from a simplified version, and those from the most commonly referenced formula are compared to Monte Carlo and experimental data. Agreement is excellent for all formulae far from the focal locus of the collimator, where it is markedly better for the new formula and its approximation. It is inferred that such formulae should be used in the cases identified by theory, namely around the focal locus of collimators of any focal length and over a substantial part of the field-of-view for short focal length collimators.


Assuntos
Processamento de Imagem Assistida por Computador/métodos , Tomografia Computadorizada de Emissão de Fóton Único/instrumentação , Calibragem , Simulação por Computador , Desenho de Equipamento , Modelos Estatísticos , Modelos Teóricos , Método de Monte Carlo , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Tomografia Computadorizada de Emissão de Fóton Único/métodos
13.
Phys Med Biol ; 61(5): 2003-13, 2016 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-26894917

RESUMO

We are designing a dual-resolution pre-clinical SPECT system based on square-pinhole apertures for use in applications with a small field-of-view (FOV), such as cardiac imaging of mice. Square pinholes allow for increased sensitivity due to more efficient projection tiling on the detector compared to circular pinholes. Aperture fabrication techniques cannot produce a perfect square, giving the square pinholes some amount of roundedness at the corners. This work investigates how this roundedness affects the physical properties of projection images in terms of spatial resolution. Different pinhole full-acceptance angles and roundedness values were simulated. To facilitate a fair comparison, properties of the non-square pinholes were manipulated to yield pinholes with approximately the same sensitivity (to within 0.1%) and FOV (to within 0.5%) as those of the square pinholes, subsequently referred to as matched apertures. The aperture size (flat-to-flat edge length) of each non-square aperture was increased until its sensitivity was approximately equal to that of the square pinhole. Next, the full acceptance angle was increased until the FOV of each non-square aperture was approximately equivalent to that of the square pinhole. Sensitivity was calculated to include both the geometric and penetrative sensitivity of a point source, as well as the packing faction of the multi-pinhole collimator. Using the sensitivity-matched and FOV-matched apertures, spatial resolution was estimated. For the 0.3 mm, 0.5 mm, and 1 mm edge-length square apertures studied, the full-width at half-maximum widened as pinhole shape changed from square to circle, while full-width tenth-maximum showed little change. These results indicate that a perfect square pinhole shape is more desirable than a rounded-square pinhole with regard to spatial resolution when sensitivity and FOV-matched pinholes are compared.


Assuntos
Coração/fisiologia , Processamento de Imagem Assistida por Computador/métodos , Modelos Teóricos , Tomografia Computadorizada de Emissão de Fóton Único/instrumentação , Animais , Simulação por Computador , Desenho de Equipamento , Camundongos , Tomografia Computadorizada de Emissão de Fóton Único/métodos
14.
IEEE Trans Med Imaging ; 24(3): 361-70, 2005 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15754986

RESUMO

The effects of uncompensated electronic and mechanical shifts may compromise the resolution of pinhole single photon emission computed tomography. The resolution degradation due to uncompensated shifts is estimated through simulated data. A method for determining the transverse mechanical and axial electronic shifts is described and evaluated. This method assumes that the tilt of the detector and the radius of rotation (ROR) are previously determined using another method. When this assumption is made, it is possible to determine the rest of the calibration parameters using a single point source. A method that determines the electronic and mechanical shifts as well as the tilt has been previously described; this method requires three point sources. It may be reasonable in most circumstances to calibrate tilt much less frequently than the mechanical shifts since the tilt is a property of the scanner whereas the mechanical shift may change every time the collimator is replaced. An alternative method for determining the ROR may also be used. Lastly, we take the view that the transverse electronic shift and the focal length change slowly and find these parameters independently.


Assuntos
Algoritmos , Artefatos , Análise de Falha de Equipamento/métodos , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Tomografia Computadorizada de Emissão de Fóton Único/instrumentação , Calibragem/normas , Campos Eletromagnéticos , Análise de Falha de Equipamento/normas , Aumento da Imagem/normas , Interpretação de Imagem Assistida por Computador/normas , Imageamento Tridimensional/normas , Mecânica , Imagens de Fantasmas , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Tomografia Computadorizada de Emissão de Fóton Único/normas
15.
IEEE Trans Med Imaging ; 24(7): 853-62, 2005 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-16011314

RESUMO

Pinhole collimation yields high sensitivity when the distance from the object to the aperture is small, as in the case of imaging small animals. Fine-resolution images may be obtained when the magnification is large since this mitigates the effect of detector resolution. Large magnifications in pinhole single-photon emission computed tomography (SPECT) may be obtained by using a collimator whose focal length is many times the radius of rotation. This may be achieved without truncation if the gamma camera is large. We describe a commercially available clinical scanner mated with pinhole collimation and an external linear stage. The pinhole collimation gives high magnification. The linear stage allows for helical pinhole SPECT. We have used the system to image radiolabeled molecules in phantoms and small animals.


Assuntos
Câmaras gama , Aumento da Imagem/instrumentação , Interpretação de Imagem Assistida por Computador/instrumentação , Tomografia Computadorizada de Emissão de Fóton Único/instrumentação , Tomografia Computadorizada de Emissão de Fóton Único/veterinária , Animais , Desenho de Equipamento , Análise de Falha de Equipamento , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Camundongos , Miniaturização , Biologia Molecular/métodos , Técnicas de Sonda Molecular , Imagens de Fantasmas , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Tomografia Computadorizada de Emissão de Fóton Único/métodos
16.
Phys Med Biol ; 50(21): 5005-17, 2005 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-16237237

RESUMO

To account for photon penetration, the formulae used to calculate the geometric resolution of a pinhole collimator use an effective diameter d(e) rather than the physical diameter of the aperture. The expressions commonly used for d(e), however, were originally derived to include penetration in sensitivity calculations. To predict the full width at half maximum (FWHM) resolution of the point-spread function (PSF) of a knife-edge pinhole collimator, we have previously proposed simple expressions for a resolution-effective diameter d(re). Unlike those for d(e), expressions for d(re) predict both a dependence on the polar angle of the source (theta) and a non-isotropic PSF. In this paper, the new theory was tested by measuring experimentally the FWHM of the PSF. Results confirm the theoretical predictions that (a) d(re) provides the best estimates of the experimental FWHM as a function of theta and of the direction in the plane of the pinhole, (b) Paix's expression for d(e) tends to overestimate the FWHM, (c) Anger's is a better approximation, but still cannot predict the dependence on theta, and (d) the FWHM decreases with decreasing theta, i.e. resolution improves for sources at the edge of the field-of-view.


Assuntos
Radioisótopos/uso terapêutico , Radioterapia/métodos , Algoritmos , Radioisótopos de Cobalto/uso terapêutico , Interpretação de Imagem Assistida por Computador/instrumentação , Interpretação de Imagem Assistida por Computador/métodos , Radioisótopos do Iodo/uso terapêutico , Modelos Estatísticos , Método de Monte Carlo , Imagens de Fantasmas , Fótons , Radioterapia/instrumentação , Sensibilidade e Especificidade , Tomografia Computadorizada de Emissão de Fóton Único/instrumentação , Tomografia Computadorizada de Emissão de Fóton Único/métodos
17.
Travel Med Infect Dis ; 13(1): 10-8, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25468523

RESUMO

BACKGROUND: Travel volumes are still increasing resulting in a more interconnected world and fostering the spread of infectious diseases. We aimed to evaluate the relevance of travel-related measles, a highly transmissible and vaccine-preventable disease. METHOD: Between 2001 and 2013, surveillance and travel-related measles data were systematically reviewed according to the PRISMA guidelines with extraction of relevant articles from Medline, Embase, GoogleScholar and from public health authorities in the Region of the Americas, Europe and Australia. RESULTS: From a total of 960 records 44 articles were included and they comprised 2128 imported measles cases between 2001 and 2011. The proportion of imported cases in Europe was low at 1-2%, which reflects the situation in a measles-endemic region. In contrast, imported and import-related measles accounted for up to 100% of all cases in regions with interrupted endemic measles transmission. Eleven air-travel related reports described 132 measles index cases leading to 47 secondary cases. Secondary transmission was significantly more likely to occur if the index case was younger or when there were multiple infectious cases on board. Further spread to health care settings was found. Measles cases associated with cruise ship travel or mass gatherings were sporadically observed. CONCLUSIONS: Within both, endemic and non-endemic home countries, pretravel health advice should assess MMR immunity routinely to avoid measles spread by nonimmune travelers. To identify measles spread as well as to increase and sustain high vaccination coverages joint efforts of public health specialists, health care practitioners and travel medicine providers are needed.


Assuntos
Sarampo/epidemiologia , Viagem , Viagem Aérea , América/epidemiologia , Austrália/epidemiologia , Europa (Continente)/epidemiologia , Humanos , Internacionalidade , Sarampo/transmissão , Vacina contra Sarampo , Navios , Vacinação
18.
IEEE Trans Med Imaging ; 21(8): 878-87, 2002 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12472261

RESUMO

Pinhole collimators are widely used to image small organs and animals. The pinhole response function (PRF) of knife-edge pinhole collimators has been estimated previously using geometric constructions without considering penetration and using "roll-off" models that employ an exponential model for the flux. An analytic expression for the PRF on the imaging plane that includes the effect of aperture penetration is derived in this paper by calculating the flux for photons passing through the aperture and those passing through the attenuating material. The PRF is then used to approximate the angular-dependent root-mean-square resolution in the directions parallel and perpendicular to the tilt of the point source. The corresponding aspect ratio is then obtained. The formulas are then compared with experimental data.


Assuntos
Aumento da Imagem/instrumentação , Aumento da Imagem/métodos , Modelos Teóricos , Tomografia Computadorizada de Emissão de Fóton Único/instrumentação , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Simulação por Computador , Imagens de Fantasmas , Fótons , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
19.
IEEE Trans Med Imaging ; 20(8): 730-41, 2001 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-11513024

RESUMO

Pinhole collimators are widely used to image small organs and animals. The sensitivity of knife-edge pinhole collimators has been previously estimated using an "effective diameter" formulation and experimentally described using a sin(x) theta fit, where theta is the angle between the line segment from the center of the aperture to the photon source and its projection onto the plane of the aperture. An analytic form of the sensitivity of the pinhole collimator is derived in this paper. A numerical formula for predicting the sin(x) theta form of the sensitivity is calculated from the analytic form. Experimental data are compared with the theoretical estimate and the sin(x) theta prediction. The agreement is excellent.


Assuntos
Tomografia Computadorizada de Emissão de Fóton Único/métodos
20.
Phys Med Biol ; 55(17): 5151-68, 2010 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-20714046

RESUMO

We have performed a theoretical study to explore the potential and limitations of synthetic collimation for SPECT imaging with stacked-detector acquisition (dual magnification). This study will be used to optimize SiliSPECT, a small-animal SPECT for imaging small volumes such as a mouse brain at high sensitivity and resolution. The synthetic collimation enables image reconstruction with a limited number of camera views and in the presence of significant multiplexing. We also developed a new formulation to quantify the multiplexed object sensitivity and investigated how this changes for different acquisition parameters such as number of pinholes and combinations of front and back detector distances for imaging objects as small as the mouse brain. In our theoretical studies, we were not only able to demonstrate better reconstruction results by incorporating two detector magnifications in comparison to either one alone, but also observed an improved image reconstruction by optimizing the detector-collimator distances to change the multiplexing ratio between the front and back detectors.


Assuntos
Encéfalo/citologia , Aumento da Imagem/instrumentação , Processamento de Imagem Assistida por Computador/instrumentação , Tomografia Computadorizada de Emissão de Fóton Único/instrumentação , Animais , Encéfalo/diagnóstico por imagem , Encéfalo/patologia , Desenho de Equipamento , Aumento da Imagem/métodos , Processamento de Imagem Assistida por Computador/métodos , Camundongos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Tomografia Computadorizada de Emissão de Fóton Único/métodos
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