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1.
J Reconstr Microsurg ; 2021 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-34404105

RESUMO

BACKGROUND: Current near-infrared spectroscopy (NIRS)-based systems for continuous flap monitoring are highly sensitive for detecting malperfusion. However, the clinical utility and user experience are limited by the wired connection between the sensor and bedside console. This wire leads to instability of the flap-sensor interface and may cause false alarms. METHODS: We present a novel wearable wireless NIRS sensor for continuous fasciocutaneous free flap monitoring. This waterproof silicone-encapsulated Bluetooth-enabled device contains two light-emitting diodes and two photodetectors in addition to a battery sufficient for 5 days of uninterrupted function. This novel device was compared with a ViOptix T.Ox monitor in a porcine rectus abdominus myocutaneous flap model of arterial and venous occlusions. RESULTS: Devices were tested in four flaps using three animals. Both devices produced very similar tissue oxygen saturation (StO2) tracings throughout the vascular clamping events, with obvious and parallel changes occurring on arterial clamping, arterial release, venous clamping, and venous release. Small interdevice variations in absolute StO2 value readings and magnitude of change were observed. The normalized cross-correlation at zero lag describing correspondence between the novel NIRS and T.Ox devices was >0.99 in each trial. CONCLUSION: The wireless NIRS flap monitor is capable of detecting StO2 changes resultant from arterial vascular occlusive events. In this porcine flap model, the functionality of this novel sensor closely mirrored that of the T.Ox wired platform. This device is waterproof, highly adhesive, skin conforming, and has sufficient battery life to function for 5 days. Clinical testing is necessary to determine if this wireless functionality translates into fewer false-positive alarms and a better user experience.

2.
Nat Neurosci ; 24(7): 1035-1045, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33972800

RESUMO

Advanced technologies for controlled delivery of light to targeted locations in biological tissues are essential to neuroscience research that applies optogenetics in animal models. Fully implantable, miniaturized devices with wireless control and power-harvesting strategies offer an appealing set of attributes in this context, particularly for studies that are incompatible with conventional fiber-optic approaches or battery-powered head stages. Limited programmable control and narrow options in illumination profiles constrain the use of existing devices. The results reported here overcome these drawbacks via two platforms, both with real-time user programmability over multiple independent light sources, in head-mounted and back-mounted designs. Engineering studies of the optoelectronic and thermal properties of these systems define their capabilities and key design considerations. Neuroscience applications demonstrate that induction of interbrain neuronal synchrony in the medial prefrontal cortex shapes social interaction within groups of mice, highlighting the power of real-time subject-specific programmability of the wireless optogenetic platforms introduced here.


Assuntos
Optogenética/instrumentação , Comportamento Social , Tecnologia sem Fio/instrumentação , Animais , Camundongos
3.
Clin Exp Metastasis ; 2021 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-33961169

RESUMO

The clinical importance of metastatic spread of cancer has been recognized for centuries, and melanoma has loomed large in historical descriptions of metastases, as well as the numerous mechanistic theories espoused. The "fatal black tumor" described by Hippocrates in 5000 BC that was later termed "melanose" by Rene Laennec in 1804 was recognized to have the propensity to metastasize by William Norris in 1820. And while the prognosis of melanoma was uniformly acknowledged to be dire, Samuel Cooper described surgical removal as having the potential to improve prognosis. Subsequent to this, in 1898 Herbert Snow was the first to recognize the potential clinical benefit of removing clinically normal lymph nodes at the time of initial cancer surgery. In describing "anticipatory gland excision," he noted that "it is essential to remove, whenever possible, those lymph glands which first receive the infective protoplasm, and bar its entrance into the blood, before they have undergone increase in bulk". This revolutionary concept marked the beginning of a debate that rages today: are regional lymph nodes the first stop for metastases ("incubator" hypothesis) or does their involvement serve as an indicator of aggressive disease with inherent metastatic potential ("marker" hypothesis). Is there a better way to improve prediction of disease outcome? This article attempts to address some of the resultant questions that were the subject of the session "Novel Frontiers in the Diagnosis of Cancer" at the 8th International Congress on Cancer Metastases, held in San Francisco, CA in October 2019. Some of these questions addressed include the significance of sentinel node metastasis in melanoma, and the optimal method for their pathologic analysis. The finding of circulating tumor cells in the blood may potentially supplant surgical techniques for detection of metastatic disease, and we are beginning to perfect techniques for their detection, understand how to apply the findings clinically, and develop clinical followup treatment algorithms based on these results. Finally, we will discuss the revolutionary field of machine learning and its applications in cancer diagnosis. Computer-based learning algorithms have the potential to improve efficiency and diagnostic accuracy of pathology, and can be used to develop novel predictors of prognosis, but significant challenges remain. This review will thus encompass latest concepts in the detection of cancer metastasis via the lymphatic system, the circulatory system, and the role of computers in enhancing our knowledge in this field.

4.
Sci Transl Med ; 13(587)2021 03 31.
Artigo em Inglês | MEDLINE | ID: mdl-33790027

RESUMO

The concentration of chloride in sweat remains the most robust biomarker for confirmatory diagnosis of cystic fibrosis (CF), a common life-shortening genetic disorder. Early diagnosis via quantitative assessment of sweat chloride allows prompt initiation of care and is critically important to extend life expectancy and improve quality of life. The collection and analysis of sweat using conventional wrist-strapped devices and iontophoresis can be cumbersome, particularly for infants with fragile skin, who often have insufficient sweat production. Here, we introduce a soft, epidermal microfluidic device ("sweat sticker") designed for the simple and rapid collection and analysis of sweat. Intimate, conformal coupling with the skin supports nearly perfect efficiency in sweat collection without leakage. Real-time image analysis of chloride reagents allows for quantitative assessment of chloride concentrations using a smartphone camera, without requiring extraction of sweat or external analysis. Clinical validation studies involving patients with CF and healthy subjects, across a spectrum of age groups, support clinical equivalence compared to existing device platforms in terms of accuracy and demonstrate meaningful reductions in rates of leakage. The wearable microfluidic technologies and smartphone-based analytics reported here establish the foundation for diagnosis of CF outside of clinical settings.


Assuntos
Fibrose Cística , Suor , Cloretos , Fibrose Cística/diagnóstico , Fibrose Cística/terapia , Humanos , Lactente , Qualidade de Vida , Smartphone
5.
Front Microbiol ; 12: 633954, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33828539

RESUMO

Cyanobacteria are ancient and versatile members of almost all aquatic food webs. In freshwater ecosystems some cyanobacteria form "bloom" populations containing potent toxins and such blooms are therefore a key focus of study. Bloom populations can be ephemeral, with rapid population declines possible, though the factors causing such declines are generally poorly understood. Cell death could be a significant factor linked to population decline. Broadly, three forms of cell death are currently recognized - accidental, regulated and programmed - and efforts are underway to identify these and standardize the use of cell death terminology, guided by work on better-studied cells. For cyanobacteria, the study of such differing forms of cell death has received little attention, and classifying cell death across the group, and within complex natural populations, is therefore hard and experimentally difficult. The population dynamics of photosynthetic microbes have, in the past, been principally explained through reference to abiotic ("bottom-up") factors. However, it has become clearer that in general, only a partial linkage exists between abiotic conditions and cyanobacteria population fluctuations in many situations. Instead, a range of biotic interactions both within and between cyanobacteria, and their competitors, pathogens and consumers, can be seen as the major drivers of the observed population fluctuations. Whilst some evolutionary processes may theoretically account for the existence of an intrinsic form of cell death in cyanobacteria, a range of biotic interactions are also likely to frequently cause the ecological incidence of cell death. New theoretical models and single-cell techniques are being developed to illuminate this area. The importance of such work is underlined by both (a) predictions of increasing cyanobacteria dominance due to anthropogenic factors and (b) the realization that influential ecosystem modeling work includes mortality terms with scant foundation, even though such terms can have a very large impact on model predictions. These ideas are explored and a prioritization of research needs is proposed.

6.
J Bone Miner Metab ; 39(4): 649-660, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33725170

RESUMO

INTRODUCTION: Static cortical bone histomorphometry utilised in forensic age-at-death estimation generally examines only the anterior femoral mid-shaft, as biomechanical strain at the posterior femur is thought to result in increased bone remodelling, osteon density and adversely affect age-at-death estimates. As osteon density increases there is a corresponding decrease in geometric variables, such as osteon area and Haversian canal diameter. The present study tests whether the inverse relationship between osteon density and osteon geometry is reflected in a modern documented Australian sample, and if this relationship differs between the anterior and posterior femoral mid-shaft. MATERIALS AND METHODS: The study sample comprises 215 femoral microradiographs (117♂ 98♀) of recorded age (18‒97 years) from the Melbourne Femur Reference Collection (MFRC). The following variables were measured in Image J across six 1 mm2 regions of interest (ROIs) from the anterior and posterior; mean intact and fragmentary secondary osteon count, osteon population density, osteon and Haversian canal area, perimeter, and diameter. RESULTS: Osteon area was positively correlated with Haversian canal size and shape metrics, and negatively correlated with osteon density. Chronological age was significantly correlated with most variables. There were significant between-group effects between the youngest (18‒34 years) and all other age groups (35‒49, 50-74 and 75 + years) for both regions. CONCLUSION: Our findings support an increased rate of remodelling associated with decreases in osteon geometry in the anterior and posterior femur. Future studies should examine static osteon histomorphometry using anterior and posterior measurements in larger samples of documented age and sex.


Assuntos
Fêmur/anatomia & histologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos , Fêmur/diagnóstico por imagem , Osteon/anatomia & histologia , Humanos , Masculino , Pessoa de Meia-Idade , Variações Dependentes do Observador , Adulto Jovem
7.
Med Phys ; 48(6): 2877-2890, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33656213

RESUMO

PURPOSE: Efficient compression of images while preserving image quality has the potential to be a major enabler of effective remote clinical diagnosis and treatment, since poor Internet connection conditions are often the primary constraint in such services. This paper presents a framework for organ-specific image compression for teleinterventions based on a deep learning approach and anisotropic diffusion filter. METHODS: The proposed method, deep learning and anisotropic diffusion (DLAD), uses a convolutional neural network architecture to extract a probability map for the organ of interest; this probability map guides an anisotropic diffusion filter that smooths the image except at the location of the organ of interest. Subsequently, a compression method, such as BZ2 and HEVC-visually lossless, is applied to compress the image. We demonstrate the proposed method on three-dimensional (3D) CT images acquired for radio frequency ablation (RFA) of liver lesions. We quantitatively evaluate the proposed method on 151 CT images using peak-signal-to-noise ratio ( PSNR ), structural similarity ( SSIM ), and compression ratio ( CR ) metrics. Finally, we compare the assessments of two radiologists on the liver lesion detection and the liver lesion center annotation using 33 sets of the original images and the compressed images. RESULTS: The results show that the method can significantly improve CR of most well-known compression methods. DLAD combined with HEVC-visually lossless achieves the highest average CR of 6.45, which is 36% higher than that of the original HEVC and outperforms other state-of-the-art lossless medical image compression methods. The means of PSNR and SSIM are 70 dB and 0.95, respectively. In addition, the compression effects do not statistically significantly affect the assessments of the radiologists on the liver lesion detection and the lesion center annotation. CONCLUSIONS: We thus conclude that the method has a high potential to be applied in teleintervention applications.


Assuntos
Compressão de Dados , Anisotropia , Processamento de Imagem Assistida por Computador , Imageamento Tridimensional , Redes Neurais de Computação , Razão Sinal-Ruído
8.
Anat Rec (Hoboken) ; 304(12): 2789-2810, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-33773067

RESUMO

The quantification of cranial sexual dimorphism (CSD) among modern humans is relevant in evolutionary studies of morphological variation and in a forensic context. Despite the abundance of quantitative studies of CSD, few have specifically examined intra-sex variability. Here we quantify CSD in a geographically homogeneous sample of adult crania, which includes Italian individuals from the 19th and 20th centuries. Cranial morphology is described with 92 3D landmarks analyzed using Procrustean geometric morphometrics (PGMM). Size and shape variables are used to compare morphological variance between sexes in the whole cranium and four individual regions. The same variables, plus Procrustes form, are used to quantify average sex differences and explore classification accuracy. Our results indicate that: (a) as predicted by Wainer's rule, males present overall more variance in size and shape, albeit this is statistically significant only for total cranial size; (b) differences between sexes are dominated by size and to a lesser extent by Procrustes form; (c) shape only accounts for a minor proportion of variance; (d) the cranial base shows almost no dimorphism for shape; and (e) facial Procrustes form is the most accurate predictor of skeletal sex. Overall, this study suggests developmental factors underlying differences in CSD among cranial regions; stresses the need for population-specific models that describe craniofacial variation as the basis for models that facilitate the estimation of sex in unidentified skeletal remains; and provides one of the first confirmations of "Wainer's rule" in relation to sexual dimorphism in mammals specific to the human cranium.

9.
Sci Adv ; 7(7)2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33568482

RESUMO

Accurate, real-time monitoring of intravascular oxygen levels is important in tracking the cardiopulmonary health of patients after cardiothoracic surgery. Existing technologies use intravascular placement of glass fiber-optic catheters that pose risks of blood vessel damage, thrombosis, and infection. In addition, physical tethers to power supply systems and data acquisition hardware limit freedom of movement and add clutter to the intensive care unit. This report introduces a wireless, miniaturized, implantable optoelectronic catheter system incorporating optical components on the probe, encapsulated by soft biocompatible materials, as alternative technology that avoids these disadvantages. The absence of physical tethers and the flexible, biocompatible construction of the probe represent key defining features, resulting in a high-performance, patient-friendly implantable oximeter that can monitor localized tissue oxygenation, heart rate, and respiratory activity with wireless, real-time, continuous operation. In vitro and in vivo testing shows that this platform offers measurement accuracy and precision equivalent to those of existing clinical standards.

10.
Z Med Phys ; 31(3): 305-315, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33593642

RESUMO

The NEMA NU-2 standard describes a protocol for measurement of scatter fraction (SF) using an axially-aligned line source, offset at 45mm from the central axis, in a cylindrical polyethylene phantom. In this work, which is an extension of our preliminary results previuosly published in the Proceedings of IEEE NSS/MIC 2018 [1], we aim to evaluate the performance of the NEMA NU-2 SF protocol in a Siemens Biograph mCT PET/CT whole-body scanner and a long axial field-of-view (LAFOV) total-body PET scanner to determine whether modifications to the NEMA NU-2 SF protocol are needed for the characterisation of scatter in such scanners. In addition, we evaluate the impact of patient body mass index (BMI) on SF in a LAFOV scanner. The Siemens Biograph mCT and a typical LAFOV PET scanner were modelled in GATE. Monte Carlo simulations were performed to validate the mCT scanner model against published experimental results. SF was estimated using a modified NEMA NU-2 protocol with variable radial offsets on both scanners and compared to ground truth SF measurements obtained with a uniform-activity cylindrical phantom. Correlation between BMI and SF in the LAFOV scanner was evaluated by simulating anthropomorphic phantoms with different BMIs and realistic 18F-FDG distributions, together with uniformly-filled 200cm long cylindrical phantoms with equivalent effective diameters. The optimal offset was found to be either 60mm or 80mm, depending on the chosen optimality metric. We conclude that modifications to NEMA NU-2 are required for accurate SF characterisation in whole-body and LAFOV scanners. Finally, SF in anthropomorphic phantoms with realistic tissue concentrations of 18F-FDG was found to be strongly correlated with SF in an equivalent-volume cylindrical phantom for the LAFOV PET scanner; BMI was also found to strongly positively correlate with the SF.


Assuntos
Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada , Tomografia por Emissão de Pósitrons , Índice de Massa Corporal , Humanos , Método de Monte Carlo , Imagens de Fantasmas
11.
ACS Nano ; 15(2): 2327-2339, 2021 02 23.
Artigo em Inglês | MEDLINE | ID: mdl-33439017

RESUMO

Minimally invasive methods for temperature sensing and thermal modulation in living tissues have extensive applications in biological research and clinical care. As alternatives to bioelectronic devices for this purpose, functional nanomaterials that self-assemble into optically active microstructures offer important features in remote sensing, injectability, and compact size. This paper introduces a transient, or bioresorbable, system based on injectable slurries of well-defined microparticles that serve as photopumped lasers with temperature-sensitive emission wavelengths (>4-300 nm °C-1). The resulting platforms can act as tissue-embedded thermal sensors and, simultaneously, as distributed vehicles for thermal modulation. Each particle consists of a spherical resonator formed by self-organized cholesteric liquid crystal molecules doped with fluorophores as gain media, encapsulated in thin shells of soft hydrogels that offer adjustable rates of bioresorption through chemical modification. Detailed studies highlight fundamental aspects of these systems including particle sensitivity, lasing threshold, and size. Additional experiments explore functionality as photothermal agents with active temperature feedback (ΔT = 1 °C) and potential routes in remote evaluation of thermal transport properties. Cytotoxicity evaluations support their biocompatibility, and ex vivo demonstrations in Casper fish illustrate their ability to measure temperature within biological tissues with resolution of 0.01 °C. This collective set of results demonstrates a range of multifunctional capabilities in thermal sensing and modulation.


Assuntos
Implantes Absorvíveis , Cristais Líquidos , Animais , Hidrogéis , Lasers , Temperatura
12.
Adv Healthc Mater ; 10(4): e2000722, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-32989913

RESUMO

Eccrine sweat contains a rich blend of electrolytes, metabolites, proteins, metal ions, and other biomarkers. Changes in the concentrations of these chemical species can indicate alterations in hydration status and they can also reflect health conditions such as cystic fibrosis, schizophrenia, and depression. Recent advances in soft, skin-interfaced microfluidic systems enable real-time measurement of local sweat loss and sweat biomarker concentrations, with a wide range of applications in healthcare. Uses in certain contexts involve, however, physical impacts on the body that can dynamically deform these platforms, with adverse effects on measurement reliability. The work presented here overcomes this limitation through the use of microfluidic structures constructed in relatively high modulus polymers, and designed in geometries that offer soft, system level mechanics when embedded low modulus elastomers. Analytical models and finite element analysis quantitatively define the relevant mechanics of these systems, and serve as the basis for layouts optimized to allow robust operation in demanding, rugged scenarios such as those encountered in football, while preserving mechanical stretchability for comfortable, water-tight bonding to the skin. Benchtop testing and on-body field studies of measurements of sweat loss and chloride concentration under imposed mechanical stresses and impacts demonstrate the key features of these platforms.


Assuntos
Microfluídica , Suor , Eletrólitos , Reprodutibilidade dos Testes , Pele
13.
J Med Entomol ; 58(1): 79-87, 2021 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-32725186

RESUMO

Forensic entomology relies on insect development data generated within a laboratory setting in the estimation of minimum postmortem interval (mPMI). The methodologies used to produce these data vary considerably within the field and there is no accepted standard approach to laboratory rearing of forensically relevant species. A wide range of rearing media are used across published studies, including different species of animal and types of tissue (e.g., muscle and liver). Differing methodologies, particularly rearing diet, can introduce considerable variation into the baseline data upon which forensic estimates of the mPMI are calculated. Consequently, research establishing a widely available, standard and/or optimal, rearing medium for blow fly development for forensic application is desirable. This study examined dietary effects on the development of two forensically relevant blow fly species: Calliphora dubia Macquart, 1855, and Chrysomya rufifacies Macquart 1842 (Diptera: Calliphoridae). Larvae of both species were reared on pork liver, pork mince, pork loin, beef liver, beef mince, and guinea pig carcass under two constant temperature regimes (24 ± 1°C and 30 ± 1°C; 70 ± 10% humidity; 12-h/12-h photoperiod) to assess the influence of temperature on developmental response to diet. Fundamental developmental data pertaining to both species are reported. Developmental response to diet was species-specific and influenced by temperature with indication that the optimal temperature for C. dubia development is below 30°C. Pork mince was the most appropriate dietary standard of the rearing media investigated for the formulation of forensic development data for both species investigated.


Assuntos
Calliphoridae/crescimento & desenvolvimento , Dieta , Animais , Comportamento Alimentar , Entomologia Forense/métodos , Larva/crescimento & desenvolvimento , Fotoperíodo , Mudanças Depois da Morte , Pupa/crescimento & desenvolvimento , Temperatura
14.
Proc Natl Acad Sci U S A ; 117(50): 31674-31684, 2020 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-33257558

RESUMO

The standard of clinical care in many pediatric and neonatal neurocritical care units involves continuous monitoring of cerebral hemodynamics using hard-wired devices that physically adhere to the skin and connect to base stations that commonly mount on an adjacent wall or stand. Risks of iatrogenic skin injuries associated with adhesives that bond such systems to the skin and entanglements of the patients and/or the healthcare professionals with the wires can impede clinical procedures and natural movements that are critical to the care, development, and recovery of pediatric patients. This paper presents a wireless, miniaturized, and mechanically soft, flexible device that supports measurements quantitatively comparable to existing clinical standards. The system features a multiphotodiode array and pair of light-emitting diodes for simultaneous monitoring of systemic and cerebral hemodynamics, with ability to measure cerebral oxygenation, heart rate, peripheral oxygenation, and potentially cerebral pulse pressure and vascular tone, through the utilization of multiwavelength reflectance-mode photoplethysmography and functional near-infrared spectroscopy. Monte Carlo optical simulations define the tissue-probing depths for source-detector distances and operating wavelengths of these systems using magnetic resonance images of the head of a representative pediatric patient to define the relevant geometries. Clinical studies on pediatric subjects with and without congenital central hypoventilation syndrome validate the feasibility for using this system in operating hospitals and define its advantages relative to established technologies. This platform has the potential to substantially enhance the quality of pediatric care across a wide range of conditions and use scenarios, not only in advanced hospital settings but also in clinics of lower- and middle-income countries.


Assuntos
Técnicas Biossensoriais , Circulação Cerebrovascular/fisiologia , Monitorização Hemodinâmica/instrumentação , Transtornos do Neurodesenvolvimento/diagnóstico , Monitorização Neurofisiológica/instrumentação , Adolescente , Criança , Desenvolvimento Infantil/fisiologia , Pré-Escolar , Feminino , Monitorização Hemodinâmica/métodos , Humanos , Lactente , Masculino , Transtornos do Neurodesenvolvimento/fisiopatologia , Monitorização Neurofisiológica/métodos , Espectroscopia de Luz Próxima ao Infravermelho/instrumentação , Dispositivos Eletrônicos Vestíveis , Tecnologia sem Fio/instrumentação
15.
Phys Med Biol ; 65(23): 235052, 2020 12 05.
Artigo em Inglês | MEDLINE | ID: mdl-33283764

RESUMO

This work presents an iterative method for the estimation of the absolute dose distribution in patients undergoing carbon ion therapy, via analysis of the distribution of positron annihilations resulting from the decay of positron-emitting fragments created in the target volume. The proposed method relies on the decomposition of the total positron-annihilation distributions into profiles of the three principal positron-emitting fragment species - 11C, 10C and 15O. A library of basis functions is constructed by simulating a range of monoenergetic 12C ion irradiations of a homogeneous polymethyl methacrylate phantom and measuring the resulting one-dimensional positron-emitting fragment profiles and dose distributions. To estimate the dose delivered during an arbitrary polyenergetic irradiation, a linear combination of factors from the fragment profile library is iteratively fitted to the decomposed positron annihilation profile acquired during the irradiation, and the resulting weights combined with the corresponding monoenergetic dose profiles to estimate the total dose distribution. A total variation regularisation term is incorporated into the fitting process to suppress high-frequency noise. The method was evaluated with 14 different polyenergetic 12C dose profiles in a polymethyl methacrylate target: one which produces a flat biological dose, 10 with randomised energy weighting factors, and three with distinct dose maxima or minima within the spread-out Bragg peak region. The proposed method is able to calculate the dose profile with mean relative errors of 0.8%, 1.0% and 1.6% from the 11C, 10C, 15O fragment profiles, respectively, and estimate the position of the distal edge of the SOBP to within an average of 0.7 mm, 1.9 mm and 1.2 mm of its true location.


Assuntos
Radioterapia com Íons Pesados/métodos , Tomografia por Emissão de Pósitrons , Doses de Radiação , Radioterapia Guiada por Imagem/métodos , Humanos , Imagens de Fantasmas , Dosagem Radioterapêutica
16.
Phys Med Biol ; 65(23): 235051, 2020 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-33336650

RESUMO

The purpose of this work is to develop a validated Geant4 simulation model of a whole-body prototype PET scanner constructed from the four-layer depth-of-interaction detectors developed at the National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Japan. The simulation model emulates the behaviour of the unique depth of interaction sensing capability of the scanner without needing to directly simulate optical photon transport in the scintillator and photodetector modules. The model was validated by evaluating and comparing performance metrics from the NEMA NU 2-2012 protocol on both the simulated and physical scanner, including spatial resolution, sensitivity, scatter fraction, noise equivalent count rates and image quality. The results show that the average sensitivities of the scanner in the field-of-view were 5.9 cps kBq-1 and 6.0 cps kBq-1 for experiment and simulation, respectively. The average spatial resolutions measured for point sources placed at several radial offsets were 5.2± 0.7 mm and 5.0± 0.8 mm FWHM for experiment and simulation, respectively. The peak NECR was 22.9 kcps at 7.4 kBq ml-1 for the experiment, while the NECR obtained via simulation was 23.3 kcps at the same activity. The scatter fractions were 44% and 41.3% for the experiment and simulation, respectively. Contrast recovery estimates performed in different regions of a simulated image quality phantom matched the experimental results with an average error of -8.7% and +3.4% for hot and cold lesions, respectively. The results demonstrate that the developed Geant4 model reliably reproduces the key NEMA NU 2-2012 performance metrics evaluated on the prototype PET scanner. A simplified version of the model is included as an advanced example in Geant4 version 10.5.


Assuntos
Método de Monte Carlo , Tomografia por Emissão de Pósitrons/instrumentação , Imagem Corporal Total/instrumentação , Desenho de Equipamento , Imagens de Fantasmas , Fótons
17.
Toxins (Basel) ; 12(8)2020 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-32764428

RESUMO

Freshwater cyanobacteria blooms represent a risk to ecological and human health through induction of anoxia and release of potent toxins; both conditions require water management to mitigate risks. Many cyanobacteria taxa may produce microcystins, a group of toxic cyclic heptapeptides. Understanding the relationships between the abiotic drivers of microcystins and their occurrence would assist in the implementation of targeted, cost-effective solutions to maintain safe drinking and recreational waters. Cyanobacteria and microcystins were measured by flow cytometry and liquid chromatography coupled to tandem mass spectrometry in two interconnected reservoirs varying in age and management regimes, in southern Britain over a 12-month period. Microcystins were detected in both reservoirs, with significantly higher concentrations in the southern lake (maximum concentration >7 µg L-1). Elevated microcystin concentrations were not positively correlated with numbers of cyanobacterial cells, but multiple linear regression analysis suggested temperature and dissolved oxygen explained a significant amount of the variability in microcystin across both reservoirs. The presence of a managed fishery in one lake was associated with decreased microcystin levels, suggestive of top down control on cyanobacterial populations. This study supports the need to develop inclusive, multifactor holistic water management strategies to control cyanobacterial risks in freshwater bodies.


Assuntos
Cianobactérias/isolamento & purificação , Lagos/análise , Lagos/microbiologia , Microcistinas/análise , Poluentes Químicos da Água/análise , Inglaterra , Monitoramento Ambiental , País de Gales , Microbiologia da Água
18.
Med Sci Law ; 60(4): 257-265, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32757743

RESUMO

Extant histomorphometric aging methods based on the analysis of the femoral cortex generally report small samples (N<100) and highly variable standard error of the estimate (SEE) values (±1.51‒16.98 years). The present paper reviews the published literature on femoral histomorphometry for age-at-death estimation in order to examine the relationship between sample size and SEE values, and makes recommendations for minimum reporting requirements for age-at-death studies based on statistical data. The SEE from a total of 33 studies are analysed. Sample size and confidence intervals are explored using Hennig and Cooper's simulation modelling. Analysis of effect size through a fixed-effect model is performed on 5/33 studies to examine the relationship between sample size and effect size. The pooled sex formulae from Nor et al., Martrille et al. and Thompson and the two sex-specific formulae of Pfeiffer are examined, as they report mean and standard deviation values for both chronological and estimated ages. The results of these analyses support sampling theory, specifically wide variation in SEE when N<100, narrowing as the sample size increases, and lower effect sizes in the larger of the five studies examined. The findings provide some support for a minimum threshold of 100‒150 individuals for histomorphometric age-at-death estimation. Analysis of effect size is suggested for future investigation in meta-analyses of forensic anthropological age-estimation studies. To ensure increased precision and meaningful comparison, large samples should be used for histomorphometry, and authors should report SEE and discrete statistics (e.g. n, mean, standard deviation) for both chronological age and estimated age.


Assuntos
Determinação da Idade pelo Esqueleto , Fêmur/patologia , Estatística como Assunto/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Intervalos de Confiança , Humanos , Pessoa de Meia-Idade , Tamanho da Amostra
19.
Sensors (Basel) ; 20(14)2020 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-32660069

RESUMO

Source positioning using hybrid angle-of-arrival (AOA) estimation and received signal strength indicator (RSSI) is attractive because no synchronization is required among unknown nodes and anchors. Conventionally, hybrid AOA/RSSI localization combines the same number of these measurements to estimate the agents' locations. However, since AOA estimation requires anchors to be equipped with large antenna arrays and complicated signal processing, this conventional combination makes the wireless sensor network (WSN) complicated. This paper proposes an unbalanced integration of the two measurements, called 1AOA/nRSSI, to simplify the WSN. Instead of using many anchors with large antenna arrays, the proposed method only requires one master anchor to provide one AOA estimation, while other anchors are simple single-antenna transceivers. By simply transforming the 1AOA/1RSSI information into two corresponding virtual anchors, the problem of integrating one AOA and N RSSI measurements is solved using the least square and subspace methods. The solutions are then evaluated to characterize the impact of angular and distance measurement errors. Simulation results show that the proposed network achieves the same level of precision as in a fully hybrid nAOA/nRSSI network with a slightly higher number of simple anchors.

20.
Environ Sci Pollut Res Int ; 27(31): 38916-38927, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32638304

RESUMO

The application of hydrogen peroxide (H2O2) as a management tool to control Microcystis blooms has become increasingly popular due to its short lifetime and targeted action. H2O2 increases intracellular reactive oxygen species resulting in oxidative stress and subsequently cell death. H2O2 is naturally produced in freshwater bodies as a result of photocatalytic reactions between dissolved organic carbon and sunlight. Previously, some studies have suggested that this environmental source of H2O2 selectively targets for toxigenic cyanobacteria strains in the genus Microcystis. Also, past studies only focused on the morphological and biochemical changes of H2O2-induced cell death in Microcystis with little information available on the effects of different H2O2 concentrations on growth, esterase activity and membrane integrity. Therefore, this study investigated the effects of non-lethal (40-4000 nM) concentrations on percentage cell death; with a focus on sub-lethal (50 µM) and lethal (275 µM; 500 µM) doses of H2O2 on growth, cells showing esterase activity and membrane integrity. The non-lethal dose experiment was part of a preliminary study. Results showed a dose- and time-dependent relationship in all three Microcystis strains post H2O2 treatment. H2O2 resulted in a significant increase in intracellular reactive oxygen species, decreased chlorophyll a content, decreased growth rate and esterase activity. Interestingly, at sub-lethal (50 µM H2O2 treatment), percentage of dead cells in microcystin-producing strains was significantly higher (p < 0.05) than that in non-microcystin-producing strains at 72 h. These findings further cement our understanding of the influence of H2O2 on different strains of Microcystis and its impact on membrane integrity and metabolic physiology: important to future toxic bloom control programmes.


Assuntos
Cianobactérias , Microcystis , Clorofila A , Peróxido de Hidrogênio , Microcistinas , Estresse Oxidativo
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