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1.
Methods Mol Biol ; 2216: 565-576, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33476024

RESUMO

In order to tackle the challenges caused by the variability in estimated MRI parameters (e.g., T2* and T2) due to low SNR a number of strategies can be followed. One approach is postprocessing of the acquired data with a filter. The basic idea is that MR images possess a local spatial structure that is characterized by equal, or at least similar, noise-free signal values in vicinities of a location. Then, local averaging of the signal reduces the noise component of the signal. In contrast, nonlocal means filtering defines the weights for averaging not only within the local vicinity, bur it compares the image intensities between all voxels to define "nonlocal" weights. Furthermore, it generally compares not only single-voxel intensities but small spatial patches of the data to better account for extended similar patterns. Here we describe how to use an open source NLM filter tool to denoise 2D MR image series of the kidney used for parametric mapping of the relaxation times T2* and T2.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers.


Assuntos
Algoritmos , Aumento da Imagem/instrumentação , Aumento da Imagem/métodos , Processamento de Imagem Assistida por Computador/métodos , Rim/fisiologia , Imagem por Ressonância Magnética/métodos , Imagens de Fantasmas , Animais , Monitorização Fisiológica , Ratos , Razão Sinal-Ruído , Software
2.
Medicine (Baltimore) ; 99(34): e21886, 2020 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-32846848

RESUMO

BACKGROUND: As the gold standard for imaging sinus disease, the main disadvantage of computed tomography (CT) of the pediatric paranasal sinus is radiation exposure. Because of this, 1 protocol for CT should reduce radiation dose while maintaining image quality. The aim of this study is to evaluate the image quality of dose-reduced paranasal sinus computed tomography (CT) using an ultralow tube voltage (70 kVp) combined with iterative reconstruction (IR) in children. METHODS: CT scans of the paranasal sinus were performed using different protocols [70 kVp protocols with IR, Group A, n = 80; 80 kVp protocols with a filtered back projection algorithm, Group B, n = 80] in 160 pediatric patients. Then, the volume-weighted CT dose index, dose-length product, and effective dose were estimated. Image noise, the signal-to-noise ratio and the diagnostic image quality were also evaluated. RESULTS: For the radiation dose, the volume-weighted CT dose index, dose-length product and effective dose values were significantly lower for the 70 kVp protocols than for the 80 kVp protocols (P < .001). Compared with the 80 kVp protocols, the 70 kVp protocols had significantly higher levels of image noise (P = .001) and a lower signal-to-noise ratio (P = .002). No significant difference in the overall subjective image quality grades was observed between these 2 groups (P = .098). CONCLUSION: The ultralow tube voltage (70 kVp) technique combined with IR enabled a significant dose reduction in CT examinations performed in the pediatric paranasal sinus while maintaining diagnostic image quality with clinically acceptable image noise.


Assuntos
Aumento da Imagem/instrumentação , Doenças dos Seios Paranasais/diagnóstico por imagem , Exposição à Radiação/efeitos adversos , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/instrumentação , Adolescente , Algoritmos , Criança , Pré-Escolar , China/epidemiologia , Estudos de Viabilidade , Feminino , Humanos , Masculino , Estudos Prospectivos , Doses de Radiação , Exposição à Radiação/estatística & dados numéricos , Razão Sinal-Ruído
3.
PLoS One ; 15(5): e0232583, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32392215

RESUMO

A modern color filter array (CFA) output is rendered into the final output image using a demosaicing algorithm. During this process, the rendered image is affected by optical and carrier cross talk of the CFA pattern and demosaicing algorithm. Although many CFA patterns have been proposed thus far, an image-quality (IQ) evaluation system capable of comprehensively evaluating the IQ of each CFA pattern has yet to be developed, although IQ evaluation items using local characteristics or specific domain have been created. Hence, we present an IQ metric system to evaluate the IQ performance of CFA patterns. The proposed CFA evaluation system includes proposed metrics such as the moiré robustness using the experimentally determined moiré starting point (MSP) and achromatic reproduction (AR) error, as well as existing metrics such as color accuracy using CIELAB, a color reproduction error using spatial CIELAB, structural information using the structure similarity, the image contrast based on MTF50, structural and color distortion using the mean deviation similarity index (MDSI), and perceptual similarity using Haar wavelet-based perceptual similarity index (HaarPSI). Through our experiment, we confirmed that the proposed CFA evaluation system can assess the IQ for an existing CFA. Moreover, the proposed system can be used to design or evaluate new CFAs by automatically checking the individual performance for the metrics used.


Assuntos
Algoritmos , Aumento da Imagem , Cor , Aumento da Imagem/instrumentação , Aumento da Imagem/métodos , Sistema Métrico , Fotografação/instrumentação , Fotografação/métodos
4.
Nat Methods ; 17(6): 571-581, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32284609

RESUMO

Temporal focusing, with its ability to focus light in time, enables scanless illumination of large surface areas at the sample with micrometer axial confinement and robust propagation through scattering tissue. In conventional two-photon microscopy, widely used for the investigation of intact tissue in live animals, images are formed by point scanning of a spatially focused pulsed laser beam, resulting in limited temporal resolution of the excitation. Replacing point scanning with temporally focused widefield illumination removes this limitation and represents an important milestone in two-photon microscopy. Temporal focusing uses a diffusive or dispersive optical element placed in a plane conjugate to the objective focal plane to generate position-dependent temporal pulse broadening that enables axially confined multiphoton absorption, without the need for tight spatial focusing. Many techniques have benefitted from temporal focusing, including scanless imaging, super-resolution imaging, photolithography, uncaging of caged neurotransmitters and control of neuronal activity via optogenetics.


Assuntos
Imageamento Tridimensional/métodos , Iluminação/métodos , Microscopia de Fluorescência por Excitação Multifotônica/métodos , Fótons , Animais , Desenho de Equipamento , Aumento da Imagem/instrumentação , Imageamento Tridimensional/instrumentação , Iluminação/instrumentação , Microscopia de Fluorescência por Excitação Multifotônica/instrumentação
5.
PLoS One ; 15(2): e0228437, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32027670

RESUMO

Although watching TV often involves multiple viewing distances and viewers, less attention has been paid to the effects of display curvature radius, viewing distance, and lateral viewing position on TV watching experience. This study examined the effects of four display curvature radii (2300R, 4000R, 6000R, and flat), two viewing distances (2.3 m and 4 m), and five lateral viewing positions (P1-P5; 0, 35, 70, 105, and 140 cm off-center) on seven TV watching experience elements (spatial presence, engagement, ecological validity, negative effects, visual comfort, image quality, and user satisfaction). Fifty-six individuals (14 per display curvature radius) were seated in pairs to watch videos, each time at a different viewing position (2 viewing distances × 5 paired lateral viewing positions). The spatial presence and engagement increased when display curvature radius approached a viewing distance and lateral viewing position approached P1, with 4000R-4m-P1 (display curvature radius-viewing distance-lateral viewing position) providing the best results. Lateral viewing position alone significantly affected five TV watching experience elements; the spatial presence and engagement decreased at P3-P5, and ecological validity, image quality, and user satisfaction decreased at P4-P5. However, display curvature radius alone did not appreciably affect TV watching experience, and viewing distance alone significantly affected visual comfort only, with a 4-m viewing distance increasing visual comfort. This study demonstrated that effective display curvature radii for watching TV are viewing distance-dependent, and less off-center lateral viewing positions (P1-P2) are recommended for TV watching experience. Finally, among the TV watching experience elements, engagement explained user satisfaction to the greatest degree.


Assuntos
Desenho de Equipamento , Aumento da Imagem/instrumentação , Televisão , Visão Ocular/fisiologia , Acomodação Ocular/fisiologia , Adolescente , Adulto , Comportamento do Consumidor , Apresentação de Dados , Ergonomia/instrumentação , Feminino , Humanos , Masculino , Percepção Espacial/fisiologia , Acuidade Visual , Percepção Visual/fisiologia , Adulto Jovem
6.
Dis Colon Rectum ; 63(2): 143-151, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31842158

RESUMO

BACKGROUND: High-resolution MRI is regarded as the best method to evaluate whether there is an involved circumferential resection margin in rectal cancer. OBJECTIVE: We explored the application of the faster region-based convolutional neural network to identify positive circumferential resection margins in high-resolution MRI images. DESIGN: This was a retrospective study. SETTINGS: The study conducted at a single surgical unit of a public university hospital. PATIENTS: We studied 240 patients with rectal cancer in the Affiliated Hospital of Qingdao University from July 2016 to August 2018, who were determined to have a positive circumferential resection margin and who had received a high-resolution MRI. All posttreatment cases were excluded from this study. MAIN OUTCOME MEASURES: The faster region-based convolutional neural network was trained by 12,258 transverse relaxation-weighted (T2-weighted imaging) images of pelvic high-resolution MRI to build an artificial intelligence platform and complete clinical tests. In this network, the proportion of positive and negative circumferential resection margin images was 1:2. In accordance with the test results of the validation group, the metrics of the receiver operating characteristic curves and the area under the curve were applied to compare the diagnostic results of the artificial intelligence platform with those of senior radiology experts. RESULTS: In this artificial intelligence platform, the accuracy, sensitivity, and specificity of the circumferential resection margin status as determined were 0.932, 0.838, and 0.956. The area under the receiver operating characteristic curves was 0.953. The time required to automatically recognize an image was 0.2 seconds. LIMITATIONS: This is a single-center retrospective study with limited data volume and a highly selected patient cohort. CONCLUSIONS: In high-resolution MRI images of rectal cancer before treatment, the application of faster region-based convolutional neural network to segment the positive circumferential resection margin has high accuracy and feasibility. See Video Abstract at http://links.lww.com/DCR/B88. EVALUACIÓN DEL MARGEN DE RESECCIÓN CIRCUNFERENCIAL DEL CÁNCER RECTAL MEDIANTE EL USO DE UNA RED NEURONAL CONVOLUCIONAL MÁS RÁPIDA BASADA EN UNA REGIÓN EN IMÁGENES DE RESONANCIA MAGNÉTICA DE ALTA RESOLUCIÓN: La resonancia magnética de alta resolución se considera el mejor método para evaluar si existe un margen de resección circunferencial involucrado en el cáncer de recto.Se exploró la aplicación de la red neuronal convolucional más rápida basada en una región para identificar márgenes de resección circunferencial positivos en imágenes de resonancia magnética de alta resolución.Este fue un estudio retrospectivo realizado en una única unidad quirúrgica de un hospital universitario público.Estudiamos 240 pacientes con cáncer rectal en el Hospital Afiliado de la Universidad de Qingdao desde el 2 de julio de 2006 hasta el 2 de agosto de 2008, a los que se determinó que tenían un margen de resección circunferencial positivo y que habían recibido una resonancia magnética de alta resolución. Todos los casos posteriores al tratamiento fueron excluidos de este estudio.La red neuronal convolucional más rápida basada en una región recibió capacitación de 12,258 imágenes de RM pélvica de alta resolución con relajación transversal para construir una plataforma de inteligencia artificial y completar pruebas clínicas. En esta red, la proporción de imágenes con margen de resección circunferencial positivo y negativo fue 1: 2. De acuerdo con los resultados de las pruebas del grupo de validación, se aplicaron las métricas de las curvas de las características operativas del receptor y del área bajo la curva para comparar los resultados de diagnóstico de la plataforma de inteligencia artificial con los de expertos de radiología de alto nivel.En esta plataforma de inteligencia artificial, la precisión, sensibilidad y especificidad del estado del margen de resección circunferencial según lo determinado fueron 0.932, 0.838 y 0.956, respectivamente. El área bajo las curvas características de operación del receptor fue de 0.953. El tiempo requerido para reconocer automáticamente una imagen fue de 0.2 segundos.Este es un estudio retrospectivo de centro único con volumen de datos limitado y una cohorte de pacientes altamente seleccionada.En las imágenes de resonancia magnética de alta resolución de cáncer rectal antes del tratamiento, la aplicación de la red neuronal convolucional más rápida basada en una región, para segmentar el margen de resección circunferencial positivo tiene una alta precisión y factibilidad. Consulte Video Resumen en http://links.lww.com/DCR/B88.


Assuntos
Imagem por Ressonância Magnética/métodos , Redes Neurais de Computação , Neoplasias Retais/diagnóstico por imagem , Neoplasias Retais/cirurgia , Idoso , Inteligência Artificial , Estudos de Viabilidade , Feminino , Humanos , Aumento da Imagem/instrumentação , Incidência , Masculino , Margens de Excisão , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Neoplasias Retais/epidemiologia , Neoplasias Retais/patologia , Estudos Retrospectivos
7.
Medicine (Baltimore) ; 98(44): e17738, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31689821

RESUMO

This study aimed to evaluate a novel real-time rotational optical coherence tomography (OCT) imaging system (OCTIS) with a fiber-optic probe to look at endometrium and to correlate the OCTIS images with standard histology. OCT could obtain real-time images resembling histological examination. With recent development of customized probes, it allows OCT to be used in the field of gynecology.This is a pilot, prospective, ex-vivo and observational study. Women underwent hysterectomy for various gynecological conditions were recruited and OCTIS images were obtained from endometrium of 15 fresh uterus specimens immediately after hysterectomy. The excised uterus was cut open and OCTIS imaging was obtained. The scanned region of endometrium was excised for histological examination and OCTIS images were precisely compared to corresponding histological images and ultrasound images. Blinded qualitative analysis on OCTIS images was performed by 2 assessors to determine inter-rating reliability on the histopathological diagnosis.Epithelium, glands, cysts, and stroma of endometrium were clearly seen by the OCTIS. Different phases of menstrual cycle of normal endometrium could be differentiated and pathological condition such as hyperplastic and dysplasic endometrium, which corresponded well with histological findings, could be identified. The inter-rater reliability between assessors on overall OCTIS endometrium and neoplastic OCTIS endometrium was moderate (Kendall τb of 0.58) and substantial (Kendall τb of 0.76), respectively.OCTIS can provide real-time, high-resolution and rotational imaging modality to view endometrial structure with high consistency with histological examination and satisfactory agreement between observers. It has a great potential to be developed in the clinical use of endometrial assessment for gynecological applications.


Assuntos
Hiperplasia Endometrial/diagnóstico por imagem , Endométrio/diagnóstico por imagem , Aumento da Imagem/métodos , Tomografia de Coerência Óptica/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Endométrio/patologia , Feminino , Humanos , Histerectomia , Aumento da Imagem/instrumentação , Pessoa de Meia-Idade , Variações Dependentes do Observador , Projetos Piloto , Período Pós-Operatório , Estudos Prospectivos , Reprodutibilidade dos Testes , Método Simples-Cego , Tomografia de Coerência Óptica/instrumentação
8.
Radiology ; 293(2): 384-393, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31573398

RESUMO

Background Commercial low-field-strength MRI systems are generally not equipped with state-of-the-art MRI hardware, and are not suitable for demanding imaging techniques. An MRI system was developed that combines low field strength (0.55 T) with high-performance imaging technology. Purpose To evaluate applications of a high-performance low-field-strength MRI system, specifically MRI-guided cardiovascular catheterizations with metallic devices, diagnostic imaging in high-susceptibility regions, and efficient image acquisition strategies. Materials and Methods A commercial 1.5-T MRI system was modified to operate at 0.55 T while maintaining high-performance hardware, shielded gradients (45 mT/m; 200 T/m/sec), and advanced imaging methods. MRI was performed between January 2018 and April 2019. T1, T2, and T2* were measured at 0.55 T; relaxivity of exogenous contrast agents was measured; and clinical applications advantageous at low field were evaluated. Results There were 83 0.55-T MRI examinations performed in study participants (45 women; mean age, 34 years ± 13). On average, T1 was 32% shorter, T2 was 26% longer, and T2* was 40% longer at 0.55 T compared with 1.5 T. Nine metallic interventional devices were found to be intrinsically safe at 0.55 T (<1°C heating) and MRI-guided right heart catheterization was performed in seven study participants with commercial metallic guidewires. Compared with 1.5 T, reduced image distortion was shown in lungs, upper airway, cranial sinuses, and intestines because of improved field homogeneity. Oxygen inhalation generated lung signal enhancement of 19% ± 11 (standard deviation) at 0.55 T compared with 7.6% ± 6.3 at 1.5 T (P = .02; five participants) because of the increased T1 relaxivity of oxygen (4.7e-4 mmHg-1sec-1). Efficient spiral image acquisitions were amenable to low field strength and generated increased signal-to-noise ratio compared with Cartesian acquisitions (P < .02). Representative imaging of the brain, spine, abdomen, and heart generated good image quality with this system. Conclusion This initial study suggests that high-performance low-field-strength MRI offers advantages for MRI-guided catheterizations with metal devices, MRI in high-susceptibility regions, and efficient imaging. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Grist in this issue.


Assuntos
Cateterismo , Aumento da Imagem/instrumentação , Imagem por Ressonância Magnética/instrumentação , Adulto , Artefatos , Cateterismo Cardíaco/instrumentação , Meios de Contraste , Desenho de Equipamento , Feminino , Humanos , Imagem por Ressonância Magnética Intervencionista/instrumentação , Metais , Razão Sinal-Ruído
10.
J Biomed Opt ; 24(8): 1-7, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31429217

RESUMO

Photoacoustic microscopy (PAM) is a fast-growing biomedical imaging technique that provides high-resolution in vivo imaging beyond the optical diffusion limit. Depending on the scalable lateral resolution and achievable penetration depth, PAM can be classified into optical resolution PAM (OR-PAM) and acoustic resolution PAM (AR-PAM). The use of a microelectromechanical systems (MEMS) scanner has improved OR-PAM imaging speed significantly and is highly beneficial in the development of miniaturized handheld devices. The shallow penetration depth of OR-PAM limits the use of such devices for a wide range of clinical applications. We report the use of a high-speed MEMS scanner for both OR-PAM and AR-PAM. A high-speed, wide-area scanning integrated OR-AR-PAM system combining MEMS scanner and raster mechanical movement was developed. A lateral resolution of 5 µm and penetration depth ∼0.9-mm in vivo was achieved using OR-PAM at 586 nm, whereas a lateral resolution of 84 µm and penetration depth of ∼2-mm in vivo was achieved using AR-PAM at 532 nm.


Assuntos
Microscopia Acústica/métodos , Técnicas Fotoacústicas/métodos , Abdome/diagnóstico por imagem , Acústica , Animais , Orelha/diagnóstico por imagem , Desenho de Equipamento , Aumento da Imagem/instrumentação , Processamento de Imagem Assistida por Computador , Lasers , Camundongos , Sistemas Microeletromecânicos , Pele/diagnóstico por imagem , Análise Espectral
11.
PLoS One ; 14(7): e0220190, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31344078

RESUMO

BACKGROUND: Quantifying reproducibility of native T1 and T2 mapping over a long period (> 1 year) is necessary to assess whether changes in T1 and T2 over repeated sessions in a longitudinal study are associated with variability due to underlying tissue composition or technical confounders. OBJECTIVES: To carry out a single-center phantom study to 1) investigate measurement reproducibility of slice-interleaved T1 (STONE) and T2 mapping over 20 months, 2) quantify sources of variability, and 3) compare reproducibility and measurements against reference spin-echo measurements. METHODS: MR imaging was performed on a 1.5 Tesla Philips Achieva scanner every 2-3 weeks over 20 months using the T1MES phantom. In each session, slice-interleaved T1 and T2 mapping was repeated 3 times for 5 slices, and maps were reconstructed using both 2-parameter and 3-parameter fit models. Reproducibility between sessions, and repeatability between repetitions and slices were evaluated using coefficients of variation (CV). Different sources of variability were quantified using variance decomposition analysis. The slice-interleaved measurement was compared to the spin-echo reference and MOLLI. RESULTS: Slice-interleaved T1 had excellent reproducibility and repeatability with a CV < 2%. The main sources of T1 variability were temperature in 2-parameter maps, and slice in 3-parameter maps. Superior between-session reproducibility to the spin-echo T1 was shown in 2-parameter maps, and similar reproducibility in 3-parameter maps. Superior reproducibility to MOLLI T1 was also shown. Similar measurements to the spin-echo T1 were observed with linear regression slopes of 0.94-0.99, but slight underestimation. Slice-interleaved T2 showed good reproducibility and repeatability with a CV < 7%. The main source of T2 variability was slice location/orientation. Between-session reproducibility was lower than the spin-echo T2 reference and showed good measurement agreement with linear regression slopes of 0.78-1.06. CONCLUSIONS: Slice-interleaved T1 and T2 mapping sequences yield excellent long-term reproducibility over 20 months.


Assuntos
Técnicas de Diagnóstico Cardiovascular , Coração/diagnóstico por imagem , Interpretação de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética , Imagens de Fantasmas , Técnicas de Diagnóstico Cardiovascular/instrumentação , Eletrocardiografia/instrumentação , Eletrocardiografia/métodos , Frequência Cardíaca/fisiologia , Humanos , Aumento da Imagem/instrumentação , Aumento da Imagem/métodos , Estudos Longitudinais , Imagem por Ressonância Magnética/instrumentação , Imagem por Ressonância Magnética/métodos , Miocárdio/patologia , Reprodutibilidade dos Testes
13.
Magn Reson Med ; 82(5): 1822-1831, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31199014

RESUMO

PURPOSE: One of the main concerns in fetal MRI is the radiofrequency power that is absorbed both by the mother and the fetus. Passive shimming using high permittivity materials in the form of "dielectric pads" has previously been shown to increase the B 1 + efficiency and homogeneity in different applications, while reducing the specific absorption rate (SAR). In this work, we study the effect of optimized dielectric pads for 3 pregnant models. METHODS: Pregnant models in the 3rd, 7th, and 9th months of gestation were used for simulations in a birdcage coil at 3T. Dielectric pads were optimized regions of interest (ROI) using previously developed methods for B 1 + efficiency and homogeneity and were designed for 2 ROIs: the entire fetus and the brain of the fetus. The SAR was evaluated in terms of the whole-body SAR, average SAR in the fetus and amniotic fluid, and maximum 10 g-averaged SAR in the mother, fetus, and amniotic fluid. RESULTS: The optimized dielectric pads increased the transmit efficiency up to 55% and increased the B 1 + homogeneity in almost every tested configuration. The B 1 + -normalized whole-body SAR was reduced by more than 31% for all body models. The B 1 + -normalized local SAR was reduced in most scenarios by up to 62%. CONCLUSION: Simulations have shown that optimized high permittivity pads can reduce SAR in pregnant subjects at the 3rd, 7th, and 9th month of gestation, while improving the transmit field homogeneity in the fetus. However, significantly more work is required to demonstrate that fetal imaging is safe under standard operating conditions.


Assuntos
Encéfalo/diagnóstico por imagem , Feto/diagnóstico por imagem , Imagem por Ressonância Magnética/métodos , Simulação por Computador , Desenho de Equipamento , Feminino , Humanos , Aumento da Imagem/instrumentação , Imagem por Ressonância Magnética/instrumentação , Modelos Anatômicos , Gravidez
14.
Opt Lett ; 44(8): 1976-1979, 2019 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-30985789

RESUMO

We report a compact, cost-effective, and field-portable lensless imaging platform for quantitative microscopy. In this platform, the object is placed on top of an image sensor chip without using a lens. We use a low-cost galvo scanner to rapidly scan an unknown laser speckle pattern on the object. To address the positioning repeatability and accuracy issues, we directly recover the positional shifts of the speckle pattern based on the phase correlation of the captured images. To bypass the resolution limit set by the imager pixel size, we employ a sub-sampled ptychographic phase retrieval process to recover the complex object. We validate our approach using a resolution target, phase target, and biological sample. Our results show that accurate, high-quality complex images can be obtained from a lensless dataset with as few as ∼10 images. We also demonstrate the reported approach to achieve a 6.4-mm by 4.6-mm field of view and a half-pitch resolution of 1 µm. The reported approach may provide a quantitative lensless imaging strategy for addressing point-of-care-, global-health-, and telemedicine-related challenges.


Assuntos
Aumento da Imagem/instrumentação , Iluminação , Microscopia/métodos , Desenho de Equipamento , Dispositivos Ópticos
15.
J Microsc ; 275(1): 24-35, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31026068

RESUMO

The quality and information content of biological images can be significantly enhanced by postacquisition processing using deconvolution and denoising. However, when imaging complex biological samples, such as neurons, stained with fluorescence labels, the signal level of different structures can differ by several orders of magnitude. This poses a challenge as current image reconstruction algorithms are focused on recovering low signals and generally have sample-dependent performance, requiring tedious manual tuning. This is one of the main hurdles for their wide adoption by nonspecialists. In this work, we modify the general constrained reconstruction method (in our case utilizing a total variation constraint) so that both bright and dim structures can drive the deconvolution with equal force. In this way, we can simultaneously obtain high-quality reconstruction across a wide range of signals within a single image or image sequence. The algorithm is tested on both simulated and experimental data. When compared with current state-of-art algorithms, our algorithm outperforms others in terms of maintaining the resolution in the high-signal areas and reducing artefacts in the low-signal areas. The algorithm was also tested on image sequences where one set of parameters are used to reconstruct all images, with blind evaluation by a group of biologists demonstrating a marked preference for the images produced by our method. This means that our method is suitable for batch processing of image sequences obtained from either spatial or temporal scanning. LAY DESCRIPTION: Fluorescence microscopy images of complex biological samples contain a wide range of signal levels. This signal variation leads current reconstruction algorithms, which aim to enhance the quality of the raw images, to have sample-dependent performance. In this work, we design a new optimization that allows the reconstruction to "pay equal eqattention to" both bright and dim structures. In this way, we can simultaneously recover both bright and dim structures within a single image or image sequence, as validated when the algorithm was quantitatively tested on both simulated and experimental data. When our method was evaluated alongside current state of art algorithms by a group of biologists, our algorithm was considered qualitatively superior.


Assuntos
Algoritmos , Artefatos , Processamento de Imagem Assistida por Computador/métodos , Microscopia de Fluorescência/métodos , Televisão , Aumento da Imagem/instrumentação , Aumento da Imagem/métodos , Microtúbulos , Neurônios , Razão Sinal-Ruído
16.
Radiother Oncol ; 133: 156-162, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30935572

RESUMO

PURPOSE: Systems for magnetic resonance (MR-) guided radiotherapy enable daily MR imaging of cancer patients during treatment, which is of interest for treatment response monitoring and biomarker discovery using quantitative MRI (qMRI). Here, the performance of a 1.5 T MR-linac regarding qMRI was assessed on phantoms. Additionally, we show the feasibility of qMRI in a prostate cancer patient on this system for the first time. MATERIALS AND METHODS: Four 1.5 T MR-linac systems from four institutes were included in this study. T1 and T2 relaxation times, and apparent diffusion coefficient (ADC) maps, as well as dynamic contrast enhanced (DCE) images were acquired. Bland-Altman statistics were used, and accuracy, repeatability, and reproducibility were determined. RESULTS: Median accuracy for T1 ranged over the four systems from 2.7 to 14.3%, for T2 from 10.4 to 14.1%, and for ADC from 1.9 to 2.7%. For DCE images, the accuracy ranged from 12.8 to 35.8% for a gadolinium concentration of 0.5 mM and deteriorated for higher concentrations. Median short-term repeatability for T1 ranged from 0.6 to 5.1%, for T2 from 0.4 to 1.2%, and for ADC from 1.3 to 2.2%. DCE acquisitions showed a coefficient of variation of 0.1-0.6% in the signal intensity. Long-term repeatability was 1.8% for T1, 1.4% for T2, 1.7% for ADC, and 17.9% for DCE. Reproducibility was 11.2% for T1, 2.9% for T2, 2.2% for ADC, and 18.4% for DCE. CONCLUSION: These results indicate that qMRI on the Unity MR-linac is feasible, accurate, and repeatable which is promising for treatment response monitoring and treatment plan adaptation based on daily qMRI.


Assuntos
Imagem de Difusão por Ressonância Magnética/instrumentação , Aceleradores de Partículas/instrumentação , Neoplasias da Próstata/diagnóstico por imagem , Imagem de Difusão por Ressonância Magnética/métodos , Estudos de Viabilidade , Humanos , Aumento da Imagem/instrumentação , Aumento da Imagem/métodos , Masculino , Pessoa de Meia-Idade , Imagens de Fantasmas , Neoplasias da Próstata/patologia , Reprodutibilidade dos Testes
17.
Clinics (Sao Paulo) ; 74: e573, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30994703

RESUMO

OBJECTIVES: The pedunculopontine nucleus (PPN) is considered a promising new target for neurostimulation in Parkinson's disease (PD) patients with postural instability and gait disturbance that is refractory to other treatment modalities. However, the PPN is typically difficult to visualize with magnetic resonance imaging (MRI) at clinical field strengths, which greatly limits the PPN as a viable surgical target for deep brain stimulation (DBS). Thus, the aim of this study is to directly visualize the PPN based on 7.0T ultrahigh-field MRI. METHODS: Five PD patients were enrolled and scanned using the MP2RAGE sequence on a 7.0T ultrahigh-field MRI scanner. Then, the MP2RAGE sequences were imported into a commercially available navigation system. The coordinates of the directly localized PPN poles were recorded in the navigation system relative to the anterior commissure-posterior commissure plane. RESULTS: Our results indicated that the PPN presented intermediate signal intensity in the 7.0T ultrahigh-field MR images in comparison with the surrounding structure, such as the hypo-intensity of the periaqueductal gray and the hyperintensity of the neighboring white matter tracts, in PD patients. The mean coordinates for the rostral and caudal poles of PPN were 6.50 mm and 7.20 mm lateral, 1.58 mm and 2.21 mm posterior, and 8.89 mm and 13.83 mm relative to the posterior commissure. CONCLUSION: Our findings provide, for the first time, direct visualization of the PPN using the MP2RAGE sequence on a 7.0T ultrahigh-field MRI, which may improve the accuracy of stereotactic targeting of the PPN and improve the outcomes in patients undergoing DBS.


Assuntos
Aumento da Imagem/instrumentação , Imagem por Ressonância Magnética/métodos , Doença de Parkinson/diagnóstico por imagem , Núcleo Tegmental Pedunculopontino/diagnóstico por imagem , Adulto , Confiabilidade dos Dados , Feminino , Humanos , Aumento da Imagem/métodos , Processamento de Imagem Assistida por Computador/instrumentação , Processamento de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética/instrumentação , Masculino , Pessoa de Meia-Idade , Técnicas Estereotáxicas/instrumentação
18.
ANZ J Surg ; 89(5): E174-E178, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30896062

RESUMO

BACKGROUND: Adenoma detection rate (ADR) has shown to be an independent predictor, to reduce the rate of interval colorectal cancer. Endocuff Vision is a relatively new device that has shown promise to improve the ADR. The primary objective was to conduct a randomized controlled trial to compare Endocuff Vision-assisted colonoscopy (EVAC) with standard colonoscopy (SC). The primary outcome of the study is ADR and the secondary outcomes are caecal intubation rate, terminal ileum intubation rate, scope withdrawal time, quality of bowel preparation and adverse events. METHODS: A randomized controlled trial was performed to compare EVAC versus SC. All patients who presented to the endoscopy suite at the Queen Elizabeth Hospital were assessed for eligibility. Patients were recruited from 15 June 2016 to 20 January 2017. A total of 360 patients were included; 40 were excluded. The patients were randomized using block randomization; 138 patients were recruited to SC and 182 to EVAC. RESULTS: A total of 231 polyps were retrieved during the study period. Polyp detection rate (PDR) was high in both groups: 53% in the EVAC group versus 41.1% in SC. This was statistically significant with a P-value of 0.035. ADR was similarly high in both groups: 36.81% in EVAC group versus 28.99% in SC group. ADR did not reach statistical significance. CONCLUSIONS: EVAC does improve the PDR. Though the ADR did not reach statistical significance, there is a trend towards improved adenoma detection and there is statistical significance in the overall PDR.


Assuntos
Neoplasias do Colo/diagnóstico , Colonoscópios/tendências , Colonoscopia/instrumentação , Neoplasias Colorretais/diagnóstico , Detecção Precoce de Câncer/instrumentação , Desenho de Equipamento , Centros Médicos Acadêmicos , Adenoma/diagnóstico , Idoso , Austrália , Pólipos do Colo/diagnóstico , Colonoscópios/normas , Intervalos de Confiança , Detecção Precoce de Câncer/métodos , Feminino , Humanos , Aumento da Imagem/instrumentação , Masculino , Pessoa de Meia-Idade , Razão de Chances , Segurança do Paciente , Melhoria de Qualidade
19.
J Am Coll Surg ; 228(5): 730-743, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30769112

RESUMO

BACKGROUND: Misidentifying parathyroid glands (PGs) during thyroidectomies or parathyroidectomies could significantly increase postoperative morbidity. Imaging systems based on near infrared autofluorescence (NIRAF) detection can localize PGs with high accuracy. These devices, however, depict NIRAF images on remote display monitors, where images lack spatial context and comparability with actual surgical field of view. In this study, we designed an overlay tissue imaging system (OTIS) that detects tissue NIRAF and back-projects the collected signal as a visible image directly onto the surgical field of view instead of a display monitor, and tested its ability for enhancing parathyroid visualization. STUDY DESIGN: The OTIS was first calibrated with a fluorescent ink grid and initially tested with parathyroid, thyroid, and lymph node tissues ex vivo. For in vivo measurements, the surgeon's opinion on tissue of interest was first ascertained. After the surgeon looked away, the OTIS back-projected visible green light directly onto the tissue of interest, only if the device detected relatively high NIRAF as observed in PGs. System accuracy was determined by correlating NIRAF projection with surgeon's visual confirmation for in situ PGs or histopathology report for excised PGs. RESULTS: The OTIS yielded 100% accuracy when tested ex vivo with parathyroid, thyroid, and lymph node specimens. Subsequently, the device was evaluated in 30 patients who underwent thyroidectomy and/or parathyroidectomy. Ninety-seven percent of exposed tissue of interest was visualized correctly as PGs by the OTIS, without requiring display monitors or contrast agents. CONCLUSIONS: Although OTIS holds novel potential for enhancing label-free parathyroid visualization directly within the surgical field of view, additional device optimization is required for eventual clinical use.


Assuntos
Aumento da Imagem/métodos , Imagem Óptica/métodos , Glândulas Paratireoides/diagnóstico por imagem , Espectroscopia de Luz Próxima ao Infravermelho/métodos , Adulto , Idoso , Desenho de Equipamento , Feminino , Fluorescência , Humanos , Aumento da Imagem/instrumentação , Masculino , Pessoa de Meia-Idade , Imagem Óptica/instrumentação , Doenças das Paratireoides/diagnóstico por imagem , Doenças das Paratireoides/cirurgia , Glândulas Paratireoides/cirurgia , Paratireoidectomia , Imagens de Fantasmas , Espectroscopia de Luz Próxima ao Infravermelho/instrumentação , Cirurgia Assistida por Computador , Doenças da Glândula Tireoide/diagnóstico por imagem , Doenças da Glândula Tireoide/cirurgia , Tireoidectomia
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