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1.
Sci Adv ; 8(19): eabm9132, 2022 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-35544570

RESUMO

Mobile microrobots hold remarkable potential to revolutionize health care by enabling unprecedented active medical interventions and theranostics, such as active cargo delivery and microsurgical manipulations in hard-to-reach body sites. High-resolution imaging and control of cell-sized microrobots in the in vivo vascular system remains an unsolved challenge toward their clinical use. To overcome this limitation, we propose noninvasive real-time detection and tracking of circulating microrobots using optoacoustic imaging. We devised cell-sized nickel-based spherical Janus magnetic microrobots whose near-infrared optoacoustic signature is enhanced via gold conjugation. The 5-, 10-, and 20-µm-diameter microrobots are detected volumetrically both in bloodless ex vivo tissues and under real-life conditions with a strongly light-absorbing blood background. We further demonstrate real-time three-dimensional tracking and magnetic manipulation of the microrobots circulating in murine cerebral vasculature, thus paving the way toward effective and safe operation of cell-sized microrobots in challenging and clinically relevant intravascular environments.


Assuntos
Robótica , Animais , Encéfalo/diagnóstico por imagem , Ouro , Fenômenos Magnéticos , Magnetismo , Camundongos
2.
ACS Appl Mater Interfaces ; 14(1): 172-178, 2022 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-34949083

RESUMO

Large-scale visualization of nanoparticle kinetics is essential for optimizing drug delivery and characterizing in vivo toxicity associated with engineered nanomaterials. Real-time tracking of nanoparticulate agents across multiple murine organs is hindered with the currently available whole-body preclinical imaging systems due to limitations in contrast, sensitivity, spatial, or temporal resolution. Herein, we demonstrate rapid volumetric tracking of gold nanoagent kinetics and biodistribution in mice at a suborgan level with single-sweep volumetric optoacoustic tomography (sSVOT). The imaging system accomplishes whole-body three-dimensional scans in less than 1.8 s, further attaining a high spatial resolution of 130 µm and sub-picomolar sensitivity. We visualized the clearance dynamics of purposely synthesized gold nanorods and nanorod clusters, featuring different sizes and surface chemistries as well as their corresponding accumulation within the liver and spleen. The newly discovered capacity to image rapid whole-body kinetics down to suborgan scales opens up new avenues for the development and characterization of diagnostic and therapeutic nanoagents.


Assuntos
Ouro/farmacocinética , Nanopartículas Metálicas/química , Nanotubos/química , Animais , Feminino , Ouro/química , Cinética , Camundongos Nus , Técnicas Fotoacústicas/métodos , Distribuição Tecidual , Tomografia/métodos
3.
ACS Appl Mater Interfaces ; 13(41): 48423-48432, 2021 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-34613688

RESUMO

Rapid volumetric in vivo visualization of circulating microparticles can facilitate new biomedical applications, such as blood flow characterization or targeted drug delivery. However, existing imaging modalities generally lack the sensitivity to detect the weak signals generated by individual micrometer-sized particles distributed across millimeter- to centimeter-scale depths in living mammalian tissues. Also, the temporal resolution is typically insufficient to track the particles in an entire three-dimensional region. Herein, we introduce a new type of monodisperse (4 µm) silica-core microparticle coated with a shell formed by a multilayered structure of carbon nanotubes (CNT) and gold nanoparticles (AuNP) to provide strong optoacoustic (OA) absorption-based contrast. We capitalize on the unique advantages of a state-of-the-art high-frame-rate OA tomography system to visualize and track the motion of these core-shell particles individually and volumetrically as they flow throughout the mouse brain vasculature. The feasibility of localizing individual solid particles smaller than red blood cells opens new opportunities for mapping the blood flow velocity, enhancing the resolution and visibility of OA images, and developing new biosensing assays.


Assuntos
Meios de Contraste/química , Nanopartículas Metálicas/química , Microplásticos/química , Nanotubos de Carbono/química , Animais , Encéfalo/diagnóstico por imagem , Meios de Contraste/efeitos da radiação , Feminino , Ouro/química , Ouro/efeitos da radiação , Raios Infravermelhos , Nanopartículas Metálicas/efeitos da radiação , Camundongos Nus , Microplásticos/efeitos da radiação , Nanotubos de Carbono/efeitos da radiação , Técnicas Fotoacústicas/métodos , Polietilenos/química , Polietilenos/efeitos da radiação , Compostos de Amônio Quaternário/química , Compostos de Amônio Quaternário/efeitos da radiação , Tomografia Computadorizada por Raios X/métodos
4.
J Biomed Opt ; 26(8)2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34405599

RESUMO

SIGNIFICANCE: The proposed binary tomography approach was able to recover the vasculature structures accurately, which could potentially enable the utilization of binary tomography algorithm in scenarios such as therapy monitoring and hemorrhage detection in different organs. AIM: Photoacoustic tomography (PAT) involves reconstruction of vascular networks having direct implications in cancer research, cardiovascular studies, and neuroimaging. Various methods have been proposed for recovering vascular networks in photoacoustic imaging; however, most methods are two-step (image reconstruction and image segmentation) in nature. We propose a binary PAT approach wherein direct reconstruction of vascular network from the acquired photoacoustic sinogram data is plausible. APPROACH: Binary tomography approach relies on solving a dual-optimization problem to reconstruct images with every pixel resulting in a binary outcome (i.e., either background or the absorber). Further, the binary tomography approach was compared against backprojection, Tikhonov regularization, and sparse recovery-based schemes. RESULTS: Numerical simulations, physical phantom experiment, and in-vivo rat brain vasculature data were used to compare the performance of different algorithms. The results indicate that the binary tomography approach improved the vasculature recovery by 10% using in-silico data with respect to the Dice similarity coefficient against the other reconstruction methods. CONCLUSION: The proposed algorithm demonstrates superior vasculature recovery with limited data both visually and based on quantitative image metrics.


Assuntos
Processamento de Imagem Assistida por Computador , Técnicas Fotoacústicas , Algoritmos , Animais , Imagens de Fantasmas , Ratos , Tomografia
5.
J Biophotonics ; 14(1): e202000191, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33025761

RESUMO

Photoacoustic/Optoacoustic tomography aims to reconstruct maps of the initial pressure rise induced by the absorption of light pulses in tissue. This reconstruction is an ill-conditioned and under-determined problem, when the data acquisition protocol involves limited detection positions. The aim of the work is to develop an inversion method which integrates denoising procedure within the iterative model-based reconstruction to improve quantitative performance of optoacoustic imaging. Among the model-based schemes, total-variation (TV) constrained reconstruction scheme is a popular approach. In this work, a two-step approach was proposed for improving the TV constrained optoacoustic inversion by adding a non-local means based filtering step within each TV iteration. Compared to TV-based reconstruction, inclusion of this non-local means step resulted in signal-to-noise ratio improvement of 2.5 dB in the reconstructed optoacoustic images.


Assuntos
Processamento de Imagem Assistida por Computador , Técnicas Fotoacústicas , Algoritmos , Imagens de Fantasmas , Razão Sinal-Ruído , Tomografia Computadorizada por Raios X
6.
Artigo em Inglês | MEDLINE | ID: mdl-32142429

RESUMO

Photoacoustic tomography (PAT) is a noninvasive imaging modality combining the benefits of optical contrast at ultrasonic resolution. Analytical reconstruction algorithms for photoacoustic (PA) signals require a large number of data points for accurate image reconstruction. However, in practical scenarios, data are collected using the limited number of transducers along with data being often corrupted with noise resulting in only qualitative images. Furthermore, the collected boundary data are band-limited due to limited bandwidth (BW) of the transducer, making the PA imaging with limited data being qualitative. In this work, a deep neural network-based model with loss function being scaled root-mean-squared error was proposed for super-resolution, denoising, as well as BW enhancement of the PA signals collected at the boundary of the domain. The proposed network has been compared with traditional as well as other popular deep-learning methods in numerical as well as experimental cases and is shown to improve the collected boundary data, in turn, providing superior quality reconstructed PA image. The improvement obtained in the Pearson correlation, structural similarity index metric, and root-mean-square error was as high as 35.62%, 33.81%, and 41.07%, respectively, for phantom cases and signal-to-noise ratio improvement in the reconstructed PA images was as high as 11.65 dB for in vivo cases compared with reconstructed image obtained using original limited BW data. Code is available at https://sites.google.com/site/sercmig/home/dnnpat.


Assuntos
Aprendizado Profundo , Processamento de Imagem Assistida por Computador/métodos , Técnicas Fotoacústicas/métodos , Tomografia/métodos , Imagens de Fantasmas , Transdutores
7.
J Vis Exp ; (147)2019 05 30.
Artigo em Inglês | MEDLINE | ID: mdl-31205314

RESUMO

Photoacoustic (PA) tomography (PAT) imaging is an emerging biomedical imaging modality useful in various preclinical and clinical applications. Custom-made circular ring array-based transducers and conventional bulky Nd:YAG/OPO lasers inhibit translation of the PAT system to clinics. Ultra-compact pulsed laser diodes (PLDs) are currently being used as an alternative source of near-infrared excitation for PA imaging. High-speed dynamic in vivo imaging has been demonstrated using a compact PLD-based desktop PAT system (PLD-PAT). A visualized experimental protocol using the desktop PLD-PAT system is provided in this work for dynamic in vivo brain imaging. The protocol describes the desktop PLD-PAT system configuration, preparation of animal for brain vascular imaging, and procedure for dynamic visualization of indocyanine green (ICG) dye uptake and clearance process in rat cortical vasculature.


Assuntos
Encéfalo/patologia , Lasers Semicondutores/uso terapêutico , Técnicas Fotoacústicas/métodos , Animais , Ratos
8.
Biomed Opt Express ; 10(5): 2227-2243, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-31149371

RESUMO

The methods available for solving the inverse problem of photoacoustic tomography promote only one feature-either being smooth or sharp-in the resultant image. The fusion of photoacoustic images reconstructed from distinct methods improves the individually reconstructed images, with the guided filter based approach being state-of-the-art, which requires that implicit regularization parameters are chosen. In this work, a deep fusion method based on convolutional neural networks has been proposed as an alternative to the guided filter based approach. It has the combined benefit of using less data for training without the need for the careful choice of any parameters and is a fully data-driven approach. The proposed deep fusion approach outperformed the contemporary fusion method, which was proved using experimental, numerical phantoms and in-vivo studies. The improvement obtained in the reconstructed images was as high as 95.49% in root mean square error and 7.77 dB in signal to noise ratio (SNR) in comparison to the guided filter approach. Also, it was demonstrated that the proposed deep fuse approach, trained on only blood vessel type images at measurement data SNR being 40 dB, was able to provide a generalization that can work across various noise levels in the measurement data, experimental set-ups as well as imaging objects.

9.
Opt Lett ; 44(1): 81-84, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30645563

RESUMO

Bulky, expensive Nd:YAG lasers are used in conventional photoacoustic tomography (PAT) systems, making them difficult to translate into clinics. Moreover, real-time imaging is not feasible when a single-element ultrasound transducer is used with these low-pulse-repetition-rate lasers (10-100 Hz). Low-cost pulsed laser diodes (PLDs) can be used instead for photoacoustic imaging due to their high-pulse-repetition rates and compact size. Together with acoustic-reflector-based multiple single-element ultrasound transducers, a portable desktop PAT system was developed. This second-generation PLD-based PAT achieved 0.5 s cross-sectional imaging time with high spatial resolution of ∼165 µm and an imaging depth of 3 cm. The performance of this system was characterized using phantom and in vivo studies. Dynamic in vivo imaging was also demonstrated by monitoring the fast uptake and clearance of indocyanine green in small animal (rat) brain vasculature.


Assuntos
Custos e Análise de Custo , Lasers , Técnicas Fotoacústicas/economia , Técnicas Fotoacústicas/instrumentação , Tomografia/economia , Tomografia/instrumentação , Animais , Encéfalo/metabolismo , Glândulas Mamárias Animais/diagnóstico por imagem , Ratos , Semicondutores , Fatores de Tempo
10.
IEEE Trans Med Imaging ; 38(8): 1935-1947, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-30582534

RESUMO

Photoacoustic tomography involves reconstructing the initial pressure rise distribution from the measured acoustic boundary data. The recovery of the initial pressure rise distribution tends to be an ill-posed problem in the presence of noise and when limited independent data is available, necessitating regularization. The standard regularization schemes include Tikhonov, l1 -norm, and total-variation. These regularization schemes weigh the singular values equally irrespective of the noise level present in the data. This paper introduces a fractional framework to weigh the singular values with respect to a fractional power. This fractional framework was implemented for Tikhonov, l1 -norm, and total-variation regularization schemes. Moreover, an automated method for choosing the fractional power was also proposed. It was shown theoretically and with numerical experiments that the fractional power is inversely related to the data noise level for fractional Tikhonov scheme. The fractional framework outperforms the standard regularization schemes, Tikhonov, l1 -norm, and total-variation by 54% in numerical simulations, experimental phantoms, and in vivo rat data in terms of observed contrast/signal-to-noise-ratio of the reconstructed images.


Assuntos
Técnicas Fotoacústicas/métodos , Tomografia/métodos , Algoritmos , Animais , Encéfalo/diagnóstico por imagem , Simulação por Computador , Processamento de Imagem Assistida por Computador/métodos , Imagens de Fantasmas , Ratos
11.
J Biomed Opt ; 23(10): 1-4, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30362308

RESUMO

Photoacoustic tomography tends to be an ill-conditioned problem with noisy limited data requiring imposition of regularization constraints, such as standard Tikhonov (ST) or total variation (TV), to reconstruct meaningful initial pressure rise distribution from the tomographic acoustic measurements acquired at the boundary of the tissue. However, these regularization schemes do not account for nonuniform sensitivity arising due to limited detector placement at the boundary of tissue as well as other system parameters. For the first time, two regularization schemes were developed within the Tikhonov framework to address these issues in photoacoustic imaging. The model resolution, based on spatially varying regularization, and fidelity-embedded regularization, based on orthogonality between the columns of system matrix, were introduced. These were systematically evaluated with the help of numerical and in-vivo mice data. It was shown that the performance of the proposed spatially varying regularization schemes were superior (with at least 2 dB or 1.58 times improvement in the signal-to-noise ratio) compared to ST-/TV-based regularization schemes.


Assuntos
Processamento de Imagem Assistida por Computador/métodos , Técnicas Fotoacústicas/métodos , Tomografia/métodos , Algoritmos , Animais , Encéfalo/diagnóstico por imagem , Modelos Lineares , Camundongos , Imagens de Fantasmas
12.
Med Phys ; 2018 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-29856489

RESUMO

PURPOSE: Development of simple and computationally efficient extrapolated Tikhonov filtering reconstruction methods for photoacoustic tomography. METHODS: The model-based reconstruction algorithms in photoacoustic tomography typically utilize Tikhonov regularization scheme for the reconstruction of initial pressure distribution from the measured boundary acoustic data. The automated choice of regularization parameter in these cases is computationally expensive. Moreover, the Tikhonov scheme promotes the smooth features in the reconstructed image due to the smooth regularizer, thus leading to loss of sharp features. The proposed extrapolation method estimates the solution at zero regularization assuming the solution being a function of regularization parameter and thus posing it as a zero value problem. Thus, the numerically computed zero regularization solution is expected to have better features compared to standard Tikhonov solution, with an added advantage of removing the necessity of automated choice of regularization. The reconstructed results using this method were shown in three variants (Lanczos, traditional, and exponential) of Tikhonov filtering and were compared with the standard error estimate technique. RESULTS: Four numerical (including realistic breast phantom) and two experimental phantom data were utilized to show the effectiveness of the proposed method. It was shown that the proposed method performance was superior than the standard error estimate technique, being at least four times faster in terms of computation, and provides an improvement as high as 2.6 times in terms of standard figures of merit. CONCLUSION: The developed extrapolated Tikhonov filtering methods overcome the difficulty of obtaining a suitable regularization parameter and shown to be reconstructing high-quality photoacoustic images with additional advantage of being computationally efficient, making it more appealing in real-time applications.

13.
J Biomed Opt ; 23(9): 1-22, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29943527

RESUMO

Several algorithms exist to solve the photoacoustic image reconstruction problem depending on the expected reconstructed image features. These reconstruction algorithms promote typically one feature, such as being smooth or sharp, in the output image. Combining these features using a guided filtering approach was attempted in this work, which requires an input and guiding image. This approach act as a postprocessing step to improve commonly used Tikhonov or total variational regularization method. The result obtained from linear backprojection was used as a guiding image to improve these results. Using both numerical and experimental phantom cases, it was shown that the proposed guided filtering approach was able to improve (as high as 11.23 dB) the signal-to-noise ratio of the reconstructed images with the added advantage being computationally efficient. This approach was compared with state-of-the-art basis pursuit deconvolution as well as standard denoising methods and shown to outperform them.


Assuntos
Processamento de Imagem Assistida por Computador/métodos , Técnicas Fotoacústicas/métodos , Tomografia/métodos , Algoritmos , Animais , Encéfalo/diagnóstico por imagem , Feminino , Imagens de Fantasmas , Ratos , Processamento de Sinais Assistido por Computador , Razão Sinal-Ruído
14.
J Opt Soc Am A Opt Image Sci Vis ; 35(5): 764-771, 2018 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-29726481

RESUMO

In a circular scanning photoacoustic computed tomography (PAT/PACT) system, a single-element ultrasound transducer (SUT) (rotates in full 360° around the sample) or a full-ring array transducer is used to acquire the photoacoustic (PA) data from the target object. SUT takes several minutes to acquire the PA data, whereas the full-ring array transducer takes only few seconds. Hence, for real-time imaging, full-ring circular array transducers are preferred. However, these are custom built, very expensive, and not available readily on the market, whereas SUTs are cheap and easily available. Thus, PACT systems can be made cost effective by using SUTs. To improve the data acquisition speed, multiple SUTs can be employed at the same time. This will reduce the acquisition time by N-fold if N numbers of SUTs are used, each rotating 360/N degrees. Experimentally, all SUTs cannot be placed exactly at the same distance from the scanning center. Hence, the acquired PA data from each transducer need to be reconstructed with their corresponding radii in a delay-and-sum reconstruction algorithm. This requires the exact location of each SUT from the scanning center. Here, we propose a calibration method to find out the distance from the scanning center at which each SUT acquires the PA data. Three numerical phantoms were used to show the efficacy of the proposed method, and later it was validated with experimental data (point source phantom).

15.
J Biomed Opt ; 23(7): 1-11, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29405050

RESUMO

As limited data photoacoustic tomographic image reconstruction problem is known to be ill-posed, the iterative reconstruction methods were proven to be effective in terms of providing good quality initial pressure distribution. Often, these iterative methods require a large number of iterations to converge to a solution, in turn making the image reconstruction procedure computationally inefficient. In this work, two variants of vector polynomial extrapolation techniques were deployed to accelerate two standard iterative photoacoustic image reconstruction algorithms, including regularized steepest descent and total variation regularization methods. It is shown using numerical and experimental phantom cases that these extrapolation methods that are proposed in this work can provide significant acceleration (as high as 4.7 times) along with added advantage of improving reconstructed image quality.


Assuntos
Processamento de Imagem Assistida por Computador/métodos , Técnicas Fotoacústicas/métodos , Algoritmos , Modelos Biológicos , Imagens de Fantasmas , Técnicas Fotoacústicas/instrumentação
16.
J Biomed Opt ; 22(11): 1-7, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29098811

RESUMO

Photoacoustic (PA) signals collected at the boundary of tissue are always band-limited. A deep neural network was proposed to enhance the bandwidth (BW) of the detected PA signal, thereby improving the quantitative accuracy of the reconstructed PA images. A least square-based deconvolution method that utilizes the Tikhonov regularization framework was used for comparison with the proposed network. The proposed method was evaluated using both numerical and experimental data. The results indicate that the proposed method was capable of enhancing the BW of the detected PA signal, which inturn improves the contrast recovery and quality of reconstructed PA images without adding any significant computational burden.


Assuntos
Redes Neurais de Computação , Técnicas Fotoacústicas/métodos , Análise dos Mínimos Quadrados , Técnicas Fotoacústicas/normas
17.
J Vis Exp ; (124)2017 06 21.
Artigo em Inglês | MEDLINE | ID: mdl-28671657

RESUMO

In vivo small-animal imaging has an important role to play in preclinical studies. Photoacoustic tomography (PAT) is an emerging hybrid imaging modality that shows great potential for both preclinical and clinical applications. Conventional optical parametric oscillator-based PAT (OPO-PAT) systems are bulky and expensive and cannot provide high-speed imaging. Recently, pulsed-laser diodes (PLDs) have been successfully demonstrated as an alternative excitation source for PAT. Pulsed-laser diode PAT (PLD-PAT) has been successfully demonstrated for high-speed imaging on photoacoustic phantoms and biological tissues. This work provides a visualized experimental protocol for in vivo brain imaging using PLD-PAT. The protocol includes the compact PLD-PAT system configuration and its description, animal preparation for brain imaging, and a typical experimental procedure for 2D cross-sectional rat brain imaging. The PLD-PAT system is compact and cost-effective and can provide high-speed, high-quality imaging. Brain images collected in vivo at various scan speeds are presented.


Assuntos
Encéfalo/diagnóstico por imagem , Neuroimagem/métodos , Técnicas Fotoacústicas/métodos , Animais , Feminino , Ratos
18.
J Biomed Opt ; 22(2): 26009, 2017 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-28241275

RESUMO

A typical photoacoustic tomography (PAT) system uses a Q-switched Nd:YAG laser for irradiating the sample and a single-element ultrasound transducer (UST) for acquiring the photoacoustic data. Conventionally, in PAT systems, the UST is held in a horizontal position and moved in a circular motion around the sample in full 2 ? radians. Horizontal positioning of the UST requires a large water tank to house, and load on the motor is also high. To overcome this limitation, we used the UST in the vertical plane instead of the horizontal plane. The photoacoustic (PA) waves generated from the sample are directed to the detector surface using an acoustic reflector placed at 45 deg to the transducer body. Hence, we can reduce the scanning radius, which, in turn, will reduce the size of the water tank and load on the motor, and the overall conventional PAT system size can be minimized. In this work, we demonstrate that with this system configuration, we acquire nearly similar images for phantom and in vivo data as that of the conventional PAT system using both flat and focused USTs.


Assuntos
Técnicas Fotoacústicas/instrumentação , Tomografia/instrumentação , Imagens de Fantasmas , Transdutores
19.
Chemistry ; 23(27): 6570-6578, 2017 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-28226192

RESUMO

Four new N-ethylcarbazole-linked aza-boron-dipyrromethene (aza-BODIPY) dyes (8 a,b and 9 a,b) were synthesized and characterized. The presence of the N-ethylcarbazole moiety shifts their absorption and fluorescence spectra to the near-infrared region, λ≈650-730 nm, of the electromagnetic spectrum. These dyes possess strong molar absorptivity in the range of 3-4×104 m-1 cm-1 with low fluorescence quantum yields. The triplet excited state and singlet oxygen generation of these dyes were enhanced upon iodination at the core position. The core-iodinated dyes 9 a,b showed excellent triplet quantum yields of about 90 and 75 %, with singlet oxygen generation efficiency of about 70 and 60 % relative to that of the parent dyes. Derivatives 8 a,b showed dual absorption profiles, in contrast to dyes 9 a,b, which had the characteristic absorption band of aza-BODIPY dyes. DFT calculations revealed that the electron density was spread over the iodine and dipyrromethene plane of 9 a,b, whereas in 8 a,b the electron density was distributed on the carbazole group and dipyrromethene plane of aza-BODIPY. The uniqueness of these aza-BODIPY systems is that they exhibit efficient triplet-state quantum yields, high singlet oxygen generation yields, and good photostability. Furthermore, the photoacoustic (PA) characteristics of these aza-BODIPY dyes was explored, and efficient PA signals for 8 a were observed relative to blood serum with in vitro deep-tissue imaging, thereby confirming its use as a promising PA contrast agent.


Assuntos
Compostos de Boro/química , Carbazóis/química , Meios de Contraste/química , Corantes Fluorescentes/química , Animais , Mama/patologia , Galinhas , Meios de Contraste/síntese química , Técnicas Eletroquímicas , Feminino , Corantes Fluorescentes/síntese química , Oxirredução , Técnicas Fotoacústicas , Teoria Quântica , Soro/química , Oxigênio Singlete/química , Oxigênio Singlete/metabolismo , Espectrometria de Fluorescência , Tomografia
20.
J Biomed Opt ; 21(8): 86011, 2016 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-27548773

RESUMO

For a circular scanning geometry in photoacoustic tomography, the axial/radial resolution is spatially invariant and is not affected by the ultrasound transducer (UST, detector) aperture. However, the tangential resolution is dependent on the detector aperture size and it varies spatially. Many techniques were proposed to improve the tangential resolution, such as attaching a concave lens in front of the nonfocused transducer or using a virtual point detector. Both of these methods have difficulties. Therefore, a modified delay-and-sum reconstruction algorithm has been proposed which can be used together with a standard ultrasound detector (nonfocused) to improve the tangential resolution. In this work, we validate the modified delay-and-sum algorithm experimentally for both flat and cylindrically focused USTs. More than threefold improvement in tangential resolution is observed. It is also shown that the object shape is recovered with this modified algorithm, which is very helpful for diagnosis and treatment purposes.


Assuntos
Algoritmos , Técnicas Fotoacústicas , Tomografia/métodos , Tomografia/normas , Lentes , Imagens de Fantasmas , Transdutores
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