Significance: Full-field optical angiography is critical for vascular disease research and clinical diagnosis. Existing methods struggle to improve the temporal and spatial resolutions simultaneously.
Aim: Spatiotemporal absorption fluctuation imaging (ST-AFI) is proposed to achieve dynamic blood flow imaging with high spatial and temporal resolutions.
Approach: ST-AFI is a dynamic optical angiography based on a low-coherence imaging system and U-Net. The system was used to acquire a series of dynamic red blood cell (RBC) signals and static background tissue signals, and U-Net is used to predict optical absorption properties and spatiotemporal fluctuation information. U-Net was generally used in two-dimensional blood flow segmentation as an image processing algorithm for biomedical imaging. In the proposed approach, the network simultaneously analyzes the spatial absorption coefficient differences and the temporal dynamic absorption fluctuation.
Results: The spatial resolution of ST-AFI is up to 4.33 μm, and the temporal resolution is up to 0.032 s. In vivo experiments on 2.5-day-old chicken embryos were conducted. The results demonstrate that intermittent RBCs flow in capillaries can be resolved, and the blood vessels without blood flow can be suppressed.
Conclusions: Using ST-AFI to achieve convolutional neural network (CNN)-based dynamic angiography is a novel approach that may be useful for several clinical applications. Owing to their strong feature extraction ability, CNNs exhibit the potential to be expanded to other blood flow imaging methods for the prediction of the spatiotemporal optical properties with improved temporal and spatial resolutions.
We propose a logic optical projection tomography (LOPT) method to realize full-view, three-dimensional (3-D) shape parameters measurement and visualization for opaque objects. The main innovation of LOPT is use of a logic process to obtain high-contrast and homogeneous boundary projection signals. According to the reconstructed 2-D cross-section images, the structure characteristic points in each slice are independently extracted and combined to produce a full-view 3-D image. Further, the structural shape parameters of individual parts of object such as the inscribed cylinder, center line, and double threads are obtained and visualized simultaneously. Our experimental results demonstrate that LOPT can be potentially developed as an economical optical measurement and visualization tool for some industrial application.
We propose a wide-field absolute transverse blood flow velocity measurement method in vessel centerline based on absorption intensity fluctuation modulation effect. The difference between the light absorption capacities of red blood cells and background tissue under low-coherence illumination is utilized to realize the instantaneous and average wide-field optical angiography images. The absolute fuzzy connection algorithm is used for vessel centerline extraction from the average wide-field optical angiography. The absolute transverse velocity in the vessel centerline is then measured by a cross-correlation analysis according to instantaneous modulation depth signal. The proposed method promises to contribute to the treatment of diseases, such as those related to anemia or thrombosis.
We developed high-temporal-resolution, full-field optical angiography for use in vascular occlusion tests (VOTs). In the proposed method, undersampled signals are acquired by a high-speed digital camera that separates the dynamic and static speckle signals. The two types of speckle signal are used to calculate the short-time modulation depth (STMD) of each of the camera pixels. STMD is then used to realize high-temporal-resolution, full-field optical angiography. Phantom and biological experiments conducted and demonstrated the feasibility of using our proposed method to perform VOTs and to study the reaction kinetics in microfluidic systems.
We propose a full-field optical method for the label-free and quantitative mapping of the velocities of red blood cells (RBCs) in capillaries. It integrates spatiotemporal demodulation and an autocorrelation algorithm, and measures RBC velocity according to the ratio of RBC length to lag time. Conventionally, RBC length is assumed to be a constant and lag time is taken as a variable, while our method treats both of them as variables. We use temporal demodulation and the Butterworth spatial filter to separate RBC signal from background signal, based on which we obtain the RBC length by image segmentation and lag time by autocorrelation analysis. The RBC velocity calculated now is more accurate. The validity of our method is verified by an in vivo experiment on a mouse ear. Owing to its higher image signal-to-noise ratio, our method can be used for mapping RBC velocity in the turbid tissue case.
We present the theory of laser speckle imaging improved with intensity fluctuation modulation, where the dynamic speckle pattern can be isolated from its stationary counterpart. A series of in vivo experiments demonstrate the effectiveness of our method in achieving microangiography and monitoring vascular self-recovering process. All results show the convincing performance of our imaging method in both structural and functional imaging of blood flow, which may have potential applications in biological research and disease diagnosis.
KEYWORDS: Optical coherence tomography, Interferometry, In vivo imaging, Heterodyning, Interferometers, System on a chip, Americium, Vibrometry, Bone, Ear
Studying the sound stimulated vibrations of various membranes that form the complex structure of the organ of Corti in
the cochlea of the inner ear is essential for understanding how the travelling sound wave of the basilar membrane couples
its energy to the organ structures. In this paper we report the feasibility of using phase-sensitive Fourier domain optical
coherence tomography (FD-OCT) to image the vibration of various micro-structures of the cochlea at the same time. An
excised cochlea of a guinea pig was stimulated using sounds at various frequencies and vibration image was obtained.
When measuring the apex area, vibration signal from different turns, which have different best response frequencies are
obtained in the same image. The method has the potential to measure the response from a much wider region of the
cochlea than any other currently used method. The noise floor for vibration image for the system at 200 Hz was ~0.3nm.
A real-time photoacoustic (PA) imaging system based on multi-element linear transducer array was developed and test on phantoms. A Q switched Nd:YAG laser operating at 532 nm and 20Hz repeat rate was used in our experiment as thermal source. The multi-element linear transducer array consists of 320 elements. By phase-controlled method, 64 signals, one of which gathered by 11-group element, make up of an image. It was acquired in only about 3 seconds. Phantom experiment results can map the distribution of the optical absorption correctly. Compared to other existing technology and algorithm, the PA imaging based on transducer array was characterize by speediness and convenience. It can provide a new approach for tissue functional imaging in vivo, and may have potentials in developing into an appliance for clinic diagnosis.
A technique has been developed to simultaneously acquire ultrasound and photoacoustic (PA) images base on a linear transducer array. The system uses conventional ultrasound for rapid identification of potential target(s). Once a target is identified, the ultrasound echo and PA signals can be simultaneously obtained with optimized excitation and signal collection sequence. The corresponding ultrasound impedance and optical absorption images can be reconstructed with an algorithm similar to that used for conventional ultrasound imaging. The approach can effectively reduce the artifacts associated in conventional filter back-projection algorithm used in PA imaging by linear scanning. The technique provides a potential approach for practical applications.
Ultrasound-modulated optical tomography affords a very promising noninvasive imaging method for biomedical diagnosis. In this technology ultrasonic beams are focused into a scattering medium to provided accurate localization and simultaneously modulate light inside the medium. The detected ultrasound-tagging photons will bring the information of the characteristics of the medium. Based on the high-sensitivity detection technique, we develop a unique reflective configuration that the ultrasound and light are kept coaxial, which is more convenient and practical than other configurations. A completely absorbing object imbedded in a tissue is imaged using the corresponding experimental setup designed by us which is based on the configuration.
In this paper, a novel method for photoacoustic (PA) waves to imaging is proposed. A focused probe ultrasonic beam passes through a specimen and tags the position of the interested PA signal. Reconstruction of the original PA signal in situ is accomplished by demodulating the probe-beam. The method provides new measurement system with to improve signal-to-noise ratio and to take out more original messages. Applied the proper impulse of the detector and filter-back-project algorithm, a 2D PA tomograph was obtained.
KEYWORDS: Ultrasonography, Laser beam diagnostics, Tissues, Ultrasonics, Photoacoustic spectroscopy, Tomography, Signal detection, Modulation, Absorption, Signal to noise ratio
Photoacoustic has attracted high attention in recent years, because this imaging technique can combine the advantages of ultrasound and light to improve the image resolution and diagnostic depth of tissues. In this paper, An innovative method of recording photoacoustic (PA) waves in situ is proposed. A focused probe ultrasonic beam passes through a specimen and tags the position of the interested PA signal. The probe-beam interacts nonlinearly with PA wave, which take out more information interaction area. The PA signal in situ is obtained by demodulating the probe-beam. The technique can produce PA signal with high signal-to-noise ratio maging. The filter-back-project algorithm is used for reconstruction. And the PA tomography of a phantom with diameter of 3.5cm is obtained.
A new method of measuring photoacoustic (PA) waves in situ is proposed. We make a probe ultrasonic beam to pass through the thick biotissue sample. Its focus point is used to tag the position of the PA signal overlapped by the PA interaction area in order to carry the PA information and take it out with the probe beam. When the detecting waves met the PA signal, a beating—wave is generated. Then it is received by a hydra-phone. After amplification and demodulation, a PA signal will be restored. In addition, the attenuation of PA signal in transmission could be decided by measuring the amplitude difference of probe ultrasound in front and behind the sample. It was helpful to simplify the reconstruction of the PA tomographic image and to increase SNR. The noise of the measurement system and background could be reduced when PA waveforms were discriminated. We measured the beating-wave produced by 532nm laser and 1 .4MHz probe ultrasonic beam in the thick biotissue and absorptive media, and reconstructed their PA signal waves with fine SNR.
The results of theoretical and experimental investigations of pulsed optoacoustic (PA) method for tomography of biological objects in the requency range 1-10 MHZ at the depths up to 5 centimeters are presented. Some key problems of imaging are to reduce the effect of surface PA pulse and enhance the contrast of imaging. In this paper, we propose compensation methodology to restrain the noise signal of the surface, and apply the methodology to reconstruct PA tomography,
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.