scholarly journals Resolution Limits in Photoacoustic Imaging Caused by Acoustic Attenuation

2019 ◽  
Vol 5 (1) ◽  
pp. 13 ◽  
Author(s):  
Peter Burgholzer ◽  
Johannes Bauer-Marschallinger ◽  
Bernhard Reitinger ◽  
Thomas Berer
Keyword(s):  
Acoustic Waves ◽  
Photoacoustic Imaging ◽  
Signal To Noise Ratio ◽  
Finite Size ◽  
Photoacoustic Signal ◽  
Dissipated Energy ◽  
Reconstruction Method ◽  
Square Root ◽  
Resolution Limit ◽  
Acoustic Attenuation

In conventional photoacoustic tomography, several effects contribute to the loss of resolution, such as the limited bandwidth and the finite size of the transducer, or the space-dependent speed of sound. They can all be compensated (in principle) technically or numerically. Frequency-dependent acoustic attenuation also limits spatial resolution by reducing the bandwidth of the photoacoustic signal, which can be numerically compensated only up to a theoretical limit given by thermodynamics. The entropy production, which is the dissipated energy of the acoustic wave divided by the temperature, turns out to be equal to the information loss, which cannot be compensated for by any reconstruction method. This is demonstrated for the propagation of planar acoustic waves in water, which are induced by short laser pulses and measured by piezoelectric acoustical transducers. It turns out that for water, where the acoustic attenuation is proportional to the squared frequency, the resolution limit is proportional to the square root of the distance and inversely proportional to the square root of the logarithm of the signal-to-noise ratio. The proposed method could be used in future work for media other than water, such as biological tissue, where acoustic attenuation has a different power-law frequency dependence.

scholarly journals Photoacoustic Imaging with Capacitive Micromachined Ultrasound Transducers: Principles and Developments

Sensors ◽  
2019 ◽  
Vol 19 (16) ◽  
pp. 3617 ◽  
Author(s):  
Jasmine Chan ◽  
Zhou Zheng ◽  
Kevan Bell ◽  
Martin Le ◽  
Parsin Haji Reza ◽  
...  
Keyword(s):  
Photoacoustic Imaging ◽  
Signal To Noise Ratio ◽  
Complementary Metal Oxide Semiconductor ◽  
Photoacoustic Signal ◽  
Motion Artifacts ◽  
Oxide Semiconductor ◽  
Ring Resonators ◽  
Ultrasound Transducers ◽  
Fabrication Technique ◽  
Acoustic Techniques

Photoacoustic imaging (PAI) is an emerging imaging technique that bridges the gap between pure optical and acoustic techniques to provide images with optical contrast at the acoustic penetration depth. The two key components that have allowed PAI to attain high-resolution images at deeper penetration depths are the photoacoustic signal generator, which is typically implemented as a pulsed laser and the detector to receive the generated acoustic signals. Many types of acoustic sensors have been explored as a detector for the PAI including Fabry–Perot interferometers (FPIs), micro ring resonators (MRRs), piezoelectric transducers, and capacitive micromachined ultrasound transducers (CMUTs). The fabrication technique of CMUTs has given it an edge over the other detectors. First, CMUTs can be easily fabricated into given shapes and sizes to fit the design specifications. Moreover, they can be made into an array to increase the imaging speed and reduce motion artifacts. With a fabrication technique that is similar to complementary metal-oxide-semiconductor (CMOS), CMUTs can be integrated with electronics to reduce the parasitic capacitance and improve the signal to noise ratio. The numerous benefits of CMUTs have enticed researchers to develop it for various PAI purposes such as photoacoustic computed tomography (PACT) and photoacoustic endoscopy applications. For PACT applications, the main areas of research are in designing two-dimensional array, transparent, and multi-frequency CMUTs. Moving from the table top approach to endoscopes, some of the different configurations that are being investigated are phased and ring arrays. In this paper, an overview of the development of CMUTs for PAI is presented.

scholarly journals High-contrast photoacoustic imaging through scattering media using correlation detection of adaptive time window

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Liqi Yu ◽  
Jialin Sun ◽  
Xinjing Lv ◽  
Qi Feng ◽  
Huimei He ◽  
...  
Keyword(s):  
Light Scattering ◽  
Time Window ◽  
Photoacoustic Imaging ◽  
Signal To Noise Ratio ◽  
Photoacoustic Signal ◽  
High Contrast ◽  
Scattering Media ◽  
Window Method ◽  
Adaptive Time ◽  
Imaging Depth

AbstractPhotoacoustic imaging has the advantages of high contrast and deep imaging depth. However, with the increasing of imaging depth, the signal-to-noise ratio (SNR) of the detected signal decreases, due to the light scattering that seriously affects the recovery image quality. In this paper, we experimentally demonstrated that higher contrast photoacoustic imaging was achieved using photoacoustic wavefront shaping technology in the presence of light scattering and low SNR signals. The imaging contrast is improved from 1.51 to 5.30. More importantly, we propose a dynamic time window method for the photoacoustic signal extraction algorithm, named correlation detection of adaptive time window, which further improves the contrast of photoacoustic imaging to 9.57. Our method effectively improves the contrast of photoacoustic imaging through scattering media.

scholarly journals Photoacoustic Signal Enhancement: Towards Utilization of Low Energy Laser Diodes in Real-Time Photoacoustic Imaging

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3498 ◽  
Author(s):  
Rayyan Manwar ◽  
Matin Hosseinzadeh ◽  
Ali Hariri ◽  
Karl Kratkiewicz ◽  
Shahryar Noei ◽  
...  
Keyword(s):  
Photoacoustic Imaging ◽  
Signal To Noise Ratio ◽  
Laser Diodes ◽  
Cost Effective ◽  
Photoacoustic Signal ◽  
Low Energy ◽  
Low Snr ◽  
Energy Laser ◽  
Noisy Measurements ◽  
Low Energy Laser

In practice, photoacoustic (PA) waves generated with cost-effective and low-energy laser diodes, are weak and almost buried in noise. Reconstruction of an artifact-free PA image from noisy measurements requires an effective denoising technique. Averaging is widely used to increase the signal-to-noise ratio (SNR) of PA signals; however, it is time consuming and in the case of very low SNR signals, hundreds to thousands of data acquisition epochs are needed. In this study, we explored the feasibility of using an adaptive and time-efficient filtering method to improve the SNR of PA signals. Our results show that the proposed method increases the SNR of PA signals more efficiently and with much fewer acquisitions, compared to common averaging techniques. Consequently, PA imaging is conducted considerably faster.

scholarly journals Numerical Simulation of Enhanced Photoacoustic Generation and Wavefront Shaping by a Distributed Laser Array

2021 ◽  
Vol 11 (20) ◽  
pp. 9497
Author(s):  
Ruijie Hou ◽  
Bin Xu ◽  
Zhiying Xia ◽  
Yang Zhang ◽  
Weiping Liu ◽  
...  
Keyword(s):  
Acoustic Waves ◽  
Photoacoustic Imaging ◽  
Signal To Noise Ratio ◽  
Beam Steering ◽  
Laser Pulses ◽  
Laser Array ◽  
Flexible Control ◽  
Mechanical Waves ◽  
Laser Induced Damage ◽  
Array Generation

In photoacoustic imaging, the use of arrayed laser sources brings several advantages. Acoustic waves can be generated with flexible control of wavefronts, bringing functionality such as ultrasonic beam steering and focusing. The use of arrays reduces the optical intensity while increasing the strength of the ultrasonic wave, bringing the advantages of improved signal-to-noise ratio (SNR) while avoiding laser-induced damage. In this paper, we report a numerical model for studying the generation and shaping of acoustic wavefronts with laser arrays. The propagation of mechanical waves, photoacoustically generated by thermal expansion, is simulated and discussed in detail. In addition, a partially delayed distributed array is studied both theoretically and quantitatively. The developed model for wavefront control through time-delayed laser pulses is shown to be highly suited for the optimization of laser array generation schemes.

A Novel Approach to Photoacoustic FT-IR Spectroscopy: Rheo-Photoacoustic Measurements

1989 ◽  
Vol 43 (8) ◽  
pp. 1387-1393 ◽  
Author(s):  
William F. McDonald ◽  
Hans Goeitler ◽  
Marek W. Urban
Keyword(s):  
Molecular Structure ◽  
Thin Films ◽  
Fourier Transform ◽  
Acoustic Waves ◽  
Polymeric Materials ◽  
Photoacoustic Signal ◽  
Novel Approach ◽  
Ft Ir ◽  
Property Changes ◽  
Ft Ir Spectroscopy

A new rheo-photoacoustic Fourier transform infrared cell has been developed to perform stress-strain studies on polymeric materials. The rheo-photoacoustic measurements lead to the enhancement of the photoacoustic signal and allow one to monitor the effect of elongational forces on the molecular structure of polymers. Propagating acoustic waves are detected as a result of the deformational changes and thermal property changes upon the applied stress. Applications of this technique to fibers, films, and adhesion of thin films are presented.

An iterative reconstruction method for sparse-projection data for low-dose CT

2021 ◽  
pp. 1-16
Author(s):  
Ying Huang ◽  
Qian Wan ◽  
Zixiang Chen ◽  
Zhanli Hu ◽  
Guanxun Cheng ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Structural Similarity ◽  
Reconstructed Image ◽  
Projection Data ◽  
Reconstruction Method ◽  
X Ray ◽  
Image Structure ◽  
Reconstruction Performance ◽  
Risk Of Cancer ◽  
Suppress Noise

Reducing X-ray radiation is beneficial for reducing the risk of cancer in patients. There are two main approaches for achieving this goal namely, one is to reduce the X-ray current, and another is to apply sparse-view protocols to do image scanning and projections. However, these techniques usually lead to degradation of the reconstructed image quality, resulting in excessive noise and severe edge artifacts, which seriously affect the diagnosis result. In order to overcome such limitation, this study proposes and tests an algorithm based on guided kernel filtering. The algorithm combines the characteristics of anisotropic edges between adjacent image voxels, expresses the relevant weights with an exponential function, and adjusts the weights adaptively through local gray gradients to better preserve the image structure while suppressing noise information. Experiments show that the proposed method can effectively suppress noise and preserve the image structure. Comparing with similar algorithms, the proposed algorithm greatly improves the peak signal-to-noise ratio (PSNR), structural similarity (SSIM), and root mean square error (RMSE) of the reconstructed image. The proposed algorithm has the best effect in quantitative analysis, which verifies the effectiveness of the proposed method and good image reconstruction performance. Overall, this study demonstrates that the proposed method can reduce the number of projections required for repeated CT scans and has potential for medical applications in reducing radiation doses.

Ultrasmall hybrid protein–copper sulfide nanoparticles for targeted photoacoustic imaging of orthotopic hepatocellular carcinoma with a high signal-to-noise ratio

2019 ◽  
Vol 7 (1) ◽  
pp. 92-103 ◽  
Author(s):  
Huixiang Yan ◽  
Jingqin Chen ◽  
Ying Li ◽  
Yuanyuan Bai ◽  
Yunzhu Wu ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Copper Sulfide ◽  
Photoacoustic Imaging ◽  
Signal To Noise Ratio ◽  
Nanoparticle Synthesis ◽  
High Signal ◽  
Hybrid Protein ◽  
Signal To Noise ◽  
Noise Ratio

A schematic illustration of CuS@BSA-RGD nanoparticle synthesis and the application of photoacoustic imaging in an orthotopic HCC model.

scholarly journals Fabrication of Coaxial and Confocal Transducer Based on Sol-Gel Composite Material for Optical Resolution Photoacoustic Microscopy

Diagnostics ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 6
Author(s):  
Masayuki Tanabe ◽  
Tai Chieh Wu ◽  
Makiko Kobayashi ◽  
Che Hua Yang
Keyword(s):  
Ex Vivo ◽  
Photoacoustic Imaging ◽  
Sol Gel ◽  
Optical Resolution ◽  
Maximum Amplitude ◽  
Photoacoustic Signal ◽  
Center Frequency ◽  
Photoacoustic Microscopy ◽  
3 Dimensional ◽  
Pulse Echo

We have newly developed coaxial and confocal optical-resolution photoacoustic microscopy based on sol-gel composite materials. This transducer contains a concave-shaped piezoelectric layer with a focus depth of 5 mm and a hole with a diameter of 3 mm at the center to pass a laser beam into a phantom. Therefore, this system can directly detect an excited photoacoustic signal without prisms or acoustic lenses. We demonstrate the capability of the system through pulse-echo and photoacoustic imaging experiments. The center frequency of the fabricated transducer is approximately 7 MHz, and its relative bandwidth is 86%. An ex-vivo experiment is conducted, and photoacoustic signals are clearly obtained. As a result, 2- and 3-dimensional maximum amplitude projection images are reconstructed.

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