scholarly journals Photoacoustic Tomography with a Ring Ultrasound Transducer: A Comparison of Different Illumination Strategies

2019 ◽  
Vol 9 (15) ◽  
pp. 3094 ◽  
Author(s):  
Naser Alijabbari ◽  
Suhail S. Alshahrani ◽  
Alexander Pattyn ◽  
Mohammad Mehrmohammadi
Keyword(s):  
Point Source ◽  
Cross Section ◽  
Acoustic Waves ◽  
Signal To Noise Ratio ◽  
Laser Pulses ◽  
Point Of Entry ◽  
Main Challenge ◽  
Optimum Position ◽  
Short Laser Pulses ◽  
Pat System

Photoacoustic (PA) imaging is a methodology that uses the absorption of short laser pulses by endogenous or exogenous chromophores within human tissue, and the subsequent generation of acoustic waves acquired by an ultrasound (US) transducer, to form an image that can provide functional and molecular information. Amongst the various types of PA imaging, PA tomography (PAT) has been proposed for imaging pathologies such as breast cancer. However, the main challenge for PAT imaging is the deliverance of sufficient light energy horizontally through an imaging cross-section as well as vertically. In this study, three different illumination methods are compared for a full-ring ultrasound (US) PAT system. The three distinct illumination setups are full-ring, diffused-beam, and point source illumination. The full-ring system utilizes a cone mirror and parabolic reflector to create the ringed-shaped beam for PAT, while the diffuse scheme uses a light diffuser to expand the beam, which illuminates tissue-mimicking phantoms. The results indicate that the full-ring illumination is capable of providing a more uniform fluence irrespective of the vertical depth of the imaged cross-section, while the point source and diffused illumination methods provide a higher fluence at regions closer to the point of entry, which diminishes with depth. In addition, a set of experiments was conducted to determine the optimum position of ring-illumination with respect to the position of the acoustic detectors to achieve the highest signal-to-noise ratio.

scholarly journals LASER-INDUCED SURFACE ACOUSTIC WAVES FOR THIN FILM CHARACTERIZATION

2020 ◽  
Vol 27 ◽  
pp. 57-61
Author(s):  
Radim Kudělka ◽  
Lukáš Václavek ◽  
Jan Tomáštík ◽  
Sabina Malecová ◽  
Radim Čtvrtlík
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Young’S Modulus ◽  
Acoustic Waves ◽  
Young's Modulus ◽  
Surface Acoustic Waves ◽  
Laser Pulses ◽  
Data Application ◽  
Thin Film Characterization ◽  
Short Laser Pulses

Knowledge of mechanical properties of thin films is essential for most of their applications. However, their determination can be problematic for very thin films. LAW (Laser-induced acoustic waves) is a combined acousto-optic method capable of measuring films with thickness from few nanometers. It utilizes ultrasound surface waves which are excited via short laser pulses and detected by a PVDF foil. Properties such as Young’s modulus, Poisson’s ratio and density of both the film and the substrate as well as film thickness can be explored.Results from the LAW method are successfully compared with nanoindentation for Young’s modulus evaluation and with optical method for film thickness evaluation and also with literature data. Application of LAW for anisotropy mapping of materials with cubic crystallographic lattice is also demonstrated.

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.

Surface-acoustic-wave generation by thermoelasticity

1986 ◽  
Vol 320 (1554) ◽  
pp. 315-318 ◽  
Keyword(s):  
Acoustic Waves ◽  
Pulse Width ◽  
Surface Acoustic Waves ◽  
Laser Pulses ◽  
Simple Relation ◽  
Maximal Amplitude ◽  
Thermoelastic Effect ◽  
Acoustic Wave Generation ◽  
Short Laser Pulses ◽  
Temporal And Spatial

Short laser pulses were used for generating surface acoustic waves (SAWs) on aluminium via the thermoelastic effect. There exists a simple relation between the temporal and spatial pulse width at which the SAWs exhibit maximal amplitude.

Uniform Horizontal Groundwater Flow against Dispersion in a Shallow Aquifer: Two Analytical Models

1992 ◽  
Vol 23 (1) ◽  
pp. 1-12
Author(s):  
Ram Raj Vinda ◽  
Raja Ram Yadava ◽  
Naveen Kumar
Keyword(s):  
Point Source ◽  
Groundwater Flow ◽  
Cross Section ◽  
Analytical Solutions ◽  
Concentration Distribution ◽  
Analytical Models ◽  
Shallow Aquifer ◽  
Horizontal Cross Section ◽  
Flow Components ◽  
Reactive Pollutant

Analytical solutions converging rapidly at large and small values of times have been obtained for two mathematical models which describe the concentration distribution of a non reactive pollutant from a point source against the flow in a horizontal cross-section of a finite saturated shallow aquifer possessing uniform horizontal groundwater flow. Zero concentration or the conditions in which the flux across the extreme boundaries are proportional to the respective flow components are applied. The effects of flow and dispersion on concentration distribution are also discussed.

scholarly journals Production of ion beams in high-power laser–plasma interactions and their applications

2004 ◽  
Vol 22 (1) ◽  
pp. 19-24 ◽  
Author(s):  
F. PEGORARO ◽  
S. ATZENI ◽  
M. BORGHESI ◽  
S. BULANOV ◽  
T. ESIRKEPOV ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Medical Physics ◽  
Ion Beam ◽  
Laser Pulses ◽  
Ion Beams ◽  
Laser Plasma Interactions ◽  
Physical Mechanisms ◽  
Short Laser Pulses ◽  
Laser Pulse Intensity ◽  
Target Design

Energetic ion beams are produced during the interaction of ultrahigh-intensity, short laser pulses with plasmas. These laser-produced ion beams have important applications ranging from the fast ignition of thermonuclear targets to proton imaging, deep proton lithography, medical physics, and injectors for conventional accelerators. Although the basic physical mechanisms of ion beam generation in the plasma produced by the laser pulse interaction with the target are common to all these applications, each application requires a specific optimization of the ion beam properties, that is, an appropriate choice of the target design and of the laser pulse intensity, shape, and duration.

Mechanisms of nanoparticle formation by short laser pulses

2007 ◽  
Author(s):  
Tatiana E. Itina ◽  
Mikhail E. Povarnitsyn ◽  
Karine Gouriet ◽  
Sylvie Noël ◽  
Jörg Hermann
Keyword(s):  
Laser Pulses ◽  
Nanoparticle Formation ◽  
Short Laser Pulses

Multistate non-Hermitian Floquet dynamics in short laser pulses

2000 ◽  
Vol 61 (3) ◽  
Author(s):  
H. C. Day ◽  
Bernard Piraux ◽  
R. M. Potvliege
Keyword(s):  
Laser Pulses ◽  
Short Laser Pulses
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