scholarly journals Acoustic Reconstruction for Photothermal Imaging

2018 ◽  
Vol 5 (3) ◽  
pp. 70 ◽  
Author(s):  
Peter Burgholzer ◽  
Gregor Stockner ◽  
Guenther Mayr
Keyword(s):  
Initial Temperature ◽  
Short Pulse ◽  
Infrared Camera ◽  
Sample Surface ◽  
Heat Diffusion ◽  
Reconstruction Method ◽  
Initial Temperature Distribution ◽  
Point Spread ◽  
Spread Function ◽  
Temporal Transformation

Pulsed illumination of a sample, e.g., of a biological tissue, causes a sudden temperature increase of light absorbing structures, such as blood vessels, which results in an outgoing acoustic wave, as well as heat diffusion, of the absorbed energy. Both of the signals, pressure and temperature, can be measured at the sample surface and are used to reconstruct the initial temperature or pressure distribution, called photoacoustic or photothermal reconstruction respectively. We have demonstrated that both signals at the same surface pixel are connected by a temporal transformation. This allows for the calculation of a so-called acoustical virtual wave from the surface temperature evolution as measured by an infrared camera. The virtual wave is the solution of a wave equation and can be used to reconstruct the initial temperature distribution immediately after the excitation pulse. This virtual wave reconstruction method was used for the reconstruction of inclined steel rods in an epoxy sample, which were heated by a short pulse. The reconstructed experimental images show clearly the degradation of the spatial resolution with increasing depth, which is theoretically described by a depth-dependent thermographic point-spread-function.

scholarly journals Companion Detection Limits with Adaptive Optics Coronagraphy

2004 ◽  
Vol 202 ◽  
pp. 99-102
Author(s):  
B. R. Oppenheimer ◽  
R. G. Dekany ◽  
M. Troy ◽  
T. Hayward ◽  
B. Brandl
Keyword(s):  
Adaptive Optics ◽  
Focal Plane ◽  
Near Infrared ◽  
Dynamic Range ◽  
Infrared Camera ◽  
Nearby Star ◽  
Point Spread ◽  
Spread Function ◽  
Adaptive Optics System ◽  
Circular Disks

We present a study of the Palomar Adaptive Optics System and the PHARO near infrared camera in coronagraphic mode. The camera provides two different focal plane occulting masks–opaque circular disks 0.43 and 0.97″ across. Three different pupil plane apodizing masks (Lyot masks) are also provided. The six different combinations of Lyot mask and focal plane mask suppress differently the point spread function of a bright star centered on the focal plane mask. We obtained images of the bright nearby star Gliese 614 with all six different configurations in the K filter. We measured the dynamic range achievable with these configurations. Within 2.5″, the dynamic range is at least 8 magnitudes at the 5σ level and as high as 12 in a 1 s exposure. This represents a substantial gain over similar techniques without adaptive optics.

Defect Recognition for Honeycomb Sandwich Composites Using Pulsed Thermography

2013 ◽  
Vol 773 ◽  
pp. 542-548
Author(s):  
Huo Yan ◽  
Hui Juan Li
Keyword(s):  
Thermal Diffusivity ◽  
Surface Temperature ◽  
Short Pulse ◽  
Infrared Camera ◽  
Sample Surface ◽  
Honeycomb Core ◽  
Flat Bottom ◽  
Pulsed Thermography ◽  
Defect Recognition ◽  
Subsurface Defects

Typical defects such as delamination and water/oil ingression existed in honeycomb composites during manufacturing and in-service period. The defects can reduce the performance of the composites significantly. The paper presented a nondestructive defect recognition method for honeycomb composites using pulsed thermography. In this study, based on analysis of the heat transfer in the object with two different medias, the relationship between the surface temperature and the thermal property of subsurface defects has been deduced; the surface temperature expression is put forward to consider the interaction of subsurface defects. In order to simulate the defects, CFRP sandwiched sample with different subsurface defects (debonding, water in the honeycomb core and oil in the honeycomb core) of the same volume inserted in the machined flat-bottom holes, the sample is heated with a short pulse of light, and the sample surface temperature is captured by infrared camera, and the data is processed to measure thermal diffusivity for the subsurface defects. The order of the measured thermal diffusivity is according with the theoretical value. The experiment results provide the feasibility of different defects recognition, and the influence factors are discussed.

RECONSTRUCTION OF DYNAMIC PET IMAGES USING ACCURATE SYSTEM POINT SPREAD FUNCTION MODELING: EFFECTS ON PARAMETRIC IMAGES

2010 ◽  
Vol 10 (01) ◽  
pp. 73-94 ◽  
Author(s):  
D. D'AMBROSIO ◽  
G. FIACCHI ◽  
M. MARENGO ◽  
S. BOSCHI ◽  
S. FANTI ◽  
...  
Keyword(s):  
Parameter Estimation ◽  
Point Spread Function ◽  
Physiological Parameters ◽  
Reconstruction Method ◽  
Dynamic Pet ◽  
Partial Volume ◽  
Parametric Images ◽  
Point Spread ◽  
Spread Function ◽  
System Point

Quantitative analysis of positron emission tomography (PET) dynamic images allows to estimate physiological parameters such as glucose metabolic rate (GMR), perfusion, and cardiac output (CO). However, several physical effects such as photon attenuation, scatter and partial volume can reduce the accuracy of parameter estimation. The main goal of this work was to improve small animal PET image quality by introducing system point spread function (PSF) in the reconstruction scheme and to evaluate the effect of partial volume correction (PVC) on physiological parameter estimation. Images reconstructed respectively using constant and spatially variant (SV) PSFs and no PSF modeling was compared. The proposed algorithms were tested on simulated and real phantoms and mice images. Results show that the SV-PSF-based reconstruction method provides a significant contrast improvement of small animals PET cardiac images and, thus, the effects of PVC on physiological parameters were evaluated using such algorithm. Simulations show that the proposed PVC method reduces errors with respect to the true values for parametric images of GMR and perfusion. A reduction of CO percentage error with respect to the original value was also obtained using the SF-PSF approach. In conclusion, SV-PSF reconstruction method provides a more accurate estimation of several physiological parameters obtained from a dynamic PET scan.

scholarly journals X-raying the evolution of SN 1987A

2017 ◽  
Vol 12 (S331) ◽  
pp. 284-289
Author(s):  
Vinay L. Kashyap ◽  
David van Dyk ◽  
Katy McKeough ◽  
Frank Primini ◽  
Diab Jerius ◽  
...  
Keyword(s):  
Point Spread Function ◽  
Reconstruction Algorithm ◽  
Reconstruction Method ◽  
X Ray ◽  
Multi Scale ◽  
Sn 1987A ◽  
Point Spread ◽  
Spread Function ◽  
High Resolution Images ◽  
Empirical Point

AbstractSN 1987A has been observed with the Chandra X-ray Observatory over the entire course of the mission. We have re-analyzed the archival data by constructing an empirical point spread function and reconstructing high-resolution images using a Bayesian multi-scale image reconstruction algorithm. We are able to resolve structure in the equatorial ring of SN 1987A with unprecedented detail, at scales of $\approx \frac{1}{4}$ arcsec. We describe how the point spread function is constructed, and the reconstruction method, and explore the evolution of the inner ring at different epochs and passbands.

Blind deconvolution in autocorrelation inversion for multi-view light sheet microscopy

2021 ◽  
Author(s):  
Elena Corbetta ◽  
Alessia Candeo ◽  
Andrea Bassi ◽  
Daniele Ancora
Keyword(s):  
Point Spread Function ◽  
Blind Deconvolution ◽  
Light Sheet ◽  
Reconstruction Method ◽  
Light Sheet Microscopy ◽  
Point Spread ◽  
Spread Function ◽  
Unknown Point

AbstractCombining the information coming from multi-view acquisitions is a problem of great interest in light-sheet microscopy. Aligning the views and increasing the resolution of their fusion can be challenging, especially if the setup is not fully calibrated. Here, we tackle these issues by proposing a new reconstruction method based on autocorrelation inversion that avoids alignment procedures. On top of this, we add a blind deconvolution step to improve the resolution of the final reconstruction. Our method permits us to achieve inherently aligned, highly resolved reconstructions while, at the same time, estimating the unknown point-spread function of the system.

Experimental Point Spread Function of Fm Pulse Imaging Scheme

1995 ◽  
Vol 17 (2) ◽  
pp. 114-141 ◽  
Author(s):  
N.A.H.K. Rao ◽  
S. Mehra ◽  
J. Bridges ◽  
S. Venkatraman
Keyword(s):  
Point Spread Function ◽  
Pulse Compression ◽  
Short Pulse ◽  
Side Lobe ◽  
Theoretical Framework ◽  
Media Analysis ◽  
Experimental Point ◽  
Peak Intensity ◽  
Point Spread ◽  
Spread Function

In this paper, we have examined the possibility of incorporating pulse compression techniques into a conventional medical B-scan imaging scheme. Linear frequency modulation fm, one form of pulse coding among many others, has been used in this study. With this approach, one can overcome current peak intensity limitations. A theoretical framework that includes medium propagation effects, transducer bandwidth and diffraction effects is presented, which could be used to examine the system point spread function under this imaging scheme. A prototype experimental set-up and signal processing are described and used for simple imaging tasks in attenuating and nonattenuating media. Analysis of the experimental point spread functions shows that resolution similar to conventional short pulse imaging can be achieved. However, the existence of large range side lobe levels usually associated with pulse compression processing can degrade contrast resolution in medical ultrasound. We have considered various different factors that can affect the range side lobe levels and examined their effect either experimentally or through simulations. The technique has the potential for improving signal-to-noise ratio (SNR), maximum penetration depth and resolution without exceeding peak intensity limitations. Some possible applications are discussed that merit further evaluation. Our work demonstrates the feasibility of this technique and presents a theoretical framework that can be used in future studies aimed at evaluating image quality, system performance, and possible artifacts under such an imaging scheme.

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