scholarly journals Respiration resolved imaging with continuous stable state 2D acquisition using linear frequency SWEEP

2019 ◽  
Vol 82 (5) ◽  
pp. 1631-1645 ◽  
Author(s):  
L. H. Jackson ◽  
A. N. Price ◽  
J. Hutter ◽  
A. Ho ◽  
T. A. Roberts ◽  
...  
Keyword(s):  
Stable State ◽  
Frequency Sweep ◽  
Linear Frequency

scholarly journals Laser Photothermoacoustic Heterodyned Lock-in Depth Profilometry in Turbid Tissue Phantoms

2021 ◽  
Author(s):  
Ying Fang ◽  
Andreas Mandelis ◽  
Gloria Spirou ◽  
I. Alex Vitkin ◽  
William M. Whelan
Keyword(s):  
Frequency Domain ◽  
Delay Time ◽  
Turbid Media ◽  
Laser Source ◽  
Depth Information ◽  
Chirp Signal ◽  
Sweep Method ◽  
Frequency Sweep ◽  
Linear Frequency ◽  
Lock In

Frequency-domain correlation and spectral analysis photothermoacoustic FD-PTA imaging is a promisingnew technique, which is being developed to detect tumor masses in turbid biological tissue. Unlike conventional biomedical photoacoustics which uses time-of-flight acoustic information induced by a pulsed laser to indicate the tumor size and location, in this research, a new FD-PTA instrument featuring frequency sweep chirp and heterodyne modulation and lock-in detection of a continuous-wave laser source at 1064 nm wavelength is constructed and tested for its depth profilometric capabilities with regard to turbid media imaging. Owing to the linear relationship between the depth of acoustic signal generation and the delay time of signal arrival to the transducer, information specific to a particular depth can be associated with a particular frequency in the chirp signal. Scanning laser-fluence modulation frequencies with a linear frequency sweep method preserves the depth-to-delay time linearity and recovers FD-PTA signals from a range of depths. Combining with the depth information carried by the back-propagated acoustic chirp signal at each scanning position, one could rapidly generate subsurface three-dimensional images of the scanning area at optimal signal-to-noise ratios and low laser fluences, a combination of tasks that is difficult or impossible by use of pulsed photoacoustic detection. In this paper, results of PTA scans performed on tissue mimicking control phantoms with various optical, acoustical, and geometrical properties are presented. A mathematical model is developed to study the laser-induced photothermoacoustic waves in turbid media. The model includes both the scattering and absorption properties of the turbid medium. A good agreement is obtained between the experimental and numerical results. It is concluded that frequency domain photothermoacoustics using a linear frequency sweep method and heterodyne lock-in detection has the potential to be a reliable tool for biomedical depth-profilometric imaging.

scholarly journals Laser Photothermoacoustic Heterodyned Lock-in Depth Profilometry in Turbid Tissue Phantoms

2021 ◽  
Author(s):  
Ying Fang ◽  
Andreas Mandelis ◽  
Gloria Spirou ◽  
I. Alex Vitkin ◽  
William M. Whelan
Keyword(s):  
Frequency Domain ◽  
Delay Time ◽  
Turbid Media ◽  
Laser Source ◽  
Depth Information ◽  
Chirp Signal ◽  
Sweep Method ◽  
Frequency Sweep ◽  
Linear Frequency ◽  
Lock In

Frequency-domain correlation and spectral analysis photothermoacoustic FD-PTA imaging is a promisingnew technique, which is being developed to detect tumor masses in turbid biological tissue. Unlike conventional biomedical photoacoustics which uses time-of-flight acoustic information induced by a pulsed laser to indicate the tumor size and location, in this research, a new FD-PTA instrument featuring frequency sweep chirp and heterodyne modulation and lock-in detection of a continuous-wave laser source at 1064 nm wavelength is constructed and tested for its depth profilometric capabilities with regard to turbid media imaging. Owing to the linear relationship between the depth of acoustic signal generation and the delay time of signal arrival to the transducer, information specific to a particular depth can be associated with a particular frequency in the chirp signal. Scanning laser-fluence modulation frequencies with a linear frequency sweep method preserves the depth-to-delay time linearity and recovers FD-PTA signals from a range of depths. Combining with the depth information carried by the back-propagated acoustic chirp signal at each scanning position, one could rapidly generate subsurface three-dimensional images of the scanning area at optimal signal-to-noise ratios and low laser fluences, a combination of tasks that is difficult or impossible by use of pulsed photoacoustic detection. In this paper, results of PTA scans performed on tissue mimicking control phantoms with various optical, acoustical, and geometrical properties are presented. A mathematical model is developed to study the laser-induced photothermoacoustic waves in turbid media. The model includes both the scattering and absorption properties of the turbid medium. A good agreement is obtained between the experimental and numerical results. It is concluded that frequency domain photothermoacoustics using a linear frequency sweep method and heterodyne lock-in detection has the potential to be a reliable tool for biomedical depth-profilometric imaging.

scholarly journals Optical linear frequency sweep based on a mode-spacing swept comb and multi-loop phase-locking for FMCW interferometry

2021 ◽  
Vol 29 (2) ◽  
pp. 604
Author(s):  
Weilin Xie ◽  
Yingxia Meng ◽  
Yuxiang Feng ◽  
Haijun Zhou ◽  
Ling Zhang ◽  
...  
Keyword(s):  
Phase Locking ◽  
Mode Spacing ◽  
Frequency Sweep ◽  
Linear Frequency

The Advantages of Cryotechniques: Application To Bioluminescent Cells

1990 ◽  
Vol 48 (1) ◽  
pp. 486-487
Author(s):  
Gisèle Nicolas ◽  
Jean-Marie Bassot ◽  
Marie-Thérèse Nicolas
Keyword(s):  
Endoplasmic Reticulum ◽  
Striated Muscle ◽  
Light Emission ◽  
Stable State ◽  
Freeze Substitution ◽  
Initial Step ◽  
Point Of Interest ◽  
Cell Components ◽  
Excellent Preservation ◽  
External Water

The use of fast-freeze fixation (FFF) followed by freeze-substitution (FS) brings substantial advantages which are due to the extreme rapidity of this fixation compared to the conventional one. The initial step, FFF, physically immobilizes most molecules and therefore arrests the biological reactions in a matter of milliseconds. The second step, FS, slowly removes the water content still in solid state and, at the same time, chemically fixes the other cell components in absence of external water. This procedure results in an excellent preservation of the ultrastructure, avoids osmotic artifacts,maintains in situ most soluble substances and keeps up a number of cell activities including antigenicities. Another point of interest is that the rapidity of the initial immobilization enables the capture of unstable structures which, otherwise, would slip towards a more stable state. When combined with electrophysiology, this technique arrests the ultrastructural modifications at a well defined state, allowing a precise timing of the events.We studied the epithelium of the elytra of the scale-worm, Harmothoe lunulata which has excitable, conductible and bioluminescent properties. The intracellular sites of the light emission are paracrystals of endoplasmic reticulum (PER), named photosomes (Fig.1). They are able to flash only when they are coupled with plasma membrane infoldings by dyadic or triadic junctions (Fig.2) basically similar to those of the striated muscle fibers. We have studied them before, during and after stimulation. FFF-FS showed that these complexes are labile structures able to diffentiate and dedifferentiate within milliseconds. Moreover, a transient network of endoplasmic reticulum was captured which we have named intermediate endoplasmic reticulum (IER) surrounding the PER (Fig.1). Numerous gap junctions are found in the membranous infoldings of the junctional complexes (Fig.3). When cryofractured, they cleave unusually (Fig.4-5). It is tempting to suggest that they play an important role in the conduction of the excitation.

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