scholarly journals Recent Technical Progression in Photoacoustic Imaging—Towards Using Contrast Agents and Multimodal Techniques

2021 ◽  
Vol 11 (21) ◽  
pp. 9804
Author(s):  
Zuomin Zhao ◽  
Teemu Myllylä
Keyword(s):  
Optical Absorption ◽  
Spatial Resolution ◽  
Photoacoustic Imaging ◽  
Imaging Techniques ◽  
Theoretical Background ◽  
Ultrasonic Transducers ◽  
Optical Absorption Spectroscopy ◽  
Hybrid Technique ◽  
Optical Sensitivity ◽  
Good Spatial Resolution

For combining optical and ultrasonic imaging methodologies, photoacoustic imaging (PAI) is the most important and successful hybrid technique, which has greatly contributed to biomedical research and applications. Its theoretical background is based on the photoacoustic effect, whereby a modulated or pulsed light is emitted into tissue, which selectively absorbs the optical energy of the light at optical wavelengths. This energy produces a fast thermal expansion in the illuminated tissue, generating pressure waves (or photoacoustic waves) that can be detected by ultrasonic transducers. Research has shown that optical absorption spectroscopy offers high optical sensitivity and contrast for ingredient determination, for example, while ultrasound has demonstrated good spatial resolution in biomedical imaging. Photoacoustic imaging combines these advantages, i.e., high contrast through optical absorption and high spatial resolution due to the low scattering of ultrasound in tissue. In this review, we focus on advances made in PAI in the last five years and present categories and key devices used in PAI techniques. In particular, we highlight the continuously increasing imaging depth achieved by PAI, particularly when using exogenous reagents. Finally, we discuss the potential of combining PAI with other imaging techniques.

scholarly journals High spatial resolution measurements of NO<sub>2</sub> applying Topographic Target Light scattering-Differential Optical Absorption Spectroscopy (ToTaL-DOAS)

2008 ◽  
Vol 8 (24) ◽  
pp. 7595-7601 ◽  
Author(s):  
E. Frins ◽  
U. Platt ◽  
T. Wagner
Keyword(s):  
Light Scattering ◽  
Optical Absorption ◽  
Spatial Resolution ◽  
Absorption Spectroscopy ◽  
High Spatial Resolution ◽  
Differential Optical Absorption Spectroscopy ◽  
Optical Absorption Spectroscopy ◽  
Air Masses ◽  
Target Light ◽  
Mixing Ratios

Abstract. Topographic Target Light scattering – Differential Optical Absorption Spectroscopy (ToTaL-DOAS), also called Target-DOAS, is a novel experimental procedure to retrieve trace gas concentrations present in the low atmosphere. Scattered sunlight (diffuse or specular) reflected from natural or artificial targets located at different distances are analyzed to retrieve the spatial distribution of the concentration of different trace gases like NO2, SO2 and others. We report high spatial resolution measurements of NO2 mixing ratios in the city of Montevideo (Uruguay) observing three buildings as targets with a Mini-DOAS instrument. Our instrument was 146 m, 196 m, and 280 m apart from three different buildings located along a main Avenue. We obtain temporal variation of NO2 mixing ratios between 30 ppb and 65 ppb from measurements of November 2007 and mixing ratios up to 50 ppb from measurements of August and September 2008. Our measurements demonstrate that ToTaL-DOAS observations can be made over relative short distances. In polluted air masses, the retrieved absorption signal was found to be sufficiently strong to allow measurements over distances in the range of several tens of meters.

The Application of High Resolution Chemical Imaging Techniques for Butyl Rubber Blends

2008 ◽  
Vol 81 (2) ◽  
pp. 265-275 ◽  
Author(s):  
Donald A. Winesett ◽  
Andy H. Tsou
Keyword(s):  
High Resolution ◽  
Sample Preparation ◽  
Spatial Resolution ◽  
Secondary Ion Mass Spectrometry ◽  
Imaging Techniques ◽  
Chemical Species ◽  
Chemical Imaging ◽  
Rubber Blends ◽  
Tof Sims ◽  
Good Spatial Resolution

Abstract Atomic Force Microscopy (AFM), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) imaging, and Scanning Transmission X-ray Microscopy (STXM) are applied to identical series of elastomeric blends to evaluate the relative strengths and weaknesses of each imaging technique. AFM is a high resolution, high contrast technique with straight forward sample preparation that derives contrast through elastic modulus variations, but, when used in a conventional mode, has limited chemical specificity. ToF-SIMS imaging can map phases, detect trace levels (ppm) of additives and other chemical species based on relatively straight forward sample preparation, but has poorer spatial resolution and the instrumentation is expensive. STXM has excellent chemical specificity and good spatial resolution but is only available at a beamline and requires more advanced sample preparation. Each technique will be overviewed briefly and relative merits of each will be compared based on evaluations of some commercially relevant rubber blend materials.

scholarly journals High spatial resolution measurements of NO<sub>2</sub> applying Topographic Target Light scattering-Differential Optical Absorption Spectroscopy (ToTaL-DOAS)

2008 ◽  
Vol 8 (3) ◽  
pp. 10257-10273
Author(s):  
E. Frins ◽  
U. Platt ◽  
T. Wagner
Keyword(s):  
Light Scattering ◽  
Optical Absorption ◽  
Spatial Resolution ◽  
Absorption Spectroscopy ◽  
High Spatial Resolution ◽  
Differential Optical Absorption Spectroscopy ◽  
Optical Absorption Spectroscopy ◽  
Air Masses ◽  
Target Light ◽  
Mixing Ratios

Abstract. Tomographic Target Light scattering – Differential Optical Absorption Spectroscopy (ToTaL-DOAS), also called Target-DOAS, is a novel experimental procedure to retrieve trace gas concentrations present in the low atmosphere. Scattered sunlight (partially or totally) reflected from natural or artificial targets of similar albedo located at different distances is analyzed to retrieve the concentration of different trace gases like NO2, SO2 and others. We report high spatial resolution measurements of NO2 mixing ratios in the city of Montevideo (Uruguay) observing three buildings as targets with a Mini-DOAS instrument. Our instrument was 146 m apart from the first building, 196 m from the second and 286 m from the third one. All three buildings are located along a main Avenue. We obtain temporal variation of NO2 mixing ratios between 30 ppb and 65 ppb (±2 ppb). Our measurements demonstrate that ToTaL-DOAS measurements can be made over very short distances. In polluted air masses, the retrieved absorption signal was found to be strong enough to allow measurements over distances in the range of several ten meters, and achieve a spatial resolution of 50 m approximately.

Label-Free Photoacoustic Cell-Tracking In Real-Time

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Liangzhong Xiang ◽  
Moiz Ahmad ◽  
Xiang Hu ◽  
Zhen Cheng ◽  
Lei Xing
Keyword(s):  
Optical Absorption ◽  
Real Time ◽  
Cell Tracking ◽  
Near Infrared ◽  
Photoacoustic Imaging ◽  
Imaging Techniques ◽  
Melanoma Cells ◽  
Photoacoustic Microscopy ◽  
Label Free ◽  
Tracking Method

AbstractCell-tracking method has an important role in detection of metastatic circulating tumor cells (CTCs) and cell-based therapies. Label-free imaging techniques are desirable for cell-tracking because they enable long time observations without photobleaching in living cells or tissues where labeling is not always possible. Photoacoustic microscopy is a label-free imaging technique that offers rich contrast based on nonfluorescent cellular optical absorption associated with intrinsic chromophores and pigments. We show here that photoacoustic imaging is feasible for detecting very low numbers (x 104) of melanoma cells without labeling because of the strong instinct optical absorption of melanin in near-infrared wavelength. Flowing melanoma cells are imaged with micrometerresolution (40 μm) and penetration depths of centimeters (13 mm) in real-time. Photoacoustic imaging as a new cell-tracking method provides a novel modality for cancer screening and offers insights into the underlying biological process of cancer growth and metastasis and cell therapy.

Fault Localization and Functional Testing of ICs by Lock-in Thermography

2002 ◽  
Author(s):  
O. Breitenstein ◽  
J.P. Rakotoniaina ◽  
F. Altmann ◽  
J. Schulz ◽  
G. Linse
Keyword(s):  
Spatial Resolution ◽  
Electronic Device ◽  
Imaging Techniques ◽  
Heat Diffusion ◽  
Acquisition Time ◽  
Temperature Modulation ◽  
Heat Sources ◽  
Ir Camera ◽  
Free Running ◽  
Lock In

Abstract In this paper new thermographic techniques with significant improved temperature and/or spatial resolution are presented and compared with existing techniques. In infrared (IR) lock-in thermography heat sources in an electronic device are periodically activated electrically, and the surface is imaged by a free-running IR camera. By computer processing and averaging the images over a certain acquisition time, a surface temperature modulation below 100 µK can be resolved. Moreover, the effective spatial resolution is considerably improved compared to stead-state thermal imaging techniques, since the lateral heat diffusion is suppressed in this a.c. technique. However, a serious limitation is that the spatial resolution is limited to about 5 microns due to the IR wavelength range of 3 -5 µm used by the IR camera. Nevertheless, we demonstrate that lock-in thermography reliably allows the detection of defects in ICs if their power exceeds some 10 µW. The imaging can be performed also through the silicon substrate from the backside of the chip. Also the well-known fluorescent microthermal imaging (FMI) technique can be be used in lock-in mode, leading to a temperature resolution in the mK range, but a spatial resolution below 1 micron.

scholarly journals Total Ozone Columns from the Environmental Trace Gases Monitoring Instrument (EMI) Using the DOAS Method

2021 ◽  
Vol 13 (11) ◽  
pp. 2098
Author(s):  
Yuanyuan Qian ◽  
Yuhan Luo ◽  
Fuqi Si ◽  
Haijin Zhou ◽  
Taiping Yang ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Total Ozone ◽  
Scattered Light ◽  
Trace Gases ◽  
Rapid Change ◽  
Differential Optical Absorption Spectroscopy ◽  
Optical Absorption Spectroscopy ◽  
Monitoring Instrument ◽  
Monthly Average

Global measurements of total ozone are necessary to evaluate ozone hole recovery above Antarctica. The Environmental Trace Gases Monitoring Instrument (EMI) onboard GaoFen 5, launched in May 2018, was developed to measure and monitor the global total ozone column (TOC) and distributions of other trace gases. In this study, some of the first global TOC results of the EMI using the differential optical absorption spectroscopy (DOAS) method and validation with ground-based TOC measurements and data derived from Ozone Monitoring Instrument (OMI) and TROPOspheric Monitoring Instrument (TROPOMI) observations are presented. Results show that monthly average EMI TOC data had a similar spatial distribution and a high correlation coefficient (R ≥ 0.99) with both OMI and TROPOMI TOC. Comparisons with ground-based measurements from the World Ozone and Ultraviolet Radiation Data Centre also revealed strong correlations (R > 0.9). Continuous zenith sky measurements from zenith scattered light differential optical absorption spectroscopy instruments in Antarctica were also used for validation (R = 0.9). The EMI-derived observations were able to account for the rapid change in TOC associated with the sudden stratospheric warming event in October 2019; monthly average TOC in October 2019 was 45% higher compared to October 2018. These results indicate that EMI TOC derived using the DOAS method is reliable and has the potential to be used for global TOC monitoring.

Optical Absorption Spectroscopy of DNA-Wrapped HiPco Carbon Nanotubes

2019 ◽  
Vol 943 ◽  
pp. 95-99
Author(s):  
Li Jun Wang ◽  
Kazuo Umemura
Keyword(s):  
Carbon Nanotubes ◽  
Aqueous Solution ◽  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Optical Characterization ◽  
Optical Absorption Spectroscopy ◽  
Double Stranded Dna

Optical absorption spectroscopy provides evidence for individually dispersed carbon nanotubes. A common method to disperse SWCNTs into aqueous solution is to sonicate the mixture in the presence of a double-stranded DNA (dsDNA). In this paper, optical characterization of dsDNA-wrapped HiPco carbon nanotubes (dsDNA-SWCNT) was carried out using near infrared (NIR) spectroscopy and photoluminescence (PL) experiments. The findings suggest that SWCNT dispersion is very good in the environment of DNA existing. Additionally, its dispersion depends on dsDNA concentration.

scholarly journals Satellite monitoring of different vegetation types by differential optical absorption spectroscopy (DOAS) in the red spectral range

2007 ◽  
Vol 7 (1) ◽  
pp. 69-79 ◽  
Author(s):  
T. Wagner ◽  
S. Beirle ◽  
T. Deutschmann ◽  
M. Grzegorski ◽  
U. Platt
Keyword(s):  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Spectral Range ◽  
Near Infrared ◽  
Vegetation Type ◽  
Differential Optical Absorption Spectroscopy ◽  
Trace Gas ◽  
Satellite Monitoring ◽  
Optical Absorption Spectroscopy ◽  
Vegetation Types

Abstract. A new method for the satellite remote sensing of different types of vegetation and ocean colour is presented. In contrast to existing algorithms relying on the strong change of the reflectivity in the red and near infrared spectral region, our method analyses weak narrow-band (few nm) reflectance structures (i.e. "fingerprint" structures) of vegetation in the red spectral range. It is based on differential optical absorption spectroscopy (DOAS), which is usually applied for the analysis of atmospheric trace gas absorptions. Since the spectra of atmospheric absorption and vegetation reflectance are simultaneously included in the analysis, the effects of atmospheric absorptions are automatically corrected (in contrast to other algorithms). The inclusion of the vegetation spectra also significantly improves the results of the trace gas retrieval. The global maps of the results illustrate the seasonal cycles of different vegetation types. In addition to the vegetation distribution on land, they also show patterns of biological activity in the oceans. Our results indicate that improved sets of vegetation spectra might lead to more accurate and more specific identification of vegetation type in the future.

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