High-pulse energy supercontinuum laser for high-resolution spectroscopic photoacoustic imaging of lipids in the 1650-1850 nm region.

Science.gov (United States)

Dasa, Manoj Kumar; Markos, Christos; Maria, Michael; Petersen, Christian R; Moselund, Peter M; Bang, Ole

2018-04-01

We propose a cost-effective high-pulse energy supercontinuum (SC) source based on a telecom range diode laser-based amplifier and a few meters of standard single-mode optical fiber, with a pulse energy density as high as ~25 nJ/nm in the 1650-1850 nm regime (factor >3 times higher than any SC source ever used in this wavelength range). We demonstrate how such an SC source combined with a tunable filter allows high-resolution spectroscopic photoacoustic imaging and the spectroscopy of lipids in the first overtone transition band of C-H bonds (1650-1850 nm). We show the successful discrimination of two different lipids (cholesterol and lipid in adipose tissue) and the photoacoustic cross-sectional scan of lipid-rich adipose tissue at three different locations. The proposed high-pulse energy SC laser paves a new direction towards compact, broadband and cost-effective source for spectroscopic photoacoustic imaging.

Intrauterine photoacoustic and ultrasound imaging probe

Science.gov (United States)

Miranda, Christopher; Barkley, Joel; Smith, Barbara S.

2018-04-01

Intrauterine photoacoustic and ultrasound imaging are probe-based imaging modalities with translational potential for use in detecting endometrial diseases. This deep-tissue imaging probe design allows for the retrofitting of commercially available endometrial sampling curettes. The imaging probe presented here has a 2.92-mm diameter and approximate length of 26 cm, which allows for entry into the human endometrial cavity, making it possible to use photoacoustic imaging and high-resolution ultrasound to characterize the uterus. We demonstrate the imaging probes' ability to provide structural information of an excised pig uterus using ultrasound imaging and detect photoacoustic signals at a radial depth of 1 cm.

Photoacoustic Imaging in Oxygen Detection

Directory of Open Access Journals (Sweden)

Fei Cao

2017-12-01

Full Text Available Oxygen level, including blood oxygen saturation (sO2 and tissue oxygen partial pressure (pO2, are crucial physiological parameters in life science. This paper reviews the importance of these two parameters and the detection methods for them, focusing on the application of photoacoustic imaging in this scenario. sO2 is traditionally detected with optical spectra-based methods, and has recently been proven uniquely efficient by using photoacoustic methods. pO2, on the other hand, is typically detected by PET, MRI, or pure optical approaches, yet with limited spatial resolution, imaging frame rate, or penetration depth. Great potential has also been demonstrated by employing photoacoustic imaging to overcome the existing limitations of the aforementioned techniques.

Three-dimensional Hessian matrix-based quantitative vascular imaging of rat iris with optical-resolution photoacoustic microscopy in vivo

Science.gov (United States)

Zhao, Huangxuan; Wang, Guangsong; Lin, Riqiang; Gong, Xiaojing; Song, Liang; Li, Tan; Wang, Wenjia; Zhang, Kunya; Qian, Xiuqing; Zhang, Haixia; Li, Lin; Liu, Zhicheng; Liu, Chengbo

2018-04-01

For the diagnosis and evaluation of ophthalmic diseases, imaging and quantitative characterization of vasculature in the iris are very important. The recently developed photoacoustic imaging, which is ultrasensitive in imaging endogenous hemoglobin molecules, provides a highly efficient label-free method for imaging blood vasculature in the iris. However, the development of advanced vascular quantification algorithms is still needed to enable accurate characterization of the underlying vasculature. We have developed a vascular information quantification algorithm by adopting a three-dimensional (3-D) Hessian matrix and applied for processing iris vasculature images obtained with a custom-built optical-resolution photoacoustic imaging system (OR-PAM). For the first time, we demonstrate in vivo 3-D vascular structures of a rat iris with a the label-free imaging method and also accurately extract quantitative vascular information, such as vessel diameter, vascular density, and vascular tortuosity. Our results indicate that the developed algorithm is capable of quantifying the vasculature in the 3-D photoacoustic images of the iris in-vivo, thus enhancing the diagnostic capability of the OR-PAM system for vascular-related ophthalmic diseases in vivo.

Graphene-based ultrasonic detector for photoacoustic imaging

Science.gov (United States)

Yang, Fan; Song, Wei; Zhang, Chonglei; Fang, Hui; Min, Changjun; Yuan, Xiaocong

2018-03-01

Taking advantage of optical absorption imaging contrast, photoacoustic imaging technology is able to map the volumetric distribution of the optical absorption properties within biological tissues. Unfortunately, traditional piezoceramics-based transducers used in most photoacoustic imaging setups have inadequate frequency response, resulting in both poor depth resolution and inaccurate quantification of the optical absorption information. Instead of the piezoelectric ultrasonic transducer, we develop a graphene-based optical sensor for detecting photoacoustic pressure. The refractive index in the coupling medium is modulated due to photoacoustic pressure perturbation, which creates the variation of the polarization-sensitive optical absorption property of the graphene. As a result, the photoacoustic detection is realized through recording the reflectance intensity difference of polarization light. The graphene-based detector process an estimated noise-equivalentpressure (NEP) sensitivity of 550 Pa over 20-MHz bandwidth with a nearby linear pressure response from 11.0 kPa to 53.0 kPa. Further, a graphene-based photoacoustic microscopy is built, and non-invasively reveals the microvascular anatomy in mouse ears label-freely.

Simultaneous functional photoacoustic and ultrasonic endoscopy of internal organs in vivo.

Science.gov (United States)

Yang, Joon-Mo; Favazza, Christopher; Chen, Ruimin; Yao, Junjie; Cai, Xin; Maslov, Konstantin; Zhou, Qifa; Shung, K Kirk; Wang, Lihong V

2012-08-01

At present, clinicians routinely apply ultrasound endoscopy in a variety of interventional procedures that provide treatment solutions for diseased organs. Ultrasound endoscopy not only produces high-resolution images, but also is safe for clinical use and broadly applicable. However, for soft tissue imaging, its mechanical wave-based image contrast fundamentally limits its ability to provide physiologically specific functional information. By contrast, photoacoustic endoscopy possesses a unique combination of functional optical contrast and high spatial resolution at clinically relevant depths, ideal for imaging soft tissues. With these attributes, photoacoustic endoscopy can overcome the current limitations of ultrasound endoscopy. Moreover, the benefits of photoacoustic imaging do not come at the expense of existing ultrasound functions; photoacoustic endoscopy systems are inherently compatible with ultrasound imaging, thereby enabling multimodality imaging with complementary contrast. Here we present simultaneous photoacoustic and ultrasonic dual-mode endoscopy and show its ability to image internal organs in vivo, thus illustrating its potential clinical application.

Intrauterine photoacoustic and ultrasound imaging probe.

Science.gov (United States)

Miranda, Christopher; Barkley, Joel; Smith, Barbara

2018-04-01

Intrauterine photoacoustic and ultrasound imaging are probe-based imaging modalities with translational potential for use in detecting endometrial diseases. This deep-tissue imaging probe design allows for the retrofitting of commercially available endometrial sampling curettes. The imaging probe presented here has a 2.92-mm diameter and approximate length of 26 cm, which allows for entry into the human endometrial cavity, making it possible to use photoacoustic imaging and high-resolution ultrasound to characterize the uterus. We demonstrate the imaging probes' ability to provide structural information of an excised pig uterus using ultrasound imaging and detect photoacoustic signals at a radial depth of 1 cm. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Photoacoustic imaging of teeth for dentine imaging and enamel characterization

Science.gov (United States)

Periyasamy, Vijitha; Rangaraj, Mani; Pramanik, Manojit

2018-02-01

Early detection of dental caries, cracks and lesions is needed to prevent complicated root canal treatment and tooth extraction procedures. Resolution of clinically used x-ray imaging is low, hence optical imaging techniques such as optical coherence tomography, fluorescence imaging, and Raman imaging are widely experimented for imaging dental structures. Photoacoustic effect is used in photon induced photoacoustic streaming technique to debride the root canal. In this study, the extracted teeth were imaged using photoacoustic tomography system at 1064 nm. The degradation of enamel and dentine is an indicator of onset of dental caries. Photoacoustic microscopy (PAM) was used to study the tooth enamel. Images were acquired using acoustic resolution PAM system. This was done to identify microscopic cracks and dental lesion at different anatomical sites (crown and cementum). The PAM tooth profile is an indicator of calcium distribution which is essential for demineralization studies.

A SIMULTANEOUS MULTI-PROBE DETECTION LABEL-FREE OPTICAL-RESOLUTION PHOTOACOUSTIC MICROSCOPY TECHNIQUE BASED ON MICROCAVITY TRANSDUCER

Directory of Open Access Journals (Sweden)

YONGBO WU

2013-07-01

Full Text Available We demonstrate the feasibility of simultaneous multi-probe detection for an optical-resolution photoacoustic microscopy (OR-PAM system. OR-PAM has elicited the attention of biomedical imaging researchers because of its optical absorption contrast and high spatial resolution with great imaging depth. OR-PAM allows label-free and noninvasive imaging by maximizing the optical absorption of endogenous biomolecules. However, given the inadequate absorption of some biomolecules, detection sensitivity at the same incident intensity requires improvement. In this study, a modulated continuous wave with power density less than 3 mW/cm2 (1/4 of the ANSI safety limit excited the weak photoacoustic (PA signals of biological cells. A microcavity transducer is developed based on the bulk modulus of gas five orders of magnitude lower than that of solid; air pressure variation is inversely proportional to cavity volume at the same temperature increase. Considering that a PA wave expands in various directions, detecting PA signals from different positions and adding them together can increase detection sensitivity and signal-to-noise ratio. Therefore, we employ four detectors to acquire tiny PA signals simultaneously. Experimental results show that the developed OR-PAM system allows the label-free imaging of cells with weak optical absorption.

In vivo photoacoustic imaging of mouse embryos

Science.gov (United States)

Laufer, Jan; Norris, Francesca; Cleary, Jon; Zhang, Edward; Treeby, Bradley; Cox, Ben; Johnson, Peter; Scambler, Pete; Lythgoe, Mark; Beard, Paul

2012-06-01

The ability to noninvasively image embryonic vascular anatomy in mouse models is an important requirement for characterizing the development of the normal cardiovascular system and malformations in the heart and vascular supply. Photoacoustic imaging, which can provide high resolution non invasive images of the vasculature based upon optical absorption by endogenous hemoglobin, is well suited to this application. In this study, photoacoustic images of mouse embryos were obtained ex vivo and in vivo. The images show intricate details of the embryonic vascular system to depths of up to 10 mm, which allowed whole embryos to be imaged in situ. To achieve this, an all-optical photoacoustic scanner and a novel time reversal image reconstruction algorithm, which provide deep tissue imaging capability while maintaining high spatial resolution and contrast were employed. This technology may find application as an imaging tool for preclinical embryo studies in developmental biology as well as more generally in preclinical and clinical medicine for studying pathologies characterized by changes in the vasculature.

High-Resolution Laser Photoacoustic Spectroscopy of OCS in the 12 000-13 000 cm -1 Region

Science.gov (United States)

Tranchart, S.; Hadj Bachir, I.; Huet, T. R.; Olafsson, A.; Destombes, J.-L.; Naı¨m, S.; Fayt, A.

1999-08-01

A spectrum of natural OCS has been recorded in the near-infrared region using the laser photoacoustic technique. The source is a titanium-sapphire laser pumped by an Ar+ laser. The tunable 1.5 W beam was sent through the photoacoustic cell. This windowless longitudinal resonant cell was designed with two λ/4 buffer volumes at both ends in order to reduce the noise and so to increase the sensitivity (αmin ≈ 10-9 cm-1). The spectrum of OCS, at a pressure of 90 Torr, has been recorded in the regions 11 953-12 084, 12 829-12 890, and 12 998-13 001 cm-1. In addition to the 0006-0000 band of 16O12C32S recently identified by Ch. Hornberger, B. Boor, R. Stuber, W. Demtröder, S. Naı̈m, and A. Fayt, J. Mol. Spectrosc. 179, 237-245, 1996, new weaker bands have been observed: 0405-0000, 1 1003-0000, 1006-0000, 1405-0000, 0206-0000, and 0116-0110, and also the 0006-0000 band of 16O12C34S. Effective state parameters are deduced from the band-by-band least-squares fits. The new data have also been introduced in the global analysis which takes into account the l-type resonance and the main anharmonic interactions and so allows a full understanding of the perturbations and the intensity transfers.

Dual-wavelength optical-resolution photoacoustic microscopy for cells with gold nanoparticle bioconjugates in three-dimensional cultures

Science.gov (United States)

Lee, Po-Yi; Liu, Wei-Wen; Chen, Shu-Ching; Li, Pai-Chi

2016-03-01

Three-dimensional (3D) in vitro models bridge the gap between typical two-dimensional cultures and in vivo conditions. However, conventional optical imaging methods such as confocal microscopy and two-photon microscopy cannot accurately depict cellular processing in 3D models due to limited penetration of photons. We developed a dualwavelength optical-resolution photoacoustic microscopy (OR-PAM), which provides sufficient penetration depth and spatial resolution, for studying CD8+ cytotoxic T lymphocytes (CTLs) trafficking in an in vitro 3D tumor microenvironment. CTLs play a cardinal role in host defense against tumor. Efficient trafficking of CTLs to the tumor microenvironment is a critical step for cancer immunotherapy. For the proposed system, gold nanospheres and indocyanine green (ICG) have been remarkable choices for contrast agents for photoacoustic signals due to their excellent biocompatibility and high optical absorption. With distinct absorption spectrums, targeted cells with gold nanospheres and ICG respectively can be identified by switching 523-nm and 800-nm laser irradiation. Moreover, we use an x-y galvanometer scanner to obtain high scanning rate. In the developed system, lateral and axial resolutions were designed at 1.6 μm and 5 μm, respectively. We successfully showed that dual-spectral OR-PAM can map either the distribution of CTLs with gold nanospheres at a visible wavelength of 523 nm or the 3D structure of tumor spheres with ICG in an in vitro 3D microenvironment. Our OR-PAM can provide better biological relevant information in cellular interaction and is potential for preclinical screening of anti-cancer drugs.

Photoacoustic projection imaging using an all-optical detector array

Science.gov (United States)

Bauer-Marschallinger, J.; Felbermayer, K.; Berer, T.

2018-02-01

We present a prototype for all-optical photoacoustic projection imaging. By generating projection images, photoacoustic information of large volumes can be retrieved with less effort compared to common photoacoustic computed tomography where many detectors and/or multiple measurements are required. In our approach, an array of 60 integrating line detectors is used to acquire photoacoustic waves. The line detector array consists of fiber-optic MachZehnder interferometers, distributed on a cylindrical surface. From the measured variation of the optical path lengths of the interferometers, induced by photoacoustic waves, a photoacoustic projection image can be reconstructed. The resulting images represent the projection of the three-dimensional spatial light absorbance within the imaged object onto a two-dimensional plane, perpendicular to the line detector array. The fiber-optic detectors achieve a noise-equivalent pressure of 24 Pascal at a 10 MHz bandwidth. We present the operational principle, the structure of the array, and resulting images. The system can acquire high-resolution projection images of large volumes within a short period of time. Imaging large volumes at high frame rates facilitates monitoring of dynamic processes.

Lensless high-resolution photoacoustic imaging scanner for in vivo skin imaging

Science.gov (United States)

Ida, Taiichiro; Iwazaki, Hideaki; Omuro, Toshiyuki; Kawaguchi, Yasushi; Tsunoi, Yasuyuki; Kawauchi, Satoko; Sato, Shunichi

2018-02-01

We previously launched a high-resolution photoacoustic (PA) imaging scanner based on a unique lensless design for in vivo skin imaging. The design, imaging algorithm and characteristics of the system are described in this paper. Neither an optical lens nor an acoustic lens is used in the system. In the imaging head, four sensor elements are arranged quadrilaterally, and by checking the phase differences for PA waves detected with these four sensors, a set of PA signals only originating from a chromophore located on the sensor center axis is extracted for constructing an image. A phantom study using a carbon fiber showed a depth-independent horizontal resolution of 84.0 ± 3.5 µm, and the scan direction-dependent variation of PA signals was about ± 20%. We then performed imaging of vasculature phantoms: patterns of red ink lines with widths of 100 or 200 μm formed in an acrylic block co-polymer. The patterns were visualized with high contrast, showing the capability for imaging arterioles and venues in the skin. Vasculatures in rat burn models and healthy human skin were also clearly visualized in vivo.

DFB laser diodes for sensing applications using photoacoustic spectroscopy

International Nuclear Information System (INIS)

Koeth, J; Fischer, M; Legge, M; Seufert, J; Roessner, K; Groninga, H

2010-01-01

We present typical device characteristics of novel DFB laser diodes which are employed in various sensing applications including high resolution photoacoustic spectroscopy. The laser diodes discussed are based on a genuine fabrication technology which allows for the production of ultra stable devices within a broad spectral range from 760 nm up to 3000 nm wavelength. The devices exhibit narrow linewidths down to <1 MHz which makes them ideally suited for all photoacoustic sensing applications where a high spectral purity is required. As an example we will focus on a typical medical application where these diodes are used for breath analysis using photoacoustic spectroscopy.

Photoacoustic thermal flowmetry with a single light source

Science.gov (United States)

Liu, Wei; Lan, Bangxin; Hu, Leo; Chen, Ruimin; Zhou, Qifa; Yao, Junjie

2017-09-01

We report a photoacoustic thermal flowmetry based on optical-resolution photoacoustic microscopy (OR-PAM) using a single laser source for both thermal tagging and photoacoustic excitation. When an optically absorbing medium is flowing across the optical focal zone of OR-PAM, a small volume of the medium within the optical focus is repeatedly illuminated and heated by a train of laser pulses with a high repetition rate. The average temperature of the heated volume at each laser pulse is indicated by the photoacoustic signal excited by the same laser pulse due to the well-established linear relationship between the Grueneisen coefficient and the local temperature. The thermal dynamics of the heated medium volume, which are closely related to the flow speed, can therefore be measured from the time course of the detected photoacoustic signals. Here, we have developed a lumped mathematical model to describe the time course of the photoacoustic signals as a function of the medium's flow speed. We conclude that the rising time constant of the photoacoustic signals is linearly dependent on the flow speed. Thus, the flow speed can be quantified by fitting the measured photoacoustic signals using the derived mathematical model. We first performed proof-of-concept experiments using defibrinated bovine blood flowing in a plastic tube. The experiment results have demonstrated that the proposed method has high accuracy (˜±6%) and a wide range of measurable flow speeds. We further validated the method by measuring the blood flow speeds of the microvasculature in a mouse ear in vivo.

Noninvasive photoacoustic computed tomography of mouse brain metabolism in vivo

OpenAIRE

Yao, Junjie; Xia, Jun; Maslov, Konstantin I.; Nasiriavanaki, Mohammadreza; Tsytsarev, Vassiliy; Demchenko, Alexei V.; Wang, Lihong V.

2012-01-01

We have demonstrated the feasibility of imaging mouse brain metabolism using photoacoustic computed tomography (PACT), a fast, noninvasive and functional imaging modality with optical contrast and acoustic resolution. Brain responses to forepaw stimulations were imaged transdermally and transcranially. 2-NBDG, which diffuses well across the blood–brain-barrier, provided exogenous contrast for photoacoustic imaging of glucose response. Concurrently, hemoglobin provided endogenous contrast for ...

Label-free photoacoustic microscopy of peripheral nerves

Science.gov (United States)

Matthews, Thomas Paul; Zhang, Chi; Yao, Da-Kang; Maslov, Konstantin; Wang, Lihong V.

2014-01-01

Peripheral neuropathy is a common neurological problem that affects millions of people worldwide. Diagnosis and treatment of this condition are often hindered by the difficulties in making objective, noninvasive measurements of nerve fibers. Photoacoustic microscopy (PAM) has the ability to obtain high resolution, specific images of peripheral nerves without exogenous contrast. We demonstrated the first proof-of-concept imaging of peripheral nerves using PAM. As validated by both standard histology and photoacoustic spectroscopy, the origin of photoacoustic signals is myelin, the primary source of lipids in the nerves. An extracted sciatic nerve sandwiched between two layers of chicken tissue was imaged by PAM to mimic the in vivo case. Ordered fibrous structures inside the nerve, caused by the bundles of myelin-coated axons, could be observed clearly. With further technical improvements, PAM can potentially be applied to monitor and diagnose peripheral neuropathies.

High resolution photoacoustic imaging of microvasculature in normal and cancerous bladders

Science.gov (United States)

Xie, Zhixing; Roberts, William; Carson, Paul L.; Liu, Xiaojun; Tao, Chao; Wang, Xueding

2013-03-01

We explored the potential of an emerging laser-based technology, photoacoustic imaging (PAI), for bladder cancer diagnosis through high resolution imaging of microvasculature in the interior bladder tissues. Images of ex vivo canine bladders demonstrated the excellent ability of PAI to map three-dimensional microvasculature in optically scattering bladder tissues. By comparing the results from human bladder specimens affected by cancer to those from the normal control, the feasibility of PAI in differentiating malignant from benign bladder tissues was explored. The reported distinctive morphometric characteristics of tumor microvasculature can be seen in the images from cancer samples, suggesting that PAI may allow in vivo assessment of neoangiogenesis that is closely associated with bladder cancer generation and progression. By presenting subsurface morphological and physiological information in bladder tissues, PAI, when performed in a similar way to that in conventional endoscopy, provides an opportunity for improved diagnosis, staging and treatment guidance of bladder cancer.

Numerical Study of Photoacoustic Pressure for Cancer Therapy

Directory of Open Access Journals (Sweden)

Thomas Grosges

2016-11-01

Full Text Available A commonly used therapy for cancer is based on the necrosis of cells induced by heating through the illumination of nanoparticles embedded in cells. Recently, the photoacoustic pressure shock induced by the illumination pulse was proved and this points to another means of cell destruction. The purpose of this study is to propose a model of the photoacoustic pressure in cells. The numerical resolution of the problem requires the accurate computation of the electromagnetism, the temperature and the pressure around the nanostructures embedded in a cell. Here, the problem of the interaction between an electromagnetic excitation and a gold nanoparticle embedded in a cell domain is solved. The variations of the thermal and photoacoustic pressures are studied in order to analyze the pressure shock wave inducing the collapse of the cell’s membrane in cancer therapy.

Fiber-optic annular detector array for large depth of field photoacoustic macroscopy

Directory of Open Access Journals (Sweden)

Johannes Bauer-Marschallinger

2017-03-01

Full Text Available We report on a novel imaging system for large depth of field photoacoustic scanning macroscopy. Instead of commonly used piezoelectric transducers, fiber-optic based ultrasound detection is applied. The optical fibers are shaped into rings and mainly receive ultrasonic signals stemming from the ring symmetry axes. Four concentric fiber-optic rings with varying diameters are used in order to increase the image quality. Imaging artifacts, originating from the off-axis sensitivity of the rings, are reduced by coherence weighting. We discuss the working principle of the system and present experimental results on tissue mimicking phantoms. The lateral resolution is estimated to be below 200 μm at a depth of 1.5 cm and below 230 μm at a depth of 4.5 cm. The minimum detectable pressure is in the order of 3 Pa. The introduced method has the potential to provide larger imaging depths than acoustic resolution photoacoustic microscopy and an imaging resolution similar to that of photoacoustic computed tomography.

Fiber-optic annular detector array for large depth of field photoacoustic macroscopy.

Science.gov (United States)

Bauer-Marschallinger, Johannes; Höllinger, Astrid; Jakoby, Bernhard; Burgholzer, Peter; Berer, Thomas

2017-03-01

We report on a novel imaging system for large depth of field photoacoustic scanning macroscopy. Instead of commonly used piezoelectric transducers, fiber-optic based ultrasound detection is applied. The optical fibers are shaped into rings and mainly receive ultrasonic signals stemming from the ring symmetry axes. Four concentric fiber-optic rings with varying diameters are used in order to increase the image quality. Imaging artifacts, originating from the off-axis sensitivity of the rings, are reduced by coherence weighting. We discuss the working principle of the system and present experimental results on tissue mimicking phantoms. The lateral resolution is estimated to be below 200 μm at a depth of 1.5 cm and below 230 μm at a depth of 4.5 cm. The minimum detectable pressure is in the order of 3 Pa. The introduced method has the potential to provide larger imaging depths than acoustic resolution photoacoustic microscopy and an imaging resolution similar to that of photoacoustic computed tomography.

Improvement of resolution in full-view linear-array photoacoustic computed tomography using a novel adaptive weighting method

Science.gov (United States)

Omidi, Parsa; Diop, Mamadou; Carson, Jeffrey; Nasiriavanaki, Mohammadreza

2017-03-01

Linear-array-based photoacoustic computed tomography is a popular methodology for deep and high resolution imaging. However, issues such as phase aberration, side-lobe effects, and propagation limitations deteriorate the resolution. The effect of phase aberration due to acoustic attenuation and constant assumption of the speed of sound (SoS) can be reduced by applying an adaptive weighting method such as the coherence factor (CF). Utilizing an adaptive beamforming algorithm such as the minimum variance (MV) can improve the resolution at the focal point by eliminating the side-lobes. Moreover, invisibility of directional objects emitting parallel to the detection plane, such as vessels and other absorbing structures stretched in the direction perpendicular to the detection plane can degrade resolution. In this study, we propose a full-view array level weighting algorithm in which different weighs are assigned to different positions of the linear array based on an orientation algorithm which uses the histogram of oriented gradient (HOG). Simulation results obtained from a synthetic phantom show the superior performance of the proposed method over the existing reconstruction methods.

The characterization of an economic and portable LED-based photoacoustic imaging system to facilitate molecular imaging

Directory of Open Access Journals (Sweden)

Ali Hariri

2018-03-01

Full Text Available Photoacoustic imaging (PAI is a non-invasive, high-resolution hybrid imaging modality that combines optical excitation and ultrasound detection. PAI can image endogenous chromophores (melanin, hemoglobin, etc. and exogenous contrast agents in different medical applications. However, most current equipment uses sophisticated and complicated OPO lasers with tuning and stability features inconsistent with broad clinical deployment. As the number of applications of PAI in medicine increases, there is an urgent need to make the imaging equipment more compact, portable, and affordable. Here, portable light emitting diode – based photoacoustic imaging (PLED-PAI was introduced and characterized in terms of system specifications, light source characterizations, photoacoustic spatial/temporal resolution, and penetration. The system uses two LED arrays attached to the sides of a conventional ultrasound transducer. The LED pulse repetition rate is tunable between 1 K Hz, 2 K Hz, 3 K Hz, and 4 K Hz. The axial resolution was 0.268 mm, and the lateral resolution was between 0.55 and 0.59 mm. The system could detect optical absorber (pencil lead at a depth of 3.2 cm and the detection limits of indocyanine green (ICG and methylene blue (MB were 9 μM and 0.78 mM. In vivo imaging of labeled human mesenchymal stem cells was achieved to confirm compatibility with small animal imaging. The characterization we report here may have value to other groups evaluating commercially available photoacoustic imaging equipment. Keywords: Portable photoacoustic imaging, LED, Optoacoustic imaging, Molecular imaging

Integrated photoacoustic/ultrasound imaging: applications and new techniques

NARCIS (Netherlands)

van den Berg, P.J.

2017-01-01

Photoacoustic imaging (PAI) is a unique combination of optical sensitivity to tissue chromophores like hemoglobin, and ultrasonic resolution. Research in this PhD thesis is made possible by the development of a probe that combines PAI with regular ultrasound imaging. This probe is handheld and

High-speed photoacoustic imaging using an LED-based photoacoustic imaging system

Science.gov (United States)

Sato, Naoto; Kuniyil Ajith Singh, Mithun; Shigeta, Yusuke; Hanaoka, Takamitsu; Agano, Toshitaka

2018-02-01

Recently we developed a multispectral LED-based photoacoustic/ultrasound imaging system (AcousticX) and have been continuously working on its technical/functional improvements. AcousticX is a linear array ultrasound transducer (128 elements, 10 MHz)-based system in which LED arrays (selectable wavelengths, pulse repetition frequency: 4 kHz, pulse width: tunable from 40 - 100 ns) are fixed on both sides of the transducer to illuminate the tissue for photoacoustic imaging. The ultrasound/photoacoustic data from all 128 elements can be simultaneously acquired, processed and displayed. We already demonstrated our system's capability to perform photoacoustic/ultrasound imaging for dynamic imaging of the tissue at a frame rate of 10 Hz (for example to visualize the pulsation of arteries in vivo in human subjects). In this work, we present the development of a new high-speed imaging mode in AcousticX. In this mode, instead of toggling between ultrasound and photoacoustic measurements, it is possible to continuously acquire only photoacoustic data for 1.5 seconds with a time interval of 1 ms. With this improvement, we can record photoacoustic signals from the whole aperture (38 mm) at fast rate and can be reviewed later at different speeds for analyzing dynamic changes in the photoacoustic signals. We believe that AcousticX with this new high-speed mode opens up a feasible technical path for multiple dynamic studies, for example one which focus on imaging the response of voltage sensitive dyes. We envisage to improve the acquisition speed further in future for exploring ultra-high-speed applications.

A photoacoustic tomography system for imaging of biological tissues

International Nuclear Information System (INIS)

Su Yixiong; Zhang Fan; Xu Kexin; Yao Jianquan; Wang, Ruikang K

2005-01-01

Non-invasive laser-induced photoacoustic tomography (PAT) is a promising imaging modality in the biomedical optical imaging field. This technology, based on the intrinsic optical properties of tissue and ultrasonic detection, overcomes the resolution disadvantage of pure-optical imaging caused by strong light scattering and the contrast and speckle disadvantages of pure ultrasonic imaging. Here, we report a PAT experimental system constructed in our laboratory. In our system, a Q-switched Nd : YAG pulse laser operated at 532 nm with a 8 ns pulse width is used to generate a photoacoustic signal. By using this system, the two-dimensional distribution of optical absorption in the tissue-mimicking phantom is reconstructed and has an excellent agreement with the original ones. The spatial resolution of the imaging system approaches 100 μm through about 4 cm of highly scattering medium

Speed of sound and photoacoustic imaging with an optical camera based ultrasound detection system

Science.gov (United States)

Nuster, Robert; Paltauf, Guenther

2017-07-01

CCD camera based optical ultrasound detection is a promising alternative approach for high resolution 3D photoacoustic imaging (PAI). To fully exploit its potential and to achieve an image resolution SOS) in the image reconstruction algorithm. Hence, in the proposed work the idea and a first implementation are shown how speed of sound imaging can be added to a previously developed camera based PAI setup. The current setup provides SOS-maps with a spatial resolution of 2 mm and an accuracy of the obtained absolute SOS values of about 1%. The proposed dual-modality setup has the potential to provide highly resolved and perfectly co-registered 3D photoacoustic and SOS images.

Isometric multimodal photoacoustic microscopy based on optically transparent micro-ring ultrasonic detection.

Science.gov (United States)

Dong, Biqin; Li, Hao; Zhang, Zhen; Zhang, Kevin; Chen, Siyu; Sun, Cheng; Zhang, Hao F

2015-01-01

Photoacoustic microscopy (PAM) is an attractive imaging tool complementary to established optical microscopic modalities by providing additional molecular specificities through imaging optical absorption contrast. While the development of optical resolution photoacoustic microscopy (ORPAM) offers high lateral resolution, the acoustically-determined axial resolution is limited due to the constraint in ultrasonic detection bandwidth. ORPAM with isometric spatial resolution along both axial and lateral direction is yet to be developed. Although recently developed sophisticated optical illumination and reconstruction methods offer improved axial resolution in ORPAM, the image acquisition procedures are rather complicated, limiting their capabilities for high-speed imaging and being easily integrated with established optical microscopic modalities. Here we report an isometric ORPAM based on an optically transparent micro-ring resonator ultrasonic detector and a commercial inverted microscope platform. Owing to the superior spatial resolution and the ease of integrating our ORPAM with established microscopic modalities, single cell imaging with extrinsic fluorescence staining, intrinsic autofluorescence, and optical absorption can be achieved simultaneously. This technique holds promise to greatly improve the accessibility of PAM to the broader biomedical researchers.

The characterization of an economic and portable LED-based photoacoustic imaging system to facilitate molecular imaging.

Science.gov (United States)

Hariri, Ali; Lemaster, Jeanne; Wang, Junxin; Jeevarathinam, AnanthaKrishnan S; Chao, Daniel L; Jokerst, Jesse V

2018-03-01

Photoacoustic imaging (PAI) is a non-invasive, high-resolution hybrid imaging modality that combines optical excitation and ultrasound detection. PAI can image endogenous chromophores (melanin, hemoglobin, etc.) and exogenous contrast agents in different medical applications. However, most current equipment uses sophisticated and complicated OPO lasers with tuning and stability features inconsistent with broad clinical deployment. As the number of applications of PAI in medicine increases, there is an urgent need to make the imaging equipment more compact, portable, and affordable. Here, portable light emitting diode - based photoacoustic imaging (PLED-PAI) was introduced and characterized in terms of system specifications, light source characterizations, photoacoustic spatial/temporal resolution, and penetration. The system uses two LED arrays attached to the sides of a conventional ultrasound transducer. The LED pulse repetition rate is tunable between 1 K Hz, 2 K Hz, 3 K Hz, and 4 K Hz. The axial resolution was 0.268 mm, and the lateral resolution was between 0.55 and 0.59 mm. The system could detect optical absorber (pencil lead) at a depth of 3.2 cm and the detection limits of indocyanine green (ICG) and methylene blue (MB) were 9 μM and 0.78 mM. In vivo imaging of labeled human mesenchymal stem cells was achieved to confirm compatibility with small animal imaging. The characterization we report here may have value to other groups evaluating commercially available photoacoustic imaging equipment.

Photoacoustic imaging of human lymph nodes with endogenous lipid and hemoglobin contrast

Science.gov (United States)

Guggenheim, James A.; Allen, Thomas J.; Plumb, Andrew; Zhang, Edward Z.; Rodriguez-Justo, Manuel; Punwani, Shonit; Beard, Paul C.

2015-05-01

Lymph nodes play a central role in metastatic cancer spread and are a key clinical assessment target. Abnormal node vascularization, morphology, and size may be indicative of disease but can be difficult to visualize with sufficient accuracy using existing clinical imaging modalities. To explore the potential utility of photoacoustic imaging for the assessment of lymph nodes, images of ex vivo samples were obtained at multiple wavelengths using a high-resolution three-dimensional photoacoustic scanner. These images showed that hemoglobin based contrast reveals nodal vasculature and lipid-based contrast reveals the exterior node size, shape, and boundary integrity. These two sources of complementary contrast may allow indirect observation of cancer, suggesting a future role for photoacoustic imaging as a tool for the clinical assessment of lymph nodes.

Characterization of seeds with different moisture content by photoacoustic microscopy

Energy Technology Data Exchange (ETDEWEB)

Dominguez Pacheco, Arturo; Hernandez Aguilar, Claudia; Marinez Ortiz, Efrain [Instituto Politecnico Nacional, Sepi-Esime, Zacatenco. Unidad Profesional ' Adolfo Lopez Mateos' . Col. Lindavista. Mexico D.F., CP 07738 (Mexico); Cruz-Orea, Alfredo; Ayala-Maycotte, Esther, E-mail: fartur@hotmail.co [Departamento de Fisica, CINVESTAV - IPN, A. P. 14-740, Mexico D.F., C.P. 07360 (Mexico)

2010-03-01

Photoacoustic (PA) technique has important applications for material characterization and nondestructive evaluation of opaque solid materials. PA microscopy allows the acquisition of information of samples with inhomogeneous structures as agricultural seeds. A determining factor for seed safe storage is their moisture content. Seeds stored at high moisture content exhibit increased respiration, heating, and fungal invasion resulting in poor seed vigor and viability. Low moisture content, in the seed to be stored, is the best prevention for these problems. In this study, Photoacoustic Microscopy (PAM) was used to characterize seeds with different moisture content. In the PAM experimental setup the photoacoustic cell and its sensor, an electret microphone, are mounted on an x-y stage of mobile axes, with spatial resolution of 70 {mu}m. The excitation light source is a fiber coupled laser diode, at 650 nm wavelength, modulated in intensity at 1 Hz of frequency, by the reference oscillator of a lock-in amplifier. By using a microscope objective the laser beam was focused on the seed surface. The resolution was enough to obtain differences in the obtained images, which are dependent on the moisture content. This method, to study differences in the seed moisture content, is nondestructive and could be useful for a sustainable Agriculture.

Photoacoustic Point Source

International Nuclear Information System (INIS)

Calasso, Irio G.; Craig, Walter; Diebold, Gerald J.

2001-01-01

We investigate the photoacoustic effect generated by heat deposition at a point in space in an inviscid fluid. Delta-function and long Gaussian optical pulses are used as sources in the wave equation for the displacement potential to determine the fluid motion. The linear sound-generation mechanism gives bipolar photoacoustic waves, whereas the nonlinear mechanism produces asymmetric tripolar waves. The salient features of the photoacoustic point source are that rapid heat deposition and nonlinear thermal expansion dominate the production of ultrasound

Reflection-artifact-free photoacoustic imaging using PAFUSion (photoacoustic-guided focused ultrasound)

Science.gov (United States)

Kuniyil Ajith Singh, Mithun; Jaeger, Michael; Frenz, Martin; Steenbergen, Wiendelt

2016-03-01

Reflection artifacts caused by acoustic inhomogeneities are a main challenge to deep-tissue photoacoustic imaging. Photoacoustic transients generated by the skin surface and superficial vasculature will propagate into the tissue and reflect back from echogenic structures to generate reflection artifacts. These artifacts can cause problems in image interpretation and limit imaging depth. In its basic version, PAFUSion mimics the inward travelling wave-field from blood vessel-like PA sources by applying focused ultrasound pulses, and thus provides a way to identify reflection artifacts. In this work, we demonstrate reflection artifact correction in addition to identification, towards obtaining an artifact-free photoacoustic image. In view of clinical applications, we implemented an improved version of PAFUSion in which photoacoustic data is backpropagated to imitate the inward travelling wave-field and thus the reflection artifacts of a more arbitrary distribution of PA sources that also includes the skin melanin layer. The backpropagation is performed in a synthetic way based on the pulse-echo acquisitions after transmission on each single element of the transducer array. We present a phantom experiment and initial in vivo measurements on human volunteers where we demonstrate significant reflection artifact reduction using our technique. The results provide a direct confirmation that reflection artifacts are prominent in clinical epi-photoacoustic imaging, and that PAFUSion can reduce these artifacts significantly to improve the deep-tissue photoacoustic imaging.

Model-Based Photoacoustic Image Reconstruction using Compressed Sensing and Smoothed L0 Norm

OpenAIRE

Mozaffarzadeh, Moein; Mahloojifar, Ali; Nasiriavanaki, Mohammadreza; Orooji, Mahdi

2018-01-01

Photoacoustic imaging (PAI) is a novel medical imaging modality that uses the advantages of the spatial resolution of ultrasound imaging and the high contrast of pure optical imaging. Analytical algorithms are usually employed to reconstruct the photoacoustic (PA) images as a result of their simple implementation. However, they provide a low accurate image. Model-based (MB) algorithms are used to improve the image quality and accuracy while a large number of transducers and data acquisition a...

Miniature fibre optic probe for minimally invasive photoacoustic sensing

Science.gov (United States)

Mathews, Sunish J.; Zhang, Edward Z.; Desjardins, Adrien E.; Beard, Paul C.

2016-03-01

A miniature (175 μm) all-optical photoacoustic probe has been developed for minimally invasive sensing and imaging applications. The probe comprises a single optical fibre which delivers the excitation light and a broadband 50 MHz Fabry-Pérot (F-P) ultrasound sensor at the distal end for detecting the photoacoustic waves. A graded index lens proximal to the F-P sensor is used to reduce beam walk-off and thus increase sensitivity as well as confine the excitation beam in order to increase lateral spatial resolution. The probe was evaluated in non-scattering media and found to provide lateral and axial resolutions of < 100 μm and < 150 μm respectively for distances up to 1 cm from the tip of the probe. The ability of the probe to detect a blood vessel mimicking phantom at distances up to 7 mm from the tip was demonstrated in order to illustrate its potential suitability for needle guidance applications.

A novel fiber laser development for photoacoustic microscopy

Science.gov (United States)

Yavas, Seydi; Aytac-Kipergil, Esra; Arabul, Mustafa U.; Erkol, Hakan; Akcaalan, Onder; Eldeniz, Y. Burak; Ilday, F. Omer; Unlu, Mehmet B.

2013-03-01

Photoacoustic microscopy, as an imaging modality, has shown promising results in imaging angiogenesis and cutaneous malignancies like melanoma, revealing systemic diseases including diabetes, hypertension, tracing drug efficiency and assessment of therapy, monitoring healing processes such as wound cicatrization, brain imaging and mapping. Clinically, photoacoustic microscopy is emerging as a capable diagnostic tool. Parameters of lasers used in photoacoustic microscopy, particularly, pulse duration, energy, pulse repetition frequency, and pulse-to-pulse stability affect signal amplitude and quality, data acquisition speed and indirectly, spatial resolution. Lasers used in photoacoustic microscopy are typically Q-switched lasers, low-power laser diodes, and recently, fiber lasers. Significantly, the key parameters cannot be adjusted independently of each other, whereas microvasculature and cellular imaging, e.g., have different requirements. Here, we report an integrated fiber laser system producing nanosecond pulses, covering the spectrum from 600 nm to 1100 nm, developed specifically for photoacoustic excitation. The system comprises of Yb-doped fiber oscillator and amplifier, an acousto-optic modulator and a photonic-crystal fiber to generate supercontinuum. Complete control over the pulse train, including generation of non-uniform pulse trains, is achieved via the AOM through custom-developed field-programmable gate-array electronics. The system is unique in that all the important parameters are adjustable: pulse duration in the range of 1-3 ns, pulse energy up to 10 μJ, repetition rate from 50 kHz to 3 MHz. Different photocoustic imaging probes can be excited with the ultrabroad spectrum. The entire system is fiber-integrated; guided-beam-propagation rendersit misalignment free and largely immune to mechanical perturbations. The laser is robust, low-cost and built using readily available components.

Realistic tissue visualization using photoacoustic image

Science.gov (United States)

Cho, Seonghee; Managuli, Ravi; Jeon, Seungwan; Kim, Jeesu; Kim, Chulhong

2018-02-01

Visualization methods are very important in biomedical imaging. As a technology that understands life, biomedical imaging has the unique advantage of providing the most intuitive information in the image. This advantage of biomedical imaging can be greatly improved by choosing a special visualization method. This is more complicated in volumetric data. Volume data has the advantage of containing 3D spatial information. Unfortunately, the data itself cannot directly represent the potential value. Because images are always displayed in 2D space, visualization is the key and creates the real value of volume data. However, image processing of 3D data requires complicated algorithms for visualization and high computational burden. Therefore, specialized algorithms and computing optimization are important issues in volume data. Photoacoustic-imaging is a unique imaging modality that can visualize the optical properties of deep tissue. Because the color of the organism is mainly determined by its light absorbing component, photoacoustic data can provide color information of tissue, which is closer to real tissue color. In this research, we developed realistic tissue visualization using acoustic-resolution photoacoustic volume data. To achieve realistic visualization, we designed specialized color transfer function, which depends on the depth of the tissue from the skin. We used direct ray casting method and processed color during computing shader parameter. In the rendering results, we succeeded in obtaining similar texture results from photoacoustic data. The surface reflected rays were visualized in white, and the reflected color from the deep tissue was visualized red like skin tissue. We also implemented the CUDA algorithm in an OpenGL environment for real-time interactive imaging.

Rationally encapsulated gold nanorods improving both linear and nonlinear photoacoustic imaging contrast in vivo.

Science.gov (United States)

Gao, Fei; Bai, Linyi; Liu, Siyu; Zhang, Ruochong; Zhang, Jingtao; Feng, Xiaohua; Zheng, Yuanjin; Zhao, Yanli

2017-01-07

Photoacoustic tomography has emerged as a promising non-invasive imaging technique that integrates the merits of high optical contrast with high ultrasound resolution in deep scattering medium. Unfortunately, the blood background in vivo seriously impedes the quality of imaging due to its comparable optical absorption with contrast agents, especially in conventional linear photoacoustic imaging modality. In this study, we demonstrated that two hybrids consisting of gold nanorods (Au NRs) and zinc tetra(4-pyridyl)porphyrin (ZnTPP) exhibited a synergetic effect in improving optical absorption, conversion efficiency from light to heat, and thermoelastic expansion, leading to a notable enhancement in both linear (four times greater) and nonlinear (more than six times) photoacoustic signals as compared with conventional Au NRs. Subsequently, we carefully investigated the interesting factors that may influence photoacoustic signal amplification, suggesting that the coating of ZnTPP on Au NRs could result in the reduction of gold interfacial thermal conductance with a solvent, so that the heat is more confined within the nanoparticle clusters for a significant enhancement of local temperature. Hence, both the linear and nonlinear photoacoustic signals are enhanced on account of better thermal confinement. The present work not only shows that ZnTPP coated Au NRs could serve as excellent photoacoustic nanoamplifiers, but also brings a perspective for photoacoustic image-guided therapy.

Validating tyrosinase homologue melA as a photoacoustic reporter gene for imaging Escherichia coli

Science.gov (United States)

Paproski, Robert J.; Li, Yan; Barber, Quinn; Lewis, John D.; Campbell, Robert E.; Zemp, Roger

2015-10-01

To understand the pathogenic processes for infectious bacteria, appropriate research tools are required for replicating and characterizing infections. Fluorescence and bioluminescence imaging have primarily been used to image infections in animal models, but optical scattering in tissue significantly limits imaging depth and resolution. Photoacoustic imaging, which has improved depth-to-resolution ratio compared to conventional optical imaging, could be useful for visualizing melA-expressing bacteria since melA is a bacterial tyrosinase homologue which produces melanin. Escherichia coli-expressing melA was visibly dark in liquid culture. When melA-expressing bacteria in tubes were imaged with a VisualSonics Vevo LAZR system, the signal-to-noise ratio of a 9× dilution sample was 55, suggesting that ˜20 bacteria cells could be detected with our system. Multispectral (680, 700, 750, 800, 850, and 900 nm) analysis of the photoacoustic signal allowed unmixing of melA-expressing bacteria from blood. To compare photoacoustic reporter gene melA (using Vevo system) with luminescent and fluorescent reporter gene Nano-lantern (using Bruker Xtreme In-Vivo system), tubes of bacteria expressing melA or Nano-lantern were submerged 10 mm in 1% Intralipid, spaced between melA-expressing bacteria even when the tubes were less than 1 mm from each other, while bioluminescence and fluorescence imaging could not resolve the two tubes of Nano-lantern-expressing bacteria even when the tubes were spaced 10 mm from each other. After injecting 100-μL of melA-expressing bacteria in the back flank of a chicken embryo, photoacoustic imaging allowed visualization of melA-expressing bacteria up to 10-mm deep into the embryo. Photoacoustic signal from melA could also be separated from deoxy- and oxy-hemoglobin signal observed within the embryo and chorioallantoic membrane. Our results suggest that melA is a useful photoacoustic reporter gene for visualizing bacteria, and further work

Noninvasive photoacoustic computed tomography of mouse brain metabolism in vivo

Science.gov (United States)

Yao, Junjie; Xia, Jun; Maslov, Konstantin I.; Nasiriavanaki, Mohammadreza; Tsytsarev, Vassiliy; Demchenko, Alexei V.; Wang, Lihong V.

2012-01-01

We have demonstrated the feasibility of imaging mouse brain metabolism using photoacoustic computed tomography (PACT), a fast, noninvasive and functional imaging modality with optical contrast and acoustic resolution. Brain responses to forepaw stimulations were imaged transdermally and transcranially. 2-NBDG, which diffuses well across the blood-brain-barrier, provided exogenous contrast for photoacoustic imaging of glucose response. Concurrently, hemoglobin provided endogenous contrast for photoacoustic imaging of hemodynamic response. Glucose and hemodynamic responses were quantitatively decoupled by using two-wavelength measurements. We found that glucose uptake and blood perfusion around the somatosensory region of the contralateral hemisphere were both increased by stimulations, indicating elevated neuron activity. While the glucose response area was more homogenous and confined within the somatosensory region, the hemodynamic response area had a clear vascular pattern and spread wider than the somatosensory region. Our results demonstrate that 2-NBDG-enhanced PACT is a promising tool for noninvasive studies of brain metabolism. PMID:22940116

Non-invasive imaging of epileptic seizures in vivo using photoacoustic tomography

Energy Technology Data Exchange (ETDEWEB)

Zhang Qizhi; Carney, Paul R; Yuan Zhen; Jiang Huabei [J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL 32611 (United States); Liu Zhao [Department of Pediatrics, Division of Pediatric Neurology, University of Florida, Gainesville, FL 32610 (United States); Chen Huanxin; Roper, Steven N [Department of Neurosurgery, University of Florida, Gainesville, FL 32610-0265 (United States)], E-mail: hjiang@bme.ufl.edu

2008-04-07

Non-invasive laser-induced photoacoustic tomography (PAT) is an emerging imaging modality that has the potential to image the dynamic function of the brain due to its unique ability of imaging biological tissues with high optical contrast and ultrasound resolution. Here we report the first application of our finite-element-based PAT for imaging of epileptic seizures in an animal model. In vivo photoacoustic images were obtained in rats with focal seizures induced by microinjection of bicuculline, a GABA{sub A} antagonist, into the neocortex. The seizure focus was accurately localized by PAT as confirmed with gold-standard electroencephalogram (EEG). Compared to the existing neuroimaging modalities, PAT not only has the unprecedented advantage of high spatial and temporal resolution in a single imaging modality, but also is portable and low in cost, making it possible to bring brain imaging to the bedside.

In vivo imaging of cell nuclei by photoacoustic microscopy without staining

Science.gov (United States)

Yao, Da-Kang; Chen, Ruimin; Maslov, Konstantin; Zhou, Qifa; Wang, Lihong V.

2012-02-01

Ultraviolet photoacoustic microscopy (UVPAM) can image cell nuclei in vivo with high contrast and resolution noninvasively without staining. Here, we used UV light at wavelengths of 210-310 nm for excitation of DNA and RNA to produce photoacoustic waves. We applied the UVPAM to in vivo imaging of cell nuclei in mouse skin, and obtained UVPAM images of the unstained cell nuclei at wavelengths of 245-282 nm as ultrasound gel was used for acoustic coupling. The largest ratio of contrast to noise was found for the images of cell nuclei at a 250 nm wavelength.

Fast and compact optical-resolution photoacoustic microscopy using a water-proofing two-axis MEMS scanner, and a step forward to clinical applications

Science.gov (United States)

Kim, Jin Young; Lee, Changho; Lim, Geunbae; Kim, Chulhong

2016-03-01

Optical-resolution photoacoustic microscopy (OR-PAM) is a novel microscopic tool to provide in vivo optically sensitive images in biomedical research. Conventional OR-PAM systems are typically slow and bulky because of the linear scanning stages with stepping motors. For practical purposes, however, fast imaging speed and small footprint are crucial. To address these issues, we have developed a real-time compact OR-PAM system equipped with a waterproof two-axis MEMS scanner. The OR-PAM system consists of key components such as an ultrasonic transducer with a bandwidth of 50 MHz, an opto-acoustic beam combiner (BC), and an MEMS scanner. These are all installed inside a small water tank, with dimensions of 30 mm × 90 mm × 30 mm along the x-, y-, and z-axes, respectively. A pulsed laser with a repetition rate of 50 kHz is confocally aligned with the photoacoustic (PA) waves in the BC to maximize the SNRs. The fast scanning ability of the MEMS scanner fully utilizes the A-scan speed of 50 kHz. For instance, the B- and C-scan imaging speeds are 125 Hz and 0.625 Hz, respectively, when the acquired PA maximum amplitude projection image has 200 × 200 pixels along the x- and y-axes, respectively. The measured lateral resolution of 3.6 μm and axial resolution of 27 μm are sufficient to resolve the small capillaries. Finally, we have successfully obtained in vivo PA images of iris microvasculatures in mice. This real-time and compact OR-PAM system is optimized to examine small animals in clinical studies.

Listening to light scattering in turbid media: quantitative optical scattering imaging using photoacoustic measurements with one-wavelength illumination

International Nuclear Information System (INIS)

Yuan, Zhen; Li, Xiaoqi; Xi, Lei

2014-01-01

Biomedical photoacoustic tomography (PAT), as a potential imaging modality, can visualize tissue structure and function with high spatial resolution and excellent optical contrast. It is widely recognized that the ability of quantitatively imaging optical absorption and scattering coefficients from photoacoustic measurements is essential before PAT can become a powerful imaging modality. Existing quantitative PAT (qPAT), while successful, has been focused on recovering absorption coefficient only by assuming scattering coefficient a constant. An effective method for photoacoustically recovering optical scattering coefficient is presently not available. Here we propose and experimentally validate such a method for quantitative scattering coefficient imaging using photoacoustic data from one-wavelength illumination. The reconstruction method developed combines conventional PAT with the photon diffusion equation in a novel way to realize the recovery of scattering coefficient. We demonstrate the method using various objects having scattering contrast only or both absorption and scattering contrasts embedded in turbid media. The listening-to-light-scattering method described will be able to provide high resolution scattering imaging for various biomedical applications ranging from breast to brain imaging. (papers)

Biomedical photoacoustics: fundamentals, instrumentation and perspectives on nanomedicine.

Science.gov (United States)

Zou, Chunpeng; Wu, Beibei; Dong, Yanyan; Song, Zhangwei; Zhao, Yaping; Ni, Xianwei; Yang, Yan; Liu, Zhe

Photoacoustic imaging (PAI) is an integrated biomedical imaging modality which combines the advantages of acoustic deep penetration and optical high sensitivity. It can provide functional and structural images with satisfactory resolution and contrast which could provide abundant pathological information for disease-oriented diagnosis. Therefore, it has found vast applications so far and become a powerful tool of precision nanomedicine. However, the investigation of PAI-based imaging nanomaterials is still in its infancy. This perspective article aims to summarize the developments in photoacoustic technologies and instrumentations in the past years, and more importantly, present a bright outlook for advanced PAI-based imaging nanomaterials as well as their emerging biomedical applications in nanomedicine. Current challenges and bottleneck issues have also been discussed and elucidated in this article to bring them to the attention of the readership.

In vivo study of rat cortical hemodynamics using a stereotaxic-apparatus-compatible photoacoustic microscope.

Science.gov (United States)

Guo, Heng; Chen, Qian; Qi, Weizhi; Chen, Xingxing; Xi, Lei

2018-04-19

Brain imaging is an important technique in cognitive neuroscience. In this article, we designed a stereotaxic-apparatus-compatible photoacoustic microscope for the studies of rat cortical hemodynamics. Compared with existing optical resolution photoacoustic microscopy (ORPAM) systems, the probe owns feature of fast, light and miniature. In this microscope, we integrated a miniaturized ultrasound transducer with a center frequency of 10 MHz to detect photoacoustic signals and a 2-dimensional (2D) microelectromechanical system (MEMS) scanner to achieve raster scanning of the optical focus. Based on phantom evaluation, this imaging probe has a high lateral resolution of 3.8 μm and an effective imaging domain of 2 × 2 mm 2 . Different from conventional ORPAMs, combining with standard stereotaxic apparatus enables broad studies of rodent brains without any motion artifact. To show its capability, we successfully captured red blood cell flow in the capillary, monitored the vascular changes during bleeding and blood infusion and visualized cortical hemodynamics induced by middle cerebral artery occlusion. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mathematics of Photoacoustic and Thermoacoustic Tomography

KAUST Repository

Kuchment, Peter; Kunyansky, Leonid

2011-01-01

The chapter surveys the mathematical models, problems, and algorithms of the thermoacoustic tomography (TAT) and photoacoustic tomography (PAT). TAT and PAT represent probably the most developed of the several novel “hybrid” methods of medical imaging. These new modalities combine different physical types of waves (electromagnetic and acoustic in case of TAT and PAT) in such a way that the resolution and contrast of the resulting method are much higher than those achievable using only acoustic or electromagnetic measurements.

Study on Dihydrated Praseodymium Acetylacetonate by Photoacoustic Spectra with Broad Wavelength Range

Institute of Scientific and Technical Information of China (English)

于锡娟; 伍荣护; 宋慧宇; 苏庆德

2003-01-01

The UV-Vis, NIR and MIR photoacoustic spectra of Pr(aa)3*2H2O were measured and most f-f transition peaks of Pr3+ are detected. The peak split and peak shift are studied also. The covalency parameter is calculated and it turns out that the covalent bonds between Pr(Ⅲ) ions and ligands exist. The results conclude that photoacoustic spectroscopy offers a unique and complementary method in analysis of solid rare earth complexes. Compared with conventional FT-IR transmission and absorption approaches, PAS has the advantages of fast, nondestructive analysis and high resolution.

Multispectral photoacoustic characterization of ICG and porcine blood using an LED-based photoacoustic imaging system

Science.gov (United States)

Shigeta, Yusuke; Sato, Naoto; Kuniyil Ajith Singh, Mithun; Agano, Toshitaka

2018-02-01

Photoacoustic imaging is a hybrid biomedical imaging modality that has emerged over the last decade. In photoacoustic imaging, pulsed-light absorbed by the target emits ultrasound that can be detected using a conventional ultrasound array. This ultrasound data can be used to reconstruct the location and spatial details of the intrinsic/extrinsic light absorbers in the tissue. Recently we reported on the development of a multi-wavelength high frame-rate LED-based photoacoustic/ultrasound imaging system (AcousticX). In this work, we photoacoustically characterize the absorption spectrum of ICG and porcine blood using LED arrays with multiple wavelengths (405, 420, 470, 520, 620, 660, 690, 750, 810, 850, 925, 980 nm). Measurements were performed in a simple reflection mode configuration in which LED arrays where fixed on both sides of the linear array ultrasound probe. Phantom used consisted of micro-test tubes filled with ICG and porcine blood, which were placed in a tank filled with water. The photoacoustic spectrum obtained from our measurements matches well with the reference absorption spectrum. These results demonstrate the potential capability of our system in performing clinical/pre-clinical multispectral photoacoustic imaging.

Adaptive photoacoustic imaging using the Mallart-Fink focusing factor

Science.gov (United States)

Li, Meng-Lin

2008-02-01

Focusing errors caused by sound velocity heterogeneities widen the mainlobe and elevate the sidelobes, thus degrading both spatial and contrast resolutions in photoacoustic imaging. We propose an adaptive array-based photoacoustic imaging technique that uses the Mallart-Fink (MF) focusing factor weighting to reduce the effect of such focusing errors. The definition of the MF focusing factor indicates that the MF focusing factor at the main lobe of the point-spread function is high (close to 1, without speckle noise being present, which is the case in photoacoustic imaging), whereas it is low at the sidelobes. Based on this property, the elevated sidelobes caused by sound velocity heterogeneities in the tissue can be suppressed after being multiplied by the corresponding map of the MF focusing factor on each imaging point; thus the focusing quality can be improved. This technique makes no assumption of sources of focusing errors and directly suppresses the unwanted sidelobe contributions. Numerical experiments with near field phase screen and displaced phase screen models were performed here to verify the proposed adaptive weighting technique. The effect of the signal-to-noise ratio on the MF focusing factor is also discussed.

Signal-Characteristic analysis with respect to backing material of PVDF-based high-frequency ultrasound for photoacoustic microscopy

Energy Technology Data Exchange (ETDEWEB)

Lee, Jun Su; Chang, Jin Ho [Dept. of Electronic Engineering, Sogang University, Seoul (Korea, Republic of)

2015-04-15

Photoacoustic microscopy is capable of providing high-resolution molecular images, and its spatial resolution is typically determined by ultrasonic transducers used to receive the photoacoustic signals. Therefore, ultrasonic transducers for photoacoustic microscopy (PAM) should have a high operating frequency, broad bandwidth, and high signal-reception efficiency. Polyvinylidene fluoride (PVDF) is a suitable material. To take full advantage of this material, the selection of the backing material is crucial, as it influences the center frequency and bandwidth of the transducer. Therefore, we experimentally determined the most suitable backing material among EPO-TEK 301, E-Solder 3022, and RTV. For this, three PVDF high-frequency single-element transducers were fabricated with each backing material. The center frequency and -6 dB bandwidth of each transducer were ascertained by a pulse-echo test. The spatial resolution of each transducer was examined using wire-target images. The experimental results indicated that EPO-TEK 301 is the most suitable backing material for a PAM transducer. This material provides the highest signal magnitude and a reasonable bandwidth because a large portion of the energy propagates toward the front medium, and the PVDF resonates in the half-wave mode.

Photoacoustic signal amplification through plasmonic nanoparticle aggregation

OpenAIRE

Bayer, Carolyn L.; Nam, Seung Yun; Chen, Yun-Sheng; Emelianov, Stanislav Y.

2013-01-01

Photoacoustic imaging, using targeted plasmonic metallic nanoparticles, is a promising noninvasive molecular imaging method. Analysis of the photoacoustic signal generated by plasmonic metallic nanoparticles is complex because of the dependence upon physical properties of both the nanoparticle and the surrounding environment. We studied the effect of the aggregation of gold nanoparticles on the photoacoustic signal amplitude. We found that the photoacoustic signal from aggregated silica-coate...

Whole-organ atlas imaged by label-free high-resolution photoacoustic microscopy assisted by a microtome

Science.gov (United States)

Wong, Terence T. W.; Zhang, Ruiying; Hsu, Hsun-Chia; Maslov, Konstantin I.; Shi, Junhui; Chen, Ruimin; Shung, K. Kirk; Zhou, Qifa; Wang, Lihong V.

2018-02-01

In biomedical imaging, all optical techniques face a fundamental trade-off between spatial resolution and tissue penetration. Therefore, obtaining an organelle-level resolution image of a whole organ has remained a challenging and yet appealing scientific pursuit. Over the past decade, optical microscopy assisted by mechanical sectioning or chemical clearing of tissue has been demonstrated as a powerful technique to overcome this dilemma, one of particular use in imaging the neural network. However, this type of techniques needs lengthy special preparation of the tissue specimen, which hinders broad application in life sciences. Here, we propose a new label-free three-dimensional imaging technique, named microtomy-assisted photoacoustic microscopy (mPAM), for potentially imaging all biomolecules with 100% endogenous natural staining in whole organs with high fidelity. We demonstrate the first label-free mPAM, using UV light for label-free histology-like imaging, in whole organs (e.g., mouse brains), most of them formalin-fixed and paraffin- or agarose-embedded for minimal morphological deformation. Furthermore, mPAM with dual wavelength illuminations is also employed to image a mouse brain slice, demonstrating the potential for imaging of multiple biomolecules without staining. With visible light illumination, mPAM also shows its deep tissue imaging capability, which enables less slicing and hence reduces sectioning artifacts. mPAM could potentially provide a new insight for understanding complex biological organs.

Nonlinear photoacoustic spectroscopy of hemoglobin

Energy Technology Data Exchange (ETDEWEB)

Danielli, Amos; Maslov, Konstantin; Favazza, Christopher P.; Xia, Jun; Wang, Lihong V., E-mail: LHWANG@WUSTL.EDU [Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130 (United States)

2015-05-18

As light intensity increases in photoacoustic imaging, the saturation of optical absorption and the temperature dependence of the thermal expansion coefficient result in a measurable nonlinear dependence of the photoacoustic (PA) signal on the excitation pulse fluence. Here, under controlled conditions, we investigate the intensity-dependent photoacoustic signals from oxygenated and deoxygenated hemoglobin at varied optical wavelengths and molecular concentrations. The wavelength and concentration dependencies of the nonlinear PA spectrum are found to be significantly greater in oxygenated hemoglobin than in deoxygenated hemoglobin. These effects are further influenced by the hemoglobin concentration. These nonlinear phenomena provide insights into applications of photoacoustics, such as measurements of average inter-molecular distances on a nm scale or with a tuned selection of wavelengths, a more accurate quantitative PA tomography.

Nonlinear photoacoustic spectroscopy of hemoglobin.

Science.gov (United States)

Danielli, Amos; Maslov, Konstantin; Favazza, Christopher P; Xia, Jun; Wang, Lihong V

2015-05-18

As light intensity increases in photoacoustic imaging, the saturation of optical absorption and the temperature dependence of the thermal expansion coefficient result in a measurable nonlinear dependence of the photoacoustic (PA) signal on the excitation pulse fluence. Here, under controlled conditions, we investigate the intensity-dependent photoacoustic signals from oxygenated and deoxygenated hemoglobin at varied optical wavelengths and molecular concentrations. The wavelength and concentration dependencies of the nonlinear PA spectrum are found to be significantly greater in oxygenated hemoglobin than in deoxygenated hemoglobin. These effects are further influenced by the hemoglobin concentration. These nonlinear phenomena provide insights into applications of photoacoustics, such as measurements of average inter-molecular distances on a nm scale or with a tuned selection of wavelengths, a more accurate quantitative PA tomography.

Nonlinear photoacoustic spectroscopy of hemoglobin

International Nuclear Information System (INIS)

Danielli, Amos; Maslov, Konstantin; Favazza, Christopher P.; Xia, Jun; Wang, Lihong V.

2015-01-01

As light intensity increases in photoacoustic imaging, the saturation of optical absorption and the temperature dependence of the thermal expansion coefficient result in a measurable nonlinear dependence of the photoacoustic (PA) signal on the excitation pulse fluence. Here, under controlled conditions, we investigate the intensity-dependent photoacoustic signals from oxygenated and deoxygenated hemoglobin at varied optical wavelengths and molecular concentrations. The wavelength and concentration dependencies of the nonlinear PA spectrum are found to be significantly greater in oxygenated hemoglobin than in deoxygenated hemoglobin. These effects are further influenced by the hemoglobin concentration. These nonlinear phenomena provide insights into applications of photoacoustics, such as measurements of average inter-molecular distances on a nm scale or with a tuned selection of wavelengths, a more accurate quantitative PA tomography

A new acoustic lens material for large area detectors in photoacoustic breast tomography

NARCIS (Netherlands)

Xia, W.; Piras, D.; van Hespen, Johannes C.G.; Steenbergen, Wiendelt; Manohar, Srirang

2013-01-01

Objectives We introduce a new acoustic lens material for photoacoustic tomography (PAT) to improve lateral resolution while possessing excellent acoustic acoustic impedance matching with tissue to minimize lens induced image artifacts. Background A large surface area detector due to its high

Photoacoustic investigation of QCL modulation techniques

International Nuclear Information System (INIS)

Germer, M; Wolff, M

2010-01-01

High detection sensitivity and spectral selectivity is important for gas analysers to identify the measured compound and to detect low concentrations. We investigated three different modulation methods - pulse gate modulation, pulse frequency modulation and chopper modulation - for a new pulsed quantum cascade laser based photoacoustic sensor. The spectral selectivity and the detection limit for the three modulation methods are compared by measuring nitric oxide absorption lines and different concentrations. The highest detection sensitivity of 70 ppb was achieved with pulse gate modulation but at the lowest spectral resolution. The highest spectral resolution was achieved with chopper modulation but at the lowest detection sensitivity. It is demonstrated that for the three modulation methods a compromise has to be made between selectivity and sensitivity for each measuring task.

CO 2 laser photoacoustic spectra and vibrational modes of heroin ...

Indian Academy of Sciences (India)

Heroin, morphine and narcotine are very large molecules having 50, 40 and 53 atoms respectively. Moderately high resolution photoacoustic (PA) spectra have been recorded in 9.6 m and 10.6 m regions of CO2 laser. It is very difficult to assign the modes of vibrations for PA bands by comparison with conventional low ...

Whole-body and multispectral photoacoustic imaging of adult zebrafish

Science.gov (United States)

Huang, Na; Xi, Lei

2016-10-01

Zebrafish is a top vertebrate model to study developmental biology and genetics, and it is becoming increasingly popular for studying human diseases due to its high genome similarity to that of humans and the optical transparency in embryonic stages. However, it becomes difficult for pure optical imaging techniques to volumetric visualize the internal organs and structures of wild-type zebrafish in juvenile and adult stages with excellent resolution and penetration depth. Even with the establishment of mutant lines which remain transparent over the life cycle, it is still a challenge for pure optical imaging modalities to image the whole body of adult zebrafish with micro-scale resolution. However, the method called photoacoustic imaging that combines all the advantages of the optical imaging and ultrasonic imaging provides a new way to image the whole body of the zebrafish. In this work, we developed a non-invasive photoacoustic imaging system with optimized near-infrared illumination and cylindrical scanning to image the zebrafish. The lateral and axial resolution yield to 80 μm and 600 μm, respectively. Multispectral strategy with wavelengths from 690 nm to 930 nm was employed to image various organs inside the zebrafish. From the reconstructed images, most major organs and structures inside the body can be precisely imaged. Quantitative and statistical analysis of absorption for organs under illumination with different wavelengths were carried out.

A 3D imaging system integrating photoacoustic and fluorescence orthogonal projections for anatomical, functional and molecular assessment of rodent models

Science.gov (United States)

Brecht, Hans P.; Ivanov, Vassili; Dumani, Diego S.; Emelianov, Stanislav Y.; Anastasio, Mark A.; Ermilov, Sergey A.

2018-03-01

We have developed a preclinical 3D imaging instrument integrating photoacoustic tomography and fluorescence (PAFT) addressing known deficiencies in sensitivity and spatial resolution of the individual imaging components. PAFT is designed for simultaneous acquisition of photoacoustic and fluorescence orthogonal projections at each rotational position of a biological object, enabling direct registration of the two imaging modalities. Orthogonal photoacoustic projections are utilized to reconstruct large (21 cm3 ) volumes showing vascularized anatomical structures and regions of induced optical contrast with spatial resolution exceeding 100 µm. The major advantage of orthogonal fluorescence projections is significant reduction of background noise associated with transmitted or backscattered photons. The fluorescence imaging component of PAFT is used to boost detection sensitivity by providing low-resolution spatial constraint for the fluorescent biomarkers. PAFT performance characteristics were assessed by imaging optical and fluorescent contrast agents in tissue mimicking phantoms and in vivo. The proposed PAFT technology will enable functional and molecular volumetric imaging using fluorescent biomarkers, nanoparticles, and other photosensitive constructs mapped with high fidelity over robust anatomical structures, such as skin, central and peripheral vasculature, and internal organs.

Development and validation of a short-lag spatial coherence theory for photoacoustic imaging

Science.gov (United States)

Graham, Michelle T.; Lediju Bell, Muyinatu A.

2018-02-01

We previously derived spatial coherence theory to be implemented for studying theoretical properties of ShortLag Spatial Coherence (SLSC) beamforming applied to photoacoustic images. In this paper, our newly derived theoretical equation is evaluated to generate SLSC images of a point target and a 1.2 mm diameter target and corresponding lateral profiles. We compared SLSC images simulated solely based on our theory to SLSC images created after beamforming acoustic channel data from k-Wave simulations of 1.2 mm-diameter disc target. This process was repeated for a point target and the full width at half the maximum signal amplitudes were measured to estimate the resolution of each imaging system. Resolution as a function of lag was comparable for the first 10% of the receive aperture (i.e., the short-lag region), after which resolution measurements diverged by a maximum of 1 mm between the two types of simulated images. These results indicate the potential for both simulation methods to be utilized as independent resources to study coherence-based photoacoustic beamformers when imaging point-like targets.

Photoacoustic spectroscopy of β-hematin

International Nuclear Information System (INIS)

Samson, Edward B; Goldschmidt, Benjamin S; Whiteside, Paul J D; Sudduth, Amanda S M; Custer, John R; Viator, John A; Beerntsen, Brenda

2012-01-01

Malaria affects over 200 million individuals annually, resulting in 800 000 fatalities. Current tests use blood smears and can only detect the disease when 0.1–1% of blood cells are infected. We are investigating the use of photoacoustic flowmetry to sense as few as one infected cell among 10 million or more normal blood cells, thus diagnosing infection before patients become symptomatic. Photoacoustic flowmetry is similar to conventional flow cytometry, except that rare cells are targeted by nanosecond laser pulses to induce ultrasonic responses. This system has been used to detect single melanoma cells in 10 ml of blood. Our objective is to apply photoacoustic flowmetry to detection of the malaria pigment hemozoin, which is a byproduct of parasite-digested hemoglobin in the blood. However, hemozoin is difficult to purify in quantities greater than a milligram, so a synthetic analog, known as β-hematin was derived from porcine hemin. The specific purpose of this study is to establish the efficacy of using β-hematin, rather than hemozoin, for photoacoustic measurements. We characterized β-hematin using UV–vis spectroscopy, TEM, and FTIR, then tested the effects of laser irradiation on the synthetic product. We finally determined its absorption spectrum using photoacoustic excitation. UV–vis spectroscopy verified that β-hematin was distinctly different from its precursor. TEM analysis confirmed its previously established nanorod shape, and comparison of the FTIR results with published spectroscopy data showed that our product had the distinctive absorbance peaks at 1661 and 1206 cm −1 . Also, our research indicated that prolonged irradiation dramatically alters the physical and optical properties of the β-hematin, resulting in increased absorption at shorter wavelengths. Nevertheless, the photoacoustic absorption spectrum mimicked that generated by UV–vis spectroscopy, which confirms the accuracy of the photoacoustic method and strongly suggests

Phase transition of TiO{sub 2} thin films detected by the pulsed laser photoacoustic technique

Energy Technology Data Exchange (ETDEWEB)

Perez-Pacheco, A.; Castaneda-Guzman, R.; Oliva Montes de Oca, C.; Esparza-Garcia, A. [Universidad Nacional Autonoma de Mexico, CCADET-UNAM, Laboratorio de Fotofisica y Peliculas Delgadas, Cd. Universitaria, A.P. 70-186, Mexico D.F. (Mexico); Perez Ruiz, S.J. [CCADET-UNAM, Acustica y Vibraciones, Mexico D.F. (Mexico)

2011-03-15

In this work, we present characterization of titanium oxide thin films by photoacoustic measurements to determine the ablation threshold and phase transitions from amorphous to crystalline states. The important advantages of this method are that it does not require amplification at the detection stage and that it is a non-destructive technique. The correlation analysis of the photoacoustic signals allows us to visualize the ablation threshold and the phase transitions with enhanced sensitivity. This correlation analysis clearly exhibits the changes in the thin-film morphology due to controlled variations of the fluence (energy/area) and the temperature of the surrounding medium. This is particularly important for those cases where the crystalline changes caused by temperature variations need to be monitored. The thin-film samples were prepared by the sputtering technique at room temperature in the amorphous state. The phase transformations were induced by controlled temperature scanning and then corroborated with Raman spectroscopy measurements. (orig.)

Noninvasive photoacoustic computed tomography of mouse brain metabolism in vivo

Science.gov (United States)

Yao, Junjie; Xia, Jun; Maslov, Konstantin; Avanaki, Mohammadreza R. N.; Tsytsarev, Vassiliy; Demchenko, Alexei V.; Wang, Lihong V.

2013-03-01

To control the overall action of the body, brain consumes a large amount of energy in proportion to its volume. In humans and many other species, the brain gets most of its energy from oxygen-dependent metabolism of glucose. An abnormal metabolic rate of glucose and/or oxygen usually reflects a diseased status of brain, such as cancer or Alzheimer's disease. We have demonstrated the feasibility of imaging mouse brain metabolism using photoacoustic computed tomography (PACT), a fast, noninvasive and functional imaging modality with optical contrast and acoustic resolution. Brain responses to forepaw stimulations were imaged transdermally and transcranially. 2-NBDG, which diffuses well across the blood-brain-barrier, provided exogenous contrast for photoacoustic imaging of glucose response. Concurrently, hemoglobin provided endogenous contrast for photoacoustic imaging of hemodynamic response. Glucose and hemodynamic responses were quantitatively unmixed by using two-wavelength measurements. We found that glucose uptake and blood perfusion around the somatosensory region of the contralateral hemisphere were both increased by stimulations, indicating elevated neuron activity. The glucose response amplitude was about half that of the hemodynamic response. While the glucose response area was more homogenous and confined within the somatosensory region, the hemodynamic response area showed a clear vascular pattern and spread about twice as wide as that of the glucose response. The PACT of mouse brain metabolism was validated by high-resolution open-scalp OR-PAM and fluorescence imaging. Our results demonstrate that 2-NBDG-enhanced PACT is a promising tool for noninvasive studies of brain metabolism.

Evolution of a MEMS Photoacoustic Chemical Sensor

National Research Council Canada - National Science Library

Pellegrino, Paul M; Polcawich, Ronald G

2003-01-01

.... Initial MEMS work is centered on fabrication of a lead zirconate titanate (PZT) microphone subsystem to be incorporated in the full photoacoustic device. Preliminary results were very positive for the macro-photoacoustic cell, PZT membrane microphones design / fabrication and elementary monolithic MEMS photoacoustic cavity.

Detection, mapping, and quantification of single walled carbon nanotubes in histological specimens with photoacoustic microscopy.

Science.gov (United States)

Avti, Pramod K; Hu, Song; Favazza, Christopher; Mikos, Antonios G; Jansen, John A; Shroyer, Kenneth R; Wang, Lihong V; Sitharaman, Balaji

2012-01-01

In the present study, the efficacy of multi-scale photoacoustic microscopy (PAM) was investigated to detect, map, and quantify trace amounts [nanograms (ng) to micrograms (µg)] of SWCNTs in a variety of histological tissue specimens consisting of cancer and benign tissue biopsies (histological specimens from implanted tissue engineering scaffolds). Optical-resolution (OR) and acoustic-resolution (AR)--Photoacoustic microscopy (PAM) was employed to detect, map and quantify the SWCNTs in a variety of tissue histological specimens and compared with other optical techniques (bright-field optical microscopy, Raman microscopy, near infrared (NIR) fluorescence microscopy). Both optical-resolution and acoustic-resolution PAM, allow the detection and quantification of SWCNTs in histological specimens with scalable spatial resolution and depth penetration. The noise-equivalent detection sensitivity to SWCNTs in the specimens was calculated to be as low as ∼7 pg. Image processing analysis further allowed the mapping, distribution, and quantification of the SWCNTs in the histological sections. The results demonstrate the potential of PAM as a promising imaging technique to detect, map, and quantify SWCNTs in histological specimens, and could complement the capabilities of current optical and electron microscopy techniques in the analysis of histological specimens containing SWCNTs.

Detection, mapping, and quantification of single walled carbon nanotubes in histological specimens with photoacoustic microscopy.

Directory of Open Access Journals (Sweden)

Pramod K Avti

Full Text Available In the present study, the efficacy of multi-scale photoacoustic microscopy (PAM was investigated to detect, map, and quantify trace amounts [nanograms (ng to micrograms (µg] of SWCNTs in a variety of histological tissue specimens consisting of cancer and benign tissue biopsies (histological specimens from implanted tissue engineering scaffolds.Optical-resolution (OR and acoustic-resolution (AR--Photoacoustic microscopy (PAM was employed to detect, map and quantify the SWCNTs in a variety of tissue histological specimens and compared with other optical techniques (bright-field optical microscopy, Raman microscopy, near infrared (NIR fluorescence microscopy.Both optical-resolution and acoustic-resolution PAM, allow the detection and quantification of SWCNTs in histological specimens with scalable spatial resolution and depth penetration. The noise-equivalent detection sensitivity to SWCNTs in the specimens was calculated to be as low as ∼7 pg. Image processing analysis further allowed the mapping, distribution, and quantification of the SWCNTs in the histological sections.The results demonstrate the potential of PAM as a promising imaging technique to detect, map, and quantify SWCNTs in histological specimens, and could complement the capabilities of current optical and electron microscopy techniques in the analysis of histological specimens containing SWCNTs.

Photoacoustic imaging of breast tumor vascularization: a comparison with MRI and histopathology

Science.gov (United States)

Heijblom, Michelle; Piras, Daniele; van den Engh, Frank M.; Klaase, Joost M.; Brinkhuis, Mariël.; Steenbergen, Wiendelt; Manohar, Srirang

2013-06-01

Breast cancer is the most common form of cancer and the leading cause of cancer death among females. Early diagnosis improves the survival chances for the disease and that is why there is an ongoing search for improved methods for visualizing breast cancer. One of the hallmarks of breast cancer is the increase in tumor vascularization that is associated with angiogenesis: a crucial factor for survival of malignancies. Photoacoustic imaging can visualize the malignancyassociated increased hemoglobin concentration with optical contrast and ultrasound resolution, without the use of ionizing radiation or contrast agents and is therefore theoretically an ideal method for breast imaging. Previous clinical studies using the Twente Photoacoustic Mammoscope (PAM), which works in forward mode using a single wavelength (1064 nm), showed that malignancies can indeed be identified in the photoacoustic imaging volume as high contrast areas. However, the specific appearance of the malignancies led to questions about the contrast mechanism in relation to tumor vascularization. In this study, the photoacoustic lesion appearance obtained with an updated version of PAM is compared with the lesion appearance on Magnetic Resonance Imaging (MRI), both in general (19 patients) and on an individual basis (7 patients). Further, in 3 patients an extended histopathology protocol is being performed in which malignancies are stained for vascularity using an endothelial antibody: CD31. The correspondence between PAM and MRI and between PAM and histopathology makes it likely that the high photoacoustic contrast at 1064 nm is indeed largely the consequence of the increased tumor vascularization.

Three-Dimensional Photoacoustic Tomography using Delay Multiply and Sum Beamforming Algorithm

OpenAIRE

Paridar, Roya; Mozaffarzadeh, Moein; Mahloojifar, Ali; Nasiriavanaki, Mohammadreza; Orooji, Mahdi

2018-01-01

Photoacoustic imaging (PAI), is a promising medical imaging technique that provides the high contrast of the optical imaging and the resolution of ultrasound (US) imaging. Among all the methods, Three-dimensional (3D) PAI provides a high resolution and accuracy. One of the most common algorithms for 3D PA image reconstruction is delay-and-sum (DAS). However, the quality of the reconstructed image obtained from this algorithm is not satisfying, having high level of sidelobes and a wide mainlob...

Functional photoacoustic microscopy of diabetic vasculature

Science.gov (United States)

Krumholz, Arie; Wang, Lidai; Yao, Junjie; Wang, Lihong V.

2012-06-01

We used functional photoacoustic microscopy to image diabetes-induced damage to the microvasculature. To produce an animal model for Type 1 diabetes, we used streptozotocin (STZ), which is particularly toxic to the insulin-producing beta cells of the pancreas in mammals. A set number of ND4 Swiss Webster mice received intraperitoneal injections of STZ for five consecutive days at 50 mg/kg. Most mice developed a significant rise in blood glucose level (~400 mg/dL) within three weeks of the first injection. Changes in vasculature and hemodynamics were monitored for six weeks. The mouse ear was imaged with an optical-resolution photoacoustic microscope at a main blood vessel branch from the root of the ear. There are noticeable and measurable changes associated with the disease, including decreased vessel diameter and possible occlusion due to vessel damage and polyurea. We also observed an increase in the blood flow speed in the vein and a decrease in the artery, which could be due to compensation for the dehydration and vessel diameter changes. Functional and metabolic parameters such as hemoglobin oxygen saturation, oxygen extraction fraction, and oxygen consumption rate were also measured, but showed no significant change.

In vivo functional photoacoustic microscopy of cutaneous microvasculature in human skin.

Science.gov (United States)

Favazza, Christopher P; Cornelius, Lynn A; Wang, Lihong V

2011-02-01

Microcirculation is an important component of the cardiovascular system and can be used to assess systemic cardiovascular health. Numerous studies have investigated cutaneous microcirculation as an indicator of cardiovascular related diseases. Such research has shown promising results; however, there are many limitations regarding the employed measurement techniques, such as poor depth and spatial resolution and measurement versatility. Here we show the results of functional cutaneous microvascular experiments measured with photoacoustic microscopy, which provides high spatial resolution and multiparameter measurements. In a set of experiments, microvascular networks located in the palms of volunteers were perturbed by periodic ischemic events, and the subsequent hemodynamic response to the stimulus was recorded. Results indicate that during periods of arterial occlusion, the relative oxygen saturation of the capillary vessels decreased below resting levels, and temporarily increased above resting levels immediately following the occlusion. Furthermore, a hyperemic reaction to the occlusions was measured, and the observation agreed well with similar measurements using more conventional imaging techniques. Due to its exceptional capability to functionally image vascular networks with high spatial resolution, photoacoustic microscopy could be a beneficial biomedical tool to assess microvascular functioning and applied to patients with diseases that affect cardiovascular health. © 2011 Society of Photo-Optical Instrumentation Engineers.

Dual-modal photoacoustic and ultrasound imaging of dental implants

Science.gov (United States)

Lee, Donghyun; Park, Sungjo; Kim, Chulhong

2018-02-01

Dental implants are common method to replace decayed or broken tooth. As the implant treatment procedures varies according to the patients' jawbone, bone ridge, and sinus structure, appropriate examinations are necessary for successful treatment. Currently, radiographic examinations including periapical radiology, panoramic X-ray, and computed tomography are commonly used for diagnosing and monitoring. However, these radiographic examinations have limitations in that patients and operators are exposed to radioactivity and multiple examinations are performed during the treatment. In this study, we demonstrated photoacoustic (PA) and ultrasound (US) combined imaging of dental implant that can lower the total amount of absorbed radiation dose in dental implant treatment. An acoustic resolution PA macroscopy and a clinical PA/US system was used for dental implant imaging. The acquired dual modal PA/US imaging results support that the proposed photoacoustic imaging strategy can reduce the radiation dose rate during dental implant treatment.

Quantitative spatially resolved measurement of tissue chromophore concentrations using photoacoustic spectroscopy: application to the measurement of blood oxygenation and haemoglobin concentration

Science.gov (United States)

Laufer, Jan; Delpy, Dave; Elwell, Clare; Beard, Paul

2007-01-01

A new approach based on pulsed photoacoustic spectroscopy for non-invasively quantifying tissue chromophore concentrations with high spatial resolution has been developed. The technique is applicable to the quantification of tissue chromophores such as oxyhaemoglobin (HbO2) and deoxyhaemoglobin (HHb) for the measurement of physiological parameters such as blood oxygen saturation (SO2) and total haemoglobin concentration. It can also be used to quantify the local accumulation of targeted contrast agents used in photoacoustic molecular imaging. The technique employs a model-based inversion scheme to recover the chromophore concentrations from photoacoustic measurements. This comprises a numerical forward model of the detected time-dependent photoacoustic signal that incorporates a multiwavelength diffusion-based finite element light propagation model to describe the light transport and a time-domain acoustic model to describe the generation, propagation and detection of the photoacoustic wave. The forward model is then inverted by iteratively fitting it to measurements of photoacoustic signals acquired at different wavelengths to recover the chromophore concentrations. To validate this approach, photoacoustic signals were generated in a tissue phantom using nanosecond laser pulses between 740 nm and 1040 nm. The tissue phantom comprised a suspension of intralipid, blood and a near-infrared dye in which three tubes were immersed. Blood at physiological haemoglobin concentrations and oxygen saturation levels ranging from 2% to 100% was circulated through the tubes. The signal amplitude from different temporal sections of the detected photoacoustic waveforms was plotted as a function of wavelength and the forward model fitted to these data to recover the concentrations of HbO2 and HHb, total haemoglobin concentration and SO2. The performance was found to compare favourably to that of a laboratory CO-oximeter with measurement resolutions of ±3.8 g l-1 (±58 µM) and ±4

Quantitative spatially resolved measurement of tissue chromophore concentrations using photoacoustic spectroscopy: application to the measurement of blood oxygenation and haemoglobin concentration

Energy Technology Data Exchange (ETDEWEB)

Laufer, Jan; Delpy, Dave; Elwell, Clare; Beard, Paul [Department of Medical Physics and Bioengineering, University College London, Malet Place Engineering Building, London WC1E 6BT (United Kingdom)

2007-01-07

A new approach based on pulsed photoacoustic spectroscopy for non-invasively quantifying tissue chromophore concentrations with high spatial resolution has been developed. The technique is applicable to the quantification of tissue chromophores such as oxyhaemoglobin (HbO{sub 2}) and deoxyhaemoglobin (HHb) for the measurement of physiological parameters such as blood oxygen saturation (SO{sub 2}) and total haemoglobin concentration. It can also be used to quantify the local accumulation of targeted contrast agents used in photoacoustic molecular imaging. The technique employs a model-based inversion scheme to recover the chromophore concentrations from photoacoustic measurements. This comprises a numerical forward model of the detected time-dependent photoacoustic signal that incorporates a multiwavelength diffusion-based finite element light propagation model to describe the light transport and a time-domain acoustic model to describe the generation, propagation and detection of the photoacoustic wave. The forward model is then inverted by iteratively fitting it to measurements of photoacoustic signals acquired at different wavelengths to recover the chromophore concentrations. To validate this approach, photoacoustic signals were generated in a tissue phantom using nanosecond laser pulses between 740 nm and 1040 nm. The tissue phantom comprised a suspension of intralipid, blood and a near-infrared dye in which three tubes were immersed. Blood at physiological haemoglobin concentrations and oxygen saturation levels ranging from 2% to 100% was circulated through the tubes. The signal amplitude from different temporal sections of the detected photoacoustic waveforms was plotted as a function of wavelength and the forward model fitted to these data to recover the concentrations of HbO{sub 2} and HHb, total haemoglobin concentration and SO{sub 2}. The performance was found to compare favourably to that of a laboratory CO-oximeter with measurement resolutions of {+-}3

Quantitative spatially resolved measurement of tissue chromophore concentrations using photoacoustic spectroscopy: application to the measurement of blood oxygenation and haemoglobin concentration

International Nuclear Information System (INIS)

Laufer, Jan; Delpy, Dave; Elwell, Clare; Beard, Paul

2007-01-01

A new approach based on pulsed photoacoustic spectroscopy for non-invasively quantifying tissue chromophore concentrations with high spatial resolution has been developed. The technique is applicable to the quantification of tissue chromophores such as oxyhaemoglobin (HbO 2 ) and deoxyhaemoglobin (HHb) for the measurement of physiological parameters such as blood oxygen saturation (SO 2 ) and total haemoglobin concentration. It can also be used to quantify the local accumulation of targeted contrast agents used in photoacoustic molecular imaging. The technique employs a model-based inversion scheme to recover the chromophore concentrations from photoacoustic measurements. This comprises a numerical forward model of the detected time-dependent photoacoustic signal that incorporates a multiwavelength diffusion-based finite element light propagation model to describe the light transport and a time-domain acoustic model to describe the generation, propagation and detection of the photoacoustic wave. The forward model is then inverted by iteratively fitting it to measurements of photoacoustic signals acquired at different wavelengths to recover the chromophore concentrations. To validate this approach, photoacoustic signals were generated in a tissue phantom using nanosecond laser pulses between 740 nm and 1040 nm. The tissue phantom comprised a suspension of intralipid, blood and a near-infrared dye in which three tubes were immersed. Blood at physiological haemoglobin concentrations and oxygen saturation levels ranging from 2% to 100% was circulated through the tubes. The signal amplitude from different temporal sections of the detected photoacoustic waveforms was plotted as a function of wavelength and the forward model fitted to these data to recover the concentrations of HbO 2 and HHb, total haemoglobin concentration and SO 2 . The performance was found to compare favourably to that of a laboratory CO-oximeter with measurement resolutions of ±3.8 g l -1 (±58 �

Hybrid Photoacoustic/Ultrasound Tomograph for Real-Time Finger Imaging.

Science.gov (United States)

Oeri, Milan; Bost, Wolfgang; Sénégond, Nicolas; Tretbar, Steffen; Fournelle, Marc

2017-10-01

We report a target-enclosing, hybrid tomograph with a total of 768 elements based on capacitive micromachined ultrasound transducer technology and providing fast, high-resolution 2-D/3-D photoacoustic and ultrasound tomography tailored to finger imaging. A freely programmable ultrasound beamforming platform sampling data at 80 MHz was developed to realize plane wave transmission under multiple angles. A multiplexing unit enables the connection and control of a large number of elements. Fast image reconstruction is provided by GPU processing. The tomograph is composed of four independent and fully automated movable arc-shaped transducers, allowing imaging of all three finger joints. The system benefits from photoacoustics, yielding high optical contrast and enabling visualization of finger vascularization, and ultrasound provides morphologic information on joints and surrounding tissue. A diode-pumped, Q-switched Nd:YAG laser and an optical parametric oscillator are used to broaden the spectrum of emitted wavelengths to provide multispectral imaging. Custom-made optical fiber bundles enable illumination of the region of interest in the plane of acoustic detection. Precision in positioning of the probe in motion is ensured by use of a motor-driven guide slide. The current position of the probe is encoded by the stage and used to relate ultrasound and photoacoustic signals to the corresponding region of interest of the suspicious finger joint. The system is characterized in phantoms and a healthy human finger in vivo. The results obtained promise to provide new opportunities in finger diagnostics and establish photoacoustic/ultrasound-tomography in medical routine. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Clinical photoacoustic imaging of cancer

Energy Technology Data Exchange (ETDEWEB)

Valluru, Keerthi S.; Willmann, Juergen K. [Dept. of Radiology, Molecular Imaging Program at Stanford, Stanford University School of Medicine, Stanford (United States)

2016-08-15

Photoacoustic imaging is a hybrid technique that shines laser light on tissue and measures optically induced ultrasound signal. There is growing interest in the clinical community over this new technique and its possible clinical applications. One of the most prominent features of photoacoustic imaging is its ability to characterize tissue, leveraging differences in the optical absorption of underlying tissue components such as hemoglobin, lipids, melanin, collagen and water among many others. In this review, the state-of-the-art photoacoustic imaging techniques and some of the key outcomes pertaining to different cancer applications in the clinic are presented.

Validating tyrosinase homologue MelA as a photoacoustic reporter gene for imaging Escherichia coli

Science.gov (United States)

Paproski, Robert J.; Li, Yan; Barber, Quinn; Lewis, John D.; Campbell, Robert; Zemp, Roger

2015-03-01

Antibiotic drug resistance is a major worldwide issue. Development of new therapies against pathogenic bacteria requires appropriate research tools for replicating and characterizing infections. Previously fluorescence and bioluminescence modalities have been used to image infectious burden in animal models but scattering significantly limits imaging depth and resolution. We hypothesize that photoacoustic imaging, which has improved depth-toresolution ratio, could be useful for visualizing MelA-expressing bacteria since MelA is a bacterial tyrosinase homologue involved in melanin production. Using an inducible expression system, E. coli expressing MelA were visibly black in liquid culture. Phosphate buffered saline (PBS), MelA-expressing bacteria (at different dilutions in PBS), and chicken embryo blood were injected in plastic tubes which were imaged using a VisualSonics Vevo LAZR system. Photoacoustic imaging at 6 different wavelengths (680, 700, 750, 800, 850 and 900nm) enabled spectral de-mixing to distinguish melanin signals from blood. The signal to noise ratio of 9x diluted MelA bacteria was 55, suggesting that ~20 bacteria cells could be detected with our system. When MelA bacteria were injected as a 100 μL bolus into a chicken embryo, photoacoustic signals from deoxy- and oxy- hemoglobin as well as MelA-expressing bacteria could be separated and overlaid on an ultrasound image, allowing visualization of the bacterial location. Photoacoustic imaging may be a useful tool for visualizing bacterial infections and further work incorporating photoacoustic reporters into infectious bacterial strains is warranted.

In vivo studies of transdermal nanoparticle delivery with microneedles using photoacoustic microscopy

Science.gov (United States)

Moothanchery, Mohesh; Seeni, Razina Z.; Xu, Chenjie; Pramanik, Manojit

2017-01-01

Microneedle technology allows micron-sized conduits to be formed within the outermost skin layers for both localized and systemic delivery of therapeutics including nanoparticles. Histological methods are often employed for characterization, and unfortunately do not allow for the in vivo visualization of the delivery process. This study presents the utilization of optical resolution-photoacoustic microscopy to characterize the transdermal delivery of nanoparticles using microneedles. Specifically, we observe the in vivo transdermal delivery of gold nanoparticles using microneedles in mice ear and study the penetration, diffusion, and spatial distribution of the nanoparticles in the tissue. The promising results reveal that photoacoustic microscopy can be used as a potential imaging modality for the in vivo characterization of microneedles based drug delivery. PMID:29296482

Photoacoustic-Based Multimodal Nanoprobes: from Constructing to Biological Applications.

Science.gov (United States)

Gao, Duyang; Yuan, Zhen

2017-01-01

Multimodal nanoprobes have attracted intensive attentions since they can integrate various imaging modalities to obtain complementary merits of single modality. Meanwhile, recent interest in laser-induced photoacoustic imaging is rapidly growing due to its unique advantages in visualizing tissue structure and function with high spatial resolution and satisfactory imaging depth. In this review, we summarize multimodal nanoprobes involving photoacoustic imaging. In particular, we focus on the method to construct multimodal nanoprobes. We have divided the synthetic methods into two types. First, we call it "one for all" concept, which involves intrinsic properties of the element in a single particle. Second, "all in one" concept, which means integrating different functional blocks in one particle. Then, we simply introduce the applications of the multifunctional nanoprobes for in vivo imaging and imaging-guided tumor therapy. At last, we discuss the advantages and disadvantages of the present methods to construct the multimodal nanoprobes and share our viewpoints in this area.

Multi-source quantitative photoacoustic tomography in a diffusive regime

International Nuclear Information System (INIS)

Bal, Guillaume; Ren, Kui

2011-01-01

Photoacoustic tomography (PAT) is a novel hybrid medical imaging technique that aims to combine the large contrast of optical coefficients with the high-resolution capabilities of ultrasound. We assume that the first step of PAT, namely the reconstruction of a map of absorbed radiation from ultrasound boundary measurement, has been done. We focus on quantitative photoacoustic tomography, which aims at quantitatively reconstructing the optical coefficients from knowledge of the absorbed radiation map. We present a non-iterative procedure to reconstruct such optical coefficients, namely the diffusion and absorption coefficients, and the Grüneisen coefficient when the propagation of radiation is modeled by a second-order elliptic equation. We show that PAT measurements allow us to uniquely reconstruct only two out of the above three coefficients, even when data are collected using an arbitrary number of radiation illuminations. We present uniqueness and stability results for the reconstructions of two such parameters and demonstrate the accuracy of the reconstruction algorithm with numerical reconstructions from two-dimensional synthetic data

Cavity-enhanced resonant photoacoustic spectroscopy with optical feedback cw diode lasers: A novel technique for ultratrace gas analysis and high-resolution spectroscopy.

Science.gov (United States)

Hippler, Michael; Mohr, Christian; Keen, Katherine A; McNaghten, Edward D

2010-07-28

Cavity-enhanced resonant photoacoustic spectroscopy with optical feedback cw diode lasers (OF-CERPAS) is introduced as a novel technique for ultratrace gas analysis and high-resolution spectroscopy. In the scheme, a single-mode cw diode laser (3 mW, 635 nm) is coupled into a high-finesse linear cavity and stabilized to the cavity by optical feedback. Inside the cavity, a build-up of laser power to at least 2.5 W occurs. Absorbing gas phase species inside the cavity are detected with high sensitivity by the photoacoustic effect using a microphone embedded in the cavity. To increase sensitivity further, coupling into the cavity is modulated at a frequency corresponding to a longitudinal resonance of an organ pipe acoustic resonator (f=1.35 kHz and Q approximately 10). The technique has been characterized by measuring very weak water overtone transitions near 635 nm. Normalized noise-equivalent absorption coefficients are determined as alpha approximately 4.4x10(-9) cm(-1) s(1/2) (1 s integration time) and 2.6x10(-11) cm(-1) s(1/2) W (1 s integration time and 1 W laser power). These sensitivities compare favorably with existing state-of-the-art techniques. As an advantage, OF-CERPAS is a "zero-background" method which increases selectivity and sensitivity, and its sensitivity scales with laser power.

Photoacoustic imaging of mesenchymal stem cells in living mice via silica-coated gold nanorods

Science.gov (United States)

Jokerst, Jesse V.; Thangaraj, Mridhula; Gambhir, Sanjiv S.

2014-03-01

Imaging is crucial for stem cell therapy to monitor the location(s), numbers, and state of the implanted cells. Real-time imaging in particular can ensure proper cell delivery for best engraftment. However, established imaging tools such as MRI are limited by their temporal resolution for guidance during delivery. In contrast, photoacoustic imaging is ideally suited for real time, image-guided therapy. Here, we use silica-coated gold nanorods as photoacoustic contrast agents and deploy them to image and quantitate mesenchymal stem cells during implant into the muscle tissue of live mice. Silica-coated gold nanorods (SiGNRs) were created with standard methods and loaded into mesenchymal stem cells (MSCs) without transfection agents. There was no significant (pmuscle tissue to simulate a muscular dystrophy patient. Mice (N=5) treated with these SiGNRlabeled MSCs exhibited no adverse events and implants up to 5 mm deep were easily visualized. The in vivo detection limit was 90,000 cells in a 100 uL bolus in mouse thigh muscle. Here, the B-mode signal is useful for orienting the treatment area and visualizing the delivery catheter while the photoacoustic mode offers cell-specific content. The photoacoustic signal was validated with histology a long-term fluorescent tracking dye after MSC transplant.

Photoacoustic Spectroscopy Analysis of Traditional Chinese Medicine

Science.gov (United States)

Chen, Lu; Zhao, Bin-xing; Xiao, Hong-tao; Tong, Rong-sheng; Gao, Chun-ming

2013-09-01

Chinese medicine is a historic cultural legacy of China. It has made a significant contribution to medicine and healthcare for generations. The development of Chinese herbal medicine analysis is emphasized by the Chinese pharmaceutical industry. This study has carried out the experimental analysis of ten kinds of Chinese herbal powder including Fritillaria powder, etc., based on the photoacoustic spectroscopy (PAS) method. First, a photoacoustic spectroscopy system was designed and constructed, especially a highly sensitive solid photoacoustic cell was established. Second, the experimental setup was verified through the characteristic emission spectrum of the light source, obtained by using carbon as a sample in the photoacoustic cell. Finally, as the photoacoustic spectroscopy analysis of Fritillaria, etc., was completed, the specificity of the Chinese herb medicine analysis was verified. This study shows that the PAS can provide a valid, highly sensitive analytical method for the specificity of Chinese herb medicine without preparing and damaging samples.

Photoacoustic imaging of lymphatic pumping

Science.gov (United States)

Forbrich, Alex; Heinmiller, Andrew; Zemp, Roger J.

2017-10-01

The lymphatic system is responsible for fluid homeostasis and immune cell trafficking and has been implicated in several diseases, including obesity, diabetes, and cancer metastasis. Despite its importance, the lack of suitable in vivo imaging techniques has hampered our understanding of the lymphatic system. This is, in part, due to the limited contrast of lymphatic fluids and structures. Photoacoustic imaging, in combination with optically absorbing dyes or nanoparticles, has great potential for noninvasively visualizing the lymphatic vessels deep in tissues. Multispectral photoacoustic imaging is capable of separating the components; however, the slow wavelength switching speed of most laser systems is inadequate for imaging lymphatic pumping without motion artifacts being introduced into the processed images. We investigate two approaches for visualizing lymphatic processes in vivo. First, single-wavelength differential photoacoustic imaging is used to visualize lymphatic pumping in the hindlimb of a mouse in real time. Second, a fast-switching multiwavelength photoacoustic imaging system was used to assess the propulsion profile of dyes through the lymphatics in real time. These approaches may have profound impacts in noninvasively characterizing and investigating the lymphatic system.

Photoacoustic microscopy imaging for microneedle drug delivery

Science.gov (United States)

Moothanchery, Mohesh; Seeni, Razina Z.; Xu, Chenjie; Pramanik, Manojit

2018-02-01

The recent development of novel transdermal drug delivery systems (TDDS) using microneedle technology allows micron-sized conduits to be formed within the outermost skin layers attracting keen interest in skin as an interface for localized and systemic delivery of therapeutics. In light of this, researchers are using microneedles as tools to deliver nanoparticle formulations to targeted sites for effective therapy. However, in such studies the use of traditional histological methods are employed for characterization and do not allow for the in vivo visualization of drug delivery mechanism. Hence, this study presents a novel imaging technology to characterize microneedle based nanoparticle delivery systems using optical resolution-photoacoustic microscopy (OR-PAM). In this study in vivo transdermal delivery of gold nanoparticles using microneedles in mice ear and the spatial distribution of the nanoparticles in the tissue was successfully illustrated. Characterization of parameters that are relevant in drug delivery studies such as penetration depth, efficiency of delivered gold nanoparticles were monitored using the system. Photoacoustic microscopy proves an ideal tool for the characterization studies of microneedle properties and the studies shows microneedles as an ideal tool for precise and controlled drug delivery.

Enlarged acceptance angle of a finite size detector in photoacoustic imaging using acoustic lenses

NARCIS (Netherlands)

Xia, W.; Piras, D.; Heijblom, Michelle; van Hespen, Johannes C.G.; Steenbergen, Wiendelt; Manohar, Srirang; van Veldhoven, Spiridon; Prins, Christian; van Leeuwen, Ton

2011-01-01

A large surface area transducer is preferable to be used to detect extremely weak photoacoustic signals in mammography due to its high sensitivity. The lateral resolution is limited by the small acceptance angle of such a transducer. We introduce an excellent material for an acoustic lens used to

Double-Stage Delay Multiply and Sum Beamforming Algorithm: Application to Linear-Array Photoacoustic Imaging

OpenAIRE

Mozaffarzadeh, Moein; Mahloojifar, Ali; Orooji, Mahdi; Adabi, Saba; Nasiriavanaki, Mohammadreza

2018-01-01

Photoacoustic imaging (PAI) is an emerging medical imaging modality capable of providing high spatial resolution of Ultrasound (US) imaging and high contrast of optical imaging. Delay-and-Sum (DAS) is the most common beamforming algorithm in PAI. However, using DAS beamformer leads to low resolution images and considerable contribution of off-axis signals. A new paradigm namely Delay-Multiply-and-Sum (DMAS), which was originally used as a reconstruction algorithm in confocal microwave imaging...

Near-infrared multispectral photoacoustic microscopy using a graded-index fiber amplifier

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Takashi Buma

2016-09-01

Full Text Available We demonstrate optical resolution photoacoustic microscopy (OR-PAM of lipid-rich tissue using a multi-wavelength pulsed laser based on nonlinear fiber optics. 1047 nm laser pulses are converted to 1098, 1153, 1215, and 1270 nm pulses via stimulated Raman scattering in a graded-index multimode fiber. Multispectral PAM of a lipid phantom is demonstrated with our low-cost and simple technique.

Breast imaging using the Twente photoacoustic mammoscope (PAM): new clinical measurements

Science.gov (United States)

Heijblom, Michelle; Piras, Daniele; Ten Tije, Ellen; Xia, Wenfeng; van Hespen, Johan; Klaase, Joost; van den Engh, Frank; van Leeuwen, Ton; Steenbergen, Wiendelt; Manohar, Srirang

2011-07-01

Worldwide, yearly about 450,000 women die from the consequences of breast cancer. Current imaging modalities are not optimal in discriminating benign from malignant tissue. Visualizing the malignancy-associated increased hemoglobin concentration might significantly improve early diagnosis of breast cancer. Since photoacoustic imaging can visualize hemoglobin in tissue with optical contrast and ultrasound-like resolution, it is potentially an ideal method for early breast cancer imaging. The Twente Photoacoustic Mammoscope (PAM) has been developed specifically for breast imaging. Recently, a large clinical study has been started in the Medisch Spectrum Twente in Oldenzaal using PAM. In PAM, the breast is slightly compressed between a window for laser light illumination and a flat array ultrasound detector. The measurements are performed using a Q-switched Nd:YAG laser, pulsed at 1064 nm and a 1 MHz unfocused ultrasound detector array. Three-dimensional data are reconstructed using a delay and sum reconstruction algorithm. Those reconstructed images are compared with conventional imaging and histopathology. In the first phase of the study 12 patients with a malignant lesion and 2 patients with a benign cyst have been measured. The results are used to guide developments in photoacoustic mammography in order to pave the way towards an optimal technique for early diagnosis of breast cancer.

Photoacoustic spectra of rare earth pentaphosphates

International Nuclear Information System (INIS)

Strek, W.; Lukowiak, E.; Marchewka, M.; Ratajczak, H.

1987-01-01

The photoacoustic (PA) spectra of raee earth pentaphosphates of the general formula REP 5 O 14 , where RE = Pr,Nd,Ho,Er,Tm, are reported. The photoacoustic bands were identified and compared with the absorption spectra. For quantitative analysis of PA bands of lanthanide (III) ions, the intensity ratio vector is introduced characterizing the intensity distribution of f-f transitions. It was found that the relative intensities of photoacoustic bands are comparable with the intensities of absorption bands. It is concluded that the nonradiative relaxation mechanism leading to the PA signal is independent of the manifold-to-manifold J-J' radiationless transitions

Single-wavelength functional photoacoustic microscopy in biological tissue.

Science.gov (United States)

Danielli, Amos; Favazza, Christopher P; Maslov, Konstantin; Wang, Lihong V

2011-03-01

Recently, we developed a reflection-mode relaxation photoacoustic microscope, based on saturation intensity, to measure picosecond relaxation times using a nanosecond laser. Here, using the different relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, the oxygen saturation was quantified in vivo with single-wavelength photoacoustic microscopy. All previous functional photoacoustic microscopy measurements required imaging with multiple-laser-wavelength measurements to quantify oxygen saturation. Eliminating the need for multiwavelength measurements removes the influence of spectral properties on oxygenation calculations and improves the portability and cost-effectiveness of functional or molecular photoacoustic microscopy.

Double Pulse LIBS of Titanium-Based PVD-Coatings with Submicron Resolution

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K. Ermalitskaia

2016-01-01

Full Text Available The possibility for double pulse LIBS in the process of a direct layer-by-layer analysis of the titanium-based PVD-coatings on polished flat blank samples of steel and silicon and also of the TiAlN/TiN-coating on a milling cutter is considered. A method is proposed to control thickness of the radiation evaporated layer by defocusing the laser beam with respect to the surface, making it possible to attain the depth resolution of 0.1 μm. The Ti and Ti-Zr-coatings produced using the ion-assisted condensation method and subjected to streams of the nitrogen plasma in a magnetic-plasma compressor are studied.

Melanin-originated carbonaceous dots for triple negative breast cancer diagnosis by fluorescence and photoacoustic dual-mode imaging.

Science.gov (United States)

Xiao, Wei; Li, Yuan; Hu, Chuan; Huang, Yuan; He, Qin; Gao, Huile

2017-07-01

Carbonaceous dots exhibit increasing applications in diagnosis and drug delivery due to excellent photostability and biocompatibility properties. However, relative short excitation and emission of melanin carbonaceous dots (MCDs) limit the applicability in fluorescence bioimaging. Furthermore, the generally poor spatial resolution of fluorescence imaging limits potential in vivo applications. Due to a variety of beneficial properties, in this study, MCDs were prepared exhibiting great potential in fluorescence and photoacoustic dual-mode bioimaging. The MCDs exhibited a long excitation peak at 615nm and emission peak at 650nm, further highlighting the applicability in fluorescence imaging, while the absorbance peak at 633nm renders MCDs suitable for photoacoustic imaging. In vivo, the photoacoustic signal of MCDs was linearly correlated with the concentration of MCDs. Moreover, the MCDs were shown to be taken up into triple negative breast cancer cell line 4T1 in both a time- and concentration-dependent manner. In vivo fluorescence and photoacoustic imaging of subcutaneous 4T1 tumor demonstrated that MCDs could passively target triple negative breast cancer tissue by enhanced permeability and retention effects and may therefore be used for tumor dual-mode imaging. Furthermore, fluorescence distribution in tissue slices suggested that MCDs may distribute in 4T1 tumor with high efficacy. In conclusion, the MCDs studied offer potential application in fluorescence and photoacoustic dual-mode imaging. Copyright © 2017 Elsevier Inc. All rights reserved.

Single-wavelength functional photoacoustic microscopy in biological tissue

OpenAIRE

Danielli, Amos; Favazza, Christopher P.; Maslov, Konstantin; Wang, Lihong V.

2011-01-01

Recently, we developed a reflection-mode relaxation photoacoustic microscope, based on saturation intensity, to measure picosecond relaxation times using a nanosecond laser. Here, using the different relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, the oxygen saturation was quantified in vivo with single-wavelength photoacoustic microscopy. All previous functional photoacoustic microscopy measurements required ima...

Co-registered photoacoustic, thermoacoustic, and ultrasound mouse imaging

Science.gov (United States)

Reinecke, Daniel R.; Kruger, Robert A.; Lam, Richard B.; DelRio, Stephen P.

2010-02-01

We have constructed and tested a prototype test bed that allows us to form 3D photoacoustic CT images using near-infrared (NIR) irradiation (700 - 900 nm), 3D thermoacoustic CT images using microwave irradiation (434 MHz), and 3D ultrasound images from a commercial ultrasound scanner. The device utilizes a vertically oriented, curved array to capture the photoacoustic and thermoacoustic data. In addition, an 8-MHz linear array fixed in a horizontal position provides the ultrasound data. The photoacoustic and thermoacoustic data sets are co-registered exactly because they use the same detector. The ultrasound data set requires only simple corrections to co-register its images. The photoacoustic, thermoacoustic, and ultrasound images of mouse anatomy reveal complementary anatomic information as they exploit different contrast mechanisms. The thermoacoustic images differentiate between muscle, fat and bone. The photoacoustic images reveal the hemoglobin distribution, which is localized predominantly in the vascular space. The ultrasound images provide detailed information about the bony structures. Superposition of all three images onto a co-registered hybrid image shows the potential of a trimodal photoacoustic-thermoacoustic-ultrasound small-animal imaging system.

Linear-Array Photoacoustic Imaging Using Minimum Variance-Based Delay Multiply and Sum Adaptive Beamforming Algorithm

OpenAIRE

Mozaffarzadeh, Moein; Mahloojifar, Ali; Orooji, Mahdi; Kratkiewicz, Karl; Adabi, Saba; Nasiriavanaki, Mohammadreza

2017-01-01

In Photoacoustic imaging (PA), Delay-and-Sum (DAS) beamformer is a common beamforming algorithm having a simple implementation. However, it results in a poor resolution and high sidelobes. To address these challenges, a new algorithm namely Delay-Multiply-and-Sum (DMAS) was introduced having lower sidelobes compared to DAS. To improve the resolution of DMAS, a novel beamformer is introduced using Minimum Variance (MV) adaptive beamforming combined with DMAS, so-called Minimum Variance-Based D...

All-optical photoacoustic microscopy using a MEMS scanning mirror

Science.gov (United States)

Chen, Sung-Liang; Xie, Zhixing; Ling, Tao; Wei, Xunbin; Guo, L. Jay; Wang, Xueding

2013-03-01

It has been studied that a potential marker to obtain prognostic information about bladder cancer is tumor neoangiogenesis, which can be quantified by morphometric characteristics such as microvascular density. Photoacoustic microscopy (PAM) can render sensitive three-dimensional (3D) mapping of microvasculature, providing promise to evaluate the neoangiogenesis that is closely related to the diagnosis of bladder cancer. To ensure good image quality, it is desired to acquire bladder PAM images from its inside via the urethra, like conventional cystoscope. Previously, we demonstrated all-optical PAM systems using polymer microring resonators to detect photoacoustic signals and galvanometer mirrors for laser scanning. In this work, we build a miniature PAM system using a microelectromechanical systems (MEMS) scanning mirror, demonstrating a prototype of an endoscopic PAM head capable of high imaging quality of the bladder. The system has high resolutions of 17.5 μm in lateral direction and 19 μm in the axial direction at a distance of 5.4 mm. Images of printed grids and the 3D structure of microvasculature in animal bladders ex vivo by the system are demonstrated.

Multispectral photoacoustic microscopy of lipids using a pulsed supercontinuum laser.

Science.gov (United States)

Buma, Takashi; Conley, Nicole C; Choi, Sang Won

2018-01-01

We demonstrate optical resolution photoacoustic microscopy (OR-PAM) of lipid-rich tissue between 1050-1714 nm using a pulsed supercontinuum laser based on a large-mode-area photonic crystal fiber. OR-PAM experiments of lipid-rich samples show the expected optical absorption peaks near 1210 and 1720 nm. These results show that pulsed supercontinuum lasers are promising for OR-PAM applications such as label-free histology of lipid-rich tissue and imaging small animal models of disease.

PHOTOACOUSTIC SPECTROSCOPY USING A SYNCHROTRON LIGHT SOURCE

International Nuclear Information System (INIS)

JACKSON, R.S.; MICHAELIAN, K.H.; HOMES, C.C.

2001-01-01

We have investigated the use of a synchrotron as a source for infrared photoacoustic spectroscopy. A synchrotron has an intrinsically high radiance, which is beneficial when photoacoustic spectroscopy is applied to small samples, especially at long wavelengths

All-optical extravascular laser-ultrasound and photoacoustic imaging of calcified atherosclerotic plaque in excised carotid artery

Directory of Open Access Journals (Sweden)

Jami L. Johnson

2018-03-01

Full Text Available Photoacoustic (PA imaging may be advantageous as a safe, non-invasive imaging modality to image the carotid artery. However, calcification that accompanies atherosclerotic plaque is difficult to detect with PA due to the non-distinct optical absorption spectrum of hydroxyapatite. We propose reflection-mode all-optical laser-ultrasound (LUS imaging to obtain high-resolution, non-contact, non-ionizing images of the carotid artery wall and calcification. All-optical LUS allows for flexible acquisition geometry and user-dependent data acquisition for high repeatability. We apply all-optical techniques to image an excised human carotid artery. Internal layers of the artery wall, enlargement of the vessel, and calcification are observed with higher resolution and reduced artifacts with nonconfocal LUS compared to confocal LUS. Validation with histology and X-ray computed tomography (CT demonstrates the potential for LUS as a method for non-invasive imaging in the carotid artery. Keywords: Atherosclerosis, Photoacoustic imaging, Laser-ultrasound, Calcification, Reverse-time migration

Towards optimized naphthalocyanines as sonochromes for photoacoustic imaging in vivo

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Mitchell J. Duffy

2018-03-01

Full Text Available In this paper we establish a methodology to predict photoacoustic imaging capabilities from the structure of absorber molecules (sonochromes. The comparative in vitro and in vivo screening of naphthalocyanines and cyanine dyes has shown a substitution pattern dependent shift in photoacoustic excitation wavelength, with distal substitution producing the preferred maximum around 800 nm. Central ion change showed variable production of photoacoustic signals, as well as singlet oxygen photoproduction and fluorescence with the optimum for photoacoustic imaging being nickel(II. Our approach paves the way for the design, evaluation and realization of optimized sonochromes as photoacoustic contrast agents. Keywords: Naphthalocyanines, Spectroscopy

Optimizing the optical wavelength for the photoacoustic imaging of inflammatory arthritis

Science.gov (United States)

Jo, Janggun; Xu, Guan; Hu, Jack; Francis, Sheeja; Marquardt, April; Yuan, Jie; Girish, Gandikota; Wang, Xueding

2015-03-01

With the capability of assessing high resolution optical information in soft tissues at imaging depth up to several centimeters, innovative biomedical photoacoustic imaging (PAI) offers benefits to diagnosis and treatment monitoring of inflammatory arthritis, particularly in combination with more established ultrasonography (US). In this work, a PAI and US dual-modality system facilitating both imaging functions in a real-time fashion was developed and initially tested for its clinical performance on patients with active inflammatory arthritis. Photoacoustic (PA) images of metacarpophalangeal (MCP) joints were acquired at 580-nm wavelength that provides a desired balance between optical absorption of blood and attenuation in background tissue. The results from six patients and six normal volunteers used as a control demonstrated the satisfactory sensitivity of PAI in assessing the physiological changes in the joints, specifically enhanced blood flow as a result of active synovitis. This preliminary study suggests that PAI, by revealing vascular features suggestive of joint inflammation, could be a valuable supplement to musculoskeletal US for rheumatology clinic.

Indocyanine green loaded graphene oxide for high-efficient photoacoustic tumor therapy

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Baoyun Yan

2016-07-01

Full Text Available Photoacoustic therapy, using the photoacoustic effect of agents for selectively killing tumor cells, has shown promising for treating tumor. Utilization of high optical absorption probes can help to effectively improve the photoacoustic therapy efficiency. Herein, we report a novel high-absorption photoacoustic probe that is composed of indocyanine green (ICG and graphene oxide (GO, entitled GO-ICG, for photoacoustic therapy. The attached ICG with narrow absorption spectral profile has strong optical absorption in the infrared region. The absorption spectrum of the GO-ICG solution reveals that the GO-ICG particles exhibited a 10-fold higher absorbance at 780nm (its peak absorbance as compared with GO. Importantly, ICG’s fluorescence is quenched by GO via fluorescence resonance energy transfer. As a result, GO-ICG can high-efficiently convert the absorbed light energy to acoustic wave under pulsed laser irradiation. We further demonstrate that GO-ICG can produce stronger photoacoustic wave than the GO and ICG alone. Moreover, we conjugate this contrast agent with integrin αvβ3 mono-clonal antibody to molecularly target the U87-MG human glioblastoma cells for selective tumor cell killing. Finally, our results testify that the photoacoustic therapy efficiency of GO-ICG is higher than the existing photoacoustic therapy agent. Our work demonstrates that GO-ICG is a high-efficiency photoacoustic therapy agent. This novel photoacoustic probe is likely to be an available candidate for tumor therapy.

Photoacoustic reflection artifact reduction using photoacoustic-guided focused ultrasound : comparison between plane-wave and element-by-element synthetic backpropagation approach

NARCIS (Netherlands)

Kuniyil Ajith Singh, M.; Jaeger, M.; Frenz, M.; Steenbergen, Wiendelt

2017-01-01

Reflection artifacts caused by acoustic inhomogeneities constitute a major problem in epi-mode biomedical photoacoustic imaging. Photoacoustic transients from the skin and superficial optical absorbers traverse into the tissue and reflect off echogenic structures to generate reflection artifacts.

Thermoviscous analysis of open photoacoustic cells

Science.gov (United States)

Mannoor, Madhusoodanan; Kang, Sangmo

2017-11-01

Open photoacoustic cells, apart from the conventional spectroscopic applications, are increasingly useful in bio medical applications such as in vivo blood sugar measurement. Maximising the acoustic pressure amplitude and the quality factor are major design considerations associated with open cells.Conventionaly, resonant photoacoustic cells are analyzed by either transmission line analogy or Eigen mode expansion method. In this study, we conducted a more comprehensive thermo viscous analysis of open photoacoustic cells. A Helmholtz cell and a T-shaped cell, which are acoustically different, are considered for analysis. Effect of geometrical dimensions on the acoustic pressure, quality factor and the intrusion of noise are analyzed and compared between these cells. Specific attention is given to the sizing of the opening and fixtures on it to minimize the radiational losses and the intrusion of noise. Our results are useful for proper selection of the type of open photoacoustic cells for in vivo blood sugar measurement and the optimization of geometric variables of such cells. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and future planning (2017R1A2B4005006).

Small-animal whole-body imaging using a photoacoustic full ring array system

Science.gov (United States)

Xia, Jun; Guo, Zijian; Aguirre, Andres; Zhu, Quing; Wang, Lihong V.

2011-03-01

In this report, we present a novel 3D photoacoustic computed tomography (PACT) system for small-animal whole-body imaging. The PACT system, based on a 512-element full-ring transducer array, received photoacoustic signals primarily from a 2-mm-thick slice. The light was generated by a pulse laser, and can either illuminate from the top or be reshaped to illuminate the sample from the side, using a conical lens and an optical condenser. The PACT system was capable of acquiring an in-plane image in 1.6 s; by scanning the sample in the elevational direction, a 3D tomographic image could be constructed. We tested the system by imaging a cylindrical phantom made of human hairs immersed in a scattering medium. The reconstructed image achieved an in-plane resolution of 0.1 mm and an elevational resolution of 1 mm. After deconvolution in the elevational direction, the 3D image was found to match well with the phantom. The system was also used to image a baby mouse in situ; the spinal cord and ribs can be seen easily in the reconstructed image. Our results demonstrate that the PACT system has the potential to be used for fast small-animal whole-body tomographic imaging.

Original Research. Photoacoustic Microscopy in Dental Medicine

Directory of Open Access Journals (Sweden)

Stan Adrian Tudor

2017-03-01

Full Text Available Introduction: Photoacoustic microscopy, also known as optoacoustic imaging, is a comparatively new method of investigation in dental medicine, which uses a laser-generated ultrasound (short laser pulses to achieve images for interpretation. Photoacoustic microscopy can be used in a broad spectrum, from detecting tooth decay at its earliest stages to dental anatomy analysis. Material and methods: The energy emitted by the photoacoustic pulse is moderately absorbed by the target and exchanged into heat, leading to a local transitory temperature upsurge. The tension propagates and grows as ultrasonic waves, distinguished by the ultrasonic transducers which are planted apart from the tissue. The photoacoustic microscope has a tunable dye laser which passes through a condensing lens, an objective and ultimately an ultrasonic transducer attached to an acoustic lens to capture and receive information about the scanned probe from a sample moved on the X, Y dimensions. Results: The precise anatomy of layered concentric structures can be clearly observed in photoacoustic microscopy. The image value of the inner layer can be higher, indicating strong optical absorption, while the image value of the outer layer is lower, indicating weaker optical absorption. Meanwhile, the inner layer has the exact same size as the dentin structure and the outer layer has the exact same size as the enamel structure in this cross-section. Conclusions: The photoacoustic microscope (all-optical comes out to be a future and promising tool for detecting early-stage caries and lesions on the surface of the teeth, where micro-leakage occurs at the interface of tooth restoration, and also the anatomy of dental tissues.

Tunable Semiconducting Polymer Nanoparticles with INDT-Based Conjugated Polymers for Photoacoustic Molecular Imaging.

Science.gov (United States)

Stahl, Thomas; Bofinger, Robin; Lam, Ivan; Fallon, Kealan J; Johnson, Peter; Ogunlade, Olumide; Vassileva, Vessela; Pedley, R Barbara; Beard, Paul C; Hailes, Helen C; Bronstein, Hugo; Tabor, Alethea B

2017-06-21

Photoacoustic imaging combines both excellent spatial resolution with high contrast and specificity, without the need for patients to be exposed to ionizing radiation. This makes it ideal for the study of physiological changes occurring during tumorigenesis and cardiovascular disease. In order to fully exploit the potential of this technique, new exogenous contrast agents with strong absorbance in the near-infrared range, good stability and biocompatibility, are required. In this paper, we report the formulation and characterization of a novel series of endogenous contrast agents for photoacoustic imaging in vivo. These contrast agents are based on a recently reported series of indigoid π-conjugated organic semiconductors, coformulated with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, to give semiconducting polymer nanoparticles of about 150 nm diameter. These nanoparticles exhibited excellent absorption in the near-infrared region, with good photoacoustic signal generation efficiencies, high photostability, and extinction coefficients of up to three times higher than those previously reported. The absorption maximum is conveniently located in the spectral region of low absorption of chromophores within human tissue. Using the most promising semiconducting polymer nanoparticle, we have demonstrated wavelength-dependent differential contrast between vasculature and the nanoparticles, which can be used to unambiguously discriminate the presence of the contrast agent in vivo.

Photoacoustic absorption spectroscopy of single optically trapped aerosol droplets

Science.gov (United States)

Covert, Paul A.; Cremer, Johannes W.; Signorell, Ruth

2017-08-01

Photoacoustics have been widely used for the study of aerosol optical properties. To date, these studies have been performed on particle ensembles, with minimal ability to control for particle size. Here, we present our singleparticle photoacoustic spectrometer. The sensitivity and stability of the instrument is discussed, along with results from two experiments that illustrate the unique capabilities of this instrument. In the first experiment, we present a measurement of the particle size-dependence of the photoacoustic response. Our results confirm previous models of aerosol photoacoustics that had yet to be experimentally tested. The second set of results reveals a size-dependence of photochemical processes within aerosols that results from the nanofocusing of light within individual droplets.

Singular value decomposition analysis of a photoacoustic imaging system and 3D imaging at 0.7 FPS.

Science.gov (United States)

Roumeliotis, Michael B; Stodilka, Robert Z; Anastasio, Mark A; Ng, Eldon; Carson, Jeffrey J L

2011-07-04

Photoacoustic imaging is a non-ionizing imaging modality that provides contrast consistent with optical imaging techniques while the resolution and penetration depth is similar to ultrasound techniques. In a previous publication [Opt. Express 18, 11406 (2010)], a technique was introduced to experimentally acquire the imaging operator for a photoacoustic imaging system. While this was an important foundation for future work, we have recently improved the experimental procedure allowing for a more densely populated imaging operator to be acquired. Subsets of the imaging operator were produced by varying the transducer count as well as the measurement space temporal sampling rate. Examination of the matrix rank and the effect of contributing object space singular vectors to image reconstruction were performed. For a PAI system collecting only limited data projections, matrix rank increased linearly with transducer count and measurement space temporal sampling rate. Image reconstruction using a regularized pseudoinverse of the imaging operator was performed on photoacoustic signals from a point source, line source, and an array of point sources derived from the imaging operator. As expected, image quality increased for each object with increasing transducer count and measurement space temporal sampling rate. Using the same approach, but on experimentally sampled photoacoustic signals from a moving point-like source, acquisition, data transfer, reconstruction and image display took 1.4 s using one laser pulse per 3D frame. With relatively simple hardware improvements to data transfer and computation speed, our current imaging results imply that acquisition and display of 3D photoacoustic images at laser repetition rates of 10Hz is easily achieved.

Characterization of a photoacoustic system through neural networks to determine multicomponent samples

Science.gov (United States)

Zajarevich, N. M.; Peuriot, A. L.; Slezak, V. B.

2016-07-01

Photoacoustic spectroscopy for trace gases detection, based on a CO2 laser, can be used in a wide range of applications. The tunability of this laser in the mid-infrared (9.4-10.6 μm) allows the quantitative determination of different substances in multicomponent samples. In general, at traces level, the total photoacoustic amplitude at a certain wavelength may be approximated by a linear superposition of the amplitudes given by each of the species absorbing at that wavelength. However, in some cases, the sum of the individual signals is no longer valid. In particular, it is known the presence of CO2 delays the acoustic signal in relation to the laser excitation due to the exchange of vibrational energy between CO2 and N2. This phenomenon generates a slow V-T energy relaxation from a metastable N2 vibrational level and the sum of individual contributions may no longer be valid. Moreover, the resolution of a linear equation system has limitations, so the possibility to determine concentrations in photoacoustics based on neural network is proposed in this work. This procedure is tried in a particular case of a volatile organic compound, such as C2H4, and CO2 in air. The results are compared with the ones obtained with a model based on rate equations.

Investigation of an energy-gap model for photoacoustic O2A-band spectra: H2O calibration near 7180 cm−1

International Nuclear Information System (INIS)

Vess, E.M.; Anderson, C.N.; Awadalla, V.E.; Estes, E.J.; Jeon, C.; Wallace, C.J.; Hu, X.F.; Havey, D.K.

2012-01-01

Highlights: ► We investigate an energy transfer model for photoacoustic measurements of the O 2 A-band. ► We measure the response of a photoacoustic spectrometer for known quantities of H 2 O and O 2 . ► We fit multiple theoretical spectral line profiles to the data. ► We bind the relative uncertainty of the energy transfer model to less than 1%. ► We demonstrate that speed-dependence is an important line shape effect for these experiments. - Abstract: A photoacoustic spectrometer is used to evaluate the accuracy of an energy-gap model for collisional energy transfer. For photoacoustic measurements involving the b 1 Σ g + ←X 3 Σ g - transition of molecular oxygen the conversion of photon energy to thermal energy is inefficient and proceeds through the a 1 Δ g state. This results in attenuation of the photoacoustic signal. The magnitude of the attenuation can be predicted with an energy-gap model whose accuracy has been previously confirmed to within 3 ± 5%. However, this prior result does not rule out incomplete rotational relaxation of O 2 in the a 1 Δ g state. In this study, high-resolution spectra of H 2 O in air are used to calibrate the photoacoustic spectrometer. This work binds the relative uncertainty in the energy-gap relaxation factor for O 2 A-band photoacoustic signals to be approximately 1%. During one acoustic cycle, this result implies negligible collisional relaxation to the X 3 Σ g - state of O 2 and nearly complete collisional relaxation to the a 1 Δ g state.

Quartz-enhanced photo-acoustic spectroscopy for breath analyses

Science.gov (United States)

Petersen, Jan C.; Lamard, Laurent; Feng, Yuyang; Focant, Jeff-F.; Peremans, Andre; Lassen, Mikael

2017-03-01

An innovative and novel quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor for highly sensitive and selective breath gas analysis is introduced. The QEPAS sensor consists of two acoustically coupled micro- resonators (mR) with an off-axis 20 kHz quartz tuning fork (QTF). The complete acoustically coupled mR system is optimized based on finite element simulations and experimentally verified. Due to the very low fabrication costs the QEPAS sensor presents a clear breakthrough in the field of photoacoustic spectroscopy by introducing novel disposable gas chambers in order to avoid cleaning after each test. The QEPAS sensor is pumped resonantly by a nanosecond pulsed single-mode mid-infrared optical parametric oscillator (MIR OPO). Spectroscopic measurements of methane and methanol in the 3.1 μm to 3.7 μm wavelength region is conducted. Demonstrating a resolution bandwidth of 1 cm-1. An Allan deviation analysis shows that the detection limit at optimum integration time for the QEPAS sensor is 32 ppbv@190s for methane and that the background noise is solely due to the thermal noise of the QTF. Spectra of both individual molecules as well as mixtures of molecules were measured and analyzed. The molecules are representative of exhaled breath gasses that are bio-markers for medical diagnostics.

Interlaced photoacoustic and ultrasound imaging system with real-time coregistration for ovarian tissue characterization

Science.gov (United States)

Alqasemi, Umar; Li, Hai; Yuan, Guangqian; Kumavor, Patrick; Zanganeh, Saeid; Zhu, Quing

2014-07-01

Coregistered ultrasound (US) and photoacoustic imaging are emerging techniques for mapping the echogenic anatomical structure of tissue and its corresponding optical absorption. We report a 128-channel imaging system with real-time coregistration of the two modalities, which provides up to 15 coregistered frames per second limited by the laser pulse repetition rate. In addition, the system integrates a compact transvaginal imaging probe with a custom-designed fiber optic assembly for in vivo detection and characterization of human ovarian tissue. We present the coregistered US and photoacoustic imaging system structure, the optimal design of the PC interfacing software, and the reconfigurable field programmable gate array operation and optimization. Phantom experiments of system lateral resolution and axial sensitivity evaluation, examples of the real-time scanning of a tumor-bearing mouse, and ex vivo human ovaries studies are demonstrated.

An optimized ultrasound detector for photoacoustic breast tomography

NARCIS (Netherlands)

Xia, Wenfeng; Piras, Daniele; van Hespen, Johan C. G.; van Veldhoven, Spiridon; Prins, Christian; van Leeuwen, Ton G.; Steenbergen, Wiendelt; Manohar, Srirang

2013-01-01

Photoacoustic imaging has proven to be able to detect vascularization-driven optical absorption contrast associated with tumors. In order to detect breast tumors located a few centimeter deep in tissue, a sensitive ultrasound detector is of crucial importance for photoacoustic mammography. Further,

Laser induced single spot oxidation of titanium

Energy Technology Data Exchange (ETDEWEB)

Jwad, Tahseen, E-mail: taj355@bham.ac.uk; Deng, Sunan; Butt, Haider; Dimov, S.

2016-11-30

Highlights: • A new high resolution laser induced oxidation (colouring) method is proposed (single spot oxidation). • The method is applied to control oxide films thicknesses and hence colours on titanium substrates in micro-scale. • The method enable imprinting high resolution coloured image on Ti substrate. • Optical and morphological periodic surface structures are also produced by an array of oxide spots using the proposed method. • Colour coding of two colours into one field is presented. - Abstract: Titanium oxides have a wide range of applications in industry, and they can be formed on pure titanium using different methods. Laser-induced oxidation is one of the most reliable methods due to its controllability and selectivity. Colour marking is one of the main applications of the oxidation process. However, the colourizing process based on laser scanning strategies is limited by the relative large processing area in comparison to the beam size. Single spot oxidation of titanium substrates is proposed in this research in order to increase the resolution of the processed area and also to address the requirements of potential new applications. The method is applied to produce oxide films with different thicknesses and hence colours on titanium substrates. High resolution colour image is imprinted on a sheet of pure titanium by converting its pixels’ colours into laser parameter settings. Optical and morphological periodic surface structures are also produced by an array of oxide spots and then analysed. Two colours have been coded into one field and the dependencies of the reflected colours on incident and azimuthal angles of the light are discussed. The findings are of interest to a range of application areas, as they can be used to imprint optical devices such as diffusers and Fresnel lenses on metallic surfaces as well as for colour marking.

Laser induced single spot oxidation of titanium

International Nuclear Information System (INIS)

Jwad, Tahseen; Deng, Sunan; Butt, Haider; Dimov, S.

2016-01-01

Highlights: • A new high resolution laser induced oxidation (colouring) method is proposed (single spot oxidation). • The method is applied to control oxide films thicknesses and hence colours on titanium substrates in micro-scale. • The method enable imprinting high resolution coloured image on Ti substrate. • Optical and morphological periodic surface structures are also produced by an array of oxide spots using the proposed method. • Colour coding of two colours into one field is presented. - Abstract: Titanium oxides have a wide range of applications in industry, and they can be formed on pure titanium using different methods. Laser-induced oxidation is one of the most reliable methods due to its controllability and selectivity. Colour marking is one of the main applications of the oxidation process. However, the colourizing process based on laser scanning strategies is limited by the relative large processing area in comparison to the beam size. Single spot oxidation of titanium substrates is proposed in this research in order to increase the resolution of the processed area and also to address the requirements of potential new applications. The method is applied to produce oxide films with different thicknesses and hence colours on titanium substrates. High resolution colour image is imprinted on a sheet of pure titanium by converting its pixels’ colours into laser parameter settings. Optical and morphological periodic surface structures are also produced by an array of oxide spots and then analysed. Two colours have been coded into one field and the dependencies of the reflected colours on incident and azimuthal angles of the light are discussed. The findings are of interest to a range of application areas, as they can be used to imprint optical devices such as diffusers and Fresnel lenses on metallic surfaces as well as for colour marking.

A photoacoustic technique to measure the properties of single cells

Science.gov (United States)

Strohm, Eric M.; Berndl, Elizabeth S. L.; Kolios, Michael C.

2013-03-01

We demonstrate a new technique to non-invasively determine the diameter and sound speed of single cells using a combined ultrasonic and photoacoustic technique. Two cell lines, B16-F1 melanoma cells and MCF7 breast cancer cells were examined using this technique. Using a 200 MHz transducer, the ultrasound backscatter from a single cell in suspension was recorded. Immediately following, the cell was irradiated with a 532 nm laser and the resulting photoacoustic wave recorded by the same transducer. The melanoma cells contain optically absorbing melanin particles, which facilitated photoacoustic wave generation. MCF7 cells have negligible optical absorption at 532 nm; the cells were permeabilized and stained with trypan blue prior to measurements. The measured ultrasound and photoacoustic power spectra were compared to theoretical equations with the cell diameter and sound speed as variables (Anderson scattering model for ultrasound, and a thermoelastic expansion model for photoacoustics). The diameter and sound speed were extracted from the models where the spectral shape matched the measured signals. However the photoacoustic spectrum for the melanoma cell did not match theory, which is likely because melanin particles are located around the cytoplasm, and not within the nucleus. Therefore a photoacoustic finite element model of a cell was developed where the central region was not used to generate a photoacoustic wave. The resulting power spectrum was in better agreement with the measured signal than the thermoelastic expansion model. The MCF7 cell diameter obtained using the spectral matching method was 17.5 μm, similar to the optical measurement of 16 μm, while the melanoma cell diameter obtained was 22 μm, similar to the optical measurement of 21 μm. The sound speed measured from the MCF7 and melanoma cell was 1573 and 1560 m/s, respectively, which is within acceptable values that have been published in literature.

Photoacoustic emission from fluorescent nanodiamonds enhanced with gold nanoparticles

Science.gov (United States)

Zhang, Bailin; Fang, Chia-Yi; Chang, Cheng-Chun; Peterson, Ralph; Maswadi, Saher; Glickman, Randolph D.; Chang, Huan-Cheng; Ye, Jing Yong

2012-01-01

Fluorescent nanodiamonds (FNDs) have drawn much attention in recent years for biomedical imaging applications due to their desired physical properties including excellent photostability, high biocompatibility, extended far-red fluorescence emission, and ease of surface functionalization. Here we explore a new feature of FNDs, i.e. their photoacoustic emission capability, which may lead to potential applications of using FNDs as a dual imaging contrast agent for combined fluorescence and photoacoustic imaging modalities. We observed significant enhancement of photoacoustic emission from FNDs when they were conjugated with gold nanoparticles (GNPs). PMID:22808436

Photoacoustic emission from fluorescent nanodiamonds enhanced with gold nanoparticles.

Science.gov (United States)

Zhang, Bailin; Fang, Chia-Yi; Chang, Cheng-Chun; Peterson, Ralph; Maswadi, Saher; Glickman, Randolph D; Chang, Huan-Cheng; Ye, Jing Yong

2012-07-01

Fluorescent nanodiamonds (FNDs) have drawn much attention in recent years for biomedical imaging applications due to their desired physical properties including excellent photostability, high biocompatibility, extended far-red fluorescence emission, and ease of surface functionalization. Here we explore a new feature of FNDs, i.e. their photoacoustic emission capability, which may lead to potential applications of using FNDs as a dual imaging contrast agent for combined fluorescence and photoacoustic imaging modalities. We observed significant enhancement of photoacoustic emission from FNDs when they were conjugated with gold nanoparticles (GNPs).

Semiconducting polymer dot as a highly effective contrast agent for photoacoustic imaging

Science.gov (United States)

Yuan, Zhen; Zhang, Jian

2018-02-01

In this study, we developed a novel PIID-DTBT based semiconducting polymer dots (Pdots) that have broad and strong optical absorption in the visible-light region (500 nm - 700 nm). Gold nanoparticles (GNPs) and gold nanorods (GNRs) that have been verified as an excellent photoacoustic contrast agent were compared with Pdots based on photoacoustic imaging method. Both ex vivo and in vivo experiment demonstrated Pdots have a better photoacoustic conversion efficiency at 532 nm than GNPs and similar photoacoustic performance with GNRs at 700 nm at the same mass concentration. Our work demonstrates the great potential of Pdots as a highly effective contrast agent for precise localization of lesions relative to the blood vessels based on photoacoustic tomography imaging.

Imaging and detection of early stage dental caries with an all-optical photoacoustic microscope

International Nuclear Information System (INIS)

Hughes, D A; Kirk, K J; Sampathkumar, A; Longbottom, C

2015-01-01

Tooth decay, at its earliest stages, manifests itself as small, white, subsurface lesions in the enamel. Current methods for detection in the dental clinic are visual and tactile investigations, and bite-wing X-ray radiographs. These techniques suffer from poor sensitivity and specificity at the earliest (and reversible) stages of the disease due to the small size (<100μm) of the lesion. A fine-resolution (600 nm) ultra-broadband (200 MHz) all-optical photoacoustic microscopy system was is used to image the early signs of tooth decay. Ex-vivo tooth samples exhibiting white spot lesions were scanned and were found to generate a larger (one order of magnitude) photoacoustic (PA) signal in the lesion regions compared to healthy enamel. The high contrast in the PA images potentially allows lesions to be imaged and measured at a much earlier stage than current clinical techniques allow. PA images were cross referenced with histology photographs to validate our experimental results. Our PA system provides a noncontact method for early detection of white-spot lesions with a high detection bandwidth that offers advantages over previously demonstrated ultrasound methods. The technique provides the sensing depth of an ultrasound system, but with the spatial resolution of an optical system

Transurethral light delivery for prostate photoacoustic imaging

OpenAIRE

Lediju Bell, Muyinatu A.; Guo, Xiaoyu; Song, Danny Y.; Boctor, Emad M.

2015-01-01

Photoacoustic imaging has broad clinical potential to enhance prostate cancer detection and treatment, yet it is challenged by the lack of minimally invasive, deeply penetrating light delivery methods that provide sufficient visualization of targets (e.g., tumors, contrast agents, brachytherapy seeds). We constructed a side-firing fiber prototype for transurethral photoacoustic imaging of prostates with a dual-array (linear and curvilinear) transrectal ultrasound probe. A method to calculate ...

Modeling skull's acoustic attenuation and dispersion on photoacoustic signal

Science.gov (United States)

Mohammadi, L.; Behnam, H.; Nasiriavanaki, M. R.

2017-03-01

Despite the great promising results of a recent new transcranial photoacoustic brain imaging technology, it has been shown that the presence of the skull severely affects the performance of this imaging modality. In this paper, we investigate the effect of skull on generated photoacoustic signals with a mathematical model. The developed model takes into account the frequency dependence attenuation and acoustic dispersion effects occur with the wave reflection and refraction at the skull surface. Numerical simulations based on the developed model are performed for calculating the propagation of photoacoustic waves through the skull. From the simulation results, it was found that the skull-induced distortion becomes very important and the reconstructed image would be strongly distorted without correcting these effects. In this regard, it is anticipated that an accurate quantification and modeling of the skull transmission effects would ultimately allow for skull aberration correction in transcranial photoacoustic brain imaging.

Photoacoustic tomography of human hepatic malignancies using intraoperative indocyanine green fluorescence imaging.

Directory of Open Access Journals (Sweden)

Akinori Miyata

Full Text Available Recently, fluorescence imaging following the preoperative intravenous injection of indocyanine green has been used in clinical settings to identify hepatic malignancies during surgery. The aim of this study was to evaluate the ability of photoacoustic tomography using indocyanine green as a contrast agent to produce representative fluorescence images of hepatic tumors by visualizing the spatial distribution of indocyanine green on ultrasonographic images. Indocyanine green (0.5 mg/kg, intravenous was preoperatively administered to 9 patients undergoing hepatectomy. Intraoperatively, photoacoustic tomography was performed on the surface of the resected hepatic specimens (n = 10 under excitation with an 800 nm pulse laser. In 4 hepatocellular carcinoma nodules, photoacoustic imaging identified indocyanine green accumulation in the cancerous tissue. In contrast, in one hepatocellular carcinoma nodule and five adenocarcinoma foci (one intrahepatic cholangiocarcinoma and 4 colorectal liver metastases, photoacoustic imaging delineated indocyanine green accumulation not in the cancerous tissue but rather in the peri-cancerous hepatic parenchyma. Although photoacoustic tomography enabled to visualize spatial distribution of ICG on ultrasonographic images, which was consistent with fluorescence images on cut surfaces of the resected specimens, photoacoustic signals of ICG-containing tissues decreased approximately by 40% even at 4 mm depth from liver surfaces. Photoacoustic tomography using indocyanine green also failed to identify any hepatocellular carcinoma nodules from the body surface of model mice with non-alcoholic steatohepatitis. In conclusion, photoacoustic tomography has a potential to enhance cancer detectability and differential diagnosis by ultrasonographic examinations and intraoperative fluorescence imaging through visualization of stasis of bile-excreting imaging agents in and/or around hepatic tumors. However, further technical

Photoacoustic tomography of human hepatic malignancies using intraoperative indocyanine green fluorescence imaging.

Science.gov (United States)

Miyata, Akinori; Ishizawa, Takeaki; Kamiya, Mako; Shimizu, Atsushi; Kaneko, Junichi; Ijichi, Hideaki; Shibahara, Junji; Fukayama, Masashi; Midorikawa, Yutaka; Urano, Yasuteru; Kokudo, Norihiro

2014-01-01

Recently, fluorescence imaging following the preoperative intravenous injection of indocyanine green has been used in clinical settings to identify hepatic malignancies during surgery. The aim of this study was to evaluate the ability of photoacoustic tomography using indocyanine green as a contrast agent to produce representative fluorescence images of hepatic tumors by visualizing the spatial distribution of indocyanine green on ultrasonographic images. Indocyanine green (0.5 mg/kg, intravenous) was preoperatively administered to 9 patients undergoing hepatectomy. Intraoperatively, photoacoustic tomography was performed on the surface of the resected hepatic specimens (n = 10) under excitation with an 800 nm pulse laser. In 4 hepatocellular carcinoma nodules, photoacoustic imaging identified indocyanine green accumulation in the cancerous tissue. In contrast, in one hepatocellular carcinoma nodule and five adenocarcinoma foci (one intrahepatic cholangiocarcinoma and 4 colorectal liver metastases), photoacoustic imaging delineated indocyanine green accumulation not in the cancerous tissue but rather in the peri-cancerous hepatic parenchyma. Although photoacoustic tomography enabled to visualize spatial distribution of ICG on ultrasonographic images, which was consistent with fluorescence images on cut surfaces of the resected specimens, photoacoustic signals of ICG-containing tissues decreased approximately by 40% even at 4 mm depth from liver surfaces. Photoacoustic tomography using indocyanine green also failed to identify any hepatocellular carcinoma nodules from the body surface of model mice with non-alcoholic steatohepatitis. In conclusion, photoacoustic tomography has a potential to enhance cancer detectability and differential diagnosis by ultrasonographic examinations and intraoperative fluorescence imaging through visualization of stasis of bile-excreting imaging agents in and/or around hepatic tumors. However, further technical advances are needed

Spectroscopic and photoacoustic characterization of encapsulated iron oxide super-paramagnetic nanoparticles as a new multiplatform contrast agent

Science.gov (United States)

Armanetti, Paolo; Flori, Alessandra; Avigo, Cinzia; Conti, Luca; Valtancoli, Barbara; Petroni, Debora; Doumett, Saer; Cappiello, Laura; Ravagli, Costanza; Baldi, Giovanni; Bencini, Andrea; Menichetti, Luca

2018-06-01

Recently, a number of photoacoustic (PA) agents with increased tissue penetration and fine spatial resolution have been developed for molecular imaging and mapping of pathophysiological features at the molecular level. Here, we present bio-conjugated near-infrared light-absorbing magnetic nanoparticles as a new agent for PA imaging. These nanoparticles exhibit suitable absorption in the near-infrared region, with good photoacoustic signal generation efficiency and high photo-stability. Furthermore, these encapsulated iron oxide nanoparticles exhibit strong super-paramagnetic behavior and nuclear relaxivities that make them useful as magnetic resonance imaging (MRI) contrast media as well. Their simple bio-conjugation strategy, optical and chemical stability, and straightforward manipulation could enable the development of a PA probe with magnetic and spectroscopic properties suitable for in vitro and in vivo real-time imaging of relevant biological targets.

Molecular photoacoustic imaging of follicular thyroid carcinoma

DEFF Research Database (Denmark)

Levi, Jelena; Kothapalli, Sri-Rajashekar; Bohndiek, Sarah

2013-01-01

in living mice optically, observing the increase in Alexa750 fluorescence, and photoacoustically, using a dual wavelength imaging method. Results Active forms of both MMP2 and MMP-9 enzymes were found in FTC133 tumor homogenates, with MMP-9 detected in greater amounts. The molecular imaging agent......Purpose To evaluate the potential of targeted photoacoustic imaging as a non-invasive method for detection of follicular thyroid carcinoma. Experimental Design We determined the presence and activity of two members of matrix metalloproteinase family (MMP), MMP-2 and MMP-9, suggested as biomarkers...... for malignant thyroid lesions, in FTC133 thyroid tumors subcutaneously implanted in nude mice. The imaging agent used to visualize tumors was MMP activatable photoacoustic probe, Alexa750-CXeeeeXPLGLAGrrrrrXK-BHQ3. Cleavage of the MMP activatable agent was imaged after intratumoral and intravenous injections...

Photoacoustic CO2-Sensor for Automotive Applications

OpenAIRE

Huber, J.; Weber, C.; Eberhardt, A.; Wöllenstein, J.

2016-01-01

We present a field-tested miniaturized spectroscopic CO2 sensor which is based on the photoacoustic effect. The sensor is developed for automotive applications and considers the requirements for the usage in vehicles. The sensor measures two measurement ranges simultaneously: The monitoring of the indoor air quality and the detection of possible leakages of the coolant in CO2 air-conditioning systems. The sensor consists of a miniaturized innovative photoacoustic sensor unit with integrated e...

A calibrated iterative reconstruction for quantitative photoacoustic tomography using multi-angle light-sheet illuminations

Science.gov (United States)

Wang, Yihan; Lu, Tong; Zhang, Songhe; Song, Shaoze; Wang, Bingyuan; Li, Jiao; Zhao, Huijuan; Gao, Feng

2018-02-01

Quantitative photoacoustic tomography (q-PAT) is a nontrivial technique can be used to reconstruct the absorption image with a high spatial resolution. Several attempts have been investigated by setting point sources or fixed-angle illuminations. However, in practical applications, these schemes normally suffer from low signal-to-noise ratio (SNR) or poor quantification especially for large-size domains, due to the limitation of the ANSI-safety incidence and incompleteness in the data acquisition. We herein present a q-PAT implementation that uses multi-angle light-sheet illuminations and a calibrated iterative multi-angle reconstruction. The approach can acquire more complete information on the intrinsic absorption and SNR-boosted photoacoustic signals at selected planes from the multi-angle wide-field excitations of light-sheet. Therefore, the sliced absorption maps over whole body can be recovered in a measurementflexible, noise-robust and computation-economic way. The proposed approach is validated by the phantom experiment, exhibiting promising performances in image fidelity and quantitative accuracy.

Joseph F. Keithley Award For Advances in Measurement Science Lecture: Thermophotonic and Photoacoustic Radar Imaging Methods for Biomedical and Dental Imaging

Science.gov (United States)

Mandelis, Andreas

2012-02-01

In the first part of this presentation I will introduce thermophotonic radar imaging principles and techniques using chirped or binary-phase-coded modulation, methods which can break through the maximum detection depth/depth resolution limitations of conventional photothermal waves. Using matched-filter principles, a methodology enabling parabolic diffusion-wave energy fields to exhibit energy localization akin to propagating hyperbolic wave-fields has been developed. It allows for deconvolution of individual responses of superposed axially discrete sources, opening a new field: depth-resolved thermal coherence tomography. Several examples from dental enamel caries diagnostic imaging to metal subsurface defect thermographic imaging will be discussed. The second part will introduce the field of photoacoustic radar (or sonar) biomedical imaging. I will report the development of a novel biomedical imaging system that utilizes a continuous-wave laser source with a custom intensity modulation pattern, ultrasonic phased array for signal detection and processing coupled with a beamforming algorithm for reconstruction of photoacoustic correlation images. Utilization of specific chirped modulation waveforms (``waveform engineering'') achieves dramatic signal-to-noise-ratio increase and improved axial resolution over pulsed laser photoacoustics. The talk will conclude with aspects of instrumental sensitivity of the PA Radar to optical contrast using cancerous breast tissue-mimicking phantoms, super paramagnetic iron oxide nanoparticles as contrast enhancement agents and in-vivo tissue samples.

Near infrared photoacoustic detection of heptane in synthetic air

DEFF Research Database (Denmark)

Duggen, Lars; Albu, Mihaela; Willatzen, Morten

2013-01-01

Trace contaminations of n-heptane in synthetic air is measured in the parts-per-billion (ppb) range using near infrared photoacoustic detection. We describe the fundamental theory used in the design of the photoacoustic cell for trace gas analysis and determine the detection limit of the cell...

Processing methods for photoacoustic Doppler flowmetry with a clinical ultrasound scanner

Science.gov (United States)

Bücking, Thore M.; van den Berg, Pim J.; Balabani, Stavroula; Steenbergen, Wiendelt; Beard, Paul C.; Brunker, Joanna

2018-02-01

Photoacoustic flowmetry (PAF) based on time-domain cross correlation of photoacoustic signals is a promising technique for deep tissue measurement of blood flow velocity. Signal processing has previously been developed for single element transducers. Here, the processing methods for acoustic resolution PAF using a clinical ultrasound transducer array are developed and validated using a 64-element transducer array with a -6 dB detection band of 11 to 17 MHz. Measurements were performed on a flow phantom consisting of a tube (580 μm inner diameter) perfused with human blood flowing at physiological speeds ranging from 3 to 25 mm / s. The processing pipeline comprised: image reconstruction, filtering, displacement detection, and masking. High-pass filtering and background subtraction were found to be key preprocessing steps to enable accurate flow velocity estimates, which were calculated using a cross-correlation based method. In addition, the regions of interest in the calculated velocity maps were defined using a masking approach based on the amplitude of the cross-correlation functions. These developments enabled blood flow measurements using a transducer array, bringing PAF one step closer to clinical applicability.

In vivo preclinical photoacoustic imaging of tumor vasculature development and therapy

Science.gov (United States)

Laufer, Jan; Johnson, Peter; Zhang, Edward; Treeby, Bradley; Cox, Ben; Pedley, Barbara; Beard, Paul

2012-05-01

The use of a novel all-optical photoacoustic scanner for imaging the development of tumor vasculature and its response to a therapeutic vascular disrupting agent is described. The scanner employs a Fabry-Perot polymer film ultrasound sensor for mapping the photoacoustic waves and an image reconstruction algorithm based upon attenuation-compensated acoustic time reversal. The system was used to noninvasively image human colorectal tumor xenografts implanted subcutaneously in mice. Label-free three-dimensional in vivo images of whole tumors to depths of almost 10 mm with sub-100-micron spatial resolution were acquired in a longitudinal manner. This enabled the development of tumor-related vascular features, such as vessel tortuosity, feeding vessel recruitment, and necrosis to be visualized over time. The system was also used to study the temporal evolution of the response of the tumor vasculature following the administration of a therapeutic vascular disrupting agent (OXi4503). This revealed the well-known destruction and recovery phases associated with this agent. These studies illustrate the broader potential of this technology as an imaging tool for the preclinical and clinical study of tumors and other pathologies characterized by changes in the vasculature.

Automation, development and performance of a photoacoustic spectrometer

International Nuclear Information System (INIS)

Cavalheiro, F.R.F.

1985-01-01

This work consists in the development of a circuit to interface a photoacoustic spectrometer with a microcomputer. The obtained spectra are identical to those obtained in commercial photoacoustic spectrometers. The system permits a great versatility and it has possibilities to automatize other types of experiments. The system can be duplicated from national components and at a relatively low coast. (author)

Photoacoustic mammography laboratory prototype: imaging of breast tissue phantoms

NARCIS (Netherlands)

Manohar, Srirang; Kharine, Alexei; van Hespen, Johan C. G.; Steenbergen, Wiendelt; van Leeuwen, Ton G.

2004-01-01

We present a laboratory version of a photoacoustic mammoscope, based on a parallel plate geometry. The instrument is built around a flat high-density ultrasound detector matrix. The light source is a Q-switched Nd:YAG laser with a pulse duration of 5 ns. To test the instrument, a novel photoacoustic

Photoacoustic imaging of hidden dental caries by using a fiber-based probing system

Science.gov (United States)

Koyama, Takuya; Kakino, Satoko; Matsuura, Yuji

2017-04-01

Photoacoustic method to detect hidden dental caries is proposed. It was found that high frequency ultrasonic waves are generated from hidden carious part when radiating laser light to occlusal surface of model tooth. By making a map of intensity of these high frequency components, photoacoustic images of hidden caries were successfully obtained. A photoacoustic imaging system using a bundle of hollow optical fiber was fabricated for using clinical application, and clear photoacoustic image of hidden caries was also obtained by this system.

Discrimination of organic coffee via Fourier transform infrared-photoacoustic spectroscopy.

Science.gov (United States)

Gordillo-Delgado, Fernando; Marín, Ernesto; Cortés-Hernández, Diego Mauricio; Mejía-Morales, Claudia; García-Salcedo, Angela Janet

2012-08-30

Procedures for the evaluation of the origin and quality of ground and roasted coffee are constantly needed for the associated industry due to complexity of the related market. Conventional Fourier transform infrared (FTIR) spectroscopy can be used for detecting changes in functional groups of compounds, such as coffee. However, dispersion, reflection and non-homogeneity of the sample matrix can cause problems resulting in low spectral quality. On the other hand, sample preparation frequently takes place in a destructive way. To overcome these difficulties, in this work a photoacoustic cell has been adapted as a detector in a FTIR spectrophotometer to perform a study of roasted and ground coffee from three varieties of Coffea arabica grown by organic and conventional methods. Comparison between spectra of coffee recorded by FTIR-photoacoustic spectrometry (PAS) and by FTIR spectrophotometry showed a better resolution of the former method, which, aided by principal components analysis, allowed the identification of some absorption bands that allow the discrimination between organic and conventional coffee. The results obtained provide information about the spectral behavior of coffee powder which can be useful for establishing discrimination criteria. It has been demonstrated that FTIR-PAS can be a useful experimental tool for the characterization of coffee. Copyright © 2012 Society of Chemical Industry.

Photoacoustic Fourier Transform Infrared (FTIR) Spectroscopy Of Solids

Science.gov (United States)

Vidrine, D. Warren

1981-10-01

After discovering the photoacoustic effect, Alexander Graham Bell predicted its use in spectrometers, and that it would find its greatest utility "in the ultra-red." More than ninety years were required to fulfil his first prediction, and the second is still a prophecy. There is no record whether he ever imagined that an invention being developed that same winter by a young protege of his named Albert Michelson would ever be combined with his photoacoustic effect. A century later, the combination was made by Farrow Burnham, and Eyring, using a visible-range interferometer spectrometer of their own design. Soon afterwards, Rockley and myself, working independently, applied the technique to infrared measurements of solid samples. Photoacoustic cells are now commercially available as FT-IR accessories, and the technique is in use in the field.

Cellulose nanoparticles: photoacoustic contrast agents that biodegrade to simple sugars

Science.gov (United States)

Jokerst, Jesse V.; Bohndiek, Sarah E.; Gambhir, Sanjiv S.

2014-03-01

In photoacoustic imaging, nanoparticle contrast agents offer strong signal intensity and long-term stability, but are limited by poor biodistribution and clearance profiles. Conversely, small molecules offer renal clearance, but relatively low photoacoustic signal. Here we describe a cellulose-based nanoparticle with photoacoustic signal superior to gold nanorods, but that undergoes enzymatic cleavage into constituent glucose molecules for renal clearance. Cellulose nanoparticles (CNPs) were synthesized through acidic cleavage of cellulose linters and purified with centrifugation. TEM indicated that the nanoparticles were 132 +/- 46 nm; the polydispersity index was 0.138. Ex vivo characterization showed a photoacoustic limit of detection of 0.02 mg/mL CNPs, and the photoacoustic signal of CNPs was 1.5- to 3.0-fold higher than gold nanorods (also at 700 nm resonance) on a particle-to-particle basis. Cell toxicity assays suggested that overnight doses below 0.31 mg/mL CNPs produced no significant (p>0.05) impact on cell metabolism. Intravenous doses up to 0.24 mg were tolerated well in nude mice. Subcutaneous and orthotopic tumor xenografts of the OV2008 ovarian cancer cell line were then created in nude mice. Data was collected with a Nexus128 scanner from Endra LifeSciences. Spectral data used a LAZR system from Visualsonics both at 700 nm excitation. We injected CNPs (0.024 mg, 0.048 mg, and 0.80 mg) via tail vein and showed that the tumor photoacoustic signal reached maximum increase between 10 and 20 minutes. All injected concentrations were statistically (p0.96 suggesting quantitative signal. CNP biodegradation was demonstrated ex vivo with a glucose assay. CNPs in the presence of cellulase were reduced to free glucose in under than four hours. The glucose concentration before addition of cellulase was not detectable, but increased to 92.1 μg/mL in four hours. CNPs in the absence of cellulase did not produce glucose. Small fragments of nanoparticle in the

Intravascular photoacoustic imaging of human coronary atherosclerosis

Science.gov (United States)

Jansen, Krista; van der Steen, Antonius F. W.; Springeling, Geert; van Beusekom, Heleen M. M.; Oosterhuis, J. Wolter; van Soest, Gijs

2011-03-01

We demonstrate intravascular photoacoustic imaging of human coronary atherosclerotic plaque. We specifically imaged lipid content, a key factor in vulnerable plaques that may lead to myocardial infarction. An integrated intravascular photoacoustics (IVPA) and ultrasound (IVUS) catheter with an outer diameter of 1.25 mm was developed. The catheter comprises an angle-polished optical fiber adjacent to a 30 MHz single-element transducer. The ultrasonic transducer was optically isolated to eliminate artifacts in the PA image. We performed measurements on a cylindrical vessel phantom and isolated point targets to demonstrate its imaging performance. Axial and lateral point spread function widths were 110 μm and 550 μm, respectively, for PA and 89 μm and 420 μm for US. We imaged two fresh human coronary arteries, showing different stages of disease, ex vivo. Specific photoacoustic imaging of lipid content, is achieved by spectroscopic imaging at different wavelengths between 1180 and 1230 nm.

All-Optical Photoacoustic Sensors for Steel Rebar Corrosion Monitoring

Directory of Open Access Journals (Sweden)

Cong Du

2018-04-01

Full Text Available This article presents an application of an active all-optical photoacoustic sensing system with four elements for steel rebar corrosion monitoring. The sensor utilized a photoacoustic mechanism of gold nanocomposites to generate 8 MHz broadband ultrasound pulses in 0.4 mm compact space. A nanosecond 532 nm pulsed laser and 400 μm multimode fiber were employed to incite an ultrasound reaction. The fiber Bragg gratings were used as distributed ultrasound detectors. Accelerated corrosion testing was applied to four sections of a single steel rebar with four different corrosion degrees. Our results demonstrated that the mass loss of steel rebar displayed an exponential growth with ultrasound frequency shifts. The sensitivity of the sensing system was such that 0.175 MHz central frequency reduction corresponded to 0.02 g mass loss of steel rebar corrosion. It was proved that the all-optical photoacoustic sensing system can actively evaluate the corrosion of steel rebar via ultrasound spectrum. This multipoint all-optical photoacoustic method is promising for embedment into a concrete structure for distributed corrosion monitoring.

Photoacoustic Sounds from Meteors

Czech Academy of Sciences Publication Activity Database

Spalding, R.; Tencer, J.; Sweatt, W.; Conley, B.; Hogan, R.; Boslough, M.B.; Gonzales, G.; Spurný, Pavel

2017-01-01

Roč. 7, February (2017), 41251/1-41251/6 ISSN 2045-2322 Institutional support: RVO:67985815 Keywords : photoacoustic coupling * experimental results * numerical models Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 4.259, year: 2016

Optical drug monitoring: photoacoustic imaging of nanosensors to monitor therapeutic lithium in vivo.

Science.gov (United States)

Cash, Kevin J; Li, Chiye; Xia, Jun; Wang, Lihong V; Clark, Heather A

2015-02-24

Personalized medicine could revolutionize how primary care physicians treat chronic disease and how researchers study fundamental biological questions. To realize this goal, we need to develop more robust, modular tools and imaging approaches for in vivo monitoring of analytes. In this report, we demonstrate that synthetic nanosensors can measure physiologic parameters with photoacoustic contrast, and we apply that platform to continuously track lithium levels in vivo. Photoacoustic imaging achieves imaging depths that are unattainable with fluorescence or multiphoton microscopy. We validated the photoacoustic results that illustrate the superior imaging depth and quality of photoacoustic imaging with optical measurements. This powerful combination of techniques will unlock the ability to measure analyte changes in deep tissue and will open up photoacoustic imaging as a diagnostic tool for continuous physiological tracking of a wide range of analytes.

The titanium oxide phi system

Science.gov (United States)

Galehouse, D. C.; Davis, S. P.

1980-01-01

The phy system of titanium oxide has been studied in emission in the near-infrared, with the Fourier transform spectrometer at a resolution of 8000,000. Approximately 3000 lines from 25 bands of this system have been identified, including all five 0-0 and 0-1 bands corresponding to the five natural titanium isotopes. Eleven vibrational levels have been observed, and all bands have been rotationally analyzed. Band intensities are agreement with known isotopic abundances and calculated Franck-Condon factors.

Quantitative photo-acoustic tomography with partial data

International Nuclear Information System (INIS)

Chen, Jie; Yang, Yang

2012-01-01

Photo-acoustic tomography is a newly developed hybrid imaging modality that combines a high-resolution modality with a high-contrast modality. We analyze the reconstruction of diffusion and absorption parameters in an elliptic equation and extend an earlier result of Bal and Uhlmann (2010 Inverse Problems 26 085010) to the partial data case. We show that the reconstruction can be uniquely determined by the knowledge of four internal data based on well-chosen partial boundary conditions. Stability of this reconstruction is ensured if a convexity condition is satisfied. A similar stability result is obtained without this geometric constraint if 4n well chosen partial boundary conditions are available, where n is the spatial dimension. The set of well chosen boundary measurements is characterized by some complex geometric optics solutions vanishing on a part of the boundary. (paper)

Photoacoustic imaging to detect rat brain activation after cocaine hydrochloride injection

Science.gov (United States)

Jo, Janggun; Yang, Xinmai

2011-03-01

Photoacoustic imaging (PAI) was employed to detect small animal brain activation after the administration of cocaine hydrochloride. Sprague Dawley rats were injected with different concentrations (2.5, 3.0, and 5.0 mg per kg body) of cocaine hydrochloride in saline solution through tail veins. The brain functional response to the injection was monitored by photoacoustic tomography (PAT) system with horizontal scanning of cerebral cortex of rat brain. Photoacoustic microscopy (PAM) was also used for coronal view images. The modified PAT system used multiple ultrasonic detectors to reduce the scanning time and maintain a good signal-to-noise ratio (SNR). The measured photoacoustic signal changes confirmed that cocaine hydrochloride injection excited high blood volume in brain. This result shows PAI can be used to monitor drug abuse-induced brain activation.

Sulfates as chromophores for multiwavelength photoacoustic imaging phantoms

Science.gov (United States)

Fonseca, Martina; An, Lu; Beard, Paul; Cox, Ben

2017-12-01

As multiwavelength photoacoustic imaging becomes increasingly widely used to obtain quantitative estimates, the need for validation studies conducted on well-characterized experimental phantoms becomes ever more pressing. One challenge that such studies face is the design of stable, well-characterized phantoms and absorbers with properties in a physiologically realistic range. This paper performs a full experimental characterization of aqueous solutions of copper and nickel sulfate, whose properties make them close to ideal as chromophores in multiwavelength photoacoustic imaging phantoms. Their absorption varies linearly with concentration, and they mix linearly. The concentrations needed to yield absorption values within the physiological range are below the saturation limit. The shape of their absorption spectra makes them useful analogs for oxy- and deoxyhemoglobin. They display long-term photostability (no indication of bleaching) as well as resistance to transient effects (no saturable absorption phenomena), and are therefore suitable for exposure to typical pulsed photoacoustic light sources, even when exposed to the high number of pulses required in scanning photoacoustic imaging systems. In addition, solutions with tissue-realistic, predictable, and stable scattering can be prepared by mixing sulfates and Intralipid, as long as an appropriate emulsifier is used. Finally, the Grüneisen parameter of the sulfates was found to be larger than that of water and increased linearly with concentration.

Discrimination of the glucose and the white sugar based on the pulsed laser-induced photoacoustic technique

Science.gov (United States)

Ren, Zhong; Liu, Guodong

2017-08-01

In this study, to discriminate the glucose and the white sugar gradient in the food, a noninvasive optical detection system based on pulsed laser-induced photoacoustic technique was developed. Meanwhile, the Nd: YAG 532nm pumped OPO pulsed laser was used as the excitation light source to generate of the photoacoustic signals of the glucose and white sugar. The focused ultrasonic transducer with central detection frequency of 1MHz was used to capture the photoacoustic signals. In experiments, the real-time photoacoustic signals of the glucose and the white sugar aqueous solutions were gotten and compared with each other. In addition, to discriminate the difference of the characteristic photoacoustic signals between both of them, the difference spectrum and the first order derivative technique between the peak-to-peak photoacoustic signals of the water and that of the glucose and white sugar were employed. The difference characteristic photoacoustic wavelengths between the glucose and the white sugar were found based on the established photoacoustic detection system. This study provides the potential possibility for the discrimination of the glucose and the white sugar by using the photoacoustic detection method.

Modification of a commercial spectrophotometer for photoacoustic measurement

International Nuclear Information System (INIS)

Bandyopadhyay, S.; Harris, J.M.; Eyring, E.M.

1983-01-01

This note describes how a commercial UV-VIS-NIR spectrophotometer may be adapted to function as a double beam photoacoustic spectrophotometer operating at visible wavelengths. Modification of a Varian Cary 17 spectrophotometer was carried out first by dismounting the photomultiplier tube detector module and the cell compartment of the spectrophotometer. The sample and the reference beams were focused through two externally mounted quartz lenses onto the sample and reference photoacoustic cells, respectively

Methylene blue microbubbles as a model dual-modality contrast agent for ultrasound and activatable photoacoustic imaging

Science.gov (United States)

Jeon, Mansik; Song, Wentao; Huynh, Elizabeth; Kim, Jungho; Kim, Jeesu; Helfield, Brandon L.; Leung, Ben Y. C.; Goertz, David E.; Zheng, Gang; Oh, Jungtaek; Lovell, Jonathan F.; Kim, Chulhong

2014-01-01

Ultrasound and photoacoustic imaging are highly complementary modalities since both use ultrasonic detection for operation. Increasingly, photoacoustic and ultrasound have been integrated in terms of hardware instrumentation. To generate a broadly accessible dual-modality contrast agent, we generated microbubbles (a standard ultrasound contrast agent) in a solution of methylene blue (a standard photoacoustic dye). This MB2 solution was formed effectively and was optimized as a dual-modality contrast solution. As microbubble concentration increased (with methylene blue concentration constant), photoacoustic signal was attenuated in the MB2 solution. When methylene blue concentration increased (with microbubble concentration held constant), no ultrasonic interference was observed. Using an MB2 solution that strongly attenuated all photoacoustic signal, high powered ultrasound could be used to burst the microbubbles and dramatically enhance photoacoustic contrast (>800-fold increase), providing a new method for spatiotemporal control of photoacoustic signal generation.

Titanium exposure and yellow nail syndrome

Directory of Open Access Journals (Sweden)

Ali Ataya

2015-01-01

Full Text Available Yellow nail syndrome is a rare disease of unclear etiology. We describe a patient who develops yellow nail syndrome, with primary nail and sinus manifestations, shortly after amalgam dental implants. A study of the patient's nail shedding showed elevated nail titanium levels. The patient had her dental implants removed and had complete resolution of her sinus symptoms with no change in her nail findings. Since the patient's nail findings did not resolve we do not believe titanium exposure is a cause of her yellow nail syndrome but perhaps a possible relationship exists between titanium exposure and yellow nail syndrome that requires further studies.

Sensitive Detection: Photoacoustics, Thermography, and Optical Radiation Pressure

Energy Technology Data Exchange (ETDEWEB)

Diebold, Gerald J. [Brown Univ., Providence, RI (United States)

2017-04-21

Research during the granting period has been carried out in several areas concerned with sensitive detection. An infrared pyrometer based on the photoacoustic effect has been developed. The sensitivity of this instrument to temperature differentials has been shown to be 50 mK. An investigation of transients that accompany photoacoustic waves generated by pulsed lasers has been carried out. Experiments have shown the existence of the transients, and a theory based on rapid heat diffusion has been developed. The photoacoustic effect in one dimension is known to increase without bound (in the linear acoustics regime) when an optical beam moves in a fluid at the sound speed. A solution to the wave equation for pressure has been found that describes the photoacoustic effect in a cell where an infrared optical grating moves at the sound speed. It was shown that the amplification effect exists along with a cavity resonance that can be used to great advantage in trace gas detection. The theory of the photoacoustic effect in a structure where the acoustic properties periodically vary in a one-dimensional based has been formulated based on solutions to a Mathieu equation. It was found that it is possible to excite photoacoustic waves within the band gaps to produce large amplitude acoustic waves. The idea of self-oscillation in a photoacoustic cell using a continuous laser has been investigated. A theory has been completed showing that in a compressive wave, the absorption increases as a result of the density increase leading to further absorption and hence an increased amplitude photoacoustic effect with the result that in a resonator, self-oscillation can place. Experiments have been carried out where irradiation of a suspension of absorbing carbon particles with a high power laser has been shown to result in cavitation luminescence. That is, following generation of CO and H₂ from the carbon particles through the carbon-steam reaction, an expanding gas bubble is

Photoacoustic Techniques for Trace Gas Sensing Based on Semiconductor Laser Sources

Directory of Open Access Journals (Sweden)

Vincenzo Spagnolo

2009-12-01

Full Text Available The paper provides an overview on the use of photoacoustic sensors based on semiconductor laser sources for the detection of trace gases. We review the results obtained using standard, differential and quartz enhanced photoacoustic techniques.

Photoacoustics: a historical review

NARCIS (Netherlands)

Manohar, Srirang; Razansky, D.

2016-01-01

We review the history of photoacoustics from the discovery in 1880 that modulated light produces acoustic waves to the current time, when the pulsed variant of the discovery is fast developing into a powerful biomedical imaging modality. We trace the meandering and fascinating passage of the effect

Photoacoustic technique applied to the study of skin and leather

International Nuclear Information System (INIS)

Vargas, M.; Varela, J.; Hernandez, L.; Gonzalez, A.

1998-01-01

In this paper the photoacoustic technique is used in bull skin for the determination of thermal and optical properties as a function of the tanning process steps. Our results show that the photoacoustic technique is sensitive to the study of physical changes in this kind of material due to the tanning process

Detection of Melanoma Metastases in Resected Human Lymph Nodes by Noninvasive Multispectral Photoacoustic Imaging

Directory of Open Access Journals (Sweden)

Gerrit Cornelis Langhout

2014-01-01

Full Text Available Objective. Sentinel node biopsy in patients with cutaneous melanoma improves staging, provides prognostic information, and leads to an increased survival in node-positive patients. However, frozen section analysis of the sentinel node is not reliable and definitive histopathology evaluation requires days, preventing intraoperative decision-making and immediate therapy. Photoacoustic imaging can evaluate intact lymph nodes, but specificity can be hampered by other absorbers such as hemoglobin. Near infrared multispectral photoacoustic imaging is a new approach that has the potential to selectively detect melanin. The purpose of the present study is to examine the potential of multispectral photoacoustic imaging to identify melanoma metastasis in human lymph nodes. Methods. Three metastatic and nine benign lymph nodes from eight melanoma patients were scanned ex vivo using a Vevo LAZR© multispectral photoacoustic imager and were spectrally analyzed per pixel. The results were compared to histopathology as gold standard. Results. The nodal volume could be scanned within 20 minutes. An unmixing procedure was proposed to identify melanoma metastases with multispectral photoacoustic imaging. Ultrasound overlay enabled anatomical correlation. The penetration depth of the photoacoustic signal was up to 2 cm. Conclusion. Multispectral three-dimensional photoacoustic imaging allowed for selective identification of melanoma metastases in human lymph nodes.

Near-Infrared Squaraine Dye Encapsulated Micelles for in Vivo Fluorescence and Photoacoustic Bimodal Imaging.

Science.gov (United States)

Sreejith, Sivaramapanicker; Joseph, James; Lin, Manjing; Menon, Nishanth Venugopal; Borah, Parijat; Ng, Hao Jun; Loong, Yun Xian; Kang, Yuejun; Yu, Sidney Wing-Kwong; Zhao, Yanli

2015-06-23

Combined near-infrared (NIR) fluorescence and photoacoustic imaging techniques present promising capabilities for noninvasive visualization of biological structures. Development of bimodal noninvasive optical imaging approaches by combining NIR fluorescence and photoacoustic tomography demands suitable NIR-active exogenous contrast agents. If the aggregation and photobleaching are prevented, squaraine dyes are ideal candidates for fluorescence and photoacoustic imaging. Herein, we report rational selection, preparation, and micelle encapsulation of an NIR-absorbing squaraine dye (D1) for in vivo fluorescence and photoacoustic bimodal imaging. D1 was encapsulated inside micelles constructed from a biocompatible nonionic surfactant (Pluoronic F-127) to obtain D1-encapsulated micelles (D1(micelle)) in aqueous conditions. The micelle encapsulation retains both the photophysical features and chemical stability of D1. D1(micelle) exhibits high photostability and low cytotoxicity in biological conditions. Unique properties of D1(micelle) in the NIR window of 800-900 nm enable the development of a squaraine-based exogenous contrast agent for fluorescence and photoacoustic bimodal imaging above 820 nm. In vivo imaging using D1(micelle), as demonstrated by fluorescence and photoacoustic tomography experiments in live mice, shows contrast-enhanced deep tissue imaging capability. The usage of D1(micelle) proven by preclinical experiments in rodents reveals its excellent applicability for NIR fluorescence and photoacoustic bimodal imaging.

In vivo virtual intraoperative surgical photoacoustic microscopy

International Nuclear Information System (INIS)

Han, Seunghoon; Kim, Sehui; Kim, Jeehyun; Lee, Changho; Jeon, Mansik; Kim, Chulhong

2013-01-01

We developed a virtual intraoperative surgical photoacoustic microscopy system by combining with a commercial surgical microscope and photoacoustic microscope (PAM). By sharing the common optical path in the microscope and PAM system, we could acquire the PAM and microscope images simultaneously. Moreover, by employing a beam projector to back-project 2D PAM images onto the microscope view plane as augmented reality, the conventional microscopic and 2D cross-sectional PAM images are concurrently mapped on the plane via an ocular lens of the microscope in real-time. Further, we guided needle insertion into phantom ex vivo and mice skins in vivo

In vivo virtual intraoperative surgical photoacoustic microscopy

Energy Technology Data Exchange (ETDEWEB)

Han, Seunghoon, E-mail: hsh860504@gmail.com; Kim, Sehui, E-mail: sehui0916@nate.com; Kim, Jeehyun, E-mail: jeehk@knu.ac.kr, E-mail: chulhong@postech.edu [School of Electrical Engineering and Computer Science, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Lee, Changho, E-mail: ch31037@postech.edu; Jeon, Mansik, E-mail: msjeon@postech.edu [Department of Creative IT Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Kim, Chulhong, E-mail: jeehk@knu.ac.kr, E-mail: chulhong@postech.edu [Department of Creative IT Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Department of Biomedical Engineering, The State University of New York at Buffalo, Buffalo, New York 14221 (United States)

2013-11-11

We developed a virtual intraoperative surgical photoacoustic microscopy system by combining with a commercial surgical microscope and photoacoustic microscope (PAM). By sharing the common optical path in the microscope and PAM system, we could acquire the PAM and microscope images simultaneously. Moreover, by employing a beam projector to back-project 2D PAM images onto the microscope view plane as augmented reality, the conventional microscopic and 2D cross-sectional PAM images are concurrently mapped on the plane via an ocular lens of the microscope in real-time. Further, we guided needle insertion into phantom ex vivo and mice skins in vivo.

In vivo molecular photoacoustic tomography of melanomas targeted by bioconjugated gold nanocages.

Science.gov (United States)

Kim, Chulhong; Cho, Eun Chul; Chen, Jingyi; Song, Kwang Hyun; Au, Leslie; Favazza, Christopher; Zhang, Qiang; Cobley, Claire M; Gao, Feng; Xia, Younan; Wang, Lihong V

2010-08-24

Early diagnosis, accurate staging, and image-guided resection of melanomas remain crucial clinical objectives for improving patient survival and treatment outcomes. Conventional techniques cannot meet this demand because of the low sensitivity, low specificity, poor spatial resolution, shallow penetration, and/or ionizing radiation. Here we overcome such limitations by combining high-resolution photoacoustic tomography (PAT) with extraordinarily optical absorbing gold nanocages (AuNCs). When bioconjugated with [Nle(4),D-Phe(7)]-alpha-melanocyte-stimulating hormone, the AuNCs can serve as a novel contrast agent for in vivo molecular PAT of melanomas with both exquisite sensitivity and high specificity. The bioconjugated AuNCs enhanced contrast approximately 300% more than the control, PEGylated AuNCs. The in vivo PAT quantification of the amount of AuNCs accumulated in melanomas was further validated with inductively coupled plasma mass spectrometry (ICP-MS).

Application of time-resolved glucose concentration photoacoustic signals based on an improved wavelet denoising

Science.gov (United States)

Ren, Zhong; Liu, Guodong; Huang, Zhen

2014-10-01

Real-time monitoring of blood glucose concentration (BGC) is a great important procedure in controlling diabetes mellitus and preventing the complication for diabetic patients. Noninvasive measurement of BGC has already become a research hotspot because it can overcome the physical and psychological harm. Photoacoustic spectroscopy is a well-established, hybrid and alternative technique used to determine the BGC. According to the theory of photoacoustic technique, the blood is irradiated by plused laser with nano-second repeation time and micro-joule power, the photoacoustic singals contained the information of BGC are generated due to the thermal-elastic mechanism, then the BGC level can be interpreted from photoacoustic signal via the data analysis. But in practice, the time-resolved photoacoustic signals of BGC are polluted by the varities of noises, e.g., the interference of background sounds and multi-component of blood. The quality of photoacoustic signal of BGC directly impacts the precision of BGC measurement. So, an improved wavelet denoising method was proposed to eliminate the noises contained in BGC photoacoustic signals. To overcome the shortcoming of traditional wavelet threshold denoising, an improved dual-threshold wavelet function was proposed in this paper. Simulation experimental results illustrated that the denoising result of this improved wavelet method was better than that of traditional soft and hard threshold function. To varify the feasibility of this improved function, the actual photoacoustic BGC signals were test, the test reslut demonstrated that the signal-to-noises ratio(SNR) of the improved function increases about 40-80%, and its root-mean-square error (RMSE) decreases about 38.7-52.8%.

Photoacoustic Detection of Terahertz Radiation for Chemical Sensing and Imaging Applications

Science.gov (United States)

2013-03-01

ISSN 2229-5518 [39] Jingle Liu, Benjamin Clough, and X. C. Zhang, “Enhancement of photoacoustic emission through terahertz-field driven electron...materials,” Journal of Electroceramics, vol. 2: p. 257-272, 2009. [47] Jingle Liu, Benjamin Clough, and X. C. Zhang, “Enhancement of photoacoustic

In vivo oral imaging with integrated portable photoacoustic microscopy and optical coherence tomography

Science.gov (United States)

Qin, Wei; Qi, Weizhi; Jin, Tian; Guo, Heng; Xi, Lei

2017-12-01

Oral diseases, especially oral cancers, are becoming serious health problems in humans. To image vasculatures and structures simultaneously in the human oral cavity which are tightly associated with various oral diseases, we develop a dual-modality portable optical resolution photoacoustic microscopy (ORPAM) and optical coherence tomography (OCT) system. This system utilizes a new rotary scanning mechanism and a compact design of the imaging head, making it portable and free of translation of the imaging interface or samples. Through the phantom experiments, both modalities yield high lateral resolutions of 8.1 μm (ORPAM) and 8.56 μm (OCT), respectively. The axial resolutions are measured to be 116.5 μm for ORPAM and 6.1 μm for OCT. In vivo imaging of a mouse ear was carried out to evaluate the performance of the system in biological tissues. In addition, in vivo oral imaging of a healthy human lip and monitoring recovery progress of a lip ulcer demonstrate the clinical potential of this system.

Ultrasound-guided photoacoustic imaging of lymph nodes with biocompatible gold nanoparticles as a novel contrast agent (Conference Presentation)

Science.gov (United States)

Sun, In-Cheol; Dumani, Diego; Emelianov, Stanislav Y.

2017-02-01

A key step in staging cancer is the diagnosis of metastasis that spreads through lymphatic system. For this reason, researchers develop various methods of sentinel lymph node mapping that often use a radioactive tracer. This study introduces a safe, cost-effective, high-resolution, high-sensitivity, and real-time method of visualizing the sentinel lymph node: ultrasound-guided photoacoustic (US/PA) imaging augmented by a contrast agent. In this work, we use clearable gold nanoparticles covered by a biocompatible polymer (glycol chitosan) to enhance cellular uptake by macrophages abundant in lymph nodes. We incubate macrophages with glycol-chitosan-coated gold nanoparticles (0.05 mg Au/ml), and then fix them with paraformaldehyde solution for an analysis of in vitro dark-field microscopy and cell phantom. The analysis shows enhanced cellular uptake of nanoparticles by macrophages and strong photoacoustic signal from labeled cells in tissue-mimicking cell phantoms consisting gelatin solution (6 %) with silica gel (25 μm, 0.3%) and fixed macrophages (13 X 105 cells). The in-vivo US/PA imaging of cervical lymph nodes in healthy mice (nu/nu, female, 5 weeks) indicates a strong photoacoustic signal from a lymph node 10 minutes post-injection (2.5 mg Au/ml, 80 μl). The signal intensity and the nanoparticle-labeled volume of tissue within the lymph node continues to increase until 4 h post-injection. Histological analysis further confirms the accumulation of gold nanoparticles within the lymph nodes. This work suggests the feasibility of molecular/cellular US/PA imaging with biocompatible gold nanoparticles as a photoacoustic contrast agent in the diagnosis of lymph-node-related diseases.

Photoacoustic image reconstruction: a quantitative analysis

Science.gov (United States)

Sperl, Jonathan I.; Zell, Karin; Menzenbach, Peter; Haisch, Christoph; Ketzer, Stephan; Marquart, Markus; Koenig, Hartmut; Vogel, Mika W.

2007-07-01

Photoacoustic imaging is a promising new way to generate unprecedented contrast in ultrasound diagnostic imaging. It differs from other medical imaging approaches, in that it provides spatially resolved information about optical absorption of targeted tissue structures. Because the data acquisition process deviates from standard clinical ultrasound, choice of the proper image reconstruction method is crucial for successful application of the technique. In the literature, multiple approaches have been advocated, and the purpose of this paper is to compare four reconstruction techniques. Thereby, we focused on resolution limits, stability, reconstruction speed, and SNR. We generated experimental and simulated data and reconstructed images of the pressure distribution using four different methods: delay-and-sum (DnS), circular backprojection (CBP), generalized 2D Hough transform (HTA), and Fourier transform (FTA). All methods were able to depict the point sources properly. DnS and CBP produce blurred images containing typical superposition artifacts. The HTA provides excellent SNR and allows a good point source separation. The FTA is the fastest and shows the best FWHM. In our study, we found the FTA to show the best overall performance. It allows a very fast and theoretically exact reconstruction. Only a hardware-implemented DnS might be faster and enable real-time imaging. A commercial system may also perform several methods to fully utilize the new contrast mechanism and guarantee optimal resolution and fidelity.

Detection of Molecular Oxygen at Low Concentrations Using Quartz Enhanced Photoacoustic Spectroscopy

Directory of Open Access Journals (Sweden)

Andreas Pohlkötter

2010-09-01

Full Text Available Molecular oxygen is detected at low concentrations using photoacoustic spectroscopy despite its unfavorable photoacoustic properties. The system consists of a seed laser diode, a tapered amplifier and a quartz tuning fork based spectrophone, thus employing quartz enhanced photoacoustic spectroscopy (QEPAS. With this system a detection limit of 13 ppm is reached with a compact and long term stable setup. Further improvement of the detection limit is possible by adding suitable gases to the sample gas that promote the radiationless de-excitation of the oxygen molecules.

Speckle-based off-axis holographic detection for non-contact photoacoustic tomography

Directory of Open Access Journals (Sweden)

Buj C.

2015-09-01

Full Text Available A very fast innovative holographic off-axis non-contact detection method for Photoacoustic Tomography (PAT is introduced. It overcomes the main problems of most state-of-the-art photoacoustic imaging approaches that are long acquisition times and the requirement of acoustic contact. In order to increase the acquisition speed significantly, the surface displacements of the object, caused by the photoacoustic pressure waves, are measured interferometrically in two dimensions. Phase alterations in the observed speckle field are used to identify changes in the object’s topography. A sampling rate of up to 80 MHz is feasible, which reduces the occurrence of motion artefacts.

Photoacoustic and photothermal spectroscopies

International Nuclear Information System (INIS)

Sawada, Tsuguo; Kitamori, Takehiko; Nakamura, Masato

1995-01-01

Photoacoustic and photothermal spectroscopy methods can be effectively applied to the analysis of microparticles in condensed matter. A more violent photothermal conversion phenomenon of a particle, laser breakdown and accompanying plasma and acoustic emission, was applied to individual detection and analysis of ultrafine particles in ultrapure water. Laser-like nonlinear emission from the plasma was observed. (author)

Targeted nanodiamonds as phenotype-specific photoacoustic contrast agents for breast cancer.

Science.gov (United States)

Zhang, Ti; Cui, Huizhong; Fang, Chia-Yi; Cheng, Kun; Yang, Xinmai; Chang, Huan-Cheng; Forrest, M Laird

2015-03-01

The aim is to develop irradiated nanodiamonds (INDs) as a molecularly targeted contrast agent for high-resolution and phenotype-specific detection of breast cancer with photoacoustic (PA) imaging. The surface of acid treated radiation-damaged nanodiamonds was grafted with PEG to improve its stability and circulation time in blood, followed by conjugation to an anti-HER2 peptide with a final nanoparticle size of approximately 92 nm. Immunocompetent mice bearing orthotopic HER2-positive or negative tumors were administered INDs and PA imaged using an 820-nm near-infrared laser. PA images demonstrated that INDs accumulate in tumors and completely delineated the entire tumor within 10 h. HER2 targeting significantly enhanced imaging of HER2-positive tumors. Pathological examination demonstrated INDs are nontoxic. PA technology is adaptable to low-cost bedside medicine, and with new contrast agents described herein, PA can achieve high-resolution (sub-mm) and phenotype-specific monitoring of cancer growth.

Photoacoustic spectroscopic differences between normal and malignant thyroid tissues

Science.gov (United States)

Li, Li; Xie, Wengming; Li, Hui

2012-12-01

The thyroid is one of the main endocrine glands of human body, which plays a crucial role in the body's metabolism. Thyroid cancer mortality ranks only second to ovarian cancer in endocrine cancer. Routine diagnostic methods of thyroid diseases in present clinic exist misdiagnosis and missed diagnosis to varying degrees. Those lead to miss the best period of cancer treatment--early. Photoacoustic spectroscopy technology is a new tool, which provides an effective and noninvasive way for biomedical materials research, being highly sensitive and without sample pretreatment. In this paper, we use photoacoustic spectroscopy technology (PAST) to detect the absorption spectrum between normal and malignant thyroid tissues. The result shows that the photoacoustic spectroscopy technology (PAST) could differentiate malignant thyroid tissue from normal thyroid tissue very well. This technique combined with routine diagnostic methods has the potential to increase the diagnostic accuracy in clinical thyroid cancer diagnosis.

Feasibility evaluation of 3D photoacoustic imaging of blood vessel structure using multiple wavelengths with a handheld probe

Science.gov (United States)

Uchimoto, Yo; Namita, Takeshi; Kondo, Kengo; Yamakawa, Makoto; Shiina, Tsuyoshi

2018-02-01

Photoacoustic imaging is anticipated for use in portraying blood vessel structures (e.g. neovascularization in inflamed regions). To reduce invasiveness and enhance ease handling, we developed a handheld photoacoustic imaging system using multiple wavelengths. The usefulness of the proposed system was investigated in phantom experiments and in vivo measurements. A silicon tube was embedded into chicken breast meat to simulate the blood vessel. The tube was filled with ovine blood. Then laser light was guided to the phantom surface by an optical fiber bundle close to the linear ultrasound probe. Photoacoustic images were obtained at 750-950 nm wavelengths. Strong photoacoustic signals from the boundary between blood and silicon tube are observed in these images. The shape of photoacoustic spectrum at the boundary resembles that of the HbO2 absorption spectrum at 750-920 nm. In photoacoustic images, similarity between photoacoustic spectrum and HbO2 absorption spectrum was evaluated by calculating the normalized correlation coefficient. Results show high correlation in regions of strong photoacoustic signals in photoacoustic images. These analyses demonstrate the feasibility of portraying blood vessel structures under practical conditions. To evaluate the feasibility of three-dimensional vascular imaging, in vivo experiments were conducted using three wavelengths. A right hand and ultrasound probe were set in degassed water. By scanning a probe, cross-sectional ultrasound and photoacoustic images were obtained at each location. Then, all ultrasound or photoacoustic images were piled up respectively. Then three-dimensional images were constructed. Resultant images portrayed blood vessel-like structures three-dimensionally. Furthermore, to distinguish blood vessels from other tissues (e.g. skin), distinguishing images of them were constructed by comparing photoacoustic signal intensity among three wavelengths. The resultant image portrayed blood vessels as

Quantum cascade laser-based photoacoustic sulfuryl fluoride sensing

Science.gov (United States)

Minini, Kariza Mayra Silva; Bueno, Sâmylla Cristina Espécie; da Silva, Marcelo Gomes; Sthel, Marcelo Silva; Vargas, Helion; Angster, Judit; Miklós, András

2017-02-01

Although sulfuryl fluoride (SO2F2) is an efficient fumigant that does not react with the surface of indoor materials and does not reduce the stratospheric ozone shield, there are some concerns about its use. It is a toxic gas that attacks the central nervous system, and its global warming potential (GWP) value is 4780 for 100 years' time. Therefore, it is a clear necessity of implementing detection methods for tracing such a molecule. In this work a sensitive photoacoustic setup was built to detect SO2F2 at concentrations of parts per billion by volume (ppbv). The symmetric S-O stretching mode was excited by a continuous-wave quantum cascade laser with radiation wavenumber ranging from 1275.7 to 1269.3 cm-1. The photoacoustic signal was generated by modulating the laser wavenumber at the first longitudinal mode of the photoacoustic cell with amplitude depth of 5 × 10-3 cm-1. The detection of a minimum SO2F2 concentration of 20 ppbv was achieved.

Novel applications of photoacoustic spectroscopy in life sciences

Science.gov (United States)

Stolik, S.

2004-10-01

The Photoacoustic Spectroscopy, based on the generation of acoustic waves following the absorption of the modulated light by an enclosed material, was discovered in 1880 by Alexander Graham Bell. There are a lot of remarkable achievements in this topic since those days. It has been intended to present a relatively new tool to the researchers in biological areas and, simultaneously, to propose new fields of investigation to those who have been attracted by physics. The application of Photoacoustic trace gas detection to the determination of ethylene content in mice exhalation is described as a biomarker of free radicals production. It has been demonstrated the feasibility of studying the lipid peroxidation in vivo by this technique. Specifically, the results of δ-aminolevulinic acid administration in mice are presented. This drug has been used to induce Protoporphyrin IX production and ultimately to apply the Photodynamic Therapy, a recent method in cancer treatment. A kinetic study of Protoporphyrin IX production in mice skin and blood after δ-aminolevulinic acid administration in different doses is also shown. This study was performed using Photoacoustic Spectroscopy in solids.

In vivo molecular photoacoustic tomography of melanomas targeted by bio-conjugated gold nanocages

Science.gov (United States)

Kim, Chulhong; Cho, Eun Chul; Chen, Jingyi; Song, Kwang Hyun; Au, Leslie; Favazza, Christopher; Zhang, Qiang; Cobley, Claire M.; Gao, Feng; Xia, Younan; Wang, Lihong V.

2010-01-01

Early diagnosis, accurate staging, and image-guided resection of melanomas remain crucial clinical objectives for improving patient survival and treatment outcomes. Conventional techniques cannot meet this demand because of the low sensitivity, low specificity, poor spatial resolution, shallow penetration, and/or ionizing radiation. Here we overcome such limitations by combining high-resolution photoacoustic tomography (PAT) with extraordinarily optical absorbing gold nanocages (AuNCs). When bio-conjugated with [Nle4,D-Phe7]-α-melanocyte-stimulating hormone, the AuNCs can serve as a novel contrast agent for in vivo molecular PAT of melanomas with both exquisite sensitivity and high specificity. The bio-conjugated AuNCs enhanced contrast ~300% more than the control, PEGylated AuNCs. The in vivo PAT quantification of the amount of AuNCs accumulated in melanomas was further validated with inductively coupled plasma mass spectrometry (ICP-MS). PMID:20731439

In vivo photoacoustic microscopy of human cutaneous microvasculature and a nevus.

Science.gov (United States)

Favazza, Christopher P; Jassim, Omar; Cornelius, Lynn A; Wang, Lihong V

2011-01-01

In several human volunteers, photoacoustic microscopy (PAM) has been utilized for noninvasive cutaneous imaging of the skin microvasculature and a melanocytic nevus. Microvascular networks in both acral and nonacral skin were imaged, and multiple features within the skin have been identified, including the stratum corneum, epidermal-dermal junction, and subpapillary vascular plexus. Several vascular and structural differences between acral and nonacral skin were also observed in the photoacoustic images. In addition, a nevus was photoacoustically imaged, excised, and histologically analyzed. The photoacoustic images allowed for in vivo measurement of tumor thickness, depth, and microvasculature-values confirmed by histologic examination. The presented images demonstrate the potential of PAM to aid in the study and evaluation of cutaneous microcirculation and analysis of pigmented lesions. Through its ability to three-dimensionally image the structure and function of the microvasculature and pigmented lesions, PAM can have a clinical impact in diagnosis and assessment of systemic diseases that affect the microvasculature such as diabetes and cardiovascular disease, cutaneous malignancies such as melanoma, and potentially other skin disorders.

Influence of nanoscale temperature rises on photoacoustic generation: Discrimination between optical absorbers based on thermal nonlinearity at high frequency.

Science.gov (United States)

Simandoux, Olivier; Prost, Amaury; Gateau, Jérôme; Bossy, Emmanuel

2015-03-01

In this work, we experimentally investigate thermal-based nonlinear photoacoustic generation as a mean to discriminate between different types of absorbing particles. The photoacoustic generation from solutions of dye molecules and gold nanospheres (same optical densities) was detected using a high frequency ultrasound transducer (20 MHz). Photoacoustic emission was observed with gold nanospheres at low fluence for an equilibrium temperature around 4 °C, where the linear photoacoustic effect in water vanishes, highlighting the nonlinear emission from the solution of nanospheres. The photoacoustic amplitude was also studied as a function of the equilibrium temperature from 2 °C to 20 °C. While the photoacoustic amplitude from the dye molecules vanished around 4 °C, the photoacoustic amplitude from the gold nanospheres remained significant over the whole temperature range. Our preliminary results suggest that in the context of high frequency photoacoustic imaging, nanoparticles may be discriminated from molecular absorbers based on nanoscale temperature rises.

Photoacoustic imaging in scattering media by combining a correlation matrix filter with a time reversal operator.

Science.gov (United States)

Rui, Wei; Tao, Chao; Liu, Xiaojun

2017-09-18

Acoustic scattering medium is a fundamental challenge for photoacoustic imaging. In this study, we reveal the different coherent properties of the scattering photoacoustic waves and the direct photoacoustic waves in a matrix form. Direct waves show a particular coherence on the antidiagonals of the matrix, whereas scattering waves do not. Based on this property, a correlation matrix filter combining with a time reversal operator is proposed to preserve the direct waves and recover the image behind a scattering layer. Both numerical simulations and photoacoustic imaging experiments demonstrate that the proposed approach effectively increases the image contrast and decreases the background speckles in a scattering medium. This study might improve the quality of photoacoustic imaging in an acoustic scattering environment and extend its applications.

An underwater ranging system based on photoacoustic effect occurring on target surface

Science.gov (United States)

Ni, Kai; Hu, Kai; Li, Xinghui; Wang, Lidai; Zhou, Qian; Wang, Xiaohao

2016-11-01

In this paper, an underwater ranging system based on photoacoustic effect occurring on target surface is proposed. In this proposal, laser pulse generated by blue-green laser is directly incident on target surface, where the photoacoustic effect occurs and a sound source is formed. And then the sound wave which is also called photoacoustic signal is received by the ultrasonic receiver after passing through water. According to the time delay between transmitting laser and receiving photoacoustic signal, and sound velocity in water, the distance between the target and the ultrasonic receiver can be calculated. Differing from underwater range finding by only laser, this approach can avoid backscattering of laser beam, so easier to implement. Experimental system according to this principle has been constructed to verify the feasibility of this technology. The experimental results showed that a ranging accuracy of 1 mm can be effectively achieved when the target is close to the ultrasonic receiver.

In vivo photoacoustic monitoring of anti-obesity photothermal lipolysis

Science.gov (United States)

Lee, Donghyun; Lee, Jung Ho; Hahn, Sei Kwang; Kim, Chulhong

2018-02-01

Obesity with a body mass index is greater than 30 kg/m2 is one of the rapidly growing diseases in advanced societies and can lead to stroke, type 2 diabetes, and heart failure. Common methods of removing subcutaneous adipose tissues are liposuction and laser treatment. In this study, we used photoacoustic imaging to monitor the anti-obesity photothermal degradation process. To improve the photothermal lipid degradation efficiency without any invasive methods, we synthesized hyaluronic acid hollow hold nanosphere adipocyte targeting sequence peptide (HA-HAuNS-ATS) conjugates. The conjugate enhanced the skin penetration ability and biodegradability of the nanoparticles using hyaluronate and enhanced the targeting effect on adipose tissue with adipocyte targeting sequence peptide. Thus, the conjugate can be delivered to the adipose tissue by simply spreading the conjugate on the skin without any invasive method. Then, the photothermal lipolysis and delivery of the conjugate were photoacoustically monitored in vivo. These results demonstrate the potential for photoacoustic method to be applied for photothermal lipolysis monitoring.

Laser Fluence Recognition Using Computationally Intelligent Pulsed Photoacoustics Within the Trace Gases Analysis

Science.gov (United States)

Lukić, M.; Ćojbašić, Ž.; Rabasović, M. D.; Markushev, D. D.; Todorović, D. M.

2017-11-01

In this paper, the possibilities of computational intelligence applications for trace gas monitoring are discussed. For this, pulsed infrared photoacoustics is used to investigate SF6-Ar mixtures in a multiphoton regime, assisted by artificial neural networks. Feedforward multilayer perceptron networks are applied in order to recognize both the spatial characteristics of the laser beam and the values of laser fluence Φ from the given photoacoustic signal and prevent changes. Neural networks are trained in an offline batch training regime to simultaneously estimate four parameters from theoretical or experimental photoacoustic signals: the laser beam spatial profile R(r), vibrational-to-translational relaxation time τ _{V-T} , distance from the laser beam to the absorption molecules in the photoacoustic cell r* and laser fluence Φ . The results presented in this paper show that neural networks can estimate an unknown laser beam spatial profile and the parameters of photoacoustic signals in real time and with high precision. Real-time operation, high accuracy and the possibility of application for higher intensities of radiation for a wide range of laser fluencies are factors that classify the computational intelligence approach as efficient and powerful for the in situ measurement of atmospheric pollutants.

Photoacoustic emission from Au nanoparticles arrayed on thermal insulation layer.

Science.gov (United States)

Namura, Kyoko; Suzuki, Motofumi; Nakajima, Kaoru; Kimura, Kenji

2013-04-08

Efficient photoacoustic emission from Au nanoparticles on a porous SiO(2) layer was investigated experimentally and theoretically. The Au nanoparticle arrays/porous SiO(2)/SiO(2)/Ag mirror sandwiches, namely, local plasmon resonators, were prepared by dynamic oblique deposition (DOD). Photoacoustic measurements were performed on the local plasmon resonators, whose optical absorption was varied from 0.03 (3%) to 0.95 by varying the thickness of the dielectric SiO(2) layer. The sample with high absorption (0.95) emitted a sound that was eight times stronger than that emitted by graphite (0.94) and three times stronger than that emitted by the sample without the porous SiO(2) layer (0.93). The contribution of the porous SiO(2) layer to the efficient photoacoustic emission was analyzed by means of a numerical method based on a one-dimensional heat transfer model. The result suggested that the low thermal conductivity of the underlying porous layer reduces the amount of heat escaping from the substrate and contributes to the efficient photoacoustic emission from Au nanoparticle arrays. Because both the thermal conductivity and the spatial distribution of the heat generation can be controlled by DOD, the local plasmon resonators produced by DOD are suitable for the spatio-temporal modulation of the local temperature.

Photoacoustic measurements of photokinetics in single optically trapped aerosol droplets

Science.gov (United States)

Covert, Paul; Cremer, Johannes; Signorell, Ruth; Thaler, Klemens; Haisch, Christoph

2017-04-01

It is well established that interaction of light with atmospheric aerosols has a large impact on the Earth's climate. However, uncertainties in the magnitude of this impact remain large, due in part to broad distributions of aerosol size, composition, and chemical reactivity. In this context, photoacoustic spectroscopy is commonly used to measure light absorption by aerosols. Here, we present photoacoustic measurements of single, optically-trapped nanodroplets to reveal droplet size-depencies of photochemical and physical processes. Theoretical considerations have pointed to a size-dependence in the magnitude and phase of the photoacoustic response from aerosol droplets. This dependence is thought to originate from heat transfer processes that are slow compared to the acoustic excitation frequency. In the case of a model aerosol, our measurements of single particle absorption cross-section versus droplet size confirm these theoretical predictions. In a related study, using the same model aerosol, we also demonstrate a droplet size-dependence of photochemical reaction rates [1]. Within sub-micron sized particles, photolysis rates were observed to be an order of magnitude greater than those observed in larger droplets. [1] J. W. Cremer, K. M. Thaler, C. Haisch, and R. Signorell. Photoacoustics of single laser-trapped nanodroplets for the direct observation of nanofocusing in aerosol photokinetics. Nat. Commun., 7:10941, 2016.

Photoacoustical and pyroelectric dosimetry of X-ray radiation in diagnostic region

International Nuclear Information System (INIS)

Carvalho, A.A. de.

1987-01-01

Three new types of radiation dosimeters, designed to measure X rays in its diagnostic region are described: the pulsed photoacoustical radiation dosimeter, the pyroelectric radiation dosimeter and the pulsed pyroelectric radiation dosimeter. The photoacoustical radiation dosimeter with the scope of to compare its carachteristics with the carachteristics of the new developed dosimeters is also studied. A methodology for calibration of a photoacoustical dosimeter which doesn't require the calibration of its response in a known field of ionizing radiation is proposed. A theoretical model to explain the results produced by the pulsed pyroelectric radiation dosimeter is presented. The obtained results show that the developed dosimeters are of calorimetric type, being linear its response with the X ray energy fluence rate. (author) [pt

Amplified photoacoustic performance and enhanced photothermal stability of reduced graphene oxide coated gold nanorods for sensitive photoacoustic imaging.

Science.gov (United States)

Moon, Hyungwon; Kumar, Dinesh; Kim, Haemin; Sim, Changbeom; Chang, Jin-Ho; Kim, Jung-Mu; Kim, Hyuncheol; Lim, Dong-Kwon

2015-03-24

We report a strongly amplified photoacoustic (PA) performance of the new functional hybrid material composed of reduced graphene oxide and gold nanorods. Due to the excellent NIR light absorption properties of the reduced graphene oxide coated gold nanorods (r-GO-AuNRs) and highly efficient heat transfer process through the reduced graphene oxide layer, r-GO-AuNRs exhibit excellent photothermal stability and significantly higher photoacoustic amplitudes than those of bare-AuNRs, nonreduced graphene oxide coated AuNRs (GO-AuNRs), or silica-coated AuNR, as demonstrated in both in vitro and in vivo systems. The linear response of PA amplitude from reduced state controlled GO on AuNR indicates the critical role of GO for a strong photothermal effect of r-GO-AuNRs. Theoretical studies with finite-element-method lab-based simulation reveal that a 4 times higher magnitude of the enhanced electromagnetic field around r-GO-AuNRs can be generated compared with bare AuNRs or GO-AuNRs. Furthermore, the r-GO-AuNRs are expected to be a promising deep-tissue imaging probe because of extraordinarily high PA amplitudes in the 4-11 MHz operating frequency of an ultrasound transducer. Therefore, the r-GO-AuNRs can be a useful imaging probe for highly sensitive photoacoustic images and NIR sensitive therapeutics based on a strong photothermal effect.

Enhanced linear-array photoacoustic beamforming using modified coherence factor

Science.gov (United States)

Mozaffarzadeh, Moein; Yan, Yan; Mehrmohammadi, Mohammad; Makkiabadi, Bahador

2018-02-01

Photoacoustic imaging (PAI) is a promising medical imaging modality providing the spatial resolution of ultrasound imaging and the contrast of optical imaging. For linear-array PAI, a beamformer can be used as the reconstruction algorithm. Delay-and-sum (DAS) is the most prevalent beamforming algorithm in PAI. However, using DAS beamformer leads to low-resolution images as well as high sidelobes due to nondesired contribution of off-axis signals. Coherence factor (CF) is a weighting method in which each pixel of the reconstructed image is weighted, based on the spatial spectrum of the aperture, to mainly improve the contrast. We demonstrate that the numerator of the formula of CF contains a DAS algebra and propose the use of a delay-multiply-and-sum beamformer instead of the available DAS on the numerator. The proposed weighting technique, modified CF (MCF), has been evaluated numerically and experimentally compared to CF. It was shown that MCF leads to lower sidelobes and better detectable targets. The quantitative results of the experiment (using wire targets) show that MCF leads to for about 45% and 40% improvement, in comparison with CF, in the terms of signal-to-noise ratio and full-width-half-maximum, respectively.

Noninvasive photoacoustic measurement of absorption coefficient using internal light irradiation of cylindrical diffusing fiber

Science.gov (United States)

Peng, Dong-qing; Zhu, Li-li; Li, Zhi-fang; Li, Hui

2017-09-01

Absorption coefficient of biological tissue is an important parameter in biomedicine, but its determination remains a challenge. In this paper, we propose a method using focusing photoacoustic imaging technique and internal light irradiation of cylindrical diffusing fiber (CDF) to quantify the target optical absorption coefficient. Absorption coefficients for ink absorbers are firstly determined through photoacoustic and spectrophotometric measurements at the same excitation, which demonstrates the feasibility of this method. Also, the optical absorption coefficients of ink absorbers with several concentrations are measured. Finally, the two-dimensional scanning photoacoustic image is obtained. Optical absorption coefficient measurement and simultaneous photoacoustic imaging of absorber non-invasively are the typical characteristics of the method. This method can play a significant role for non-invasive determination of blood oxygen saturation, the absorption-based imaging and therapy.

Photo-Acoustic Ultrasound Imaging to Distinguish Benign from Malignant Prostate Cancer

Science.gov (United States)

2016-09-01

tissue phantoms and animal models of disease . 15. SUBJECT TERMS Photoacoustic, Ultrasound imaging, transurethral probe 16. SECURITY CLASSIFICATION...visible, ultrasound images are unable to discriminate between benign or malignant cancers. In photoacoustic imaging, laser energy is transmitted ...40 g/L concentration of sea plaque agarose into DI water heated to approximately 80°C. A 10 g/L concentration of silica powder was then added to

An experimental and theoretical approach to the study of the photoacoustic signal produced by cancer cells

Directory of Open Access Journals (Sweden)

Rafael Pérez Solano

2012-03-01

Full Text Available The distinctive spectral absorption characteristics of cancer cells make photoacoustic techniques useful for detection in vitro and in vivo. Here we report on our evaluation of the photoacoustic signal produced by a series of monolayers of different cell lines in vitro. Only the melanoma cell line HS936 produced a detectable photoacoustic signal in which amplitude was dependent on the number of cells. This finding appears to be related to the amount of melanin available in these cells. Other cell lines (i.e. HL60, SK-Mel-1, T47D, Hela, HT29 and PC12 exhibited values similar to a precursor of melanin (tyrosinase, but failed to produce sufficient melanin to generate a photoacoustic signal that could be distinguished from background noise. To better understand this phenomenon, we determined a formula for the time-domain photoacoustic wave equation for a monolayer of cells in a non-viscous fluid on the thermoelastic regime. The theoretical results showed that the amplitude and profile of the photoacoustic signal generated by a cell monolayer depended upon the number and distribution of the cells and the location of the point of detection. These findings help to provide a better understanding of the factors involved in the generation of a photoacoustic signal produced by different cells in vitro and in vivo.

Titanium

Science.gov (United States)

Woodruff, Laurel G.; Bedinger, George M.; Piatak, Nadine M.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

2017-12-19

Titanium is a mineral commodity that is essential to the smooth functioning of modern industrial economies. Most of the titanium produced is refined into titanium dioxide, which has a high refractive index and is thus able to impart a durable white color to paint, paper, plastic, rubber, and wallboard. Because of their high strength-to-weight ratio and corrosion resistance, titanium metal and titanium metal alloys are used in the aerospace industry as well as for welding rod coatings, biological implants, and consumer goods.Ilmenite and rutile are currently the principal titanium-bearing ore minerals, although other minerals, including anatase, perovskite, and titanomagnetite, could have economic importance in the future. Ilmenite is currently being mined from two large magmatic deposits hosted in rocks of Proterozoic-age anorthosite plutonic suites. Most rutile and nearly one-half of the ilmenite produced are from heavy-mineral alluvial, fluvial, and eolian deposits. Titanium-bearing minerals occur in diverse geologic settings, but many of the known deposits are currently subeconomic for titanium because of complications related to the mineralogy or because of the presence of trace contaminants that can compromise the pigment production process.Global production of titanium minerals is currently dominated by Australia, Canada, Norway, and South Africa; additional amounts are produced in Brazil, India, Madagascar, Mozambique, Sierra Leone, and Sri Lanka. The United States accounts for about 4 percent of the total world production of titanium minerals and is heavily dependent on imports of titanium mineral concentrates to meet its domestic needs.Titanium occurs only in silicate or oxide minerals and never in sulfide minerals. Environmental considerations for titanium mining are related to waste rock disposal and the impact of trace constituents on water quality. Because titanium is generally inert in the environment, human health risks from titanium and titanium

Laser colouring on titanium alloys: characterisation and potential applications

OpenAIRE

Franceschini, Federica; Demir, Ali Gökhan; Dowding, Colin; Previtali, Barbara; Griffiths, Jonathan David

2014-01-01

Oxides of titanium exhibit vivid colours that can be generated naturally or manipulated through controlled oxidation processes. The application of a laser beam for colouring titanium permits flexible manipulation of the oxidized geometry with high spatial resolution. The laser-based procedure can be applied in an ambient atmosphere to generate long-lasting coloured marks. Today, these properties are largely exploited in artistic applications such as jewellery, eyewear frames, watch components...

Toward in-vivo photoacoustic imaging of human ovarian tissue for cancer detection

Science.gov (United States)

Aguirre, Andres; Kumavor, Patrick; Ardeshirpour, Yasaman; Sanders, Mary M.; Brewer, Molly; Zhu, Quing

2011-03-01

Currently, most of the cancers in the ovary are detected when they have already metastasized to other parts of the body. As a result, ovarian cancer has the highest mortality of all gynecological cancers with a 5-year survival rate of 30% or less [1]. The reason is the lack of reliable symptoms as well as the lack of efficacious screening techniques [2,3]. Thus, there is an urgent need to improve the current diagnostic techniques. We have investigated the potential role of co-registered photoacoustic and ultrasound imaging in ovarian cancer detection. In an effort to bring this technique closer to clinical application, we have developed a co-registered ultrasound and photoacoustic transvaginal probe. A fiber coupling assembly has been developed to deliver the light from around the transducer for reflection geometry imaging. Co-registered ultrasound and photoacoustic images of swine ovaries through vagina wall muscle and human ovaries using the aforementioned probe, demonstrate the potential of photoacoustic imaging to non-invasively detect ovarian cancer in vivo.

Quartz-Enhanced Photoacoustic Spectroscopy: A Review

Science.gov (United States)

Patimisco, Pietro; Scamarcio, Gaetano; Tittel, Frank K.; Spagnolo, Vincenzo

2014-01-01

A detailed review on the development of quartz-enhanced photoacoustic sensors (QEPAS) for the sensitive and selective quantification of molecular trace gas species with resolved spectroscopic features is reported. The basis of the QEPAS technique, the technology available to support this field in terms of key components, such as light sources and quartz-tuning forks and the recent developments in detection methods and performance limitations will be discussed. Furthermore, different experimental QEPAS methods such as: on-beam and off-beam QEPAS, quartz-enhanced evanescent wave photoacoustic detection, modulation-cancellation approach and mid-IR single mode fiber-coupled sensor systems will be reviewed and analysed. A QEPAS sensor operating in the THz range, employing a custom-made quartz-tuning fork and a THz quantum cascade laser will be also described. Finally, we evaluated data reported during the past decade and draw relevant and useful conclusions from this analysis. PMID:24686729

Quartz-Enhanced Photoacoustic Spectroscopy: A Review

Directory of Open Access Journals (Sweden)

Pietro Patimisco

2014-03-01

Full Text Available A detailed review on the development of quartz-enhanced photoacoustic sensors (QEPAS for the sensitive and selective quantification of molecular trace gas species with resolved spectroscopic features is reported. The basis of the QEPAS technique, the technology available to support this field in terms of key components, such as light sources and quartz-tuning forks and the recent developments in detection methods and performance limitations will be discussed. Furthermore, different experimental QEPAS methods such as: on-beam and off-beam QEPAS, quartz-enhanced evanescent wave photoacoustic detection, modulation-cancellation approach and mid-IR single mode fiber-coupled sensor systems will be reviewed and analysed. A QEPAS sensor operating in the THz range, employing a custom-made quartz-tuning fork and a THz quantum cascade laser will be also described. Finally, we evaluated data reported during the past decade and draw relevant and useful conclusions from this analysis.

Inverse transport theory of photoacoustics

International Nuclear Information System (INIS)

Bal, Guillaume; Jollivet, Alexandre; Jugnon, Vincent

2010-01-01

We consider the reconstruction of optical parameters in a domain of interest from photoacoustic data. Photoacoustic tomography (PAT) radiates high-frequency electromagnetic waves into the domain and measures acoustic signals emitted by the resulting thermal expansion. Acoustic signals are then used to construct the deposited thermal energy map. The latter depends on the constitutive optical parameters in a nontrivial manner. In this paper, we develop and use an inverse transport theory with internal measurements to extract information on the optical coefficients from knowledge of the deposited thermal energy map. We consider the multi-measurement setting in which many electromagnetic radiation patterns are used to probe the domain of interest. By developing an expansion of the measurement operator into singular components, we show that the spatial variations of the intrinsic attenuation and the scattering coefficients may be reconstructed. We also reconstruct coefficients describing anisotropic scattering of photons, such as the anisotropy coefficient g(x) in a Henyey–Greenstein phase function model. Finally, we derive stability estimates for the reconstructions

In vivo Photoacoustic Imaging of Prostate Cancer Using Targeted Contrast Agent

Science.gov (United States)

2016-11-01

AD______________ AWARD NUMBER: W81XWH-14-1-0242 TITLE: In Vivo Photoacoustic Imaging of Prostate Cancer Using Targeted Contrast Agent PRINCIPAL...TITLE AND SUBTITLE In vivo Photoacoustic Imaging of Prostate Cancer Using T argeted Contrast Agent 5a. CONTRACT NUMBER W81XWH-14-1-0242 5b. GRANT...diagnose prostate cancer based on the near-infrared optical absorption of either endogenous tissue constituents or exogenous contrast agents . Although

Quantifying bone thickness, light transmission, and contrast interrelationships in transcranial photoacoustic imaging

Science.gov (United States)

Lediju Bell, Muyinatu A.; Ostrowski, Anastasia K.; Li, Ke; Kaanzides, Peter; Boctor, Emad

2015-03-01

We previously introduced photoacoustic imaging to detect blood vessels surrounded by bone and thereby eliminate the deadly risk of carotid artery injury during endonasal, transsphenoidal surgeries. Light would be transmitted through an optical fiber attached to the surgical drill, while a transcranial probe placed on the temporal region of the skull receives photoacoustic signals. This work quantifies changes in photoacoustic image contrast as the sphenoid bone is drilled. Frontal bone from a human adult cadaver skull was cut into seven 3 cm x 3 cm chips and sanded to thicknesses ranging 1-4 mm. For 700-940 nm wavelengths, the average optical transmission through these specimens increased from 19% to 44% as bone thickness decreased, with measurements agreeing with Monte Carlo simulations within 5%. These skull specimens were individually placed in the optical pathway of a 3.5 mm diameter, cylindrical, vessel-mimicking photoacoustic target, as the laser wavelength was varied between 700-940 nm. The mean optical insertion loss and photoacoustic image contrast loss due to the bone specimens were 56-80% and 46-79%, respectively, with the majority of change observed when the bone was <=2 mm thick. The decrease in contrast is directly proportional to insertion loss over this thickness range by factors of 0.8-1.1 when multiple wavelengths are considered. Results suggest that this proportional relationship may be used to determine the amount of bone that remains to be drilled when the thickness is 2 mm or less.

Photoacoustic Imaging of Port-Wine Stains

NARCIS (Netherlands)

Kolkman, R.G.M.; Mulder, M.J.; Mulder, Miranda J.; Glade, Conrad P.; Steenbergen, Wiendelt; van Leeuwen, Ton

2008-01-01

Background and Objective: To optimize laser therapy of port-wine stains (PWSs), information about the vasculature as well as lesion depth is valuable. In this study we investigated the use of photoacoustic imaging (PAI) to obtain this information. - Study Design/Materials and Methods: PAI uses

Recording membrane potential changes through photoacoustic voltage sensitive dye

Science.gov (United States)

Zhang, Haichong K.; Kang, Jeeun; Yan, Ping; Abou, Diane S.; Le, Hanh N. D.; Thorek, Daniel L. J.; Kang, Jin U.; Gjedde, Albert; Rahmim, Arman; Wong, Dean F.; Loew, Leslie M.; Boctor, Emad M.

2017-03-01

Monitoring of the membrane potential is possible using voltage sensitive dyes (VSD), where fluorescence intensity changes in response to neuronal electrical activity. However, fluorescence imaging is limited by depth of penetration and high scattering losses, which leads to low sensitivity in vivo systems for external detection. In contrast, photoacoustic (PA) imaging, an emerging modality, is capable of deep tissue, noninvasive imaging by combining near infrared light excitation and ultrasound detection. In this work, we develop the theoretical concept whereby the voltage-dependent quenching of dye fluorescence leads to a reciprocal enhancement of PA intensity. Based on this concept, we synthesized a novel near infrared photoacoustic VSD (PA-VSD) whose PA intensity change is sensitive to membrane potential. In the polarized state, this cyanine-based probe enhances PA intensity while decreasing fluorescence output in a lipid vesicle membrane model. With a 3-9 μM VSD concentration, we measured a PA signal increase in the range of 5.3 % to 18.1 %, and observed a corresponding signal reduction in fluorescence emission of 30.0 % to 48.7 %. A theoretical model successfully accounts for how the experimental PA intensity change depends on fluorescence and absorbance properties of the dye. These results not only demonstrate the voltage sensing capability of the dye, but also indicate the necessity of considering both fluorescence and absorbance spectral sensitivities in order to optimize the characteristics of improved photoacoustic probes. Together, our results demonstrate photoacoustic sensing as a potential new modality for sub-second recording and external imaging of electrophysiological and neurochemical events in the brain.

In vivo detection of hemoglobin oxygen saturation and carboxyhemoglobin saturation with multiwavelength photoacoustic microscopy.

Science.gov (United States)

Chen, Zhongjiang; Yang, Sihua; Xing, Da

2012-08-15

A method for noninvasively detecting hemoglobin oxygen saturation (SO2) and carboxyhemoglobin saturation (SCO) in subcutaneous microvasculature with multiwavelength photoacoustic microscopy is presented. Blood samples mixed with different concentrations of carboxyhemoglobin were used to test the feasibility and accuracy of photoacoustic microscopy compared with the blood-gas analyzer. Moreover, fixed-point detection of SO2 and SCO in mouse ear was obtained, and the changes from normoxia to carbon monoxide hypoxia were dynamically monitored in vivo. Experimental results demonstrate that multiwavelength photoacoustic microscopy can detect SO2 and SCO, which has future potential clinical applications.

Superconducting microphone for photoacoustic spectroscopy

International Nuclear Information System (INIS)

Ribeiro, P.C.; Labrunie, M.; Weid, J.P. von der; Symko, O.G.

1982-07-01

A superconducting microphone has been developed for photoacoustic spectroscopy at low temperatures. The microphone consists of a thin mylar membrane coated with a film of lead whose motion is detected by a SQUID magnetometer. For the simple set-up presented here, the limiting pressure sensitivity is 7.5x10 -14 atmospheres/√Hz. (Author) [pt

Targeted Nanodiamonds as Phenotype Specific Photoacoustic Contrast Agents for Breast Cancer

Science.gov (United States)

Zhang, Ti; Cui, Huizhong; Fang, Chia-Yi; Cheng, Kun; Yang, Xinmai; Chang, Huan-Cheng; Forrest, M. Laird

2015-01-01

Aim The aim is to develop irradiated nanodiamonds (INDs) as a molecularly-targeted contrast agent for high resolution and phenotype-specific detection of breast cancer with photoacoustic (PA) imaging. Materials & Methods The surface of acid treated radiation-damaged nanodiamonds was grafted with polyethylene glycol (PEG) to improve its stability and circulation time in blood, followed by conjugation to an anti-Human epidermal growth factor receptor-2 (HER2) peptide (KCCYSL) with a final nanoparticle size of ca. 92 nm. Immunocompetent mice bearing orthotopic HER2 positive or negative tumors were administered INDs and PA imaged using an 820-nm near infrared laser. Results PA images demonstrated that INDs accumulate in tumors and completely delineated the entire tumor within 10 hours. HER2 targeting significantly enhanced imaging of HER2-positive tumors. Pathological examination demonstrated INDs are non-toxic. Conclusions PA technology is adaptable to low-cost bedside medicine, and with new contrast agents described herein, PA can achieve high resolution (sub-mm) and phenotype specific monitoring of cancer growth. PMID:25723091

Photoacoustic imaging at 1064nm wavelength with exogenous contrast agents

Science.gov (United States)

Upputuri, Paul Kumar; Jiang, Yuyan; Pu, Kanyi; Pramanik, Manojit

2018-02-01

Photoacoustic (PA) imaging is a promising imaging modality for both preclinical research and clinical practices. Laser wavelengths in the first near infrared window (NIR-I, 650-950 nm) have been widely used for photoacoustic imaging. As compared with NIR-I window, scattering of photons by biological tissues is largely reduced in the second NIR (NIR-II) window, leading to enhanced imaging fidelity. However, the lack of biocompatible NIR-II absorbing exogenous agents prevented the use of this window for in vivo imaging. In recent years, few studies have been reported on photoacoustic imaging in NIR-II window using exogenous contrast agents. In this work, we discuss the recent work on PA imaging using 1064 nm wavelength, the fundamental of Nd:YAG laser, as an excitation wavelength. The PA imaging at 1064 nm is advantageous because of the low and homogeneous signal from tissue background, enabling high contrast in PA imaging when NIR-II absorbing contrast agents are employed.

Effects of optical attenuation, heat diffusion, and acoustic coherence in photoacoustic signals produced by nanoparticles

Science.gov (United States)

Alba-Rosales, J. E.; Ramos-Ortiz, G.; Escamilla-Herrera, L. F.; Reyes-Ramírez, B.; Polo-Parada, L.; Gutiérrez-Juárez, G.

2018-04-01

The behavior of the photoacoustic signal produced by nanoparticles as a function of their concentration was studied in detail. As the concentration of nanoparticles is increased in a sample, the peak-to-peak photoacoustic amplitude increases linearly up to a certain value, after which an asymptotic saturated behavior is observed. To elucidate the mechanisms responsible for these observations, we evaluate the effects of nanoparticles concentration, the optical attenuation, and the effects of heat propagation from nano-sources to their surroundings. We found that the saturation effect of the photoacoustic signal as a function of the concentration of nanoparticles is explained by a combination of two different mechanisms. As has been suggested previously, but not modeled correctly, the most important mechanism is attributed to optical attenuation. The second mechanism is due to an interference destructive process attributed to the superimposition of the photoacoustic amplitudes generated for each nanoparticle, and this explanation is reinforced through our experimental and simulations results; based on this, it is found that the linear behavior of the photoacoustic amplitude could be restricted to optical densities ≤0.5.

An algorithm for total variation regularized photoacoustic imaging

DEFF Research Database (Denmark)

Dong, Yiqiu; Görner, Torsten; Kunis, Stefan

2014-01-01

Recovery of image data from photoacoustic measurements asks for the inversion of the spherical mean value operator. In contrast to direct inversion methods for specific geometries, we consider a semismooth Newton scheme to solve a total variation regularized least squares problem. During the iter......Recovery of image data from photoacoustic measurements asks for the inversion of the spherical mean value operator. In contrast to direct inversion methods for specific geometries, we consider a semismooth Newton scheme to solve a total variation regularized least squares problem. During...... the iteration, each matrix vector multiplication is realized in an efficient way using a recently proposed spectral discretization of the spherical mean value operator. All theoretical results are illustrated by numerical experiments....

Quantitative ultrasound and photoacoustic imaging for the assessment of vascular parameters

CERN Document Server

Meiburger, Kristen M

2017-01-01

This book describes the development of quantitative techniques for ultrasound and photoacoustic imaging in the assessment of architectural and vascular parameters. It presents morphological vascular research based on the development of quantitative imaging techniques for the use of clinical B-mode ultrasound images, and preclinical architectural vascular investigations on quantitative imaging techniques for ultrasounds and photoacoustics. The book is divided into two main parts, the first of which focuses on the development and validation of quantitative techniques for the assessment of vascular morphological parameters that can be extracted from B-mode ultrasound longitudinal images of the common carotid artery. In turn, the second part highlights quantitative imaging techniques for assessing the architectural parameters of vasculature that can be extracted from 3D volumes, using both contrast-enhanced ultrasound (CEUS) imaging and photoacoustic imaging without the addition of any contrast agent. Sharing and...

Photoacoustic spectroscopy of CO2 laser in the detection of gaseous molecules

International Nuclear Information System (INIS)

Lima, G R; Sthel, M S; Da Silva, M G; Schramm, D U S; De Castro, M P P; Vargas, H

2011-01-01

The detection of trace gases is very important for a variety of applications, including the monitoring of atmospheric pollutants, industrial process control, measuring air quality in workplaces, research into fruits physiological processes and medical diagnosis of diseases through the analysis of exhaled gases. The implementation of these and many other applications requiring gas sensors able to meet high sensitivity and selectivity. In this work, a photoacoustic laser spectrometer with CO 2 emission in the infrared range and a resonant photoacoustic cell was used. We obtain the resonance frequency of 2.4 kHz to photoacoustic cell, was estimated detection limit of the spectrometer for molecules of ethylene (C 2 H 4 ), 16 ppbV and ammonia (NH 3 ) 42 ppbV.

Photoacoustic spectroscopy of CO2 laser in the detection of gaseous molecules

Science.gov (United States)

Lima, G. R.; Sthel, M. S.; da Silva, M. G.; Schramm, D. U. S.; de Castro, M. P. P.; Vargas, H.

2011-01-01

The detection of trace gases is very important for a variety of applications, including the monitoring of atmospheric pollutants, industrial process control, measuring air quality in workplaces, research into fruits physiological processes and medical diagnosis of diseases through the analysis of exhaled gases. The implementation of these and many other applications requiring gas sensors able to meet high sensitivity and selectivity. In this work, a photoacoustic laser spectrometer with CO2 emission in the infrared range and a resonant photoacoustic cell was used. We obtain the resonance frequency of 2.4 kHz to photoacoustic cell, was estimated detection limit of the spectrometer for molecules of ethylene (C2H4), 16 ppbV and ammonia (NH3) 42 ppbV.

Photoacoustic imaging of port-wine stains

NARCIS (Netherlands)

Kolkman, Roy G. M.; Mulder, Miranda J.; Glade, Conrad P.; Steenbergen, Wiendelt; van Leeuwen, Ton G.

2008-01-01

BACKGROUND AND OBJECTIVE: To optimize laser therapy of port-wine stains (PWSs), information about the vasculature as well as lesion depth is valuable. In this study we investigated the use of photoacoustic imaging (PAI) to obtain this information. STUDY DESIGN/MATERIALS AND METHODS: PAI uses pulsed

Magneto-optical nanoparticles for cyclic magnetomotive photoacoustic imaging

Science.gov (United States)

Arnal, Bastien; Yoon, Soon Joon; Li, Junwei; Gao, Xiaohu; O'Donnell, Matthew

2018-05-01

Photoacoustic imaging is a highly promising tool to visualize molecular events with deep tissue penetration. Like most other modalities, however, image contrast under in vivo conditions is far from optimal due to background signals from tissue. Using iron oxide-gold core-shell nanoparticles, we previously demonstrated that magnetomotive photoacoustic (mmPA) imaging can dramatically reduce the influence of background signals and produce high-contrast molecular images. Here we report two significant advances toward clinical translation of this technology. First, we introduce a new class of compact, uniform, magneto-optically coupled core-shell nanoparticle, prepared through localized copolymerization of polypyrrole (PPy) on an iron oxide nanoparticle surface. The resulting iron oxide-PPy nanoparticles solve the photo-instability and small-scale synthesis problems previously encountered by the gold coating approach, and extend the large optical absorption coefficient of the particles beyond 1000 nm in wavelength. In parallel, we have developed a new generation of mmPA imaging featuring cyclic magnetic motion and ultrasound speckle tracking, with an image capture frame rate several hundred times faster than the photoacoustic speckle tracking method demonstrated previously. These advances enable robust artifact elimination caused by physiologic motion and first application of the mmPA technology in vivo for sensitive tumor imaging.

A strategy to measure electrophysiological changes with photoacoustic imaging (Conference Presentation)

Science.gov (United States)

Sepela, Rebecka J.; Sherlock, Benjamin E.; Tian, Lin; Marcu, Laura; Sack, Jon

2017-03-01

Photoacoustic imaging is an emerging technology capable of both functional and structural biological imaging. Absorption and scattering in tissue limit the penetration depth of conventional microscopy techniques to live cell imaging. This technology could permit photoacoustic imaging of electrophysiological dynamics in deep tissue, such as the brain. Further optimization of this technology could lead to concurrent imaging of neural activity and hemodynamic responses, a crucial step towards understanding neurovascular coupling in the brain.

In Vitro and In Vivo Evaluations of A High Affinity and Specificity Photoacoustic Nanoparticle Targeting to Cancer

DEFF Research Database (Denmark)

Ma, Lixin; Xu, Hang; Lee, Li Ean

oxide (SIO) nanoparticle as a potent cancer cell selective PA contrast agent, with a high binding affinity and selectivity to the gastrin releasing peptide receptor (GRPR) which is overexpressed in many human cancers including prostate cancer, breast cancer and small cell lung cancer etc.......Photoacoustic (PA) imaging uses a short-pulsed laser to create ultrasound signals for the high resolution acoustic imaging. The development of targeting PA contrast agents offers a unique opportunity to improve the early detection of cancer cells. This work aims to develop a silica coated iron...

Photoacoustic Multicomponent Analyzer for Atmospheric Compounds, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — We propose to build a compact, rugged field-deployable laser photoacoustic spectrometric (LPAS) sensor for continuous, real-time measurements of multiple chemical...

Dual-mode photoacoustic and ultrasound system for real-time in-vivo ovarian cancer imaging

Science.gov (United States)

Mostafa, Atahar; Nandy, Sreyankar; Amidi, Eghbal; Zhu, Quing

2018-02-01

More than 80% of the ovarian cancers are diagnosed at late stages and the survival rate is less than 50%. Currently, there is no effective screening technique available and transvaginal US can only tell if the ovaries are enlarged or not. We have developed a new real-time co-registered US and photoacoustic system for in vivo imaging and characterization of ovaries. US is used to localize ovaries and photoacoustic imaging provides functional information about ovarian tissue angiogenesis and oxygenation saturation. The system consists of a tunable laser and a commercial US system from Alpinion Inc. The Alpinion system is cable of providing channel data for both US pulse-echo and photoacoustic imaging and can be programmed as a computer terminal for display US and photoacoustic images side by side or in coregistered mode. A transvaginal ultrasound probe of 6-MHz center frequency and bandwidth of 3-10 MHz is coupled with four optical fibers surrounded the US probe to deliver the light to tissue. The light from optical fibers is homogenized to ensure the power delivered to the tissue surface is below the FDA required limit. Physicians can easily navigate the probe and use US to look for ovaries and then turn on photoacoustic mode to provide real-time tumor vasculature and So2 saturation maps. With the optimized system, we have successfully imaged first group of 7 patients of malignant, abnormal and benign ovaries. The results have shown that both photoacoustic signal strength and spatial distribution are different between malignant and abnormal and benign ovaries.

Opportunities in the electrowinning of molten titanium from titanium dioxide

CSIR Research Space (South Africa)

Van Vuuren, DS

2005-10-01

Full Text Available used, the following forms of titanium are produced: titanium sponge, sintered electrode sponge, powder, molten titanium, electroplated titanium, hydride powder, and vapor-phase depos- ited titanium. Comparing the economics of alter- native...-up for producing titanium via the Kroll process is approximately as follows: ilmenite ($0.27/kg titanium sponge); titanium slag ($0.75/kg titanium sponge); TiCl4 ($3.09/kg titanium sponge); titanium sponge raw materials costs ($5.50/kg titanium sponge); total...

Photoacoustic detection of CO2 based on LABVIEW at 10.303 μm.

Science.gov (United States)

Zhao, Junjuan; Zhao, Zhan; Du, Lidong; Geng, Daoqu; Wu, Shaohua

2011-04-01

A detailed study on a photoacoustic carbon dioxide detection system, through sound card based on virtual instrument, is presented in this paper. In this system, the CO(2) concentration was measured with the non-resonant photoacoustic cell technique through measuring the photoacoustic signal caused by the CO(2). In order to obtain small photoacoustic signals buried in noise, a measurement software was designed with LABVIEW. It has functions of Lock-in Amplifier, digital filter, and signal generator; can also be used to achieve spectrum analysis and signal recovery; has been provided with powerful function for data processing and communication with other measuring instrument. The test results show that the entire system has an outstanding measuring performance with the sensitivity of 10 μv between 10-44 KHz. The non-resonance test of the trace gas analyte CO(2) conducted at 100 Hz demonstrated large signals (15.89 mV) for CO(2) concentrations at 600 ppm and high signal-to-noise values (∼85:1). © 2011 American Institute of Physics

Compensation of shear waves in photoacoustic tomography with layered acoustic media.

Science.gov (United States)

Schoonover, Robert W; Anastasio, Mark A

2011-10-01

An image reconstruction formula is presented for photoacoustic computed tomography that accounts for conversion between longitudinal and shear waves in a planar-layered acoustic medium. We assume the optical absorber that produces the photoacoustic wave field is embedded in a single fluid layer and any elastic solid layers present are separated by one or more fluid layers. The measurement aperture is assumed to be planar. Computer simulation studies are conducted to demonstrate and investigate the proposed reconstruction formula.

Assessing carotid atherosclerosis by fiber-optic multispectral photoacoustic tomography

Science.gov (United States)

Hui, Jie; Li, Rui; Wang, Pu; Phillips, Evan; Bruning, Rebecca; Liao, Chien-Sheng; Sturek, Michael; Goergen, Craig J.; Cheng, Ji-Xin

2015-03-01

Atherosclerotic plaque at the carotid bifurcation is the underlying cause of the majority of ischemic strokes. Noninvasive imaging and quantification of the compositional changes preceding gross anatomic changes within the arterial wall is essential for diagnosis of disease. Current imaging modalities such as duplex ultrasound, computed tomography, positron emission tomography are limited by the lack of compositional contrast and the detection of flow-limiting lesions. Although high-resolution magnetic resonance imaging has been developed to characterize atherosclerotic plaque composition, its accessibility for wide clinical use is limited. Here, we demonstrate a fiber-based multispectral photoacoustic tomography system for excitation of lipids and external acoustic detection of the generated ultrasound. Using sequential ultrasound imaging of ex vivo preparations we achieved ~2 cm imaging depth and chemical selectivity for assessment of human arterial plaques. A multivariate curve resolution alternating least squares analysis method was applied to resolve the major chemical components, including intravascular lipid, intramuscular fat, and blood. These results show the promise of detecting carotid plaque in vivo through esophageal fiber-optic excitation of lipids and external acoustic detection of the generated ultrasound. This imaging system has great potential for serving as a point-ofcare device for early diagnosis of carotid artery disease in the clinic.

Enhanced linear-array photoacoustic beamforming using modified coherence factor.

Science.gov (United States)

Mozaffarzadeh, Moein; Yan, Yan; Mehrmohammadi, Mohammad; Makkiabadi, Bahador

2018-02-01

Photoacoustic imaging (PAI) is a promising medical imaging modality providing the spatial resolution of ultrasound imaging and the contrast of optical imaging. For linear-array PAI, a beamformer can be used as the reconstruction algorithm. Delay-and-sum (DAS) is the most prevalent beamforming algorithm in PAI. However, using DAS beamformer leads to low-resolution images as well as high sidelobes due to nondesired contribution of off-axis signals. Coherence factor (CF) is a weighting method in which each pixel of the reconstructed image is weighted, based on the spatial spectrum of the aperture, to mainly improve the contrast. We demonstrate that the numerator of the formula of CF contains a DAS algebra and propose the use of a delay-multiply-and-sum beamformer instead of the available DAS on the numerator. The proposed weighting technique, modified CF (MCF), has been evaluated numerically and experimentally compared to CF. It was shown that MCF leads to lower sidelobes and better detectable targets. The quantitative results of the experiment (using wire targets) show that MCF leads to for about 45% and 40% improvement, in comparison with CF, in the terms of signal-to-noise ratio and full-width-half-maximum, respectively. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Fluence compensated photoacoustic tomography in small animals (Conference Presentation)

Science.gov (United States)

Hussain, Altaf; Pool, Martin; Daoudi, Khalid; de Vries, Liesbeth G.; Steenbergen, Wiendelt

2017-03-01

Light fluence inside turbid media can be experimentally mapped by measuring ultrasonically modulated light (Acousto-optics). To demonstrate the feasibility of fluence corrected Photoacoustic (PA) imaging, we have realized a tri-modality (i.e. photoacoustic, acousto-optic and ultrasound) tomographic small animal imaging system. Wherein PA imaging provides high resolution map of absorbed optical energy density, Acousto-optics yields the fluence distribution map in the corresponding PA imaging plane and Ultrasound provides morphological information. Further, normalization of the PA image with the acousto-optically measured fluence map results in an image that directly represents the optical absorption. Human epidermal growth factor receptor 2 (HER2) is commonly found overexpressed in human cancers, among which breast cancers, resulting in a more aggressive tumor phenotype. Identification of HER2-expression is clinically relevant, because cancers overexpressing this marker are amenable to HER2-directed therapies, among which antibodies trastuzumab and pertuzumab. Here, we investigate the feasibility and advantage of acousto-optically assisted fluence compensated PA imaging over PA imaging alone in visualizing and quantifying HER2 expression. For this experiment, nude mice were xenografted with human breast cancer cell lines SKBR3 and BT474 (both HER2 overexpressing), as well as HER2-negative MDA-MB-231. To visualize HER2 expression in these mice, HER2 monoclonal antibody pertuzumab (Perjeta®, Roche), was conjugated to near-infrared dye IRDye 800CW (800CW, LICOR Biosciences) at a ratio of 1∶2 antibody to 800CW. When xenograft tumors measured ≥ 100 mm3, mice received 100 µg 800CW-pertuzumab intravenously. Three days post injection, mice were scanned for fluorescence signal with an IVIS scanner. After fluorescence scans, mice were euthanized and imaged in our PA tomographic imaging system.

Photoacoustic imaging of tumor targeting with biotin conjugated nanostructured phthalocyanine assemblies

Science.gov (United States)

Lee, Seunghyun; Li, Xingshu; Lee, Dayoung; Yoon, Juyoung; Kim, Chulhong

2018-02-01

Visualizing biological markers and delivering bioactive agents to living organisms are important to biological research. In recent decades, photoacoustic imaging (PAI) has been significantly improved in the area of molecular imaging, which provides high-resolution volume imaging with high optical absorption contrast. To demonstrate the ability of nanoprobes to target tumors using PAI, we synthesize convertible nanostructured agents with strong photothermal and photoacoustic properties and linked the nanoprobe with biotin to target tumors in small animal model. Interestingly, these nanoprobes allow partial to disassemble in the presence of targeted proteins that switchable photoactivity, thus the nanoprobes provides a fluorescent-cancer imaging with high signal-to-background ratios. The proposed nanoprobe produce a much stronger PA signal compared to the same concentration of methylene blue (MB), which is widely used in clinical study and contrast agent for PAI. The biotin conjugated nanoprobe has high selectivity for biotin receptor positive cancer cells such as A549 (human lung cancer). Then we subsequently examined the PA properties of the nanoprobe that are inherently suitable for in vivo PAI. After injecting of the nanoprobe via intravenous method, we observed the mice's whole body by PA imaging and acquired the PA signal near the cancer. The PA signal increased linearly with time after injection and the fluorescence signal near the cancer was confirmed by fluorescence imaging. The ability to target a specific cancer of the nanoprobe was well verified by PA imaging. This study provides valuable perspective on the advancement of clinical translations and in the design of tumor-targeting phototheranostic agents that could act as new nanomedicines.

Photoacoustic Spectroscopy with Quantum Cascade Lasers for Trace Gas Detection

Directory of Open Access Journals (Sweden)

Gaetano Scamarcio

2006-10-01

Full Text Available Various applications, such as pollution monitoring, toxic-gas detection, noninvasive medical diagnostics and industrial process control, require sensitive and selectivedetection of gas traces with concentrations in the parts in 109 (ppb and sub-ppb range.The recent development of quantum-cascade lasers (QCLs has given a new aspect toinfrared laser-based trace gas sensors. In particular, single mode distributed feedback QCLsare attractive spectroscopic sources because of their excellent properties in terms of narrowlinewidth, average power and room temperature operation. In combination with these lasersources, photoacoustic spectroscopy offers the advantage of high sensitivity and selectivity,compact sensor platform, fast time-response and user friendly operation. This paper reportsrecent developments on quantum cascade laser-based photoacoustic spectroscopy for tracegas detection. In particular, different applications of a photoacoustic trace gas sensoremploying a longitudinal resonant cell with a detection limit on the order of hundred ppb ofozone and ammonia are discussed. We also report two QC laser-based photoacousticsensors for the detection of nitric oxide, for environmental pollution monitoring andmedical diagnostics, and hexamethyldisilazane, for applications in semiconductormanufacturing process.

THEORY OF SIGNAL GENERATION IN A PHOTOACOUSTIC CELL

OpenAIRE

Bein , B.; Pelzl , J.

1983-01-01

Based on the fundamental physical equations governing the dynamical behaviour of a gas, the pressure signal is derived for a gas-filled photoacoustic cell in contact with a radiation-heated solid sample.

In vivo deep brain imaging of rats using oral-cavity illuminated photoacoustic computed tomography

Science.gov (United States)

Lin, Li; Xia, Jun; Wong, Terence T. W.; Zhang, Ruiying; Wang, Lihong V.

2015-03-01

We demonstrate, by means of internal light delivery, photoacoustic imaging of the deep brain of rats in vivo. With fiber illumination via the oral cavity, we delivered light directly into the bottom of the brain, much more than can be delivered by external illumination. The study was performed using a photoacoustic computed tomography (PACT) system equipped with a 512-element full-ring transducer array, providing a full two-dimensional view aperture. Using internal illumination, the PACT system provided clear cross sectional photoacoustic images from the palate to the middle brain of live rats, revealing deep brain structures such as the hypothalamus, brain stem, and cerebral medulla.

In vivo integrated photoacoustic and confocal microscopy of hemoglobin oxygen saturation and oxygen partial pressure.

Science.gov (United States)

Wang, Yu; Hu, Song; Maslov, Konstantin; Zhang, Yu; Xia, Younan; Wang, Lihong V

2011-04-01

We developed dual-modality microscope integrating photoacoustic microscopy (PAM) and fluorescence confocal microscopy (FCM) to noninvasively image hemoglobin oxygen saturation (sO₂) and oxygen partial pressure (pO₂) in vivo in single blood vessels with high spatial resolution. While PAM measures sO₂ by imaging hemoglobin optical absorption at two wavelengths, FCM quantifies pO₂ using phosphorescence quenching. The variations of sO₂ and pO₂ values in multiple orders of vessel branches under hyperoxic (100% oxygen) and normoxic (21% oxygen) conditions correlate well with the oxygen-hemoglobin dissociation curve. In addition, the total concentration of hemoglobin is imaged by PAM at an isosbestic wavelength.

Photoacoustic imaging of blood vessels with a double-ring sensor featuring a narrow angular aperture

NARCIS (Netherlands)

Kolkman, R.G.M.; Hondebrink, Erwin; Steenbergen, Wiendelt; van Leeuwen, Ton; de Mul, F.F.M.

2004-01-01

A photoacoustic double-ring sensor, featuring a narrow angular aperture, is developed for laser-induced photoacoustic imaging of blood vessels. An integrated optical fiber enables reflection-mode detection of ultrasonic waves. By using the cross-correlation between the signals detected by the two

Determination of the optical absorption spectra of thin layers from their photoacoustic spectra

Science.gov (United States)

Bychto, Leszek; Maliński, Mirosław; Patryn, Aleksy; Tivanov, Mikhail; Gremenok, Valery

2018-05-01

This paper presents a new method for computations of the optical absorption coefficient spectra from the normalized photoacoustic amplitude spectra of thin semiconductor samples deposited on the optically transparent and thermally thick substrates. This method was tested on CuIn(Te0.7Se0.3)2 thin films. From the normalized photoacoustic amplitude spectra, the optical absorption coefficient spectra were computed with the new formula as also with the numerical iterative method. From these spectra, the value of the energy gap of the thin film material and the type of the optical transitions were determined. From the experimental optical transmission spectra, the optical absorption coefficient spectra were computed too, and compared with the optical absorption coefficient spectra obtained from photoacoustic spectra.

High-pulse energy supercontinuum laser for high-resolution spectroscopic photoacoustic imaging of lipids in the 1650-1850 nm region

DEFF Research Database (Denmark)

Dasa, Manoj Kumar; Markos, Christos; Maria, Michael

2018-01-01

We propose a cost-effective high-pulse energy supercontinuum (SC) source based on a telecom range diode laser-based amplifier and a few meters of standard single-mode optical fiber, with a pulse energy density as high as ∼25 nJ/nm in the 1650-1850 nm regime (factor >3 times higher than any SC...... discrimination of two different lipids (cholesterol and lipid in adipose tissue) and the photoacoustic cross-sectional scan of lipid-rich adipose tissue at three different locations. The proposed high-pulse energy SC laser paves a new direction towards compact, broadband and cost-effective source...

Microstructural variation in titanium oxide thin films deposited by DC magnetron sputtering

International Nuclear Information System (INIS)

Pandian, Ramanathaswamy; Natarajan, Gomathi; Kamruddin, M.; Tyagi, A.K.

2013-01-01

We report on the microstructural evolution of titanium oxide thin films deposited by reactive DC magnetron sputtering using titanium metal target. By varying the ratio of sputter-gas mixture containing argon, oxygen and nitrogen various phases of titanium oxide, almost pure rutile, rutile-rich and anatase-rich nano-crystalline, were deposited on Si substrates at room temperature. Using high-resolution scanning electron microscopy, X-ray diffraction and micro-Raman techniques the microstructure of the films were revealed. The relationship between the microstructure of the films and the oxygen partial pressure during sputtering is discussed

Dry coupling for whole-body small-animal photoacoustic computed tomography

Science.gov (United States)

Yeh, Chenghung; Li, Lei; Zhu, Liren; Xia, Jun; Li, Chiye; Chen, Wanyi; Garcia-Uribe, Alejandro; Maslov, Konstantin I.; Wang, Lihong V.

2017-04-01

We have enhanced photoacoustic computed tomography with dry acoustic coupling that eliminates water immersion anxiety and wrinkling of the animal and facilitates incorporating complementary modalities and procedures. The dry acoustic coupler is made of a tubular elastic membrane enclosed by a closed transparent water tank. The tubular membrane ensures water-free contact with the animal, and the closed water tank allows pressurization for animal stabilization. The dry coupler was tested using a whole-body small-animal ring-shaped photoacoustic computed tomography system. Dry coupling was found to provide image quality comparable to that of conventional water coupling.

Improved photoacoustic dosimetry for retinal laser surgery

Science.gov (United States)

Dufour, Suzie; Brown, Robert B.; Gallant, Pascal; Mermut, Ozzy

2018-02-01

Lasers are employed for numerous medical interventions by exploiting ablative, disruptive or thermal effects. In ocular procedures, lasers have been used for decades to treat diseases such as diabetic retinopathy, macular edema and aged related macular degeneration via photocoagulation of retinal tissues. Although laser photocoagulation is well established in today's practice, efforts to improve clinical outcomes by reducing the collateral damage from thermal diffusion is leading to novel treatments using shorter (μs) laser pulses (e.g. selective retinal therapy) which result in physical rather than thermal damage. However, for these new techniques to be widely utilized, a method is required to ensure safe but sufficient dosage has been applied, since no visible effects can be seen by ophthalmoscopy directly post treatment. Photoacoustic feedback presents an attractive solution, as the signal is dependent directly on absorbed dosage. Here, we present a method that takes advantage of temporal pulse formatting technology to minimize variation in absorbed dose in ophthalmic laser treatment and provide intelligent dosimetry feedback based on photoacoustic (PA) response. This method tailors the pulse to match the frequency response of the sample and/or detection chain. Depending on the system, this may include the absorbing particle size, the laser beam diameter, the laser pulse duration, tissue acoustic properties and the acoustic detector frequency response. A significant improvement (<7x) of photoacoustic signal-to-noise ratio over equivalent traditional pulse formats have been achieved, while spectral analysis of the detected signal provides indications of cavitation events and other sample properties.

Photoacoustic spectroscopy, FTIR spectra and thermal diffusivity investigation of emeraldine pellet

International Nuclear Information System (INIS)

Phing, T.E.; Fanny, C.Y.J.; Wan Mahmood Mat Yunus

2001-01-01

Photoacoustic spectra for both emeraldine base and emeraldine salt in bulk form were measured in the wavelength range of 350 nm to 700 nm. The Fourier transform Infrared spectroscopy (FTIR) have also been studied to determine the structure changes due to the protonation process. For the thermal diffusivity measurement, the open photoacoustic cell (OPC) technique has been used. It was found that the emeraldine salt exhibit higher thermal diffusivity compare to emeraldine base and this is similar to the higher conductivity characteristics of emeraldine salt. (Author)

Cell Attachment Following Instrumentation with Titanium and Plastic Instruments, Diode Laser, and Titanium Brush on Titanium, Titanium-Zirconium, and Zirconia Surfaces.

Science.gov (United States)

Lang, Melissa S; Cerutis, D Roselyn; Miyamoto, Takanari; Nunn, Martha E

2016-01-01

The aim of this study was to evaluate the surface characteristics and gingival fibroblast adhesion of disks composed of implant and abutment materials following brief and repeated instrumentation with instruments commonly used in procedures for implant maintenance, stage-two implant surgery, and periimplantitis treatment. One hundred twenty disks (40 titanium, 40 titaniumzirconium, 40 zirconia) were grouped into treatment categories of instrumentation by plastic curette, titanium curette, diode microlaser, rotary titanium brush, and no treatment. Twenty strokes were applied to half of the disks in the plastic and titanium curette treatment categories, while half of the disks received 100 strokes each to simulate implant maintenance occurring on a repetitive basis. Following analysis of the disks by optical laser profilometry, disks were cultured with human gingival fibroblasts. Cell counts were conducted from scanning electron microscopy (SEM) images. Differences in surface roughness across all instruments tested for zirconia disks were negligible, while both titanium disks and titaniumzirconium disks showed large differences in surface roughness across the spectrum of instruments tested. The rotary titanium brush and the titanium curette yielded the greatest overall mean surface roughness, while the plastic curette yielded the lowest mean surface roughness. The greatest mean cell counts for each disk type were as follows: titanium disks with plastic curettes, titanium-zirconium disks with titanium curettes, and zirconia disks with the diode microlaser. Repeated instrumentation did not result in cumulative changes in surface roughness of implant materials made of titanium, titanium-zirconium, or zirconia. Instrumentation with plastic implant curettes on titanium and zirconia surfaces appeared to be more favorable than titanium implant curettes in terms of gingival fibroblast attachment on these surfaces.

Vascular elastic photoacoustic tomography in humans

Science.gov (United States)

Hai, Pengfei; Zhou, Yong; Liang, Jinyang; Li, Chiye; Wang, Lihong V.

2016-03-01

Quantification of vascular elasticity can help detect thrombosis and prevent life-threatening conditions such as acute myocardial infarction or stroke. Here, we propose vascular elastic photoacoustic tomography (VE-PAT) to measure vascular elasticity in humans. VE-PAT was developed by incorporating a linear-array-based photoacoustic computed tomography system with a customized compression stage. By measuring the deformation of blood vessels under uniaxial loading, VE-PAT was able to quantify the vascular compliance. We first demonstrated the feasibility of VE-PAT in blood vessel phantoms. In large vessel phantoms, VE-PAT detected a decrease in vascular compliance due to simulated thrombosis, which was validated by a standard compression test. In small blood vessel phantoms embedded 3 mm deep in gelatin, VE-PAT detected elasticity changes at depths that are difficult to image using other elasticity imaging techniques. We then applied VE-PAT to assess vascular compliance in a human subject and detected a decrease in vascular compliance when an occlusion occurred downstream from the measurement point, demonstrating the potential of VE-PAT in clinical applications such as detection of deep venous thrombosis.

Pulsed laser photoacoustic spectrometer for study of solid materials

International Nuclear Information System (INIS)

Patel, N.D.; Kartha, V.B.

1991-01-01

The technique of photoacoustic spectroscopy has wide applications bacause it is extremely sensitive, and can be used to obtain spectra in wide spectral range for solids, liquids, gases, solutions, crystals etc. which may be usually difficult by conventional methods. For studying a variety of materials, a pulsed laser photoacoustic spectrometer has been set up in the laboratory. The report discusses the design and performance of the instrument. Some of the spectra of materials like Nd 2 O 9 powder, Nd-YAG crystal, CoCl 2 6H 2 O etc. are shown. A detailed discussion on assignment of the spectra of Nd-YAG is also presented. (author). 4 refs., 5 figs., 1 tab

Whole-body ring-shaped confocal photoacoustic computed tomography of small animals in vivo

Science.gov (United States)

Xia, Jun; Chatni, Muhammad R.; Maslov, Konstantin; Guo, Zijian; Wang, Kun; Anastasio, Mark; Wang, Lihong V.

2012-05-01

We report a novel small-animal whole-body imaging system called ring-shaped confocal photoacoustic computed tomography (RC-PACT). RC-PACT is based on a confocal design of free-space ring-shaped light illumination and 512-element full-ring ultrasonic array signal detection. The free-space light illumination maximizes the light delivery efficiency, and the full-ring signal detection ensures a full two-dimensional view aperture for accurate image reconstruction. Using cylindrically focused array elements, RC-PACT can image a thin cross section with 0.10 to 0.25 mm in-plane resolutions and 1.6 s/frame acquisition time. By translating the mouse along the elevational direction, RC-PACT provides a series of cross-sectional images of the brain, liver, kidneys, and bladder.

Accuracy of a novel photoacoustic-based approach to surgical guidance performed with and without a da Vinci robot

Science.gov (United States)

Gandhi, Neeraj; Kim, Sungmin; Kazanzides, Peter; Lediju Bell, Muyinatu A.

2017-03-01

Minimally invasive surgery carries the deadly risk of rupturing major blood vessels, such as the internal carotid arteries hidden by bone in endonasal transsphenoidal surgery. We propose a novel approach to surgical guidance that relies on photoacoustic-based vessel separation measurements to assess the extent of safety zones during these type of surgical procedures. This approach can be implemented with or without a robot or navigation system. To determine the accuracy of this approach, a custom phantom was designed and manufactured for modular placement of two 3.18-mm diameter vessel-mimicking targets separated by 10-20 mm. Photoacoustic images were acquired as the optical fiber was swept across the vessels in the absence and presence of teleoperation with a research da Vinci Surgical System. When the da Vinci was used, vessel positions were recorded based on the fiber position (calculated from the robot kinematics) that corresponded to an observed photoacoustic signal. In all cases, compounded photoacoustic data from a single sweep displayed the four vessel boundaries in one image. Amplitude- and coherence-based photoacoustic images were used to estimate vessel separations, resulting in 0.52-0.56 mm mean absolute errors, 0.66-0.71 mm root mean square errors, and 65-68% more accuracy compared to fiber position measurements obtained through the da Vinci robot kinematics. Results indicate that with further development, photoacoustic image-based measurements of anatomical landmarks could be a viable method for real-time path planning in multiple interventional photoacoustic applications.

Applying photoacoustics to quantification of melanin concentration in retinal pigment epithelium (Conference Presentation)

Science.gov (United States)

Shu, Xiao; Zhang, Hao F.; Liu, Wenzhong

2016-03-01

The melanin in the retinal pigment epithelium (RPE) protects retina and other ocular tissues by photo-screening and acting as antioxidant and free radical scavenger. It helps maintain normal visual functions since human eye is subjected to lifelong high oxygen stress and photon exposure. Loss of the RPE melanin weakens the protection mechanism and jeopardizes ocular health. Local decrease in the RPE melanin concentration is believed to be both a cause and a sign of early-stage age-related macular degeneration (AMD), the leading blinding disease in developed world. Current technology cannot quantitatively measure the RPE melanin concentration which might be a promising marker in early AMD screening. Photoacoustic ophthalmoscopy (PAOM), as an emerging optical absorption-based imaging technology, can potentially be applied to measure the RPE melanin concentration if the dependence of the detectable photoacoustic (PA) signal amplitudes on the RPE melanin concentrations is verified. In this study, we tested the feasibility of using PA signal ratio from RPE melanin and the nearby retinal blood vessels as an indicator of the RPE melanin variation. A novel whole eye optical model was designed and Monte Carlo modeling of light (MCML) was employed. We examined the influences on quantification from PAOM axial resolution, the depth and diameter of the retinal blood vessel, and the RPE thickness. The results show that the scheme is robust to individual histological and illumination variations. This study suggests that PAOM is capable of quantitatively measuring the RPE melanin concentration in vivo.

Photoacoustic and spectroscopic characterization of the ablation process in orthogonal double-pulse configuration

International Nuclear Information System (INIS)

Sobral, H; Sanchez-Ake, C; Sangines, R; Alvarez-Zauco, E; Jimenez-Duran, K

2011-01-01

A photoacoustic technique was used as an alternative method to monitor the crater volume and its role in the emission line intensification in double-pulse pre-ablation configuration. The crater volume was measured using confocal microscopy and correlated with the changes in the photoacoustic signal. Laser emission spectroscopy was used to characterize the emission enhancement as a function of the delay between lasers and the first pulse energy. Optimum delay was found to be in the microsecond timescale corresponding to the maximum of the crater volume and the largest change between the single- and the double-pulse photoacoustic signals. Only a slight intensification was detected with increasing first pulse energy above the first pulse ablation threshold; however, the crater volume did not significantly change and the possible involved mechanisms are discussed.

Removal of symptomatic craniofacial titanium hardware following craniotomy: Case series and review

Directory of Open Access Journals (Sweden)

Sheri K. Palejwala

2015-06-01

Full Text Available Titanium craniofacial hardware has become commonplace for reconstruction and bone flap fixation following craniotomy. Complications of titanium hardware include palpability, visibility, infection, exposure, pain, and hardware malfunction, which can necessitate hardware removal. We describe three patients who underwent craniofacial reconstruction following craniotomies for trauma with post-operative courses complicated by medically intractable facial pain. All three patients subsequently underwent removal of the symptomatic craniofacial titanium hardware and experienced rapid resolution of their painful parasthesias. Symptomatic plates were found in the region of the frontozygomatic suture or MacCarty keyhole, or in close proximity with the supraorbital nerve. Titanium plates, though relatively safe and low profile, can cause local nerve irritation or neuropathy. Surgeons should be cognizant of the potential complications of titanium craniofacial hardware and locations that are at higher risk for becoming symptomatic necessitating a second surgery for removal.

Oxidative stress and pathogenic attack in plants, studied by laser based photoacoustic trace gas detection

NARCIS (Netherlands)

Santosa, Ignatius Edi

2002-01-01

Photoacoustic detection has proven to be a sensitive method, which is suitable for trace gas measurement. In this thesis, we improved the photoacoustic detection system to measure new biologically interesting gases, ethane (C2H6) and nitric oxide (NO). A new design of grating holder is incorporated

A UV-Vis photoacoustic spectrophotometer.

Science.gov (United States)

Wiegand, Joseph R; Mathews, L Dalila; Smith, Geoffrey D

2014-06-17

A novel photoacoustic spectrophotometer (PAS) for the measurement of gas-phase and aerosol absorption over the UV-visible region of the spectrum is described. Light from a broadband Hg arc lamp is filtered in eight separate bands from 300 to 700 nm using bandpass interference filters (centered at 301 nm, 314 nm, 364 nm, 405 nm, 436 nm, 546 nm, 578 and 687 nm) and modulated with an optical chopper before entering the photoacoustic cell. All wavelength bands feature a 20-s detection limit of better than 3.0 Mm(-1) with the exception of the lower-intensity 687 nm band for which it is 10.2 Mm(-1). Validation measurements of gas-phase acetone and nigrosin aerosol absorption cross sections at several wavelengths demonstrate agreement to within 10% with those measured previously (for acetone) and those predicted by Mie theory (for nigrosin). The PAS instrument is used to measure the UV-visible absorption spectrum of ambient aerosol demonstrating a dramatic increase in the UV region with absorption increasing by 300% from 405 to 301 nm. This type of measurement throughout the UV-visible region and free from artifacts associated with filter-based methods has not been possible previously, and we demonstrate its promise for classifying and quantifying different types of light-absorbing ambient particles.

A novel drill design for photoacoustic guided surgeries

Science.gov (United States)

Shubert, Joshua; Lediju Bell, Muyinatu A.

2018-02-01

Fluoroscopy is currently the standard approach for image guidance of surgical drilling procedures. In addition to the harmful radiation dose to the patient and surgeon, fluoroscopy fails to visualize critical structures such as blood vessels and nerves within the drill path. Photoacoustic imaging is a well-suited imaging method to visualize these structures and it does not require harmful ionizing radiation. However, there is currently no clinical system available to deliver light to occluded drill bit tips. To address this challenge, a prototype drill was designed, built, and tested using an internal light delivery system that allows laser energy to be transferred from a stationary laser source to the tip of a spinning drill bit. Photoacoustic images were successfully obtained with the drill bit submerged in water and with the drill tip inserted into a thoracic vertebra from a human cadaver.

Photoacoustic imaging in both soft and hard biological tissue

International Nuclear Information System (INIS)

Li, T; Dewhurst, R J

2010-01-01

To date, most Photoacoustic (PA) imaging results have been from soft biotissues. In this study, a PA imaging system with a near-infrared pulsed laser source has been applied to obtain 2-D and 3-D images from both soft tissue and post-mortem dental samples. Imaging results showed that the PA technique has the potential to image human oral disease, such as early-stage teeth decay. For non-invasive photoacoustic imaging, the induced temperature and pressure rises within biotissues should not cause physical damage to the tissue. Several simulations based on the thermoelastic effect have been applied to predict initial temperature and pressure fields within a tooth sample. Predicted initial temperature and pressure rises are below corresponding safety limits.

Simultaneous ultrasound and photoacoustics based flow cytometry

Science.gov (United States)

Gnyawali, Vaskar; Strohm, Eric M.; Tsai, Scott S. H.; Kolios, Michael C.

2018-04-01

We have developed a flow cytometer based on simultaneous detection of ultrasound and photoacoustic waves from individual particles/cells flowing in a microfluidic channel. Our polydimethylsiloxane (PDMS) based hydrodynamic 3-dimensional (3D) flow-focusing microfluidic device contains a cross-junction channel, a micro-needle (ID 100 μm and OD 200 μm) insert, and a 3D printed frame to hold and align a high frequency (center frequency 375 MHz) ultrasound transducer. The focused flow passes through a narrow focal zone with lateral and axial focal lengths of 6-8 μm and 15-20 μm, respectively. Both the lateral and axial alignments are achieved by screwing the transducer to the frame onto the PDMS device. Individual particles pass through an interrogation zone in the microfluidic channel with a collinearly aligned ultrasound transducer and a focused 532 nm wavelength laser beam. The particles are simultaneously insonified by high-frequency ultrasound and irradiated by a laser beam. The ultrasound backscatter and laser generated photoacoustic waves are detected for each passing particle. The backscattered ultrasound and photoacoustic signal are strongly dependent on the size, morphology, mechanical properties, and material properties of the flowing particles; these parameters can be extracted by analyzing unique features in the power spectrum of the signals. Frequencies less than 100 MHz do not have these unique spectral signatures. We show that we can reliably distinguish between different particles in a sample using the acoustic-based flow cytometer. This technique, when extended to biomedical applications, allows us to rapidly analyze the spectral signatures from individual single cells of a large cell population, with applications towards label-free detection and characterization of healthy and diseased cells.

Photoacoustic/ultrasound dual-modality contrast agent and its application to thermotherapy.

Science.gov (United States)

Wang, Yu-Hsin; Liao, Ai-Ho; Chen, Jui-Hao; Wang, Churng-Ren Chris; Li, Pai-Chi

2012-04-01

This study investigates a photoacoustic/ultrasound dual-modality contrast agent, including extending its applications from image-contrast enhancement to combined diagnosis and therapy with site-specific targeting. The contrast agent comprises albumin-shelled microbubbles with encapsulated gold nanorods (AuMBs). The gas-filled microbubbles, whose diameters range from submicrometer to several micrometers, are not only echogenic but also can serve as drug-delivery vehicles. The gold nanorods are used to enhance the generation of both photoacoustic and photothermal signals. The optical absorption peak of the gold nanorods is tuned to 760 nm and is invariant after microbubble encapsulation. Dual-modality contrast enhancement is first described here, and the applications to cellular targeting and laser-induced thermotherapy in a phantom are demonstrated. Photoacoustic imaging can be used to monitor temperature increases during the treatment. The targeting capability of AuMBs was verified, and the temperature increased by 26°C for a laser power of 980 mW, demonstrating the potential of combined diagnosis and therapy with the dual-modality agent. Targeted photo- or acoustic-mediated delivery is also possible.

Ultrasound to video registration using a bi-plane transrectal probe with photoacoustic markers

Science.gov (United States)

Cheng, Alexis; Kang, Hyun Jae; Zhang, Haichong K.; Taylor, Russell H.; Boctor, Emad M.

2016-03-01

Modern surgical scenarios typically provide surgeons with additional information through fusion of video and other imaging modalities. To provide this information, the tools and devices used in surgery must be registered together with interventional guidance equipment and surgical navigation systems. In this work, we focus explicitly on registering ultrasound with a stereo camera system using photoacoustic markers. Previous work has shown that photoacoustic markers can be used in this registration task to achieve target registration errors lower than the current available systems. Photoacoustic markers are defined as a set of non-collinear laser spots projected onto some surface. They can be simultaneously visualized by a stereo camera system and an ultrasound transducer because of the photoacoustic effect. In more recent work, the three-dimensional ultrasound volume was replaced by images from a single ultrasound image pose from a convex array transducer. The feasibility of this approach was demonstrated, but the accuracy was lacking due to the physical limitations of the convex array transducer. In this work, we propose the use of a bi-plane transrectal ultrasound transducer. The main advantage of using this type of transducer is that the ultrasound elements are no longer restricted to a single plane. While this development would be limited to prostate applications, liver and kidney applications are also feasible if a suitable transducer is built. This work is demonstrated in two experiments, one without photoacoustic sources and one with. The resulting target registration error for these experiments were 1.07mm±0.35mm and 1.27mm+/-0.47mm respectively, both of which are better than current available navigation systems.

Ingestible roasted barley for contrast-enhanced photoacoustic imaging in animal and human subjects.

Science.gov (United States)

Wang, Depeng; Lee, Dong Hyeun; Huang, Haoyuan; Vu, Tri; Lim, Rachel Su Ann; Nyayapathi, Nikhila; Chitgupi, Upendra; Liu, Maggie; Geng, Jumin; Xia, Jun; Lovell, Jonathan F

2018-08-01

Photoacoustic computed tomography (PACT) is an emerging imaging modality. While many contrast agents have been developed for PACT, these typically cannot immediately be used in humans due to the lengthy regulatory process. We screened two hundred types of ingestible foodstuff samples for photoacoustic contrast with 1064 nm pulse laser excitation, and identified roasted barley as a promising candidate. Twenty brands of roasted barley were further screened to identify the one with the strongest contrast, presumably based on complex chemical modifications incurred during the roasting process. Individual roasted barley particles could be detected through 3.5 cm of chicken-breast tissue and through the whole hand of healthy human volunteers. With PACT, but not ultrasound imaging, a single grain of roasted barley was detected in a field of hundreds of non-roasted particles. Upon oral administration, roasted barley enabled imaging of the gut and peristalsis in mice. Prepared roasted barley tea could be detected through 2.5 cm chicken breast tissue. When barley tea was administered to humans, photoacoustic imaging visualized swallowing dynamics in healthy volunteers. Thus, roasted barley represents an edible foodstuff that should be considered for photoacoustic contrast imaging of swallowing and gut processes, with immediate potential for clinical translation. Copyright © 2018 Elsevier Ltd. All rights reserved.

Anatomical and metabolic small-animal whole-body imaging using ring-shaped confocal photoacoustic computed tomography

Science.gov (United States)

Xia, Jun; Chatni, Muhammad; Maslov, Konstantin; Wang, Lihong V.

2013-03-01

Due to the wide use of animals for human disease studies, small animal whole-body imaging plays an increasingly important role in biomedical research. Currently, none of the existing imaging modalities can provide both anatomical and glucose metabolic information, leading to higher costs of building dual-modality systems. Even with image coregistration, the spatial resolution of the metabolic imaging modality is not improved. We present a ring-shaped confocal photoacoustic computed tomography (RC-PACT) system that can provide both assessments in a single modality. Utilizing the novel design of confocal full-ring light delivery and ultrasound transducer array detection, RC-PACT provides full-view cross-sectional imaging with high spatial resolution. Scanning along the orthogonal direction provides three-dimensional imaging. While the mouse anatomy was imaged with endogenous hemoglobin contrast, the glucose metabolism was imaged with a near-infrared dye-labeled 2-deoxyglucose. Through mouse tumor models, we demonstrate that RC-PACT may be a paradigm shifting imaging method for preclinical research.

Near-infrared light-responsive liposomal contrast agent for photoacoustic imaging and drug release applications.

Science.gov (United States)

Sivasubramanian, Kathyayini; Mathiyazhakan, Malathi; Wiraja, Christian; Upputuri, Paul Kumar; Xu, Chenjie; Pramanik, Manojit

2017-04-01

Photoacoustic imaging has become an emerging tool for theranostic applications. Not only does it help in release and therapeutic applications. We explore near-infrared light-sensitive liposomes coated with gold nanostars (AuNSs) for both imaging and drug release applications using a photoacoustic imaging system. Being amphiphilic, the liposomes lipid bilayer and the aqueous core enable encapsulation of both hydrophobic and hydrophilic drugs. The AuNSs on the surface of the liposomes act as photon absorbers due to their intrinsic surface plasmon resonance. Upon excitation by laser light at specific wavelength, AuNSs facilitate rapid release of the contents encapsulated in the liposomes due to local heating and pressure wave formation (photoacoustic wave). Herein, we describe the design and optimization of the AuNSs-coated liposomes and demonstrate the release of both hydrophobic and hydrophilic model drugs (paclitaxel and calcein, respectively) through laser excitation at near-infrared wavelength. The use of AuNSs-coated liposomes as contrast agents for photoacoustic imaging is also explored with tissue phantom experiments. In comparison to blood, the AuNSs-coated liposomes have better contrast (approximately two times) at 2-cm imaging depth.

Photoacoustic detection of NH3 in power plant emissions

International Nuclear Information System (INIS)

Rassmussen, O.

1991-01-01

The paper describes a photoacoustic spectrometer initially designed for detection of NH 3 in power plant emission with a detection limit below 1 ppm. The radiation source is a high tunable CO 2 waveguide laser emitting its own frequency standard in one of 90 laserlines. The detection is performed at reduced pressure where the vibration-rotation transitions give an unambiguous fingerprint for each trace gas. Immunity against interference is ensured by recording this characteristic spectral fingerprint over the tuning range of the laser, and problems associated with the high concentration of CO 2 or other interfering molecules are further eliminated by utilizing the effect of kinetic cooling in the photoacoustic phase. The use of a CO 2 laser as radiation source combined with the highly sensitive photoacoustic detection provides a great possibility of measuring a wide range of air pollutants in the range down to ppt concentrations. Experimental measurements have been carried out on gases like sulfur dioxide, ethylene, sulfur hexafluoride, vinylchloride, ozone, etc., and many others have been theoretically examined to give a high response in the CO 2 laser frequency range. A computerized NH 3 spectrometer has been constructed and tested under realistic conditions at a Danish power plant operating a test facility for selective non-catalytic reduction of NO x . Results of this test will be presented

Biomechanical and morphological multi-parameter photoacoustic endoscope for identification of early esophageal disease

Science.gov (United States)

Jin, Dayang; Yang, Fen; Chen, Zhongjiang; Yang, Sihua; Xing, Da

2017-09-01

The combination of phase-sensitive photoacoustic (PA) imaging of tissue viscoelasticity with the esophagus-adaptive PA endoscope (PAE) technique allows the characterization of the biomechanical and morphological changes in the early stage of esophageal disease with high accuracy. In this system, the tissue biomechanics and morphology are obtained by detecting the PA phase and PA amplitude information, respectively. The PAE has a transverse resolution of approximately 37 μm and an outer diameter of 1.2 mm, which is suitable for detecting rabbit esophagus. Here, an in-situ biomechanical and morphological study of normal and diseased rabbit esophagus (tumors of esophagus and reflux esophagitis) was performed. The in-situ findings were highly consistent with those observed by histology. In summary, we demonstrated the potential application of PAE for early clinical detection of esophageal diseases.

Some actinide speciation using laser induced photoacoustic spectroscopy

International Nuclear Information System (INIS)

Pollard, P.M.; McMillan, J.W.; Phillips, G.; Thomason, H.P.; Ewart, F.T.

1988-01-01

Laser induced photoacoustic spectroscopy is an attractive method for the speciation of actinides in solutions from nuclear disposal studies because it is essentially non-invasive and has a reasonably high sensitivity, down to ca 10 -8 M. A novel true dual beam system has been constructed and commissioned at Harwell with a performance at least equal to any others in existence. It is based on a XeCl excimer laser and a dye laser, beam splitter, two laser power monitors and photoacoustic cells. The wavelength scanning, data collection, and spectra processing and display are controlled by an Apricot computer. The sample and reference cells are housed in an inert atmosphere glove box. Early applications of the equipment described include measurements of Am and Np species under varying conditions of pH, Eh and carbonate concentration. The observations show some correlation with predictions made using the geochemical modelling code PHREEQE. (orig.)

Quinone-fused porphyrins as contrast agents for photoacoustic imaging

KAUST Repository

Banala, Srinivas; Fokong, Stanley; Brand, Christian; Andreou, Chrysafis; Krä utler, Bernhard; Rueping, Magnus; Kiessling, Fabian

2017-01-01

Photoacoustic (PA) imaging is an emerging non-invasive diagnostic modality with many potential clinical applications in oncology, rheumatology and the cardiovascular field. For this purpose, there is a high demand for exogenous contrast agents

Transversely Excited Multipass Photoacoustic Cell Using Electromechanical Film as Microphone

Directory of Open Access Journals (Sweden)

Jaakko Saarela

2010-05-01

Full Text Available A novel multipass photoacoustic cell with five stacked electromechanical films as a microphone has been constructed, tested and characterized. The photoacoustic cell is an open rectangular structure with two steel plates facing each other. The longitudinal acoustic resonances are excited transversely in an optical multipass configuration. A detection limit of 22 ppb (10−9 was achieved for flowing NO2 in N2 at normal pressure by using the maximum of 70 laser beams between the resonator plates. The corresponding minimum detectable absorption and the normalized noise-equivalent absorption coefficients were 2:2 × 10−7 cm−1 and 3:2 × 10−9 cm−1WHz−1/2, respectively.

Photoacoustic imaging of hidden dental caries by using a bundle of hollow optical fibers

Science.gov (United States)

Koyama, Takuya; Kakino, Satoko; Matsuura, Yuji

2018-02-01

Photoacoustic imaging system using a bundle of hollow-optical fibers to detect hidden dental caries is proposed. Firstly, we fabricated a hidden caries model with a brown pigment simulating a common color of caries lesion. It was found that high frequency ultrasonic waves are generated from hidden carious part when radiating Nd:YAG laser light with a 532 nm wavelength to occlusal surface of model tooth. We calculated by Fourier transform and found that the waveform from the carious part provides frequency components of approximately from 0.5 to 1.2 MHz. Then a photoacoustic imaging system using a bundle of hollow optical fiber was fabricated for clinical applications. From intensity map of frequency components in 0.5-1.2 MHz, photoacoustic images of hidden caries in the simulated samples were successfully obtained.

Hydrogen content in titanium and a titanium–zirconium alloy after acid etching

Energy Technology Data Exchange (ETDEWEB)

Frank, Matthias J.; Walter, Martin S. [Department of Biomaterials, Institute for Clinical Dentistry, University of Oslo, P.O. Box 1109, Blindern, NO-0317 Oslo (Norway); Institute of Medical and Polymer Engineering, Chair of Medical Engineering, Technische Universität München, Boltzmannstrasse 15, 85748 Garching (Germany); Lyngstadaas, S. Petter [Department of Biomaterials, Institute for Clinical Dentistry, University of Oslo, P.O. Box 1109, Blindern, NO-0317 Oslo (Norway); Wintermantel, Erich [Institute of Medical and Polymer Engineering, Chair of Medical Engineering, Technische Universität München, Boltzmannstrasse 15, 85748 Garching (Germany); Haugen, Håvard J., E-mail: h.j.haugen@odont.uio.no [Department of Biomaterials, Institute for Clinical Dentistry, University of Oslo, P.O. Box 1109, Blindern, NO-0317 Oslo (Norway)

2013-04-01

Dental implant alloys made from titanium and zirconium are known for their high mechanical strength, fracture toughness and corrosion resistance in comparison with commercially pure titanium. The aim of the study was to investigate possible differences in the surface chemistry and/or surface topography of titanium and titanium–zirconium surfaces after sand blasting and acid etching. The two surfaces were compared by X-ray photoelectron spectroscopy, secondary ion mass spectroscopy, scanning electron microscopy and profilometry. The 1.9 times greater surface hydrogen concentration of titanium zirconium compared to titanium was found to be the major difference between the two materials. Zirconium appeared to enhance hydride formation on titanium alloys when etched in acid. Surface topography revealed significant differences on the micro and nanoscale. Surface roughness was increased significantly (p < 0.01) on the titanium–zirconium alloy. High-resolution images showed nanostructures only present on titanium zirconium. - Highlights: ► TiZr alloy showed increased hydrogen levels over Ti. ► The alloying element Zr appeared to catalyze hydrogen absorption in Ti. ► Surface roughness was significantly increased for the TiZr alloy over Ti. ► TiZr alloy revealed nanostructures not observed for Ti.

Thermal diffusivity measurement for p-Si and Ag/p-Si by photoacoustic technique

Energy Technology Data Exchange (ETDEWEB)

Hussein, Mohammed Jabbar; Yunus, W. Mahmood Mat; Kamari, Halimah Mohamed; Zakaria, Azmi, E-mail: mohammed55865@yahoo.com [Department of Physics, Faculty of Science, Universiti PutraMalaysia (UPM), Serdang (Malaysia)

2015-10-15

Thermal diffusivity (TD) of p-Si and Ag/p-Si samples were measured by photoacoustic technique using open photoacoustic cell (OPC). The samples were annealed by heating them at 960, 1050, 1200, and 1300 °C for 3 h in air. The thermal diffusivity of Ag-coated samples was obtained by fitting the photoacoustic experimental data to the thermally thick equation for Rosencwaig and Gersho (RG) theory. For the single layer samples, the thermal diffusivity can be obtained by fitting as well as by obtaining the critical frequency f{sub c.} In this study, the thermal diffusivity of the p-Si samples increased with increasing the annealing temperature. The thermal diffusivity of the Ag/p-Si samples, after reaching the maximum value of about 2.73 cm{sup 2}/s at a temperature of 1200 °C, decreased due to the silver complete melt in the surface of the silicon. (author)

Thermal Diffusivity Measurement for p-Si and Ag/p-Si by Photoacoustic Technique

Science.gov (United States)

Hussein, Mohammed Jabbar; Yunus, W. Mahmood Mat; Kamari, Halimah Mohamed; Zakaria, Azmi

2015-10-01

Thermal diffusivity (TD) of p-Si and Ag/p-Si samples were measured by photoacoustic technique using open photoacoustic cell (OPC). The samples were annealed by heating them at 960, 1050, 1200, and 1300 °C for 3 h in air. The thermal diffusivity of Ag-coated samples was obtained by fitting the photoacoustic experimental data to the thermally thick equation for Rosencwaig and Gersho (RG) theory. For the single layer samples, the thermal diffusivity can be obtained by fitting as well as by obtaining the critical frequency f c . In this study, the thermal diffusivity of the p-Si samples increased with increasing the annealing temperature. The thermal diffusivity of the Ag/p-Si samples, after reaching the maximum value of about 2.73 cm2/s at a temperature of 1200 °C, decreased due to the silver complete melt in the surface of the silicon.

Mid-infrared photoacoustic spectroscopy for atmospheric NO2 measurements

Science.gov (United States)

Lassen, Mikael; Lamard, Laurent; Balslev-Harder, David; Peremans, Andre; Petersen, Jan C.

2018-02-01

A photoacoustic (PA) sensor for spectroscopic measurements of NO2-N2 at ambient pressure and temperature is demonstrated. The PA sensor is pumped resonantly by a nanosecond pulsed single-mode mid-infrared (MIR) optical parametric oscillator (OPO). Spectroscopic measurements of NO2-N2 in the 3.25 μm to 3.55 μm wavelength region with a resolution bandwidth of 5 cm-1 and with a single shot detection limit of 1.6 ppmV (μmol/mol) is demonstrated. The measurements were conducted with a constant flow rate of 300 ml/min, thus demonstrating the suitability of the gas sensor for real time trace gas measurements. The acquired spectra is compared with data from the Hitran database and good agreement is found. An Allan deviation analysis shows that the detection limit at optimum integration time for the PAS sensor is 14 ppbV (nmol/mol) at 170 seconds of integration time, corresponding to a normalized noise equivalent absorption (NNEA) coefficient of 3.3×10-7 W cm-1 Hz-1/2.

Fast and Straightforward Synthesis of Luminescent Titanium(IV Dioxide Quantum Dots

Directory of Open Access Journals (Sweden)

Václav Štengl

2017-01-01

Full Text Available The nucleus of titania was prepared by reaction of solution titanium oxosulphate with hydrazine hydrate. These titania nuclei were used for titania quantum dots synthesis by a simple and fast method. The prepared titanium(IV dioxide quantum dots were characterized by measurement of X-ray powder diffraction (XRD, X-ray photoelectron spectroscopy (XPS, atomic force microscopy (AFM, high-resolution electron microscopy (HRTEM, and selected area electron diffraction (SAED. The optical properties were determined by photoluminescence (PL spectra. The prepared titanium(IV dioxide quantum dots have the narrow range of UV excitation (365–400 nm and also a close range of emission maxima (450–500 nm.

Titanium ; dream new material

International Nuclear Information System (INIS)

Lee, Yong Tae; Kim Seung Eon; Heoon, Yong Taek; Jung, Hui Won

2001-11-01

The contents of this book are history of Titanium, present situation of Titanium industry, property of Titanium alloy, types of it, development of new alloy of Titanium smelting of Titanium, cast of Titanium and heat treatment of Titanium, Titanium alloy for plane, car parts, biological health care, and sport leisure and daily life, prospect, and Titanium industrial development of Titanium in China.

Detection and capture of single circulating melanoma cells using photoacoustic flowmetry

Science.gov (United States)

O'Brien, Christine; Mosley, Jeffrey; Goldschmidt, Benjamin S.; Viator, John A.

2010-02-01

Photoacoustic flowmetry has been used to detect single circulating melanoma cells in vitro. Circulating melanoma cells are those cells that travel in the blood and lymph systems to create secondary tumors and are the hallmark of metastasis. This technique involves taking blood samples from patients, separating the white blood and melanoma cells from whole blood and irradiating them with a pulsed laser in a flowmetry set up. Rapid, visible wavelength laser pulses on the order of 5 ns can induce photoacoustic waves in melanoma cells due to their melanin content, while surrounding white blood cells remain acoustically passive. We have developed a system that identifies rare melanoma cells and captures them in 50 microliter volumes using suction applied near the photoacoustic detection chamber. The 50 microliter sample is then diluted and the experiment is repeated using the new sample until only a melanoma cell remains. We have tested this system on dyed microspheres ranging in size from 300 to 500 microns. Capture of circulating melanoma cells may provide the opportunity to study metastatic cells for basic understanding of the spread of cancer and to optimize patient specific therapies.

Photoacoustic discrimination of viable and thermally coagulated blood using a two-wavelength method for burn injury monitoring

International Nuclear Information System (INIS)

Talbert, Robert J; Holan, Scott H; Viator, John A

2007-01-01

Discriminating viable from thermally coagulated blood in a burn wound can be used to profile burn depth, thus aiding the removal of necrotic tissue. In this study, we used a two-wavelength photoacoustic imaging method to discriminate coagulated and non-coagulated blood in a dermal burn phantom. Differences in the optical absorption spectra of coagulated and non-coagulated blood produce different values of the ratio of peak photoacoustic amplitude at 543 and 633 nm. The absorption values obtained from spectroscopic measurements indicate that the ratio of photoacoustic pressure for 543 and 633 nm for non-coagulated blood was 15.7:1 and 1.6:1 for coagulated blood. Using planar blood layers, we found the photoacoustic ratios to be 13.5:1 and 1.6:1, respectively. Using the differences in the ratios of coagulated and non-coagulated blood, we propose a scheme using statistical classification analysis to identify the different blood samples. Based upon these distinctly different ratios, we identified the planar blood samples with an error rate of 0%. Using a burn phantom with cylindrical vessels containing coagulated and non-coagulated blood, we achieved an error rate of 11.4%. These results have shown that photoacoustic imaging could prove to be a valuable tool in the diagnosis of burns

Quantum-cascade laser photoacoustic detection of methane emitted from natural gas powered engines

Science.gov (United States)

Rocha, M. V.; Sthel, M. S.; Silva, M. G.; Paiva, L. B.; Pinheiro, F. W.; Miklòs, A.; Vargas, H.

2012-03-01

In this work we present a laser photoacoustic arrangement for the detection of the important greenhouse gas methane. A quantum-cascade laser and a differential photoacoustic cell were employed. A detection limit of 45 ppbv in nitrogen was achieved as well as a great selectivity. The same methodology was also tested in the detection of methane issued from natural gas powered vehicles (VNG) in Brazil, which demonstrates the excellent potential of this arrangement for greenhouse gas detection emitted from real sources.

Self-Normalized Photoacoustic Technique for the Quantitative Analysis of Paper Pigments

Science.gov (United States)

Balderas-López, J. A.; Gómez y Gómez, Y. M.; Bautista-Ramírez, M. E.; Pescador-Rojas, J. A.; Martínez-Pérez, L.; Lomelí-Mejía, P. A.

2018-03-01

A self-normalized photoacoustic technique was applied for quantitative analysis of pigments embedded in solids. Paper samples (filter paper, Whatman No. 1), attached with the pigment: Direct Fast Turquoise Blue GL, were used for this study. This pigment is a blue dye commonly used in industry to dye paper and other fabrics. The optical absorption coefficient, at a wavelength of 660 nm, was measured for this pigment at various concentrations in the paper substrate. It was shown that Beer-Lambert model for light absorption applies well for pigments in solid substrates and optical absorption coefficients as large as 220 cm^{-1} can be measured with this photoacoustic technique.

Self-assembled nanomaterials for photoacoustic imaging

Science.gov (United States)

Wang, Lei; Yang, Pei-Pei; Zhao, Xiao-Xiao; Wang, Hao

2016-01-01

In recent years, extensive endeavors have been paid to construct functional self-assembled nanomaterials for various applications such as catalysis, separation, energy and biomedicines. To date, different strategies have been developed for preparing nanomaterials with diversified structures and functionalities via fine tuning of self-assembled building blocks. In terms of biomedical applications, bioimaging technologies are urgently calling for high-efficient probes/contrast agents for high-performance bioimaging. Photoacoustic (PA) imaging is an emerging whole-body imaging modality offering high spatial resolution, deep penetration and high contrast in vivo. The self-assembled nanomaterials show high stability in vivo, specific tolerance to sterilization and prolonged half-life stability and desirable targeting properties, which is a kind of promising PA contrast agents for biomedical imaging. Herein, we focus on summarizing recent advances in smart self-assembled nanomaterials with NIR absorption as PA contrast agents for biomedical imaging. According to the preparation strategy of the contrast agents, the self-assembled nanomaterials are categorized into two groups, i.e., the ex situ and in situ self-assembled nanomaterials. The driving forces, assembly modes and regulation of PA properties of self-assembled nanomaterials and their applications for long-term imaging, enzyme activity detection and aggregation-induced retention (AIR) effect for diagnosis and therapy are emphasized. Finally, we conclude with an outlook towards future developments of self-assembled nanomaterials for PA imaging.

Self-assembled nanomaterials for photoacoustic imaging.

Science.gov (United States)

Wang, Lei; Yang, Pei-Pei; Zhao, Xiao-Xiao; Wang, Hao

2016-02-07

In recent years, extensive endeavors have been paid to construct functional self-assembled nanomaterials for various applications such as catalysis, separation, energy and biomedicines. To date, different strategies have been developed for preparing nanomaterials with diversified structures and functionalities via fine tuning of self-assembled building blocks. In terms of biomedical applications, bioimaging technologies are urgently calling for high-efficient probes/contrast agents for high-performance bioimaging. Photoacoustic (PA) imaging is an emerging whole-body imaging modality offering high spatial resolution, deep penetration and high contrast in vivo. The self-assembled nanomaterials show high stability in vivo, specific tolerance to sterilization and prolonged half-life stability and desirable targeting properties, which is a kind of promising PA contrast agents for biomedical imaging. Herein, we focus on summarizing recent advances in smart self-assembled nanomaterials with NIR absorption as PA contrast agents for biomedical imaging. According to the preparation strategy of the contrast agents, the self-assembled nanomaterials are categorized into two groups, i.e., the ex situ and in situ self-assembled nanomaterials. The driving forces, assembly modes and regulation of PA properties of self-assembled nanomaterials and their applications for long-term imaging, enzyme activity detection and aggregation-induced retention (AIR) effect for diagnosis and therapy are emphasized. Finally, we conclude with an outlook towards future developments of self-assembled nanomaterials for PA imaging.

Comparison of Deconvolution Filters for Photoacoustic Tomography.

Directory of Open Access Journals (Sweden)

Dominique Van de Sompel

Full Text Available In this work, we compare the merits of three temporal data deconvolution methods for use in the filtered backprojection algorithm for photoacoustic tomography (PAT. We evaluate the standard Fourier division technique, the Wiener deconvolution filter, and a Tikhonov L-2 norm regularized matrix inversion method. Our experiments were carried out on subjects of various appearances, namely a pencil lead, two man-made phantoms, an in vivo subcutaneous mouse tumor model, and a perfused and excised mouse brain. All subjects were scanned using an imaging system with a rotatable hemispherical bowl, into which 128 ultrasound transducer elements were embedded in a spiral pattern. We characterized the frequency response of each deconvolution method, compared the final image quality achieved by each deconvolution technique, and evaluated each method's robustness to noise. The frequency response was quantified by measuring the accuracy with which each filter recovered the ideal flat frequency spectrum of an experimentally measured impulse response. Image quality under the various scenarios was quantified by computing noise versus resolution curves for a point source phantom, as well as the full width at half maximum (FWHM and contrast-to-noise ratio (CNR of selected image features such as dots and linear structures in additional imaging subjects. It was found that the Tikhonov filter yielded the most accurate balance of lower and higher frequency content (as measured by comparing the spectra of deconvolved impulse response signals to the ideal flat frequency spectrum, achieved a competitive image resolution and contrast-to-noise ratio, and yielded the greatest robustness to noise. While the Wiener filter achieved a similar image resolution, it tended to underrepresent the lower frequency content of the deconvolved signals, and hence of the reconstructed images after backprojection. In addition, its robustness to noise was poorer than that of the Tikhonov

Photoacoustic imaging of vascular networks in transgenic mice

Science.gov (United States)

Laufer, J. G.; Cleary, J. O.; Zhang, E. Z.; Lythgoe, M. F.; Beard, P. C.

2010-02-01

The preferential absorption of near infrared light by blood makes photoacoustic imaging well suited to visualising vascular structures in soft tissue. In addition, the spectroscopic specificity of tissue chromophores can be exploited by acquiring images at multiple excitation wavelengths. This allows the quantification of endogenous chromophores, such as oxy- and deoxyhaemoglobin, and hence blood oxygenation, and the detection of exogenous chromophores, such as functionalised contrast agents. More importantly, this approach has the potential to visualise the spatial distribution of low concentrations of functionalised contrast agents against the strong background absorption of the endogenous chromophores. This has a large number of applications in the life sciences. One example is the structural and functional phenotyping of transgenic mice for the study of the genetic origins of vascular malformations, such as heart defects. In this study, photoacoustic images of mouse embryos have been acquired to study the development of the vasculature following specific genetic knockouts.

Research on fiber-optic cantilever-enhanced photoacoustic spectroscopy for trace gas detection

Science.gov (United States)

Chen, Ke; Zhou, Xinlei; Gong, Zhenfeng; Yu, Shaochen; Qu, Chao; Guo, Min; Yu, Qingxu

2018-01-01

We demonstrate a new scheme of cantilever-enhanced photoacoustic spectroscopy, combining a sensitivity-improved fiber-optic cantilever acoustic sensor with a tunable high-power fiber laser, for trace gas detection. The Fabry-Perot interferometer based cantilever acoustic sensor has advantages such as high sensitivity, small size, easy to install and immune to electromagnetic. Tunable erbium-doped fiber ring laser with an erbium-doped fiber amplifier is used as the light source for acoustic excitation. In order to improve the sensitivity for photoacoustic signal detection, a first-order longitudinal resonant photoacoustic cell with the resonant frequency of 1624 Hz and a large size cantilever with the first resonant frequency of 1687 Hz are designed. The size of the cantilever is 2.1 mm×1 mm, and the thickness is 10 μm. With the wavelength modulation spectrum and second-harmonic detection methods, trace ammonia (NH3) has been measured. The gas detection limits (signal-to-noise ratio = 1) near the wavelength of 1522.5 nm is achieved to be 3 ppb.

Photoacoustic imaging of early gastric cancer diagnosis based on long focal area ultrasound transducer

Science.gov (United States)

Wu, Huaqin; Li, Zuoran; Liu, Lantian; Li, Zhifang; Wu, Shulian; Li, Hui

2017-06-01

We illustrated a novel imaging method to diagnose gastric neoplasms via photoacoustic tomography (PAT). Depending on the structural characteristics of gastric cavity, we used column diffusion fiber to irradiate the stomach tissue through the esophagus, and the externally placed telecentric focus ultrasonic transducer detected photoacoustic signals from the gastric tissue. We reconstructed the distribution of light energy deposition of the simulated gastric tumor, and obtained the location and size information of gastric tumor.

Determination of optical absorption coefficient with focusing photoacoustic imaging.

Science.gov (United States)

Li, Zhifang; Li, Hui; Zeng, Zhiping; Xie, Wenming; Chen, Wei R

2012-06-01

Absorption coefficient of biological tissue is an important factor for photothermal therapy and photoacoustic imaging. However, its determination remains a challenge. In this paper, we propose a method using focusing photoacoustic imaging technique to quantify the target optical absorption coefficient. It utilizes the ratio of the amplitude of the peak signal from the top boundary of the target to that from the bottom boundary based on wavelet transform. This method is self-calibrating. Factors, such as absolute optical fluence, ultrasound parameters, and Grüneisen parameter, can be canceled by dividing the amplitudes of the two peaks. To demonstrate this method, we quantified the optical absorption coefficient of a target with various concentrations of an absorbing dye. This method is particularly useful to provide accurate absorption coefficient for predicting the outcomes of photothermal interaction for cancer treatment with absorption enhancement.

Photoacoustic microscopy of cerebral hemodynamic and oxygen-metabolic responses to anesthetics

Science.gov (United States)

Cao, Rui; Li, Jun; Ning, Bo; Sun, Naidi; Wang, Tianxiong; Zuo, Zhiyi; Hu, Song

2017-02-01

General anesthetics are known to have profound effects on cerebral hemodynamics and neuronal activities. However, it remains a challenge to directly assess anesthetics-induced hemodynamic and oxygen-metabolic changes from the true baseline under wakefulness at the microscopic level, due to the lack of an enabling technology for high-resolution functional imaging of the awake mouse brain. To address this challenge, we have developed head-restrained photoacoustic microscopy (PAM), which enables simultaneous imaging of the cerebrovascular anatomy, total concentration and oxygen saturation of hemoglobin (CHb and sO2), and blood flow in awake mice. From these hemodynamic measurements, two important metabolic parameters, oxygen extraction fraction (OEF) and the cerebral metabolic rate of oxygen (CMRO2), can be derived. Side-by-side comparison of the mouse brain under wakefulness and anesthesia revealed multifaceted cerebral responses to isoflurane, a volatile anesthetic widely used in preclinical research and clinical practice. Key observations include elevated cerebral blood flow (CBF) and reduced oxygen extraction and metabolism.

NH4HCO3 gas-generating liposomal nanoparticle for photoacoustic imaging in breast cancer

Directory of Open Access Journals (Sweden)

Xia J

2017-03-01

Full Text Available Jizhu Xia, Gang Feng, Xiaorong Xia, Lan Hao, Zhigang Wang Chongqing Key Laboratory of Ultrasound Molecular Imaging, Department of Ultrasound, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, People’s Republic of China Abstract: In this study, we have developed a biodegradable nanomaterial for photoacoustic imaging (PAI. Its biodegradation products can be fully eliminated from a living organism. It is a gas-generating nanoparticle of liposome-encapsulating ammonium bicarbonate (NH4HCO3 solution, which is safe, effective, inexpensive, and free of side effects. When lasers irradiate these nanoparticles, NH4HCO3 decomposes to produce CO2, which can absorb much of the light energy under laser irradiation with a specific wavelength, and then expand under heat to generate a thermal acoustic wave. An acoustic detector can detect this wave and show it as a photoacoustic signal on a display screen. The intensity of the photoacoustic signal is enhanced corresponding to an increase in time, concentration, and temperature. During in vivo testing, nanoparticles were injected into tumor-bearing nude mice through the caudal vein, and photoacoustic signals were detected from the tumor, reaching a peak in 4 h, and then gradually disappearing. There was no damage to the skin or subcutaneous tissue from laser radiation. Our developed gas-generating nanomaterial, NH4HCO3 nanomaterial, is feasible, effective, safe, and inexpensive. Therefore, it is a promising material to be used in clinical PAI. Keywords: Photoacoustic tomography, CO2, NH4HCO3, contrast agent, cancer

Photoacoustic point spectroscopy

Science.gov (United States)

Van Neste, Charles W [Kingston, TN; Senesac, Lawrence R [Knoxville, TN; Thundat, Thomas G [Knoxville, TN

2011-06-14

A system and method are disclosed for generating a photoacoustic spectrum in an open or closed environment with reduced noise. A source may emit a beam to a target substance coated on a detector that measures acoustic waves generated as a result of a light beam being absorbed by the target substance. By emitting a chopped/pulsed light beam to the target substance on the detector, it may be possible to determine the target's optical absorbance as the wavelength of light is changed. Rejection may decrease the intensity of the acoustic waves on the detector while absorption may increase the intensity. Accordingly, an identifying spectrum of the target may be made with the intensity variation of the detector as a function of illuminating wavelength.

Nanoscale Bonding between Human Bone and Titanium Surfaces: Osseohybridization

Directory of Open Access Journals (Sweden)

Jun-Sik Kim

2015-01-01

Full Text Available Until now, the chemical bonding between titanium and bone has been examined only through a few mechanical detachment tests. Therefore, in this study, a sandblasted and acid-etched titanium mini-implant was removed from a human patient after 2 months of placement in order to identify the chemical integration mechanism for nanoscale osseointegration of titanium implants. To prepare a transmission electron microscopy (TEM specimen, the natural state was preserved as much as possible by cryofixation and scanning electron microscope/focused ion beam (SEM-FIB milling without any chemical treatment. High-resolution TEM (HRTEM, energy dispersive X-ray spectroscopy (EDS, and scanning TEM (STEM/electron energy loss spectroscopic analysis (EELS were used to investigate the chemical composition and structure at the interface between the titanium and bone tissue. HRTEM and EDS data showed evidence of crystalline hydroxyapatite and intermixing of bone with the oxide layer of the implant. The STEM/EELS experiment provided particularly interesting results: carbon existed in polysaccharides, calcium and phosphorus existed as tricalcium phosphate (TCP, and titanium existed as oxidized titanium. In addition, the oxygen energy loss near edge structures (ELNESs showed a possibility of the presence of CaTiO3. These STEM/EELS results can be explained by structures either with or without a chemical reaction layer. The possible existence of the osseohybridization area and the form of the carbon suggest that reconsideration of the standard definition of osseointegration is necessary.

Study of the diffusion of some emulsions in the human skin by pulsed photoacoustic spectroscopy

International Nuclear Information System (INIS)

Lahjomri, F; Benamar, N; Chatri, E; Leblanc, R M

2003-01-01

We previously used pulsed photoacoustic spectroscopy (PPAS) to quantify sunscreen diffusion into human skin, and suggested a methodology to evaluate the time and the depth diffusion profile. These results were obtained by the analysis of the photoacoustic maximum response signal P max decrease, the time delay t max and the Fourier transform representation of the photoacoustic signal. In this study we present the results obtained for diffusion of four typical emulsions used in sunscreen compositions that show, for the first time, a particular behaviour for one of these emulsions due to a chemical reaction inside the skin during the diffusion process. This result provides a particularly interesting technique through the PPAS, to evaluate in situ the eventual chemical reactions that can occur during drug diffusion into human skin

A simple photoacoustic detector for highly corrosive gases

Czech Academy of Sciences Publication Activity Database

Rakovský, Jozef; Votava, Ondřej

2017-01-01

Roč. 88, č. 1 (2017), č. článku 013103. ISSN 0034-6748 R&D Projects: GA ČR GA13-11635S Institutional support: RVO:61388955 Keywords : photoacoustic spectroscopy * biosensors * laser sensors Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 1.515, year: 2016

Comparison of photoacoustic spectroscopy, conventional absorption spectroscopy, and potentiometry as probes of lanthanide speciation

International Nuclear Information System (INIS)

Torres, R.A.; Palmer, C.E.A.; Baisden, P.A.; Russo, R.E.; Silva, R.J.

1990-01-01

The authors measured the stability constants of praseodymium acetate and oxydiacetate complexes by laser-induced photoacoustic spectroscopy, conventional UV-visible absorption spectroscopy, and pH titration. For the spectroscopic studies, changes in the free Pr absorption peaks at 468 and 481 nm were monitored at varying ligand concentrations. The total Pr concentration was 1 x 10 -4 M in solutions used for the photoacoustic studies and 0.02 M for conventional spectroscopy. For the pH titrations, we used solutions whose Pr concentrations varied from 5 x 10 -3 to 5 x 10 -2 M, with total ligand-to-metal ratios ranging from 1 to 10. A comparison of the results obtained by the three techniques demonstrates that photoacoustic spectroscopy can give the same information about metal-ligand speciation as more conventional methods. It is particularly suited to those situations where the other techniques are insensitive because of limited metal concentrations

Multispectral photoacoustic method for the early detection and diagnosis of osteoporosis

Science.gov (United States)

Steinberg, Idan; Eyal, Avishay; Gannot, Israel

2013-03-01

Osteoporosis is a major health problem worldwide, with healthcare costs of billions of dollars annually. The risk of fracture depends on the bone mineral density (measured in clinical practice) as well as on the bone microstructure and functional status. Since pure ultrasonic methods can measure bone strength and spectroscopic optical methods can provide valuable functional information, a hybrid multispectral photoacoustic technique can be of great value. We have developed such a system based on a tunable Ti:Sapph laser at 750 - 950 nm, followed by an acousto-optic modulator to generate photoacoustic signals with frequencies of 0.5 - 2.5 MHz. Another system was based on two directly modulated 830nm laser diodes. The systems were used to photoacoustically excite the proximal end of a rat tibia. Spectrum analyzer with tracking generator was used for measuring both the amplitude and the phase at the distal end. Scanning along both the optical wavelength as well as the acoustic frequency enables full mapping of the bone transfer function. Analyzing this function along the wavelength axis allows deducing the gross biochemical composition related to the bone functional and pathological state. Analyzing the amplitude and phase along the acoustic frequency axis yields the speed of sound dispersion and the broadband ultrasonic attenuation - both have shown clinical relevance.

Intravascular ultrasonic-photoacoustic (IVUP) endoscope with 2.2-mm diameter catheter for medical imaging.

Science.gov (United States)

Bui, Nhat Quang; Hlaing, Kyu Kyu; Nguyen, Van Phuc; Nguyen, Trung Hau; Oh, Yun-Ok; Fan, Xiao Feng; Lee, Yong Wook; Nam, Seung Yun; Kang, Hyun Wook; Oh, Junghwan

2015-10-01

Intravascular ultrasound (IVUS) imaging is extremely important for detection and characterization of high-risk atherosclerotic plaques as well as gastrointestinal diseases. Recently, intravascular photoacoustic (IVPA) imaging has been used to differentiate the composition of biological tissues with high optical contrast and ultrasonic resolution. The combination of these imaging techniques could provide morphological information and molecular screening to characterize abnormal tissues, which would help physicians to ensure vital therapeutic value and prognostic significance for patients before commencing therapy. In this study, integration of a high-frequency IVUS imaging catheter (45MHz, single-element, unfocused, 0.7mm in diameter) with a multi-mode optical fiber (0.6mm in core diameter, 0.22 NA), an integrated intravascular ultrasonic-photoacoustic (IVUP) imaging catheter, was developed to provide spatial and functional information on light distribution in a turbid sample. Simultaneously, IVUS imaging was co-registered to IVPA imaging to construct 3D volumetric sample images. In a phantom study, a polyvinyl alcohol (PVA) tissue-mimicking arterial vessel phantom with indocyanine green (ICG) and methylene blue (MB) inclusion was used to demonstrate the feasibility of mapping the biological dyes, which are used in cardiovascular and cancer diagnostics. For the ex vivo study, an excised sample of pig intestine with ICG was utilized to target the biomarkers present in the gastrointestinal tumors or the atherosclerotic plaques with the proposed hybrid technique. The results indicated that IVUP endoscope with the 2.2-mm diameter catheter could be a useful tool for medical imaging. Copyright © 2015 Elsevier Ltd. All rights reserved.

Distal radius plate of CFR-PEEK has minimal effect compared to titanium plates on bone parameters in high-resolution peripheral quantitative computed tomography: a pilot study.

Science.gov (United States)

de Jong, Joost J A; Lataster, Arno; van Rietbergen, Bert; Arts, Jacobus J; Geusens, Piet P; van den Bergh, Joop P W; Willems, Paul C

2017-02-27

Carbon-fiber-reinforced poly-ether-ether-ketone (CFR-PEEK) has superior radiolucency compared to other orthopedic implant materials, e.g. titanium or stainless steel, thus allowing metal-artifact-free postoperative monitoring by computed tomography (CT). Recently, high-resolution peripheral quantitative CT (HRpQCT) proved to be a promising technique to monitor the recovery of volumetric bone mineral density (vBMD), micro-architecture and biomechanical parameters in stable conservatively treated distal radius fractures. When using HRpQCT to monitor unstable distal radius fractures that require volar distal radius plating for fixation, radiolucent CFR-PEEK plates may be a better alternative to currently used titanium plates to allow for reliable assessment. In this pilot study, we assessed the effect of a volar distal radius plate made from CFR-PEEK on bone parameters obtained from HRpQCT in comparison to two titanium plates. Plates were instrumented in separate cadaveric human fore-arms (n = 3). After instrumentation and after removal of the plates duplicate HRpQCT scans were made of the region covered by the plate. HRpQCT images were visually checked for artifacts. vBMD, micro-architectural and biomechanical parameters were calculated, and compared between the uninstrumented and instrumented radii. No visible image artifacts were observed in the CFR-PEEK plate instrumented radius, and errors in bone parameters ranged from -3.2 to 2.6%. In the radii instrumented with the titanium plates, severe image artifacts were observed and errors in bone parameters ranged between -30.2 and 67.0%. We recommend using CFR-PEEK plates in longitudinal in vivo studies that monitor the healing process of unstable distal radius fractures treated operatively by plating or bone graft ingrowth.

Double-Stage Delay Multiply and Sum Beamforming Algorithm: Application to Linear-Array Photoacoustic Imaging.

Science.gov (United States)

Mozaffarzadeh, Moein; Mahloojifar, Ali; Orooji, Mahdi; Adabi, Saba; Nasiriavanaki, Mohammadreza

2018-01-01

Photoacoustic imaging (PAI) is an emerging medical imaging modality capable of providing high spatial resolution of Ultrasound (US) imaging and high contrast of optical imaging. Delay-and-Sum (DAS) is the most common beamforming algorithm in PAI. However, using DAS beamformer leads to low resolution images and considerable contribution of off-axis signals. A new paradigm namely delay-multiply-and-sum (DMAS), which was originally used as a reconstruction algorithm in confocal microwave imaging, was introduced to overcome the challenges in DAS. DMAS was used in PAI systems and it was shown that this algorithm results in resolution improvement and sidelobe degrading. However, DMAS is still sensitive to high levels of noise, and resolution improvement is not satisfying. Here, we propose a novel algorithm based on DAS algebra inside DMAS formula expansion, double stage DMAS (DS-DMAS), which improves the image resolution and levels of sidelobe, and is much less sensitive to high level of noise compared to DMAS. The performance of DS-DMAS algorithm is evaluated numerically and experimentally. The resulted images are evaluated qualitatively and quantitatively using established quality metrics including signal-to-noise ratio (SNR), full-width-half-maximum (FWHM) and contrast ratio (CR). It is shown that DS-DMAS outperforms DAS and DMAS at the expense of higher computational load. DS-DMAS reduces the lateral valley for about 15 dB and improves the SNR and FWHM better than 13% and 30%, respectively. Moreover, the levels of sidelobe are reduced for about 10 dB in comparison with those in DMAS.

SU-E-J-44: Design a Platform and Phantom Model for Photoacoustic Imaging in Combination with CT

Energy Technology Data Exchange (ETDEWEB)

Sick, J; Alsanea, F; Rancilio, N; Stantz, K [Purdue University, West Lafayette, IN (United States)

2014-06-01

Purpose: Our (long-term) objective is to develop a US manipulator that will provide in situ radiation response and image-guided therapy for bladder cancer based on photoacoustic molecular imaging. Methods: A platform was devised to provide a reproducible positional frame of reference for targeting anatomic structure between MDCT and US scans, in lieu of CBCT, and to fuse photoacoustic molecular imaging. US and photoacoustic scans are taken of a patient while in the CT scanner and IRMT. Through co-registration, based on anatomical positions, we identified a common coordinate system to be used in Eclipse. A bladder phantom was constructed to validate anatomical tracking via US and photoacoustic imaging. We tested the platform using phantom model to demonstrate validity once moved from the CT couch to the linear accelerator couch. Results: This platform interlocks with Varian exact couch index points for reproducibility of positioning. Construction from low Z material and sized appropriately to fit in CT/IMRT gantry. Error in conversion from cylindrical coordinates of the manipulator to X, Y, Z coordinates of the treatment couch was less than 1mm. We measured the bladder size in 3 different directions in both Eclipse from the CT and Acuson from US. The error was less than 2mm in all directions. CT and US images were co-registered in MATLAB. Co-registration of photoacoustic images is still being developed. Conclusion: For Linear Accelerators without on board imaging, MV portal images are not a viable option for the localization of soft tissue anatomy. We believe our manipulator provides an alternative using US imaging, which will be examined in an upcoming clinical trial. We plan to examine the value of hypoxia guided treatment through photoacoustic imaging during this trial.

SU-E-J-44: Design a Platform and Phantom Model for Photoacoustic Imaging in Combination with CT

International Nuclear Information System (INIS)

Sick, J; Alsanea, F; Rancilio, N; Stantz, K

2014-01-01

Purpose: Our (long-term) objective is to develop a US manipulator that will provide in situ radiation response and image-guided therapy for bladder cancer based on photoacoustic molecular imaging. Methods: A platform was devised to provide a reproducible positional frame of reference for targeting anatomic structure between MDCT and US scans, in lieu of CBCT, and to fuse photoacoustic molecular imaging. US and photoacoustic scans are taken of a patient while in the CT scanner and IRMT. Through co-registration, based on anatomical positions, we identified a common coordinate system to be used in Eclipse. A bladder phantom was constructed to validate anatomical tracking via US and photoacoustic imaging. We tested the platform using phantom model to demonstrate validity once moved from the CT couch to the linear accelerator couch. Results: This platform interlocks with Varian exact couch index points for reproducibility of positioning. Construction from low Z material and sized appropriately to fit in CT/IMRT gantry. Error in conversion from cylindrical coordinates of the manipulator to X, Y, Z coordinates of the treatment couch was less than 1mm. We measured the bladder size in 3 different directions in both Eclipse from the CT and Acuson from US. The error was less than 2mm in all directions. CT and US images were co-registered in MATLAB. Co-registration of photoacoustic images is still being developed. Conclusion: For Linear Accelerators without on board imaging, MV portal images are not a viable option for the localization of soft tissue anatomy. We believe our manipulator provides an alternative using US imaging, which will be examined in an upcoming clinical trial. We plan to examine the value of hypoxia guided treatment through photoacoustic imaging during this trial

Effect of alkali treatment on surface morphology of titanium

Energy Technology Data Exchange (ETDEWEB)

Tan, K. J., E-mail: gd130056@siswa.uthm.edu.my; Wahab, M. A. A., E-mail: cd110006@siswa.uthm.edu.my; Mahmod, S., E-mail: cd110201@siswa.uthm.edu.my; Idris, M. I., E-mail: izwana@uthm.edu.my; Abdullah, H. Z., E-mail: hasan@uthm.edu.my [Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor (Malaysia)

2015-07-22

Alkali and heat treatments were first introduced by Kim et al. to prepare a bioactive surface on titanium. This method has been proven very effective and widely used in other studies to promote titanium osteointegration. This study aims to investigate further the effect of alkali treatment on surface morphology of high purity titanium. High purity titanium foils were immersed in NaOH aqueous solutions of 0.5 M, 5 M and 15 M at 60°C and 80 °C for 1, 3 and 7 days. The surface morphology was examined using Field Emission Scanning Electron Microscope (FESEM). The obtained phases were analysed using Fourier Transform Infrared Spectroscopy (FTIR) in the spectra range of 4000-600 cm{sup −1} at 4 cm{sup −1} resolution and 50 scans. At the same soaking temperature and soaking time, a thicker porous network was observed with increasing concentration of NaOH. At the same soaking temperature, a much porous structure was observed with increasing soaking time. At constant alkali concentration, more homogenously distributed porous surface structure was observed with increasing soaking temperature.

Characterization of the titanium Kβ spectral profile

International Nuclear Information System (INIS)

Chantler, C T; Smale, L F; Kinnane, M N; Illig, A J; Kimpton, J A; Crosby, D N

2013-01-01

Transition metals have Kα and Kβ characteristic radiation possessing complex asymmetric spectral profiles. Instrumental broadening normally encountered in x-ray experiments shifts features of profiles used for calibration, such as peak energy, by many times the quoted accuracies. We measure and characterize the titanium Kβ spectral profile. The peak energy of the titanium Kβ spectral profile is found to be 4931.966 ± 0.022 eV prior to instrumental broadening. This 4.5 ppm result decreases the uncertainty over the past literature by a factor of 2.6 and is 2.4 standard deviations from the previous standard. The spectrum is analysed and the resolution-free lineshape is extracted and listed for use in other experiments. We also incorporate improvement in analysis applied to earlier results for V Kβ. (paper)

Photoacoustic discrimination of vascular and pigmented lesions using classical and Bayesian methods

Science.gov (United States)

Swearingen, Jennifer A.; Holan, Scott H.; Feldman, Mary M.; Viator, John A.

2010-01-01

Discrimination of pigmented and vascular lesions in skin can be difficult due to factors such as size, subungual location, and the nature of lesions containing both melanin and vascularity. Misdiagnosis may lead to precancerous or cancerous lesions not receiving proper medical care. To aid in the rapid and accurate diagnosis of such pathologies, we develop a photoacoustic system to determine the nature of skin lesions in vivo. By irradiating skin with two laser wavelengths, 422 and 530 nm, we induce photoacoustic responses, and the relative response at these two wavelengths indicates whether the lesion is pigmented or vascular. This response is due to the distinct absorption spectrum of melanin and hemoglobin. In particular, pigmented lesions have ratios of photoacoustic amplitudes of approximately 1.4 to 1 at the two wavelengths, while vascular lesions have ratios of about 4.0 to 1. Furthermore, we consider two statistical methods for conducting classification of lesions: standard multivariate analysis classification techniques and a Bayesian-model-based approach. We study 15 human subjects with eight vascular and seven pigmented lesions. Using the classical method, we achieve a perfect classification rate, while the Bayesian approach has an error rate of 20%.

Structural phototransformation of WO{sub 3} thin films detected by photoacoustic analysis

Energy Technology Data Exchange (ETDEWEB)

Pacheco, Argelia Perez, E-mail: ekargy@hotmail.com [Universidad Nacional Autonoma de Mexico, Laboratorio de Fotofisica y Peliculas Delgadas-CCADET, Ciudad Universitaria, Coyoacan, A.P. 70-186, C.P. 04510, Mexico, D.F. (Mexico); Montes de Oca, C. Oliva; Castaneda-Guzman, R.; Garcia, A. Esparza [Universidad Nacional Autonoma de Mexico, Laboratorio de Fotofisica y Peliculas Delgadas-CCADET, Ciudad Universitaria, Coyoacan, A.P. 70-186, C.P. 04510, Mexico, D.F. (Mexico)

2012-11-15

Highlights: Black-Right-Pointing-Pointer The phototransformation of WO{sub 3} thin films were studied by photoacoustic technique. Black-Right-Pointing-Pointer The phase transition in WO{sub 3} thin films was induced by laser irradiation fluence. Black-Right-Pointing-Pointer The onset and end of the phototransformation in the thin films was identified. Black-Right-Pointing-Pointer The ablation threshold for each sample was identified. - Abstract: The photoacoustic technique (PA) was used to detect the phase transformation from amorphous to crystalline state of tungsten oxide (WO{sub 3}) thin films induced by UV pulsed laser radiation at low energy (<1.5 mJ). The evolution of photoacoustic signal was studied by a correlation analysis, comparing successive signals at fluences ranging from 0 to 20 mJ/cm{sup 2}. In this interval, it was possible to observe structural changes and the ablation threshold in films due to incident laser fluence effect. Thin films of WO{sub 3} were deposited by DC reactive magnetron sputtering over glass substrates at different deposition times. The results obtained by correlation analysis were compared with Raman spectroscopy data.

Micro-optical-mechanical system photoacoustic spectrometer

Science.gov (United States)

Kotovsky, Jack; Benett, William J.; Tooker, Angela C.; Alameda, Jennifer B.

2013-01-01

All-optical photoacoustic spectrometer sensing systems (PASS system) and methods include all the hardware needed to analyze the presence of a large variety of materials (solid, liquid and gas). Some of the all-optical PASS systems require only two optical-fibers to communicate with the opto-electronic power and readout systems that exist outside of the material environment. Methods for improving the signal-to-noise are provided and enable mirco-scale systems and methods for operating such systems.

Poly(vinyl alcohol) gels as photoacoustic breast phantoms revisited

NARCIS (Netherlands)

Xia, Wenfeng; Piras, Daniele; Heijblom, Michelle; Steenbergen, Wiendelt; van Leeuwen, Ton G.; Manohar, Srirang

2011-01-01

A popular phantom in photoacoustic imaging is poly(vinyl alcohol) (PVA) hydrogel fabricated by freezing and thawing (F-T) aqueous solutions of PVA. The material possesses acoustic and optical properties similar to those of tissue. Earlier work characterized PVA gels in small test specimens where

Poly(vinyl alcohol) gels as photoacoustic breast phantoms revisited

NARCIS (Netherlands)

Xia, W.; Piras, D.; Heijblom, M.; Steenbergen, Wiendelt; van Leeuwen, Ton; Manohar, Srirang

2011-01-01

A popular phantom in photoacoustic imaging is poly(vinyl alcohol) (PVA) hydrogel fabricated by freezing and thawing (F–T) aqueous solutions of PVA. The material possesses acoustic and optical properties similar to those of tissue. Earlier work characterized PVA gels in small test specimens where

Intracavity Laser Photoacoustic Spectrometer with High Sensitivity

International Nuclear Information System (INIS)

Mitrayana; Muslim; Wasono, M.A.J.

2002-01-01

A photo acoustic spectrometer set-up has been upgraded from an extra cavity into an intracavity configuration using a sealed-off CO 2 laser as the spectrometer's radiation source. The detection level of the upgrade Intracavity Photoacoustic Spectrometer (IPS) reached (200 ± 50) ppt for C 2 H 4 and (20 ± 5) ppt for SF 6 with response time (6.6 ± 0.2) s. (author)

Identification of Chinese medicinal fungus Cordyceps sinensis by depth-profiling mid-infrared photoacoustic spectroscopy

Science.gov (United States)

Du, Changwen; Zhou, Jianmin; Liu, Jianfeng

2017-02-01

With increased demand for Cordyceps sinensis it needs rapid methods to meet the challenge of identification raised in quality control. In this study Cordyceps sinensis from four typical natural habitats in China was characterized by depth-profiling Fourier transform infrared photoacoustic spectroscopy. Results demonstrated that Cordyceps sinensis samples resulted in typical photoacoustic spectral appearance, but heterogeneity was sensed in the whole sample; due to the heterogeneity Cordyceps sinensis was represented by spectra of four groups including head, body, tail and leaf under a moving mirror velocity of 0.30 cm s- 1. The spectra of the four groups were used as input of a probabilistic neural network (PNN) to identify the source of Cordyceps sinensis, and all the samples were correctly identified by the PNN model. Therefore, depth-profiling Fourier transform infrared photoacoustic spectroscopy provides novel and unique technique to identify Cordyceps sinensis, which shows great potential in quality control of Cordyceps sinensis.

Quantum Cascade Laser-Based Photoacoustic Sensor for Trace Detection of Formaldehyde Gas

Directory of Open Access Journals (Sweden)

Pietro Mario Lugarà

2009-04-01

Full Text Available We report on the development of a photoacoustic sensor for the detection of formaldehyde (CH2O using a thermoelectrically cooled distributed-feedback quantum cascade laser operating in pulsed mode at 5.6 mm. A resonant photoacoustic cell, equipped with four electret microphones, is excited in its first longitudinal mode at 1,380 Hz. The absorption line at 1,778.9 cm-1 is selected for CH2O detection. A detection limit of 150 parts per billion in volume in nitrogen is achieved using a 10 seconds time constant and 4 mW laser power. Measurements in ambient air will require water vapour filters.

Topotactic reduction yielding black titanium oxide nanostructures as metallic electronic conductors.

Science.gov (United States)

Tominaka, Satoshi

2012-10-01

Detailed analyses of reduced, single crystal, rutile-type TiO(2) via high-resolution transmission electron microscopy (TEM) are reported which reveal that the reduction proceeds topotactically via interstitial diffusion of Ti ions at low temperature, around 350 °C. This important finding encouraged the production of various nanostructured reduced titanium oxides from TiO(2) precursors with morphology retention, and in the process, the synthesis of black titanium oxide nanorods using TiO(2) nanorods was demonstrated. Interestingly, as opposed to the semiconductive behavior of Ti(2)O(3) synthesized at high temperature, topotactically synthesized Ti(2)O(3) exhibits metallic electrical resistance, and the value at room temperature is quite low (topotactically synthesized Ti(2)O(3). This work shows that topotactically reduced titanium oxides can have fascinating properties as well as nanostructures.

A Bayesian approach to spectral quantitative photoacoustic tomography

International Nuclear Information System (INIS)

Pulkkinen, A; Kaipio, J P; Tarvainen, T; Cox, B T; Arridge, S R

2014-01-01

A Bayesian approach to the optical reconstruction problem associated with spectral quantitative photoacoustic tomography is presented. The approach is derived for commonly used spectral tissue models of optical absorption and scattering: the absorption is described as a weighted sum of absorption spectra of known chromophores (spatially dependent chromophore concentrations), while the scattering is described using Mie scattering theory, with the proportionality constant and spectral power law parameter both spatially-dependent. It is validated using two-dimensional test problems composed of three biologically relevant chromophores: fat, oxygenated blood and deoxygenated blood. Using this approach it is possible to estimate the Grüneisen parameter, the absolute chromophore concentrations, and the Mie scattering parameters associated with spectral photoacoustic tomography problems. In addition, the direct estimation of the spectral parameters is compared to estimates obtained by fitting the spectral parameters to estimates of absorption, scattering and Grüneisen parameter at the investigated wavelengths. It is shown with numerical examples that the direct estimation results in better accuracy of the estimated parameters. (papers)

Sealing glasses for titanium and titanium alloys

Science.gov (United States)

Brow, Richard K.; McCollister, Howard L.; Phifer, Carol C.; Day, Delbert E.

1997-01-01

Barium lanthanoborate sealing-glass compositions are provided comprising various combinations (in terms of mole-%) of boron oxide (B.sub.2 O.sub.3), barium oxide (BaO), lanthanum oxide (La.sub.2 O.sub.3), and at least one other oxide selected from the group consisting of aluminum oxide (Al.sub.2 O.sub.3), calcium oxide (CaO), lithium oxide (Li.sub.2 O), sodium oxide (Na.sub.2 O), silicon dioxide (SiO.sub.2), or titanium dioxide (TiO.sub.2). These sealing-glass compositions are useful for forming hermetic glass-to-metal seals with titanium and titanium alloys having an improved aqueous durability and favorable sealing characteristics. Examples of the sealing-glass compositions are provided having coefficients of thermal expansion about that of titanium or titanium alloys, and with sealing temperatures less than about 900.degree. C., and generally about 700.degree.-800.degree. C. The barium lanthanoborate sealing-glass compositions are useful for components and devices requiring prolonged exposure to moisture or water, and for implanted biomedical devices (e.g. batteries, pacemakers, defibrillators, pumps).

Parallelised photoacoustic signal acquisition using a Fabry-Perot sensor and a camera-based interrogation scheme

Science.gov (United States)

Saeb Gilani, T.; Villringer, C.; Zhang, E.; Gundlach, H.; Buchmann, J.; Schrader, S.; Laufer, J.

2018-02-01

Tomographic photoacoustic (PA) images acquired using a Fabry-Perot (FP) based scanner offer high resolution and image fidelity but can result in long acquisition times due to the need for raster scanning. To reduce the acquisition times, a parallelised camera-based PA signal detection scheme is developed. The scheme is based on using a sCMOScamera and FPI sensors with high homogeneity of optical thickness. PA signals were acquired using the camera-based setup and the signal to noise ratio (SNR) was measured. A comparison of the SNR of PA signal detected using 1) a photodiode in a conventional raster scanning detection scheme and 2) a sCMOS camera in parallelised detection scheme is made. The results show that the parallelised interrogation scheme has the potential to provide high speed PA imaging.

Quantitative photoacoustic microscopy of optical absorption coefficients from acoustic spectra in the optical diffusive regime.

Science.gov (United States)

Guo, Zijian; Favazza, Christopher; Garcia-Uribe, Alejandro; Wang, Lihong V

2012-06-01

Photoacoustic (PA) microscopy (PAM) can image optical absorption contrast with ultrasonic spatial resolution in the optical diffusive regime. Conventionally, accurate quantification in PAM requires knowledge of the optical fluence attenuation, acoustic pressure attenuation, and detection bandwidth. We circumvent this requirement by quantifying the optical absorption coefficients from the acoustic spectra of PA signals acquired at multiple optical wavelengths. With the acoustic spectral method, the absorption coefficients of an oxygenated bovine blood phantom at 560, 565, 570, and 575 nm were quantified with errors of <3%. We also quantified the total hemoglobin concentration and hemoglobin oxygen saturation in a live mouse. Compared with the conventional amplitude method, the acoustic spectral method provides greater quantification accuracy in the optical diffusive regime. The limitations of the acoustic spectral method was also discussed.

Bone assessment via thermal photoacoustic measurements

Science.gov (United States)

Feng, Ting; Kozloff, Kenneth M.; Hsiao, Yi-Sing; Tian, Chao; Perosky, Joseph; Du, Sidan; Yuan, Jie; Deng, Cheri X.; Wang, Xueding

2015-03-01

The feasibility of an innovative biomedical diagnostic technique, thermal photoacoustic (TPA) measurement, for nonionizing and non-invasive assessment of bone health is investigated. Unlike conventional photoacoustic PA methods which are mostly focused on the measurement of absolute signal intensity, TPA targets the change in PA signal intensity as a function of the sample temperature, i.e. the temperature dependent Grueneisen parameter which is closely relevant to the chemical and molecular properties in the sample. Based on the differentiation measurement, the results from TPA technique is less susceptible to the variations associated with sample and system, and could be quantified with improved accurately. Due to the fact that the PA signal intensity from organic components such as blood changes faster than that from non-organic mineral under the same modulation of temperature, TPA measurement is able to objectively evaluate bone mineral density (BMD) and its loss as a result of osteoporosis. In an experiment on well established rat models of bone loss and preservation, PA measurements of rat tibia bones were conducted over a temperature range from 370 C to 440 C. The slope of PA signal intensity verses temperature was quantified for each specimen. The comparison among three groups of specimens with different BMD shows that bones with lower BMD have higher slopes, demonstrating the potential of the proposed TPA technique in future clinical management of osteoporosis.

Review of photoacoustic flow imaging: its current state and its promises.

Science.gov (United States)

van den Berg, P J; Daoudi, K; Steenbergen, W

2015-09-01

Flow imaging is an important method for quantification in many medical imaging modalities, with applications ranging from estimating wall shear rate to detecting angiogenesis. Modalities like ultrasound and optical coherence tomography both offer flow imaging capabilities, but suffer from low contrast to red blood cells and are sensitive to clutter artefacts. Photoacoustic imaging (PAI) is a relatively new field, with a recent interest in flow imaging. The recent enthusiasm for PA flow imaging is due to its intrinsic contrast to haemoglobin, which offers a new spin on existing methods of flow imaging, and some unique approaches in addition. This review article will delve into the research on photoacoustic flow imaging, explain the principles behind the many techniques and comment on their individual advantages and disadvantages.

In vivo rat deep brain imaging using photoacoustic computed tomography (Conference Presentation)

Science.gov (United States)

Lin, Li; Li, Lei; Zhu, Liren; Hu, Peng; Wang, Lihong V.

2017-03-01

The brain has been likened to a great stretch of unknown territory consisting of a number of unexplored continents. Small animal brain imaging plays an important role charting that territory. By using 1064 nm illumination from the side, we imaged the full coronal depth of rat brains in vivo. The experiment was performed using a real-time full-ring-array photoacoustic computed tomography (PACT) imaging system, which achieved an imaging depth of 11 mm and a 100 μm radial resolution. Because of the fast imaging speed of the full-ring-array PACT system, no animal motion artifact was induced. The frame rate of the system was limited by the laser repetition rate (50 Hz). In addition to anatomical imaging of the blood vessels in the brain, we continuously monitored correlations between the two brain hemispheres in one of the coronal planes. The resting states in the coronal plane were measured before and after stroke ligation surgery at a neck artery.

Real-time Near-infrared Virtual Intraoperative Surgical Photoacoustic Microscopy

Directory of Open Access Journals (Sweden)

Changho Lee

2015-09-01

Full Text Available We developed a near infrared (NIR virtual intraoperative surgical photoacoustic microscopy (NIR-VISPAM system that combines a conventional surgical microscope and an NIR light photoacoustic microscopy (PAM system. NIR-VISPAM can simultaneously visualize PA B-scan images at a maximum display rate of 45 Hz and display enlarged microscopic images on a surgeon's view plane through the ocular lenses of the surgical microscope as augmented reality. The use of the invisible NIR light eliminated the disturbance to the surgeon's vision caused by the visible PAM excitation laser in a previous report. Further, the maximum permissible laser pulse energy at this wavelength is approximately 5 times more than that at the visible spectral range. The use of a needle-type ultrasound transducer without any water bath for acoustic coupling can enhance convenience in an intraoperative environment. We successfully guided needle and injected carbon particles in biological tissues ex vivo and in melanoma-bearing mice in vivo.

Quantification of photoacoustic microscopy images for ovarian cancer detection

Science.gov (United States)

Wang, Tianheng; Yang, Yi; Alqasemi, Umar; Kumavor, Patrick D.; Wang, Xiaohong; Sanders, Melinda; Brewer, Molly; Zhu, Quing

2014-03-01

In this paper, human ovarian tissues with malignant and benign features were imaged ex vivo by using an opticalresolution photoacoustic microscopy (OR-PAM) system. Several features were quantitatively extracted from PAM images to describe photoacoustic signal distributions and fluctuations. 106 PAM images from 18 human ovaries were classified by applying those extracted features to a logistic prediction model. 57 images from 9 ovaries were used as a training set to train the logistic model, and 49 images from another 9 ovaries were used to test our prediction model. We assumed that if one image from one malignant ovary was classified as malignant, it is sufficient to classify this ovary as malignant. For the training set, we achieved 100% sensitivity and 83.3% specificity; for testing set, we achieved 100% sensitivity and 66.7% specificity. These preliminary results demonstrate that PAM could be extremely valuable in assisting and guiding surgeons for in vivo evaluation of ovarian tissue.

Iterative methods for photoacoustic tomography in attenuating acoustic media

Science.gov (United States)

Haltmeier, Markus; Kowar, Richard; Nguyen, Linh V.

2017-11-01

The development of efficient and accurate reconstruction methods is an important aspect of tomographic imaging. In this article, we address this issue for photoacoustic tomography. To this aim, we use models for acoustic wave propagation accounting for frequency dependent attenuation according to a wide class of attenuation laws that may include memory. We formulate the inverse problem of photoacoustic tomography in attenuating medium as an ill-posed operator equation in a Hilbert space framework that is tackled by iterative regularization methods. Our approach comes with a clear convergence analysis. For that purpose we derive explicit expressions for the adjoint problem that can efficiently be implemented. In contrast to time reversal, the employed adjoint wave equation is again damping and, thus has a stable solution. This stability property can be clearly seen in our numerical results. Moreover, the presented numerical results clearly demonstrate the efficiency and accuracy of the derived iterative reconstruction algorithms in various situations including the limited view case.

Surface modification of titanium and titanium alloys by ion implantation.

Science.gov (United States)

Rautray, Tapash R; Narayanan, R; Kwon, Tae-Yub; Kim, Kyo-Han

2010-05-01

Titanium and titanium alloys are widely used in biomedical devices and components, especially as hard tissue replacements as well as in cardiac and cardiovascular applications, because of their desirable properties, such as relatively low modulus, good fatigue strength, formability, machinability, corrosion resistance, and biocompatibility. However, titanium and its alloys cannot meet all of the clinical requirements. Therefore, to improve the biological, chemical, and mechanical properties, surface modification is often performed. In view of this, the current review casts new light on surface modification of titanium and titanium alloys by ion beam implantation. (c) 2010 Wiley Periodicals, Inc.

Gentamicin-Eluting Titanium Dioxide Nanotubes Grown on the Ultrafine-Grained Titanium.

Science.gov (United States)

Nemati, Sima Hashemi; Hadjizadeh, Afra

2017-08-01

Titanium (Ti)-based materials is the most appropriate choices for the applications as orthopedic and dental implants. In this regard, ultrafine-grained (UFG) titanium with an enhanced mechanical properties and surface energy has attracted more attention. Titanium dioxide (TiO 2 ) nanotubes grown on the titanium could enhance bone bonding, cellular response and are good reservoirs for loading drugs and antibacterial agents. This article investigates gentamicin loading into and release from the TiO 2 nanotubes, grown on the UFG compared to coarse-grained (CG) titanium substrate surfaces. Equal Channel Angular Pressing (ECAP) was employed to produce the UFG structure titanium. TiO 2 nanotubes were grown by the anodizing technique on both UFG and CG titanium substrate surfaces. Scanning electron microscopy (SEM) imaging confirmed TiO 2 nanotube growth on the surface. The UV-vis spectroscopy analysis results show that the amount of gentamicin load-release in the anodized UFG titanium sample is higher than that of CG one which can be explained in terms of thicker TiO 2 nanotube arrays layer formed on UFG sample. Moreover, the anodized UFG titanium samples released the drug in a longer time than CG (1 day for the UFG titanium vs. 3 h for the CG one). Regarding wettability analysis, anodized UFG titanium sample showed more enhanced hydrophilicity than CG counterpart. Therefore, the significantly smaller grain size of pure titanium provided by the ECAP technique coupled with appropriate subsequent anodization treatment not only offers a good combination of biocompatibility and adequate mechanical properties but also it provides a delayed release condition for gentamicin.

Functional photoacoustic microscopy of pH.

Science.gov (United States)

Chatni, Muhammad Rameez; Yao, Junjie; Danielli, Amos; Favazza, Christopher P; Maslov, Konstantin I; Wang, Lihong V

2011-10-01

pH is a tightly regulated indicator of metabolic activity. In mammalian systems, an imbalance of pH regulation may result from or result in serious illness. In this paper, we report photoacoustic microscopy (PAM) of a commercially available pH-sensitive fluorescent dye (SNARF-5F carboxylic acid) in tissue phantoms. We demonstrated that PAM is capable of pH imaging in absolute values at tissue depths of up to 2.0 mm, greater than possible with other forms of optical microscopy.

Photoacoustic determination of glucose concentration in whole blood by a near-infrared laser diode

Science.gov (United States)

Zhao, Zuomin; Myllylae, Risto A.

2001-06-01

The near-infrared photoacoustic technique is recognized as a potential method for the non-invasive determination of human glucose, because near-infrared light can incident a few millimeters into human tissue, where it produces an acoustic wave capable of carrying information about the composition of the tissue. This paper demonstrates a photoacoustic glucose measurement in a blood sample as a step toward a non-invasive measurement. The experimental apparatus consists of a near-infrared laser diode operating with 4 micro joules pulse energy at 905 nm, a roller pump connected to a silicon plastic tube and a cuvette for circulating the blood sample. In addition, the apparatus comprises a PZT piezoelectric transducer integrated with a battery-powered preamplifier to receive the photoacoustic signal. During the experiment, a glucose solution is mixed into a human blood sample to change its concentration. Although the absorption coefficient of glucose is much smaller than that of blood in the near-infrared region, the osmotic and hydrophilic properties of glucose decrease the reduced scattering coefficient of blood caused by the dissolved glucose surrounding the blood cells. This changes the distribution of the absorbed optical energy in blood, which, in turn, produces a change in the photoacoustic signal. Our experiment demonstrates that signal amplitudes in fresh and stored blood samples in crease about 7% and 10%, respectively, when the glucose concentration reaches the upper limit of the physiological region (500 mg/dl).

Quantitative imaging of bilirubin by photoacoustic microscopy

Science.gov (United States)

Zhou, Yong; Zhang, Chi; Yao, Da-Kang; Wang, Lihong V.

2013-03-01

Noninvasive detection of both bilirubin concentration and its distribution is important for disease diagnosis. Here we implemented photoacoustic microscopy (PAM) to detect bilirubin distribution. We first demonstrate that our PAM system can measure the absorption spectra of bilirubin and blood. We also image bilirubin distributions in tissuemimicking samples, both without and with blood mixed. Our results show that PAM has the potential to quantitatively image bilirubin in vivo for clinical applications.

Development of MEMS photoacoustic spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Robinson, Alex Lockwood; Eichenfield, Matthew S.; Griffin, Benjamin; Harvey, Heidi Alyssa; Nielson, Gregory N.; Okandan, Murat; Langlois, Eric; Resnick, Paul James; Shaw, Michael J.; Young, Ian; Givler, Richard C.; Reinke, Charles M.

2014-01-01

After years in the field, many materials suffer degradation, off-gassing, and chemical changes causing build-up of measurable chemical atmospheres. Stand-alone embedded chemical sensors are typically limited in specificity, require electrical lines, and/or calibration drift makes data reliability questionable. Along with size, these "Achilles' heels" have prevented incorporation of gas sensing into sealed, hazardous locations which would highly benefit from in-situ analysis. We report on development of an all-optical, mid-IR, fiber-optic based MEMS Photoacoustic Spectroscopy solution to address these limitations. Concurrent modeling and computational simulation are used to guide hardware design and implementation.

Functional photoacoustic imaging to observe regional brain activation induced by cocaine hydrochloride

Science.gov (United States)

Jo, Janggun; Yang, Xinmai

2011-09-01

Photoacoustic microscopy (PAM) was used to detect small animal brain activation in response to drug abuse. Cocaine hydrochloride in saline solution was injected into the blood stream of Sprague Dawley rats through tail veins. The rat brain functional change in response to the injection of drug was then monitored by the PAM technique. Images in the coronal view of the rat brain at the locations of 1.2 and 3.4 mm posterior to bregma were obtained. The resulted photoacoustic (PA) images showed the regional changes in the blood volume. Additionally, the regional changes in blood oxygenation were also presented. The results demonstrated that PA imaging is capable of monitoring regional hemodynamic changes induced by drug abuse.

A Feasibility Study of Photoacoustic Detection of Hidden Dental Caries Using a Fiber-Based Imaging System

Directory of Open Access Journals (Sweden)

Takuya Koyama

2018-04-01

Full Text Available In this paper, the feasibility of an optical fiber-based photoacoustic imaging system for detecting caries lesions inside a tooth is examined. Models of hidden caries were prepared using a pigment with an absorption spectrum similar to that of real caries lesions, and the occlusal surface of the model teeth containing the pigment was irradiated with laser pulses with a wavelength of 532 nm. An examination of the frequency spectra of the emitted photoacoustic waves revealed that the spectra from simulated caries lesions included frequency components in the range of 0.5–1.2 MHz that were not seen in the spectra from healthy parts of the teeth. This indicates that hidden caries can be detected via a photoacoustic imaging technique. Accordingly, an imaging system for clinical applications was fabricated. It consists of a bundle of hollow-optical fibers for laser radiation and an acoustic probe that is attached to the tooth surface. Results of ex vivo imaging experiments using model teeth and an extracted tooth with hidden caries lesions show that relatively large caries lesions inside teeth that are not seen in visual inspections can be detected by focusing on the above frequency components of the photoacoustic waves.

Nitrogen dioxide and kerosene-flame soot calibration of photoacoustic instruments for measurement of light absorption by aerosols

International Nuclear Information System (INIS)

Arnott, W. Patrick; Moosmu''ller, Hans; Walker, John W.

2000-01-01

A nitrogen dioxide calibration method is developed to evaluate the theoretical calibration for a photoacoustic instrument used to measure light absorption by atmospheric aerosols at a laser wavelength of 532.0 nm. This method uses high concentrations of nitrogen dioxide so that both a simple extinction and the photoacoustically obtained absorption measurement may be performed simultaneously. Since Rayleigh scattering is much less than absorption for the gas, the agreement between the extinction and absorption coefficients can be used to evaluate the theoretical calibration, so that the laser gas spectra are not needed. Photoacoustic theory is developed to account for strong absorption of the laser beam power in passage through the resonator. Findings are that the photoacoustic absorption based on heat-balance theory for the instrument compares well with absorption inferred from the extinction measurement, and that both are well within values represented by published spectra of nitrogen dioxide. Photodissociation of nitrogen dioxide limits the calibration method to wavelengths longer than 398 nm. Extinction and absorption at 532 and 1047 nm were measured for kerosene-flame soot to evaluate the calibration method, and the single scattering albedo was found to be 0.31 and 0.20 at these wavelengths, respectively

Pulsed near-infrared photoacoustic spectroscopy of blood

Science.gov (United States)

Laufer, Jan G.; Elwell, Clare E.; Delpy, Dave T.; Beard, Paul C.

2004-07-01

The aim of this study was to use pulsed near infrared photoacoustic spectroscopy to determine the oxygen saturation (SO2) of a saline suspension of red blood cells in vitro. The photoacoustic measurements were made in a cuvette which formed part of a larger circuit through which the red blood cell suspension was circulated. Oxygen saturation of the red blood cell suspension was altered between 2-3% to 100% in step increments using a membrane oxygenator and at each increment an independent measurement of oxygen saturation was made using a co-oximeter. An optical parametric oscillator laser system provided nanosecond excitation pulses at a number of wavelengths in the near-infrared spectrum (740-1040nm) which were incident on the cuvette. The resulting acoustic signals were detected using a broadband (15MHz) Fabry-Perot polymer film transducer. The optical transport coefficient and amplitude were determined from the acoustic signals as a function of wavelength. These data were then used to calculate the relative concentrations of oxy- and deoxyhaemoglobin, using their known specific absorption coefficients and an empirically determined wavelength dependence of optical scattering over the wavelength range investigated. From this, the oxygen saturation of the suspension was derived with an accuracy of +/-5% compared to the co-oximeter SO2 measurements.

Isolation of circulating tumor cells using photoacoustic flowmetry and two phase flow

Science.gov (United States)

O'Brien, Christine M.; Rood, Kyle D.; Gupta, Sagar K.; Mosley, Jeffrey D.; Goldschmidt, Benjamin S.; Sharma, Nikhilesh; Sengupta, Shramik; Viator, John A.

2011-03-01

Melanoma is the deadliest form of skin cancer, yet current diagnostic methods are inadequately sensitive. Patients must wait until secondary tumors form before malignancy can be diagnosed and treatment prescribed. Detection of cells that have broken off the original tumor and flow through the blood or lymph system can provide data for diagnosing and monitoring cancer. Our group utilizes the photoacoustic effect to detect metastatic melanoma cells, which contain the pigmented granule melanin. As a rapid laser pulse irradiates melanoma, the melanin undergoes thermo-elastic expansion and ultimately creates a photoacoustic wave. Thus, melanoma patient's blood samples can be enriched, leaving the melanoma in a white blood cell (WBC) suspension. Irradiated melanoma cells produce photoacoustic waves, which are detected with a piezoelectric transducer, while the optically transparent WBCs create no signals. Here we report an isolation scheme utilizing two-phase flow to separate detected melanoma from the suspension. By introducing two immiscible fluids through a t-junction into one flow path, the analytes are compartmentalized. Therefore, the slug in which the melanoma cell is located can be identified and extracted from the system. Two-phase immiscible flow is a label free technique, and could be used for other types of pathological analytes.

Applications of infrared photo-acoustic spectroscopy for wood samples

Science.gov (United States)

Mon-Lin Kuo; John F. McClelland; Siquan Luo; Po-Liang Chien; R.D. Walker; Chung-Yun Hse

1988-01-01

Various infrared (IR) spectroscopic techniques for the analysis of wood samples are briefly discussed. Theories and instrumentation of the newly developed photoacoustic spectroscopic (PAS) technique for measuring absorbance spectra of solids are presented. Some important applications of the PAS technique in wood science research are discussed. The application of the...

Spectroscopic photoacoustic imaging of radiofrequency ablation in the left atrium

NARCIS (Netherlands)

S. Iskander-Rizk (Sophinese); P. Kruizinga (Pieter); A.F.W. van der Steen (Ton); G. van Soest (Gijs)

2018-01-01

textabstractCatheter-based radiofrequency ablation for atrial fibrillation has long-term success in 60-70% of cases. A better assessment of lesion quality, depth, and continuity could improve the procedure’s outcome. We investigate here photoacoustic contrast between ablated and healthy atrial-wall

FT-IR-cPAS—New Photoacoustic Measurement Technique for Analysis of Hot Gases: A Case Study on VOCs

Science.gov (United States)

Hirschmann, Christian Bernd; Koivikko, Niina Susanna; Raittila, Jussi; Tenhunen, Jussi; Ojala, Satu; Rahkamaa-Tolonen, Katariina; Marbach, Ralf; Hirschmann, Sarah; Keiski, Riitta Liisa

2011-01-01

This article describes a new photoacoustic FT-IR system capable of operating at elevated temperatures. The key hardware component is an optical-readout cantilever microphone that can work up to 200 °C. All parts in contact with the sample gas were put into a heated oven, incl. the photoacoustic cell. The sensitivity of the built photoacoustic system was tested by measuring 18 different VOCs. At 100 ppm gas concentration, the univariate signal to noise ratios (1σ, measurement time 25.5 min, at highest peak, optical resolution 8 cm−1) of the spectra varied from minimally 19 for o-xylene up to 329 for butyl acetate. The sensitivity can be improved by multivariate analyses over broad wavelength ranges, which effectively co-adds the univariate sensitivities achievable at individual wavelengths. The multivariate limit of detection (3σ, 8.5 min, full useful wavelength range), i.e., the best possible inverse analytical sensitivity achievable at optimum calibration, was calculated using the SBC method and varied from 2.60 ppm for dichloromethane to 0.33 ppm for butyl acetate. Depending on the shape of the spectra, which often only contain a few sharp peaks, the multivariate analysis improved the analytical sensitivity by 2.2 to 9.2 times compared to the univariate case. Selectivity and multi component ability were tested by a SBC calibration including 5 VOCs and water. The average cross selectivities turned out to be less than 2% and the resulting inverse analytical sensitivities of the 5 interfering VOCs was increased by maximum factor of 2.2 compared to the single component sensitivities. Water subtraction using SBC gave the true analyte concentration with a variation coefficient of 3%, although the sample spectra (methyl ethyl ketone, 200 ppm) contained water from 1,400 to 100k ppm and for subtraction only one water spectra (10k ppm) was used. The developed device shows significant improvement to the current state-of-the-art measurement methods used in industrial

Converting sunlight into audible sound by means of the photoacoustic effect: The Heliophone.

Science.gov (United States)

Roozen, N B; Glorieux, C; Liu, L; Rychtáriková, M; Van der Donck, T; Jacobs, A

2016-09-01

One hundred and thirty-five years after Alexander Graham Bell and his assistant Charles Sumner Tainter explored the photoacoustic effect, and about 40 years after Rosencwaig and Gersho modeled the effect in a photoacoustic cell configuration, the phenomenon is revisited in a "Heliophone" device that converts sunlight into sound. The light is focused on a carbon blackened copper coated Kapton foil in an acoustic cell by means of a compound parabolic collimator, and its intensity is modulated by a mechanical chopper. A horn is employed to make the sound audible without electronic amplification. The description of the photoacoustic effect that was introduced by Rosencwaig and Gersho is extended to a cell-horn configuration, in which the periodically heated air above the foil acts as an oscillating piston, driving acoustic waves in the horn. The pressure in the cavity-horn assembly is calculated by considering the air layer piston as an equivalent volume velocity source. The importance of the carbon black (soot) layer to enhance light absorption, but above all to enhance the photothermal excitation efficiency, is elucidated by means of an experimentally supported physical model.

Time Reversal Reconstruction Algorithm Based on PSO Optimized SVM Interpolation for Photoacoustic Imaging

Directory of Open Access Journals (Sweden)

Mingjian Sun

2015-01-01

Full Text Available Photoacoustic imaging is an innovative imaging technique to image biomedical tissues. The time reversal reconstruction algorithm in which a numerical model of the acoustic forward problem is run backwards in time is widely used. In the paper, a time reversal reconstruction algorithm based on particle swarm optimization (PSO optimized support vector machine (SVM interpolation method is proposed for photoacoustics imaging. Numerical results show that the reconstructed images of the proposed algorithm are more accurate than those of the nearest neighbor interpolation, linear interpolation, and cubic convolution interpolation based time reversal algorithm, which can provide higher imaging quality by using significantly fewer measurement positions or scanning times.

Measurement of the Auger lifetime in GaInAsSb/GaSb heterostructures using the photoacoustic technique

International Nuclear Information System (INIS)

Riech, I.; Gomez-Herrera, M. L.; Diaz, P.; Mendoza-Alvarez, J. G.; Herrera-Perez, J. L.; Marin, E.

2001-01-01

We have studied Ga x In 1-x As y Sb 1-y /GaSb heterostructures for x=0.84 and y=0.14 using the photoacoustic technique with the heat transmission configuration. A theoretical model, which includes all the possible nonradiative recombination mechanisms that contribute to heat generation, was developed to calculate the photoacoustic signal for this type of heterostructure. The Auger recombination lifetime τ Auger was determined by fitting our experimental results to the calculated frequency dependence of the theoretical photoacoustic signal. The obtained value for τ Auger is compatible with those reported in the literature for semiconductors with band-gap energies below and above 0.5 eV, the energy region where there is a lack of experimental τ Auger values. Copyright 2001 American Institute of Physics

Photoacoustic Soot Spectrometer (PASS) Instrument Handbook

Energy Technology Data Exchange (ETDEWEB)

Dubey, M [Los Alamos National Laboratory; Springston, S [Brookhaven National Laboratory; Koontz, A [Pacific Northwest National Laboratory; Aiken, A [Los Alamos National Laboratory

2013-01-17

The photoacoustic soot spectrometer (PASS) measures light absorption by aerosol particles. As the particles pass through a laser beam, the absorbed energy heats the particles and in turn the surrounding air, which sets off a pressure wave that can be detected by a microphone. The PASS instruments deployed by ARM can also simultaneously measure the scattered laser light at three wavelengths and therefore provide a direct measure of the single-scattering albedo. The Operator Manual for the PASS-3100 is included here with the permission of Droplet Measurement Technologies, the instrument’s manufacturer.

Photoacoustic imaging for assessing ischemic kidney damage in vivo

Science.gov (United States)

Berndl, Elizabeth S. L.; He, Xiaolin; Yuen, Darren A.; Kolios, Michael C.

2018-02-01

Ischemic reperfusion injuries (IRIs) occur after blood returns to a tissue or organ after a period without oxygen or nutrients, which causes an inflammatory response leading to heterogeneous scarring of the nearby tissue and vasculature. This is associated with long-term decreases blood flow, and necrosis. Although most commonly associated with heart attacks and strokes, IRIs are also a side effect of organ transplants, when the organ is reperfused in the recipient's body after being transported from the donor to the transplant hospital. Currently, the optimal method of monitoring for IRI is limited to biopsies, which are invasive and poorly monitor the spatial heterogeneity of the damage. To non-invasively identify changes in kidneys, the left renal artery in mice (n=3) was clamped for 45 minutes to create an IRI event. Both kidneys of each animal were monitored using photoacoustics (PA) with the VevoLAZR system (Fujifilm-VisualSonics, Toronto) three, four and eight weeks after surgery. IRI-treated kidneys show increased picosirius red staining, indicative of collagen (0.601 vs 0.042, p < 0.0001), decreased size as assessed by cross-sectional area (7.8 mm2 vs 35.9 mm2 , p < 0.0001), and decreased oxygen saturation (sO2; 62% vs 77%, p = 0.02). Analysis of the photoacoustic data shows that a two-point metric, the 715:930 nm ratio of the whole kidney (1.05 vs 0.57, p = 0.049) and the optical spectral slope (OSS) (0.8 * 10-3 vs 3.0 * 10-3, p = 0.013) are both able to differentiate between IRI-treated and healthy kidneys. These data suggest that photoacoustics can be used as a non-invasive method to observe in vivo changes in the kidney due to IRI.

Photoacoustic trace gas sensing : application to fruit and insects

NARCIS (Netherlands)

Persijn, Stefan Timotheüs

2001-01-01

A novel photoacoustic spectrometer has been applied to study trace gas emissions by fruit and insects. The spectrometer is based on a newly designed CO laser that can operate on 400 laser lines between 5.1-8.0 and 2.8-4.1 micrometer (delta v=1 and 2 mode, respectively). The spectrometer is equipped

Picosecond absorption relaxation measured with nanosecond laser photoacoustics

OpenAIRE

Danielli, Amos; Favazza, Christopher P.; Maslov, Konstantin; Wang, Lihong V.

2010-01-01

Picosecond absorption relaxation—central to many disciplines—is typically measured by ultrafast (femtosecond or picosecond) pump-probe techniques, which however are restricted to optically thin and weakly scattering materials or require artificial sample preparation. Here, we developed a reflection-mode relaxation photoacoustic microscope based on a nanosecond laser and measured picosecond absorption relaxation times. The relaxation times of oxygenated and deoxygenated hemoglobin molecules, b...

Using FTIR-photoacoustic spectroscopy for phosphorus speciation analysis of biochars

DEFF Research Database (Denmark)

Bekiaris, Georgios; Peltre, Clément; Jensen, Lars Stoumann

2016-01-01

In the last decade, numerous studies have evaluated the benefits of biochar for improving soil quality. The purposes of the current study were to use Fourier transform infrared-photoacoustic spectroscopy (FTIR-PAS) to analyse P species in biochar and to determine the effect of pyrolysis temperatu...

Titanium metal: extraction to application

Energy Technology Data Exchange (ETDEWEB)

Gambogi, Joseph (USGS, Reston, VA); Gerdemann, Stephen J.

2002-09-01

In 1998, approximately 57,000 tons of titanium metal was consumed in the form of mill products (1). Only about 5% of the 4 million tons of titanium minerals consumed each year is used to produce titanium metal, with the remainder primarily used to produce titanium dioxide pigment. Titanium metal production is primarily based on the direct chlorination of rutile to produce titanium tetrachloride, which is then reduced to metal using the Kroll magnesium reduction process. The use of titanium is tied to its high strength-to-weight ratio and corrosion resistance. Aerospace is the largest application for titanium. In this paper, we discuss all aspects of the titanium industry from ore deposits through extraction to present and future applications. The methods of both primary (mining of ore, extraction, and purification) and secondary (forming and machining) operations will be analyzed. The chemical and physical properties of titanium metal will be briefly examined. Present and future applications for titanium will be discussed. Finally, the economics of titanium metal production also are analyzed as well as the advantages and disadvantages of various alternative extraction methods.

Using high-power light emitting diodes for photoacoustic imaging

DEFF Research Database (Denmark)

Hansen, R. S.

2011-01-01

for the experiment consists of a 3mm high x 5mm wide slice of green colored gelatine overlaid by a 3cm layer of colorless gelatine. The light pulses from the LED is focused on the green gelatine. The photoacoustic response from the green gelatine is detected by a single transducer on the opposite (top) surface...

Titanium disilicide formation by sputtering of titanium on heated silicon substrate

Science.gov (United States)

Tanielian, M.; Blackstone, S.

1984-09-01

We have sputter deposited titanium on bare silicon substrates at elevated temperatures. We find that at a substrate temperature of about 515 °C titanium silicide is formed due to the reaction of the titanium with the Si. The resistivity of the silicide is about 15 μΩ cm and it is not etchable in a selective titanium etch. This process can have applications in low-temperature, metal-oxide-semiconductor self-aligned silicide formation for very large scale integrated

Photoacoustic and ultrasound dual-modality imaging for inflammatory arthritis

Science.gov (United States)

Xu, Guan; Chamberland, David; Girish, Gandikota; Wang, Xueding

2014-03-01

Arthritis is a leading cause of disability, affecting 46 million of the population in the U.S. Rendering new optical contrast in articular tissues at high spatial and temporal resolution, emerging photoacoustic imaging (PAI) combined with more established ultrasound (US) imaging technologies provides unique opportunities for diagnosis and treatment monitoring of inflammatory arthritis. In addition to capturing peripheral bone and soft tissue images, PAI has the capability to quantify hemodynamic properties including regional blood oxygenation and blood volume, both abnormal in synovial tissues affected by arthritis. Therefore, PAI, especially when performed together with US, should be of considerable help for further understanding the pathophysiology of arthritis as well as assisting in therapeutic decisions, including assessing the efficacy of new pharmacological therapies. In this paper, we will review our recent work on the development of PAI for application to the diagnostic imaging and therapeutic monitoring of inflammatory arthritis. We will present the imaging results from a home-built imaging system and another one based on a commercial US. The performance of PAI in evaluating pharmacological therapy on animal model of arthritis will be shown. Moreover, our resent work on PAI and US dual-modality imaging of human peripheral joints in vivo will also be presented.

Evaluation of an optical fiber probe for in vivo measurement of the photoacoustic response of tissues

Science.gov (United States)

Beard, Paul C.; Mills, Timothy N.

1995-05-01

A miniature (1 mm diameter) all-optical photoacoustic probe for generating and detecting ultrasonic thermoelastic waves in biological media at the tip of an optical fiber has been developed. The probe provides a compact and convenient means of performing pulsed photoacoustic spectroscopy for the characterization of biological tissue. The device is based upon a transparent Fabry Perot polymer film ultrasound sensor mounted directly over the end of a multimode optical fiber. The optical fiber is used to deliver nanosecond laser pulses to the tissue producing thermoelastic waves which are then detected by the sensor. Detection sensitivities of 53 mv/MPa and a 10 kPa acoustic noise floor have been demonstrated giving excellent signal to noise ratios in a strong liquid absorber. Lower, but clearly detectable, signals in post mortem human aorta have also been observed. The performance and small physical size of the device suggest that it has the potential to perform remote in situ photoacoustic measurements in tissue.

Antibiofouling polymer coated gold nanoparticles as a dual modal contrast agent for X-ray and photoacoustic imaging

International Nuclear Information System (INIS)

Guojia Huang; Yi Yuan; Xing Da

2011-01-01

X-ray is one of the most useful diagnostic tools in hospitals in terms of frequency of use and cost, while photoacoustic (PA) imaging is a rapidly emerging non-invasive imaging technology that integrates the merits of high optical contrast with high ultrasound resolution. In this study, for the first time, we used gold nanoparticles (GNPs) as a dual modal contrast agent for X-ray and PA imaging. Soft gelatin phantoms with embedded tumor simulators of GNPs in various concentrations are clearly shown in both X-ray and PA imaging. With GNPs as a dual modal contrast agent, X-ray can fast detect the position of tumor and provide morphological information, whereas PA imaging has important potential applications in the image guided therapy of superficial tumors such as breast cancer, melanoma and Merkel cell carcinoma.

Reverse photoacoustic standoff spectroscopy

Science.gov (United States)

Van Neste, Charles W [Kingston, TN; Senesac, Lawrence R [Knoxville, TN; Thundat, Thomas G [Knoxville, TN

2011-04-12

A system and method are disclosed for generating a reversed photoacoustic spectrum at a greater distance. A source may emit a beam to a target and a detector measures signals generated as a result of the beam being emitted on the target. By emitting a chopped/pulsed light beam to the target, it may be possible to determine the target's optical absorbance by monitoring the intensity of light collected at the detector at different wavelengths. As the wavelength of light is changed, the target may absorb or reject each optical frequency. Rejection may increase the intensity at the sensing element and absorption may decrease the intensity. Accordingly, an identifying spectrum of the target may be made with the intensity variation of the detector as a function of illuminating wavelength.

In vivo ultrasound and photoacoustic monitoring of mesenchymal stem cells labeled with gold nanotracers.

Directory of Open Access Journals (Sweden)

Seung Yun Nam

Full Text Available Longitudinal monitoring of cells is required in order to understand the role of delivered stem cells in therapeutic neovascularization. However, there is not an imaging technique that is capable of quantitative, longitudinal assessment of stem cell behaviors with high spatial resolution and sufficient penetration depth. In this study, in vivo and in vitro experiments were performed to demonstrate the efficacy of ultrasound-guided photoacoustic (US/PA imaging to monitor mesenchymal stem cells (MSCs labeled with gold nanotracers (Au NTs. The Au NT labeled MSCs, injected intramuscularly in the lower limb of the Lewis rat, were detected and spatially resolved. Furthermore, our quantitative in vitro cell studies indicate that US/PA imaging is capable of high detection sensitivity (1×10⁴ cells/mL of the Au NT labeled MSCs. Finally, Au NT labeled MSCs captured in the PEGylated fibrin gel system were imaged in vivo, as well as in vitro, over a one week time period, suggesting that longitudinal cell tracking using US/PA imaging is possible. Overall, Au NT labeling of MSCs and US/PA imaging can be an alternative approach in stem cell imaging capable of noninvasive, sensitive, quantitative, longitudinal assessment of stem cell behaviors with high spatial and temporal resolutions at sufficient depths.

Leaching of Titanium and Silicon from Low-Grade Titanium Slag Using Hydrochloric Acid Leaching

Science.gov (United States)

Zhao, Longsheng; Wang, Lina; Qi, Tao; Chen, Desheng; Zhao, Hongxin; Liu, Yahui; Wang, Weijing

2018-05-01

Acid-leaching behaviors of the titanium slag obtained by selective reduction of vanadium-bearing titanomagnetite concentrates were investigated. It was found that the optimal leaching of titanium and silicon were 0.7% and 1.5%, respectively. The titanium and silicon in the titanium slag were firstly dissolved in the acidic solution to form TiO2+ and silica sol, and then rapidly reprecipitated, forming hydrochloric acid (HCl) leach residue. Most of the silicon presented in the HCl leach residue as floccules-like silica gel, while most of the titanium was distributed in the nano-sized rod-like clusters with crystallite refinement and intracrystalline defects, and, as such, 94.3% of the silicon was leached from the HCl leach residue by alkaline desilication, and 96.5% of the titanium in the titanium-rich material with some rutile structure was then digested by the concentrated sulfuric acid. This provides an alternative route for the comprehensive utilization of titanium and silicon in titanium slag.

Photoacoustic investigation of doped InP using open cell configuration

NARCIS (Netherlands)

George, S.D.; Vallabhan, C.P.G.; Heck, M.J.R.; Radhakrishnan, P.; Nampoori, V.P.N.

2002-01-01

An open cell photoacoustic (PA) configuration was employed to evaluate the thermal diffusivity of intrinsic InP as well as InP doped with tin and iron. Thermal diffusivity data were evaluated from variation of phase of PA signal as a function of modulation frequency. In doped samples, we observe a

Titanium and titanium alloys: fundamentals and applications

National Research Council Canada - National Science Library

Leyens, C; Peters, M

2003-01-01

... number of titanium alloys have paved the way for light metals to vastly expand into many industrial applications. Titanium and its alloys stand out primarily due to their high specific strength and excellent corrosion resistance, at just half the weight of steels and Ni-based superalloys. This explains their early success in the aerospace and the...

X-ray diffraction, Raman and photoacoustic studies of InSb nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Ersching, K., E-mail: kleb85@hotmail.com [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, 88040-900 Florianopolis, Santa Catarina (Brazil); Campos, C.E.M.; Lima, J.C. de; Grandi, T.A. [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, 88040-900 Florianopolis, Santa Catarina (Brazil); Souza, S.M. [Departamento de Engenharia Mecanica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, 88040-900 Florianopolis, Santa Catarina (Brazil); Pizani, P.S. [Departamento de Fisica, Universidade Federal de Sao Carlos, 13 565-905 Sao Carlos, SP (Brazil)

2010-08-01

Zinc blend InSb nanocrystals were generated by mechanical alloying and X-ray diffraction, Raman spectroscopy and photoacoustic absorption spectroscopy techniques were used to study its structural, optical and thermal properties. Annealed nanocrystals were also studied. Residual amorphous and minority crystalline (Sb and In{sub 2}O{sub 3}) phases were also observed for mechanical alloyed and thermal annealed samples, respectively. The structural parameters, phase fractions, average crystallite sizes and microstrains of all crystalline phases found in the samples were obtained from Rietveld analyses of their X-ray diffraction patterns. Raman results for both as-milled and annealed samples show the Raman active LO and TO modes of the zinc blend InSb phase and Sb-rich regions. The photoacoustic results of both samples were satisfactorily explained by thermal bending heat transfer mechanism and an increase on effective thermal diffusivity coefficient was observed after annealing.

Fluorine-free preparation of titanium carbide MXene quantum dots with high near-infrared photothermal performances for cancer therapy.

Science.gov (United States)

Yu, Xinghua; Cai, Xingke; Cui, Haodong; Lee, Seung-Wuk; Yu, Xue-Feng; Liu, Bilu

2017-11-23

Titanium carbide MXene quantum dots (QDs) were synthesized using an effective fluorine-free method as a biocompatible and highly efficient nanoagent for photothermal therapy (PTT) applications. In contrast to the traditional, hazardous and time-consuming process of HF pretreatment, our fluorine-free method is safe and simple. More importantly, abundant Al oxoanions were found to be modified on the MXene QD surface by the fluorine-free method, which endowed the QDs with strong and broad absorption in the NIR region. As a result, the as-prepared MXene QDs exhibited an extinction coefficient as large as 52.8 Lg -1 cm -1 at 808 nm and a photothermal conversion efficiency as high as 52.2%. Both the values are among the best reported so far. The as-prepared MXene QDs achieved simultaneous photoacoustic (PA) imaging and the remarkable PTT effect of tumors. Moreover, MXene QDs showed great biocompatibility without causing noticeable toxicity in vitro and in vivo, indicating their high potential for clinical applications.

Photoacoustic study of nanocrystalline silicon produced by mechanical grinding

Energy Technology Data Exchange (ETDEWEB)

Poffo, C.M. [Departamento de Engenharia Mecanica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Lima, J.C. de, E-mail: fsc1jcd@fisica.ufsc.b [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Trindade, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Souza, S.M.; Triches, D.M. [Departamento de Engenharia Mecanica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Grandi, T.A. [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Trindade, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Biasi, R.S. de [Secao de Engenharia Mecanica e de Materiais, Instituto Militar de Engenharia, 22290-270 Rio de Janeiro, RJ (Brazil)

2011-04-01

Mechanical grinding (MG) was used to produce nanocrystalline silicon and its thermal and transport properties were investigated by photoacoustic absorption spectroscopy (PAS). The experimental results suggest that in as-milled nanocrystalline silicon for 10 h the heat transfer through the crystalline and interfacial components is similar, and after annealed at 470 {sup o}C the heat transfer is controlled by crystalline component.

Photoacoustic study of nanocrystalline silicon produced by mechanical grinding

International Nuclear Information System (INIS)

Poffo, C.M.; Lima, J.C. de; Souza, S.M.; Triches, D.M.; Grandi, T.A.; Biasi, R.S. de

2011-01-01

Mechanical grinding (MG) was used to produce nanocrystalline silicon and its thermal and transport properties were investigated by photoacoustic absorption spectroscopy (PAS). The experimental results suggest that in as-milled nanocrystalline silicon for 10 h the heat transfer through the crystalline and interfacial components is similar, and after annealed at 470 o C the heat transfer is controlled by crystalline component.

Chirped or time modulated excitation compared to short pulses for photoacoustic imaging in acoustic attenuating media

Science.gov (United States)

Burgholzer, P.; Motz, C.; Lang, O.; Berer, T.; Huemer, M.

2018-02-01

In photoacoustic imaging, optically generated acoustic waves transport the information about embedded structures to the sample surface. Usually, short laser pulses are used for the acoustic excitation. Acoustic attenuation increases for higher frequencies, which reduces the bandwidth and limits the spatial resolution. One could think of more efficient waveforms than single short pulses, such as pseudo noise codes, chirped, or harmonic excitation, which could enable a higher information-transfer from the samples interior to its surface by acoustic waves. We used a linear state space model to discretize the wave equation, such as the Stoke's equation, but this method could be used for any other linear wave equation. Linear estimators and a non-linear function inversion were applied to the measured surface data, for onedimensional image reconstruction. The proposed estimation method allows optimizing the temporal modulation of the excitation laser such that the accuracy and spatial resolution of the reconstructed image is maximized. We have restricted ourselves to one-dimensional models, as for higher dimensions the one-dimensional reconstruction, which corresponds to the acoustic wave without attenuation, can be used as input for any ultrasound imaging method, such as back-projection or time-reversal method.

Synthesis of Titanium Oxycarbide from Titanium Slag by Methane-Containing Gas

Science.gov (United States)

Dang, Jie; Fatollahi-Fard, Farzin; Pistorius, Petrus Christiaan; Chou, Kuo-Chih

2018-02-01

In this study, reaction steps of a process for synthesis of titanium oxycarbide from titanium slag were demonstrated. This process involves the reduction of titanium slag by a methane-hydrogen-argon mixture at 1473 K (1200 °C) and the leaching of the reduced products by hydrofluoric acid near room temperature to remove the main impurity (Fe3Si). Some iron was formed by disproportionation of the main M3O5 phase before gaseous reduction started. Upon reduction, more iron formed first, followed by reduction of titanium dioxide to suboxides and eventually oxycarbide.

FPGA-based reconfigurable processor for ultrafast interlaced ultrasound and photoacoustic imaging.

Science.gov (United States)

Alqasemi, Umar; Li, Hai; Aguirre, Andrés; Zhu, Quing

2012-07-01

In this paper, we report, to the best of our knowledge, a unique field-programmable gate array (FPGA)-based reconfigurable processor for real-time interlaced co-registered ultrasound and photoacoustic imaging and its application in imaging tumor dynamic response. The FPGA is used to control, acquire, store, delay-and-sum, and transfer the data for real-time co-registered imaging. The FPGA controls the ultrasound transmission and ultrasound and photoacoustic data acquisition process of a customized 16-channel module that contains all of the necessary analog and digital circuits. The 16-channel module is one of multiple modules plugged into a motherboard; their beamformed outputs are made available for a digital signal processor (DSP) to access using an external memory interface (EMIF). The FPGA performs a key role through ultrafast reconfiguration and adaptation of its structure to allow real-time switching between the two imaging modes, including transmission control, laser synchronization, internal memory structure, beamforming, and EMIF structure and memory size. It performs another role by parallel accessing of internal memories and multi-thread processing to reduce the transfer of data and the processing load on the DSP. Furthermore, because the laser will be pulsing even during ultrasound pulse-echo acquisition, the FPGA ensures that the laser pulses are far enough from the pulse-echo acquisitions by appropriate time-division multiplexing (TDM). A co-registered ultrasound and photoacoustic imaging system consisting of four FPGA modules (64-channels) is constructed, and its performance is demonstrated using phantom targets and in vivo mouse tumor models.

Elastography as a hybrid imaging technique : coupling with photoacoustics and quantitative imaging

International Nuclear Information System (INIS)

Widlak, T.G.

2015-01-01

While classical imaging methods, such as ultrasound, computed tomography or magnetic resonance imaging, are well-known and mathematically understood, a host of physiological parameters relevant for diagnostic purposes cannot be obtained by them. This gap is recently being closed by the introduction of hybrid, or coupled-physics imaging methods. They connect more then one physical modality, and aim to provide quantitative information on optical, electrical or mechanical parameters with high resolution. Central to this thesis is the mechanical contrast of elastic tissue, especially Young’s modulus or the shear modulus. Different methods of qualitative elastography provide interior information of the mechanical displacement field. From this interior data the nonlinear inverse problem of quantitative elastography aims to reconstruct the shear modulus. In this thesis, the elastography problem is seen from a hybrid imaging perspective; methods from coupled-physics inspired literature and regularization theory have been employed to recover displacement and shear modulus information. The overdetermined systems approach by G. Bal is applied to the quantitative problem, and ellipticity criteria are deduced, for one and several measurements, as well as injectivity results. Together with the geometric theory of G. Chavent, the results are used for analyzing convergence of Tikhonov regularization. Also, a convergence analysis for the Levenberg Marquardt method is provided. As a second mainstream project in this thesis, elastography imaging is developed for extracting displacements from photoacoustic images. A novel method is provided for texturizing the images, and the optical flow problem for motion estimation is shown to be regularized with this texture generation. The results are tested in cooperation with the Medical University Vienna, and the methods for quantitative determination of the shear modulus evaluated in first experiments. In summary, the overdetermined systems

Photoacoustic cystography using handheld dual modal clinical ultrasound photoacoustic imaging system

Science.gov (United States)

Sivasubramanian, Kathyayini; Periyasamy, Vijitha; Austria, Dienzo Rhonnie; Pramanik, Manojit

2018-02-01

Vesicoureteral reflux is the abnormal flow of urine from your bladder back up the tubes (ureters) that connect your kidneys to your bladder. Normally, urine flows only down from your kidneys to your bladder. Vesicoureteral reflux is usually diagnosed in infants and children. The disorder increases the risk of urinary tract infections, which, if left untreated, can lead to kidney damage. X-Ray cystography is used currently to diagnose this condition which uses ionising radiation, making it harmful for patients. In this work we demonstrate the feasibility of imaging the urinary bladder using a handheld clinical ultrasound and photoacoustic dual modal imaging system in small animals (rats). Additionally, we demonstrate imaging vesicoureteral reflux using bladder mimicking phantoms. Urinary bladder imaging is done with the help of contrast agents like black ink and gold nanoparticles which have high optical absorption at 1064 nm. Imaging up to 2 cm was demonstrated with this system. Imaging was done at a framerate of 5 frames per second.

Clinical experiences with photoacoustic breast imaging: the appearance of suspicious lesions

NARCIS (Netherlands)

Heijblom, M.

2014-01-01

This thesis describes photoacoustic (PA) imaging of suspicious breast lesions. In PA imaging, the tissue of interest is illuminated by short pulses of laser light, usually in the near infrared (NIR) regime. Upon absorption by primarily the tumor vasculature, the light causes a small temperature

Photoacoustic Determination of Non-radiative Relaxation Time of Absorbing Centers in Maize Seeds

Science.gov (United States)

Domínguez-Pacheco, A.; Hernández-Aguilar, C.; Cruz-Orea, A.

2017-07-01

Using non-destructive photothermal techniques, it is possible to characterize non-homogenous materials to obtain its optical and thermal properties through photoacoustic spectroscopy (PAS). In photoacoustic (PA) phenomena, there are transient states of thermal excitation, when samples absorb the incident light; these states manifest an excitation process that generates the PA signal, being in direct relation with the non-radiative relaxation times with the sample absorbent centers. The objective of this study was to determine the non-radiative relaxation times associated with different absorbent centers of corn seeds ( Zea mays L.), by using PAS. A frequency scan was done at different wavelengths (350 nm, 470 nm and 650 nm) in order to obtain the non-radiative relaxation times with different types of maize seeds.

Titanium by design: TRIP titanium alloy

Science.gov (United States)

Tran, Jamie

Motivated by the prospect of lower cost Ti production processes, new directions in Ti alloy design were explored for naval and automotive applications. Building on the experience of the Steel Research Group at Northwestern University, an analogous design process was taken with titanium. As a new project, essential kinetic databases and models were developed for the design process and used to create a prototype design. Diffusion kinetic models were developed to predict the change in phase compositions and microstructure during heat treatment. Combining a mobility database created in this research with a licensed thermodynamic database, ThermoCalc and DICTRA software was used to model kinetic compositional changes in titanium alloys. Experimental diffusion couples were created and compared to DICTRA simulations to refine mobility parameters in the titanium mobility database. The software and database were able to predict homogenization times and the beta→alpha plate thickening kinetics during cooling in the near-alpha Ti5111 alloy. The results of these models were compared to LEAP microanalysis and found to be in reasonable agreement. Powder metallurgy was explored using SPS at GM R&D to reduce the cost of titanium alloys. Fully dense Ti5111 alloys were produced and achieved similar microstructures to wrought Ti5111. High levels of oxygen in these alloys increased the strength while reducing the ductility. Preliminary Ti5111+Y alloys were created, where yttrium additions successfully gettered excess oxygen to create oxides. However, undesirable large oxides formed, indicating more research is needed into the homogeneous distribution of the yttrium powder to create finer oxides. Principles established in steels were used to optimize the beta phase transformation stability for martensite transformation toughening in titanium alloys. The Olson-Cohen kinetic model is calibrated to shear strains in titanium. A frictional work database is established for common alloying

Functional photoacoustic microscopy of pH

Science.gov (United States)

Chatni, Muhammad Rameez; Yao, Junjie; Danielli, Amos; Favazza, Christopher P.; Maslov, Konstantin I.; Wang, Lihong V.

2011-01-01

pH is a tightly regulated indicator of metabolic activity. In mammalian systems, an imbalance of pH regulation may result from or result in serious illness. In this paper, we report photoacoustic microscopy (PAM) of a commercially available pH-sensitive fluorescent dye (SNARF-5F carboxylic acid) in tissue phantoms. We demonstrated that PAM is capable of pH imaging in absolute values at tissue depths of up to 2.0 mm, greater than possible with other forms of optical microscopy. PMID:22029342

Listening to membrane potential: photoacoustic voltage-sensitive dye recording

Science.gov (United States)

Zhang, Haichong K.; Yan, Ping; Kang, Jeeun; Abou, Diane S.; Le, Hanh N. D.; Jha, Abhinav K.; Thorek, Daniel L. J.; Kang, Jin U.; Rahmim, Arman; Wong, Dean F.; Boctor, Emad M.; Loew, Leslie M.

2017-04-01

Voltage-sensitive dyes (VSDs) are designed to monitor membrane potential by detecting fluorescence changes in response to neuronal or muscle electrical activity. However, fluorescence imaging is limited by depth of penetration and high scattering losses, which leads to low sensitivity in vivo systems for external detection. By contrast, photoacoustic (PA) imaging, an emerging modality, is capable of deep tissue, noninvasive imaging by combining near-infrared light excitation and ultrasound detection. Here, we show that voltage-dependent quenching of dye fluorescence leads to a reciprocal enhancement of PA intensity. We synthesized a near-infrared photoacoustic VSD (PA-VSD), whose PA intensity change is sensitive to membrane potential. In the polarized state, this cyanine-based probe enhances PA intensity while decreasing fluorescence output in a lipid vesicle membrane model. A theoretical model accounts for how the experimental PA intensity change depends on fluorescence and absorbance properties of the dye. These results not only demonstrate PA voltage sensing but also emphasize the interplay of both fluorescence and absorbance properties in the design of optimized PA probes. Together, our results demonstrate PA sensing as a potential new modality for recording and external imaging of electrophysiological and neurochemical events in the brain.

Quinone-fused porphyrins as contrast agents for photoacoustic imaging

KAUST Repository

Banala, Srinivas

2017-06-27

Photoacoustic (PA) imaging is an emerging non-invasive diagnostic modality with many potential clinical applications in oncology, rheumatology and the cardiovascular field. For this purpose, there is a high demand for exogenous contrast agents with high absorption coefficients in the optical window for tissue imaging, i.e. the near infrared (NIR) range between 680 and 950 nm. We herein report the photoacoustic properties of quinone-fused porphyrins inserted with different transition metals as new highly promising candidates. These dyes exhibit intense NIR absorption, a lack of fluorescence emission, and PA sensitivity in concentrations below 3 nmol mL. In this context, the highest PA signal was obtained with a Zn(ii) inserted dye. Furthermore, this dye was stable in blood serum and free thiol solution and exhibited negligible cell toxicity. Additionally, the Zn(ii) probe could be detected with an up to 3.2 fold higher PA intensity compared to the clinically most commonly used PA agent, ICG. Thus, further exploration of the \\'quinone-fusing\\' approach to other chromophores may be an efficient way to generate highly potent PA agents that do not fluoresce and shift their absorption into the NIR range.

Corrosion of titanium and titanium alloys in spent fuel repository conditions - literature review

International Nuclear Information System (INIS)

Aho-Mantila, I.; Haenninen, H.; Aaltonen, P.; Taehtinen, S.

1985-03-01

The spent nuclear fuel is planned to be disposed in Finnish bedrock. The canister of spent fuel in waste repository is one barrier to the release of radionuclides. It is possible to choose a canister material with a known, measurable corrosion rate and to make it with thickness allowing corrosion to occur. The other possibility is to use a material which is nearly immune to general corrosion. In this second category there are titanium and titanium alloys which exhibit a very high degree of resistance to general corrosion. In this literature study the corrosion properties of unalloyed titanium, titanium alloyed with palladium and titanium alloyed with molybdenum and nickel are reviewed. The two titanium alloys own in addition to the excellent general corrosion properties outstanding properties against localized corrosion like pitting or crevice corrosion. Stress corrosion cracking and corrosion fatique of titanium seem not to be a problem in the repository conditions, but the possibilities of delayed cracking caused by hydrogen should be carefully appreciated. (author)

Micromachined silicon parallel acoustic delay lines as time-delayed ultrasound detector array for real-time photoacoustic tomography

Science.gov (United States)

Cho, Y.; Chang, C.-C.; Wang, L. V.; Zou, J.

2016-02-01

This paper reports the development of a new 16-channel parallel acoustic delay line (PADL) array for real-time photoacoustic tomography (PAT). The PADLs were directly fabricated from single-crystalline silicon substrates using deep reactive ion etching. Compared with other acoustic delay lines (e.g., optical fibers), the micromachined silicon PADLs offer higher acoustic transmission efficiency, smaller form factor, easier assembly, and mass production capability. To demonstrate its real-time photoacoustic imaging capability, the silicon PADL array was interfaced with one single-element ultrasonic transducer followed by one channel of data acquisition electronics to receive 16 channels of photoacoustic signals simultaneously. A PAT image of an optically-absorbing target embedded in an optically-scattering phantom was reconstructed, which matched well with the actual size of the imaged target. Because the silicon PADL array allows a signal-to-channel reduction ratio of 16:1, it could significantly simplify the design and construction of ultrasonic receivers for real-time PAT.

Micromachined silicon parallel acoustic delay lines as time-delayed ultrasound detector array for real-time photoacoustic tomography

International Nuclear Information System (INIS)

Cho, Y; Chang, C-C; Zou, J; Wang, L V

2016-01-01

This paper reports the development of a new 16-channel parallel acoustic delay line (PADL) array for real-time photoacoustic tomography (PAT). The PADLs were directly fabricated from single-crystalline silicon substrates using deep reactive ion etching. Compared with other acoustic delay lines (e.g., optical fibers), the micromachined silicon PADLs offer higher acoustic transmission efficiency, smaller form factor, easier assembly, and mass production capability. To demonstrate its real-time photoacoustic imaging capability, the silicon PADL array was interfaced with one single-element ultrasonic transducer followed by one channel of data acquisition electronics to receive 16 channels of photoacoustic signals simultaneously. A PAT image of an optically-absorbing target embedded in an optically-scattering phantom was reconstructed, which matched well with the actual size of the imaged target. Because the silicon PADL array allows a signal-to-channel reduction ratio of 16:1, it could significantly simplify the design and construction of ultrasonic receivers for real-time PAT. (paper)

Limitations of quantitative photoacoustic measurements of blood oxygenation in small vessels

International Nuclear Information System (INIS)

Sivaramakrishnan, Mathangi; Maslov, Konstantin; Zhang, Hao F; Stoica, George; Wang, Lihong V

2007-01-01

We investigate the feasibility of obtaining accurate quantitative information, such as local blood oxygenation level (sO 2 ), with a spatial resolution of about 50 μm from spectral photoacoustic (PA) measurements. The optical wavelength dependence of the peak values of the PA signals is utilized to obtain the local blood oxygenation level. In our in vitro experimental models, the PA signal amplitude is found to be linearly proportional to the blood optical absorption coefficient when using ultrasonic transducers with central frequencies high enough such that the ultrasonic wavelengths are shorter than the light penetration depth into the blood vessels. For an optical wavelength in the 578-596 nm region, with a transducer central frequency that is above 25 MHz, the sensitivity and accuracy of sO 2 inversion is shown to be better than 4%. The effect of the transducer focal position on the accuracy of quantifying blood oxygenation is found to be negligible. In vivo oxygenation measurements of rat skin microvasculature yield results consistent with those from in vitro studies, although factors specific to in vivo measurements, such as the spectral dependence of tissue optical attenuation, dramatically affect the accuracy of sO 2 quantification in vivo

Fiber-ring laser-based intracavity photoacoustic spectroscopy for trace gas sensing.

Science.gov (United States)

Wang, Qiang; Wang, Zhen; Chang, Jun; Ren, Wei

2017-06-01

We demonstrated a novel trace gas sensing method based on fiber-ring laser intracavity photoacoustic spectroscopy. This spectroscopic technique is a merging of photoacoustic spectroscopy (PAS) with a fiber-ring cavity for sensitive and all-fiber gas detection. A transmission-type PAS gas cell (resonant frequency f0=2.68  kHz) was placed inside the fiber-ring laser to fully utilize the intracavity laser power. The PAS signal was excited by modulating the laser wavelength at f0/2 using a custom-made fiber Bragg grating-based modulator. We used this spectroscopic technique to detect acetylene (C2H2) at 1531.6 nm as a proof of principle. With a low Q-factor (4.9) of the PAS cell, our sensor achieved a good linear response (R2=0.996) to C2H2 concentration and a minimum detection limit of 390 ppbv at 2-s response time.

Linear-array photoacoustic imaging using minimum variance-based delay multiply and sum adaptive beamforming algorithm

Science.gov (United States)

Mozaffarzadeh, Moein; Mahloojifar, Ali; Orooji, Mahdi; Kratkiewicz, Karl; Adabi, Saba; Nasiriavanaki, Mohammadreza

2018-02-01

In photoacoustic imaging, delay-and-sum (DAS) beamformer is a common beamforming algorithm having a simple implementation. However, it results in a poor resolution and high sidelobes. To address these challenges, a new algorithm namely delay-multiply-and-sum (DMAS) was introduced having lower sidelobes compared to DAS. To improve the resolution of DMAS, a beamformer is introduced using minimum variance (MV) adaptive beamforming combined with DMAS, so-called minimum variance-based DMAS (MVB-DMAS). It is shown that expanding the DMAS equation results in multiple terms representing a DAS algebra. It is proposed to use the MV adaptive beamformer instead of the existing DAS. MVB-DMAS is evaluated numerically and experimentally. In particular, at the depth of 45 mm MVB-DMAS results in about 31, 18, and 8 dB sidelobes reduction compared to DAS, MV, and DMAS, respectively. The quantitative results of the simulations show that MVB-DMAS leads to improvement in full-width-half-maximum about 96%, 94%, and 45% and signal-to-noise ratio about 89%, 15%, and 35% compared to DAS, DMAS, MV, respectively. In particular, at the depth of 33 mm of the experimental images, MVB-DMAS results in about 20 dB sidelobes reduction in comparison with other beamformers.

Spectroscopic and thermal characterization of bovine enamel and dentine using the photoacoustic effect

International Nuclear Information System (INIS)

Stolf, Sandro Fernando

2003-01-01

The optical and thermal properties of dental tissues determine the nature and extent of the tissue response through the processes of absorption, transmission, reflection and scattering of the laser light and the heat produced by the absorption of that light. The spectroscopic characterization of bovine dentine and enamel, and the determination of the thermal diffusivity were the aim of this study. The photoacoustic spectra from these tissues were obtained in the Near-Infrared range 900 - 2500 nm, which is the clinical range for odontological application of most lasers. Photoacoustic spectra were taken from block, slices and powder of enamel and dentine. Also photoacoustic spectra were registered before and after 2, 5 and 10 h of topical fluoride (2.26%) application. Using the same technique spectra were taken from dentine and enamel after irradiation with Nd:YAG, Er:YAG, Ho:YLF and CO 2 . It is evident from the results that the presence of O-H in the composition of hydroxyapatite and the water present in the teeth tissue make the obtention of spectrum from components other than O-H bond a very difficult task. In this way, only bands assigned to overtones and combinations of O-H stretch were observed. The thermal diffusivity of the bovine dentine was also measured using the photoacoustic technique. The thermal diffusivity is the physical quantity which measures the rate of heat diffusion throughout the sample. For higher values of the thermal diffusivity the heat diffusion and temperature rise will be faster. As there is many studies devoted to the processes of heat transfer throughout dental tissues using bovine teeth, it is important the determination of its thermal diffusivity. The measured value was found to be a = 2.0 (±0.1).1O -3 cm 2 /s for the both direction, perpendicular and parallel to the dentinal tubules. These a lues indicate that there is no difference between the thermal diffusivities for the both directions. (author)

Simple Model of a Photoacoustic System as a CR Circuit

Science.gov (United States)

Fukuhara, Akiko; Kaneko, Fumitoshi; Ogawa, Naohisa

2012-01-01

We introduce the photoacoustic educational system (PAES), by which we can identify which gas causes the greenhouse effect in a classroom (Kaneko "et al" 2010 "J. Chem. Educ." 87 202-4). PAES is an experimental system in which a pulse of infrared (IR) is absorbed into gas as internal energy, an oscillation of pressure (sound) appears, and then we…

Music-of-Light Stethoscope: A Demonstration of the Photoacoustic Effect

Science.gov (United States)

Nikitichev, D. I.; Xia, W.; Hill, E.; Mosse, C. A.; Perkins, T.; Konyn, K.; Ourselin, S.; Desjardins, A. E.; Vercauteren, T.

2016-01-01

In this paper we present a system aimed at demonstrating the photoacoustic (PA) effect for educational purposes. PA imaging is a hybrid imaging modality that requires no contrast agent and has a great potential for spine and brain lesion characterisation, breast cancer and blood flow monitoring notably in the context of fetal surgery. It relies on…

Chitosan patterning on titanium alloys

OpenAIRE

Gilabert Chirivella, Eduardo; Pérez Feito, Ricardo; Ribeiro, Clarisse; Ribeiro, Sylvie; Correia, Daniela; González Martin, María Luisa; Manero Planella, José María; Lanceros Méndez, Senentxu; Gallego Ferrer, Gloria; Gómez Ribelles, José Luis

2017-01-01

Titanium and its alloys are widely used in medical implants because of their excellent properties. However, bacterial infection is a frequent cause of titanium-based implant failure and also compromises its osseointegration. In this study, we report a new simple method of providing titanium surfaces with antibacterial properties by alternating antibacterial chitosan domains with titanium domains in the micrometric scale. Surface microgrooves were etched on pure titanium disks at i...

On the use of titanium hydride for powder injection moulding of titanium-based alloys

International Nuclear Information System (INIS)

Carrenoo-Morelli, E.; Bidaux, J.-E.

2009-01-01

Full text: Titanium and titanium-based alloys are excellent materials for a number of engineering applications because of their high strength, lightweight, good corrosion resistance, non magnetic characteristic and biocompatibility. The current processing steps are usually costly, and there is a growing demand for net-shape solutions for manufacturing parts of increasing complexity. Powder injection moulding is becoming a competitive alternative, thanks to the advances in production of good quality base-powders, binders and sintering facilities. Titanium hydride powders, have the attractiveness of being less reactive than fine titanium powders, easier to handle, and cheaper. This paper summarizes recent advances on PIM of titanium and titanium alloys from TiH2 powders, including shape-memory NiTi alloys. (author)

In Vivo Photoacoustic and Fluorescence Cystography Using Clinically Relevant Dual Modal Indocyanine Green

Directory of Open Access Journals (Sweden)

Sungjo Park

2014-10-01

Full Text Available Conventional X-ray-based cystography uses radio-opaque materials, but this method uses harmful ionizing radiation and is not sensitive. In this study, we demonstrate nonionizing and noninvasive photoacoustic (PA and fluorescence (FL cystography using clinically relevant indocyanine green (ICG in vivo. After transurethral injection of ICG into rats through a catheter, their bladders were photoacoustically and fluorescently visualized. A deeply positioned bladder below the skin surface (i.e., ~1.5–5 mm was clearly visible in the PA and FL image using a laser pulse energy of less than 2 mJ/cm2 (1/15 of the safety limit. Then, the in vivo imaging results were validated through in situ studies. Our results suggest that dual modal cystography can provide a nonionizing and noninvasive imaging tool for bladder mapping.

In vivo tumor detection with combined MR–Photoacoustic-Thermoacoustic imaging

Directory of Open Access Journals (Sweden)

Lin Huang

2016-09-01

Full Text Available Here, we report a new method using combined magnetic resonance (MR–Photoacoustic (PA–Thermoacoustic (TA imaging techniques, and demonstrate its unique ability for in vivo cancer detection using tumor-bearing mice. Circular scanning TA and PA imaging systems were used to recover the dielectric and optical property distributions of three colon carcinoma bearing mice While a 7.0-T magnetic resonance imaging (MRI unit with a mouse body volume coil was utilized for high resolution structural imaging of the same mice. Three plastic tubes filled with soybean sauce were used as fiducial markers for the co-registration of MR, PA and TA images. The resulting fused images provided both enhanced tumor margin and contrast relative to the surrounding normal tissues. In particular, some finger-like protrusions extending into the surrounding tissues were revealed in the MR/TA infused images. These results show that the tissue functional optical and dielectric properties provided by PA and TA images along with the anatomical structure by MRI in one picture make accurate tumor identification easier. This combined MR–PA–TA-imaging strategy has the potential to offer a clinically useful triple-modality tool for accurate cancer detection and for intraoperative surgical navigation.

High-frequency annular array with coaxial illumination for dual-modality ultrasonic and photoacoustic imaging

Science.gov (United States)

Filoux, Erwan; Sampathkumar, Ashwin; Chitnis, Parag V.; Aristizábal, Orlando; Ketterling, Jeffrey A.

2013-05-01

This paper presents a combined ultrasound and photoacoustic (PA) imaging (PAI) system used to obtain high-quality, co-registered images of mouse-embryo anatomy and vasculature. High-frequency ultrasound (HFU, >20 MHz) is utilized to obtain high-resolution anatomical images of small animals while PAI provides high-contrast images of the vascular network. The imaging system is based on a 40 MHz, 5-element, 6 mm aperture annular-array transducer with a 800 μm diameter hole through its central element. The transducer was integrated in a cage-plate assembly allowing for a collimated laser beam to pass through the hole so that the optical and acoustic beams were collinear. The assembly was mounted on a two-axis, motorized stage to enable the simultaneous acquisition of co-registered HFU and PA volumetric data. Data were collected from all five elements in receive and a synthetic-focusing algorithm was applied in post-processing to beamform the data and increase the spatial resolution and depth-of-field (DOF) of the HFU and PA images. Phantom measurements showed that the system could achieve high-resolution images (down to 90 μm for HFU and 150 μm for PAI) and a large DOF of >8 mm. Volume renderings of a mouse embryo showed that the scanner allowed for visualizing morphologically precise anatomy of the entire embryo along with corresponding co-registered vasculature. Major head vessels, such as the superior sagittal sinus or rostral vein, were clearly identified as well as limb bud vasculature.

Label-free imaging of gold nanoparticles in single live cells by photoacoustic microscopy

Science.gov (United States)

Tian, Chao; Qian, Wei; Shao, Xia; Xie, Zhixing; Cheng, Xu; Liu, Shengchun; Cheng, Qian; Liu, Bing; Wang, Xueding

2016-03-01

Gold nanoparticles (AuNPs) have been extensively explored as a model nanostructure in nanomedicine and have been widely used to provide advanced biomedical research tools in diagnostic imaging and therapy. Due to the necessity of targeting AuNPs to individual cells, evaluation and visualization of AuNPs in the cellular level is critical to fully understand their interaction with cellular environment. Currently imaging technologies, such as fluorescence microscopy and transmission electron microscopy all have advantages and disadvantages. In this paper, we synthesized AuNPs by femtosecond pulsed laser ablation, modified their surface chemistry through sequential bioconjugation, and targeted the functionalized AuNPs with individual cancer cells. Based on their high optical absorption contrast, we developed a novel, label-free imaging method to evaluate and visualize intracellular AuNPs using photoacoustic microscopy (PAM). Preliminary study shows that the PAM imaging technique is capable of imaging cellular uptake of AuNPs in vivo at single-cell resolution, which provide an important tool for the study of AuNPs in nanomedicine.

Classification of titanium dioxide

International Nuclear Information System (INIS)

Macias B, L.R.; Garcia C, R.M.; Maya M, M.E.; Ita T, A. De; Palacios G, J.

2002-01-01

In this work the X-ray diffraction (XRD), Scanning Electron Microscopy (Sem) and the X-ray Dispersive Energy Spectroscopy techniques are used with the purpose to achieve a complete identification of phases and mixture of phases of a crystalline material as titanium dioxide. The problem for solving consists of being able to distinguish a sample of titanium dioxide being different than a titanium dioxide pigment. A standard sample of titanium dioxide with NIST certificate is used, which indicates a purity of 99.74% for the TiO 2 . The following way is recommended to proceed: a)To make an analysis by means of X-ray diffraction technique to the sample of titanium dioxide pigment and on the standard of titanium dioxide waiting not find differences. b) To make a chemical analysis by the X-ray Dispersive Energy Spectroscopy via in a microscope, taking advantage of the high vacuum since it is oxygen which is analysed and if it is concluded that the aluminium oxide appears in a greater proportion to 1% it is established that is a titanium dioxide pigment, but if it is lesser then it will be only titanium dioxide. This type of analysis is an application of the nuclear techniques useful for the tariff classification of merchandise which is considered as of difficult recognition. (Author)

Photoacoustic-based sO2 estimation through excised bovine prostate tissue with interstitial light delivery.

Science.gov (United States)

Mitcham, Trevor; Taghavi, Houra; Long, James; Wood, Cayla; Fuentes, David; Stefan, Wolfgang; Ward, John; Bouchard, Richard

2017-09-01

Photoacoustic (PA) imaging is capable of probing blood oxygen saturation (sO 2 ), which has been shown to correlate with tissue hypoxia, a promising cancer biomarker. However, wavelength-dependent local fluence changes can compromise sO 2 estimation accuracy in tissue. This work investigates using PA imaging with interstitial irradiation and local fluence correction to assess precision and accuracy of sO 2 estimation of blood samples through ex vivo bovine prostate tissue ranging from 14% to 100% sO 2 . Study results for bovine blood samples at distances up to 20 mm from the irradiation source show that local fluence correction improved average sO 2 estimation error from 16.8% to 3.2% and maintained an average precision of 2.3% when compared to matched CO-oximeter sO 2 measurements. This work demonstrates the potential for future clinical translation of using fluence-corrected and interstitially driven PA imaging to accurately and precisely assess sO 2 at depth in tissue with high resolution.

On image quality enhancement in photoacoustic image reconstruction by motion compensation

NARCIS (Netherlands)

Willemink, Rene; Slump, Cornelis H.; van der Heijden, Ferdinand

2006-01-01

Photoacoustic (PA) imaging is a relatively new noninvasive medical imaging modality. It is a tech- nique which is harmless for the human body and uses pulsed optical energy. The process is based on the ab- sorption of the pulse of optical energy by an object leading to local temperature increases.

Corrosion behaviour and galvanic coupling of titanium and welded titanium in LiBr solutions

International Nuclear Information System (INIS)

Blasco-Tamarit, E.; Igual-Munoz, A.; Garcia Anton, J.; Garcia-Garcia, D.

2007-01-01

Corrosion resistance and galvanic coupling of Grade 2 commercially pure titanium in its welded and non-welded condition were systematically analyzed in LiBr solutions. Galvanic corrosion was evaluated through two different methods: anodic polarization (according to the Mixed Potential Theory) and electrochemical noise (using a zero-resistance ammeter). Samples have been etched to study the microstructure. The action of lithium chromate as corrosion inhibitor has been evaluated. Titanium and welded titanium showed extremely low corrosion current densities and elevated pitting potential values (higher than 1 V). The results of both methods, anodic polarization and electrochemical noise, showed that the welded titanium was always the anodic element of the pair titanium-welded titanium, so that its corrosion resistance decreases due to the galvanic effect

Photoacoustic emission from fluorescent nanodiamonds enhanced with gold nanoparticles

OpenAIRE

Zhang, Bailin; Fang, Chia-Yi; Chang, Cheng-Chun; Peterson, Ralph; Maswadi, Saher; Glickman, Randolph D.; Chang, Huan-Cheng; Ye, Jing Yong

2012-01-01

Fluorescent nanodiamonds (FNDs) have drawn much attention in recent years for biomedical imaging applications due to their desired physical properties including excellent photostability, high biocompatibility, extended far-red fluorescence emission, and ease of surface functionalization. Here we explore a new feature of FNDs, i.e. their photoacoustic emission capability, which may lead to potential applications of using FNDs as a dual imaging contrast agent for combined fluorescence and photo...

Putative photoacoustic damage in skin induced by pulsed ArF excimer laser

Energy Technology Data Exchange (ETDEWEB)

Watanabe, S.; Flotte, T.J.; McAuliffe, D.J.; Jacques, S.L.

1988-05-01

Argon-fluoride excimer laser ablation of guinea pig stratum corneum causes deeper tissue damage than expected for thermal or photochemical mechanisms, suggesting that photoacoustic waves have a role in tissue damage. Laser irradiation (193 nm, 14-ns pulse) at two different radiant exposures, 62 and 156 mJ/cm2 per pulse, was used to ablate the 15-microns-thick stratum corneum of the skin. Light and electron microscopy of immediate biopsies demonstrated damage to fibroblasts as deep as 88 and 220 microns, respectively, below the ablation site. These depths are far in excess of the optical penetration depth of 193-nm light (1/e depth = 1.5 micron). The damage is unlikely to be due to a photochemical mechanism because (a) the photons will not penetrate to these depths, (b) it is a long distance for toxic photoproducts to diffuse, and (c) damage is proportional to laser pulse intensity and not the total dose that accumulates in the residual tissue; therefore, reciprocity does not hold. Damage due to a thermal mechanism is not expected because there is not sufficient energy deposited in the tissue to cause significant heating at such depths. The damage is most likely due to a photoacoustic mechanism because (a) photoacoustic waves can propagate deep into tissue, (b) the depth of damage increases with increasing laser pulse intensity rather than with increasing total residual energy, and (c) the effects are immediate. These effects should be considered in the evaluation of short pulse, high peak power laser-tissue interactions.

Electrowinning molten titanium from titanium dioxide

CSIR Research Space (South Africa)

Van Vuuren, DS

2005-10-01

Full Text Available the Manufacturing and Materials Industry in it quest for global competitiveness CSIR Manufacturing and Materials Technology 3 Rationale – Titanium Cost Build-up Material Cost Ilmenite $0.27/kg Ti sponge Titanium slag $0.75/kg Ti Sponge TiCl4 and TiO2 $3....10/kg Ti Sponge Ti Sponge raw materials costs $5.50/kg Ti Sponge Total Ti Sponge cost $9-$11/kg Ti Sponge Ti ingot $15-17/kg Ti Aluminium $1.7/kg Al Supporting the Manufacturing and Materials Industry in its quest for global competitivenessorting...

First application of multilayer graphene cantilever for laser photoacoustic detection

Czech Academy of Sciences Publication Activity Database

Suchánek, Jan; Dostál, Michal; Vlasáková, T.; Janda, Pavel; Klusáčková, Monika; Kubát, Pavel; Nevrlý, V.; Bitala, P.; Civiš, Svatopluk; Zelinger, Zdeněk

2017-01-01

Roč. 101, APR 2017 (2017), s. 9-14 ISSN 0263-2241 R&D Projects: GA ČR(CZ) GA14-14696S; GA MŠk(CZ) LD14022 Grant - others:COST(XE) TD1105 Institutional support: RVO:61388955 Keywords : Cantilever * Multilayer graphene * Photoacoustic detection * Methanol detection Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 2.359, year: 2016

Photoacoustic Experimental System to Confirm Infrared Absorption Due to Greenhouse Gases

Science.gov (United States)

Kaneko, Fumitoshi; Monjushiro, Hideaki; Nishiyama, Masayoshi; Kasai, Toshio; Harris, Harold H.

2010-01-01

An experimental system for detecting infrared absorption using the photoacoustic (PA) effect is described. It is aimed for use at high-school level to illustrate the difference in infrared (IR) absorption among the gases contained in the atmosphere in connection with the greenhouse effect. The experimental system can be built with readily…

Lateral resolution of eddy current imaging

International Nuclear Information System (INIS)

Hassan, W.; Blodgett, M.; Nagy, P.B.

2002-01-01

Analytical, finite element simulation, and experimental methods were used to investigate the lateral resolution of eddy current microscopy. It was found that the lateral resolution of eddy current imaging is ultimately limited by the probe-coil geometry and dimensions, but both the inspection frequency and the phase angle can be used to optimize the resolution, to some degree, at the expense of sensitivity. Electric anisotropy exhibited by noncubic crystallographic classes of materials such as titanium alloys can play a very similar role in electromagnetic materials characterization of polycrystalline metals to that of elastic anisotropy in ultrasonic materials characterization. Our results demonstrate that eddy current microscopy can be enhanced via a high-resolution, small diameter probe-coil which delivers a unique materials characterization tool well suited for the evaluation of Ti alloys

Skull's acoustic attenuation and dispersion modeling on photoacoustic signal

Science.gov (United States)

Mohammadi, Leila; Behnam, Hamid; Tavakkoli, Jahan; Nasiriavanaki, Mohammadreza

2018-02-01

Despite the promising results of the recent novel transcranial photoacoustic (PA) brain imaging technology, it has been demonstrated that the presence of the skull severely affects the performance of this imaging modality. We theoretically investigate the effects of acoustic heterogeneity induced by skull on the PA signals generated from single particles, with firstly developing a mathematical model for this phenomenon and then explore experimental validation of the results. The model takes into account the frequency dependent attenuation and dispersion effects occur with wave reflection, refraction and mode conversion at the skull surfaces. Numerical simulations based on the developed model are performed for calculating the propagation of photoacoustic waves through the skull. The results show a strong agreement between simulation and ex-vivo study. The findings are as follow: The thickness of the skull is the most PA signal deteriorating factor that affects both its amplitude (attenuation) and phase (distortion). Also we demonstrated that, when the depth of target region is low and it is comparable to the skull thickness, however, the skull-induced distortion becomes increasingly severe and the reconstructed image would be strongly distorted without correcting these effects. It is anticipated that an accurate quantification and modeling of the skull transmission effects would ultimately allow for aberration correction in transcranial PA brain imaging.

Plasmonic Titanium Nitride Nanostructures via Nitridation of Nanopatterned Titanium Dioxide

DEFF Research Database (Denmark)

Guler, Urcan; Zemlyanov, Dmitry; Kim, Jongbum

2017-01-01

Plasmonic titanium nitride nanostructures are obtained via nitridation of titanium dioxide. Nanoparticles acquired a cubic shape with sharper edges following the rock-salt crystalline structure of TiN. Lattice constant of the resulting TiN nanoparticles matched well with the tabulated data. Energy...

In vivo Microscopic Photoacoustic Spectroscopy for Non-Invasive Glucose Monitoring Invulnerable to Skin Secretion Products.

Science.gov (United States)

Sim, Joo Yong; Ahn, Chang-Geun; Jeong, Eun-Ju; Kim, Bong Kyu

2018-01-18

Photoacoustic spectroscopy has been shown to be a promising tool for non-invasive blood glucose monitoring. However, the repeatability of such a method is susceptible to changes in skin condition, which is dependent on hand washing and drying due to the high absorption of infrared excitation light to the skin secretion products or water. In this paper, we present a method to meet the challenges of mid-infrared photoacoustic spectroscopy for non-invasive glucose monitoring. By obtaining the microscopic spatial information of skin during the spectroscopy measurement, the skin region where the infrared spectra is insensitive to skin condition can be locally selected, which enables reliable prediction of the blood glucose level from the photoacoustic spectroscopy signals. Our raster-scan imaging showed that the skin condition for in vivo spectroscopic glucose monitoring had significant inhomogeneities and large variability in the probing area where the signal was acquired. However, the selective localization of the probing led to a reduction in the effects of variability due to the skin secretion product. Looking forward, this technology has broader applications not only in continuous glucose monitoring for diabetic patient care, but in forensic science, the diagnosis of malfunctioning sweat pores, and the discrimination of tumors extracted via biopsy.

Photoacoustic investigation of the effective diffusivity of two-layer semiconductors

Energy Technology Data Exchange (ETDEWEB)

Medina, J; Gurevich, Yu. G; Logvinov G, N; Rodriguez, P; Gonzalez de la Cruz, G. [Instituto Mexicano del Petroleo, Mexico, D.F. (Mexico)

2001-08-01

In this work, the problem of the effective thermal diffusivity of two-layer systems is investigated using the photoacoustic spectroscopy. The experimental results are examined in terms of the effective thermal parameters of the composite system determined from an homogeneous material which produces the same physical response under an external perturbation in the detector device. It is shown, that the effective thermal conductivity is not symmetric under exchange of the two layers of the composite; i.e., the effective thermal parameters depend upon which layer is illuminated in the photoacoustic experiments. Particular emphasis is given to the characterization of the interface thermal conductivity between the layer-system. [Spanish] En el presente trabajo se utiliza la espectroscopia fotoacustica para medir la difusividad termica de un sistema de dos capas. Los resultados experimentales son analizados en terminos de los parametros termicos efectivos determinados a partir de un material homogeneo, el cual produce la misma respuesta fisica bajo una perturbacion externa. Se puso particular enfasis en la caracterizacion de los efectos de interfase en el flujo de calor en el sistema de dos capas. Los resultados experimentales se comparan con el modelo teorico propuesto en este trabajo.

Music-of-light stethoscope: a demonstration of the photoacoustic effect

Science.gov (United States)

Nikitichev, D. I.; Xia, W.; Hill, E.; Mosse, C. A.; Perkins, T.; Konyn, K.; Ourselin, S.; Desjardins, A. E.; Vercauteren, T.

2016-07-01

In this paper we present a system aimed at demonstrating the photoacoustic (PA) effect for educational purposes. PA imaging is a hybrid imaging modality that requires no contrast agent and has a great potential for spine and brain lesion characterisation, breast cancer and blood flow monitoring notably in the context of fetal surgery. It relies on combining light excitation with ultrasound reception. Our brief was to present and explain PA imaging in a public-friendly way suitable for a variety of ages and backgrounds. We developed a simple, accessible demonstration unit using readily available materials. We used a modulated light emitting diode (LED) torch and an electronic stethoscope. The output of a music player was used for light modulation and the chest piece of the stethoscope covered by a black tape was used as an absorbing target and an enclosed chamber. This demonstration unit was presented to the public at the Bloomsbury Festival On Light in October 2015. Our stall was visited by over 100 people of varying ages. Twenty families returned in-depth evaluation questionnaires, which show that our explanations of the photoacoustic effect were well understood. Their interest in biomedical engineering was increased.

Photoacoustic and filter measurements related to aerosol light absorption during the Northern Front Range Air Quality Study (Colorado 1996/1997)

Science.gov (United States)

Moosmüller, H.; Arnott, W. P.; Rogers, C. F.; Chow, J. C.; Frazier, C. A.; Sherman, L. E.; Dietrich, D. L.

1998-11-01

A new photoacoustic instrument for the measurement of aerosol light absorption was collocated with conventional aerosol instrumentation during the 1996-1997 winter intensive monitoring period of the Northern Front Range Air Quality Study. Measurements of the light absorption efficiency for black carbon were 5 m2/g at 685 nm and 10 m2/g at 532 nm, and for elemental carbon, they were 3.6 m2/g at 685 nm. We show that these values together with previous photoacoustic measurements of aerosol light absorption shed some light on the wavelength dependence of absorption efficiency for carbonaceous aerosol in the visible and near-visible region. Integrating plate type filter measurements of aerosol light absorption result in far larger values than those measured with the photoacoustic instrument. We demonstrate that a recently published correction technique [Horvath, 1997] can yield improved agreement.

PHOTOACOUSTIC NON-DESTRUCTIVE EVALUATION AND IMAGING OF CARIES IN DENTAL SAMPLES

International Nuclear Information System (INIS)

Li, T.; Dewhurst, R. J.

2010-01-01

Dental caries is a disease wherein bacterial processes damage hard tooth structure. Traditional dental radiography has its limitations for detecting early stage caries. In this study, a photoacoustic (PA) imaging system with the near-infrared light source has been applied to postmortem dental samples to obtain 2-D and 3-D images. Imaging results showed that the PA technique can be used to image human teeth caries. For non-destructive photoacoustic evaluation and imaging, the induced temperature and pressure rises within biotissues should not cause physical damage to the tissue. For example, temperature rises above 5 deg. C within live human teeth will cause pulpal necrosis. Therefore, several simulations based on the thermoelastic effect have been applied to predict temperature and pressure fields within samples. Predicted temperature levels are below corresponding safety limits, but care is required to avoid nonlinear absorption phenomena. Furthermore, PA imaging results from the phantom provide evidence for high sensitivity, which shows the imaging potential of the PA technique for detecting early stage disease.

Artefacts in multimodal imaging of titanium, zirconium and binary titanium-zirconium alloy dental implants: an in vitro study.

Science.gov (United States)

Smeets, Ralf; Schöllchen, Maximilian; Gauer, Tobias; Aarabi, Ghazal; Assaf, Alexandre T; Rendenbach, Carsten; Beck-Broichsitter, Benedicta; Semmusch, Jan; Sedlacik, Jan; Heiland, Max; Fiehler, Jens; Siemonsen, Susanne

2017-02-01

To analyze and evaluate imaging artefacts induced by zirconium, titanium and titanium-zirconium alloy dental implants. Zirconium, titanium and titanium-zirconium alloy implants were embedded in gelatin and MRI, CT and CBCT were performed. Standard protocols were used for each modality. For MRI, line-distance profiles were plotted to quantify the accuracy of size determination. For CT and CBCT, six shells surrounding the implant were defined every 0.5 cm from the implant surface and histogram parameters were determined for each shell. While titanium and titanium-zirconium alloy induced extensive signal voids in MRI owing to strong susceptibility, zirconium implants were clearly definable with only minor distortion artefacts. For titanium and titanium-zirconium alloy, the MR signal was attenuated up to 14.1 mm from the implant. In CT, titanium and titanium-zirconium alloy resulted in less streak artefacts in comparison with zirconium. In CBCT, titanium-zirconium alloy induced more severe artefacts than zirconium and titanium. MRI allows for an excellent image contrast and limited artefacts in patients with zirconium implants. CT and CBCT examinations are less affected by artefacts from titanium and titanium-zirconium alloy implants compared with MRI. The knowledge about differences of artefacts through different implant materials and image modalities might help support clinical decisions for the choice of implant material or imaging device in the clinical setting.

Time reversal in photoacoustic tomography and levitation in a cavity

International Nuclear Information System (INIS)

Palamodov, V P

2014-01-01

A class of photoacoustic acquisition geometries in R n is considered such that the spherical mean transform admits an exact filtered back projection reconstruction formula. The reconstruction is interpreted as a time reversion mirror that reproduces exactly an arbitrary source distribution in the cavity. A series of examples of non-uniqueness of the inverse potential problem is constructed based on the same geometrical technique. (paper)

Photoacoustic Sounds from Meteors.

Energy Technology Data Exchange (ETDEWEB)

Spalding, Richard E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Tencer, John [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sweatt, William C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hogan, Roy E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Boslough, Mark B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Spurny, Pavel [Academy of Sciences of the Czech Republic (ASCR), Prague (Czech Republic)

2015-03-01

High-speed photometric observations of meteor fireballs have shown that they often produce high-amplitude light oscillations with frequency components in the kHz range, and in some cases exhibit strong millisecond flares. We built a light source with similar characteristics and illuminated various materials in the laboratory, generating audible sounds. Models suggest that light oscillations and pulses can radiatively heat dielectric materials, which in turn conductively heats the surrounding air on millisecond timescales. The sound waves can be heard if the illuminated material is sufficiently close to the observer’s ears. The mechanism described herein may explain many reports of meteors that appear to be audible while they are concurrently visible in the sky and too far away for sound to have propagated to the observer. This photoacoustic (PA) explanation provides an alternative to electrophonic (EP) sounds hypothesized to arise from electromagnetic coupling of plasma oscillation in the meteor wake to natural antennas in the vicinity of an observer.

Quantum cascade laser photoacoustic detection of nitrous oxide released from soils for biofuel production

Science.gov (United States)

Couto, F. M.; Sthel, M. S.; Castro, M. P. P.; da Silva, M. G.; Rocha, M. V.; Tavares, J. R.; Veiga, C. F. M.; Vargas, H.

2014-12-01

In order to investigate the generation of greenhouse gases in sugarcane ethanol production chain, a comparative study of N2O emission in artificially fertilized soils and soils free from fertilizers was carried out. Photoacoustic spectroscopy using quantum cascade laser with an emission ranging from 7.71 to 7.88 µm and differential photoacoustic cell were applied to detect nitrous oxide (N2O), an important greenhouse gas emitted from soils cultivated with sugar cane. Owing to calibrate the experimental setup, an initial N2O concentration was diluted with pure nitrogen and detection limit of 50 ppbv was achieved. The proposed methodology was selective and sensitive enough to detect N2O from no fertilized and artificially fertilized soils. The measured N2O concentration ranged from ppmv to ppbv.

Photoacoustic study of heated binary mixtures containing whey and skimmed-milk powders

NARCIS (Netherlands)

Doka, O.; Bicanic, D.; Frankhuizen, R.

1999-01-01

A novel methodology is proposed to determine the amount of whey powder in a binary mixture containing whey and skimmed-milk powders. This new approach is based on measurement of the amplitude of the photoacoustic (PA) signal obtained when the mixture is exposed to a controlled thermal treatment; the

Imaging and detection of early stage dental caries with an all-optical photoacoustic microscope

Science.gov (United States)

Hughes, D. A.; Sampathkumar, A.; Longbottom, C.; Kirk, K. J.

2015-01-01

Tooth decay, at its earliest stages, manifests itself as small, white, subsurface lesions in the enamel. Current methods for detection in the dental clinic are visual and tactile investigations, and bite-wing X-ray radiographs. These techniques suffer from poor sensitivity and specificity at the earliest (and reversible) stages of the disease due to the small size (tooth decay. Ex-vivo tooth samples exhibiting white spot lesions were scanned and were found to generate a larger (one order of magnitude) photoacoustic (PA) signal in the lesion regions compared to healthy enamel. The high contrast in the PA images potentially allows lesions to be imaged and measured at a much earlier stage than current clinical techniques allow. PA images were cross referenced with histology photographs to validate our experimental results. Our PA system provides a noncontact method for early detection of white-spot lesions with a high detection bandwidth that offers advantages over previously demonstrated ultrasound methods. The technique provides the sensing depth of an ultrasound system, but with the spatial resolution of an optical system.

Laser Remote Sensing and Photoacoustic Spectrometry Applied in Air Pollution Investigation

Czech Academy of Sciences Publication Activity Database

Zelinger, Zdeněk; Střižík, M.; Kubát, Pavel; Jaňour, Zbyněk; Berger, P.; Černý, A.; Engst, P.

2004-01-01

Roč. 42, - (2004), s. 403-412 ISSN 0143-8166 R&D Projects: GA AV ČR IAA3040101; GA ČR GA205/02/0898; GA MŠk OC 723.002 Institutional research plan: CEZ:AV0Z4040901 Keywords : DIAL * air pollution * laser photoacoustic spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.935, year: 2004

Direct estimate of cocoa powder content in cakes by colorimetry and photoacoustic spectroscopy

NARCIS (Netherlands)

Doka, O.; Bicanic, D.D.; Kulcsar, R.

2014-01-01

Cocoa is a very important ingredient in the food industry and largely consumed worldwide. In this investigation, colorimetry and photoacoustic spectroscopy were used to directly assess the content of cocoa powder in cakes; both methods provided satisfactory results. The calibration curve was

CO2-laser photoacoustic detection of gaseous n-pentylacetate

Czech Academy of Sciences Publication Activity Database

Herecová, L.; Hejzlar, T.; Pavlovský, J.; Míček, D.; Zelinger, Zdeněk; Kubát, Pavel; Janečková, B.; Nevrlý, Václav; Bitala, P.; Střižík, Michal; Klouda, E.; Civiš, Svatopluk

2009-01-01

Roč. 256, č. 1 (2009), s. 109-110 ISSN 0022-2852 R&D Projects: GA MŠk OC 111; GA MŠk LC06071; GA ČR GA202/06/0216; GA MŽP SPII1A0/45/07 Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z20760514 Keywords : n-pentylacetate * CO2 laser photoacoustic spectroscopy * FTIR spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.542, year: 2009

Multi-modality photoacoustic tomography, ultrasound, and light sheet microscopy for volumetric tumor margin detection

Science.gov (United States)

Sangha, Gurneet S.; Hu, Bihe; Bolus, Daniel; Wang, Mei; Skidmore, Shelby J.; Sholl, Andrew B.; Brown, J. Quincy; Goergen, Craig J.

2018-02-01

Current methods for breast tumor margin detection are invasive, time consuming, and typically result in a reoperative rate of over 25%. This marks a clear clinical need to develop improved tools to intraoperatively differentiate negative versus positive tumor margins. Here, we utilize photoacoustic tomography (PAT), ultrasound (US), and inverted Selective Plane Illumination Microscopy (iSPIM) to assess breast tumor margins in eight human breast biopsies. Our PAT/US system consists of a tunable Nd:YAG laser (NT 300, EKSPLA) coupled with a 40MHz central frequency US probe (Vevo2100, FUJIFILM Visual Sonics). This system allows for the delivery of 10Hz, 5ns pulses with fluence of 40mJ/cm2 to the tissue with PAT and US axial resolutions of 125μm and 40μm, respectively. For this study, we used a linear stepper motor to acquire volumetric PAT/US images of the breast biopsies using 1100nm light to identify bloodrich "tumor" regions and 1210nm light to identify lipid-rich "healthy" regions. iSPIM (Applied Scientific Instrumentation) is an advanced microscopy technique with lateral resolution of 1.5μm and axial resolution of 7μm. We used 488nm laser excitation and acridine orange as a general comprehensive histology stain. Our results show that PAT/US can be used to identify lipid-rich regions, dense areas of arterioles and arteries, and other internal structures such as ducts. iSPIM images correlate well with histopathology slides and can verify nuclear features, cell type and density, stromal features, and microcalcifications. Together, this multimodality approach has the potential to improve tumor margin detection with a high degree of sensitivity and specificity.

Rough surfaces of titanium and titanium alloys for implants and prostheses

International Nuclear Information System (INIS)

Conforto, E.; Aronsson, B.-O.; Salito, A.; Crestou, C.; Caillard, D.

2004-01-01

Titanium and titanium alloys for dental implants and hip prostheses were surface-treated and/or covered by metallic or ceramic rough layers after being submitted to sand blasting. The goal of these treatments is to improve the surface roughness and consequently the osteointegration, the fixation, and the stability of the implant. The microstructure of titanium and titanium alloys submitted to these treatments has been studied and correlated to their mechanical behavior. As-treated/covered and mechanically tested surfaces were characterized by scanning electron microscopy (SEM). Structural analyses performed by transmission electron microscopy (TEM), mainly in cross-section, reveal the degree of adherence and cohesion between the surface layer and the substrate (implant). We observed that, although the same convenient surface roughness was obtained with the two types of process, many characteristics as structural properties and mechanical behavior are very different

Linear-array photoacoustic imaging using minimum variance-based delay multiply and sum adaptive beamforming algorithm.

Science.gov (United States)

Mozaffarzadeh, Moein; Mahloojifar, Ali; Orooji, Mahdi; Kratkiewicz, Karl; Adabi, Saba; Nasiriavanaki, Mohammadreza

2018-02-01

In photoacoustic imaging, delay-and-sum (DAS) beamformer is a common beamforming algorithm having a simple implementation. However, it results in a poor resolution and high sidelobes. To address these challenges, a new algorithm namely delay-multiply-and-sum (DMAS) was introduced having lower sidelobes compared to DAS. To improve the resolution of DMAS, a beamformer is introduced using minimum variance (MV) adaptive beamforming combined with DMAS, so-called minimum variance-based DMAS (MVB-DMAS). It is shown that expanding the DMAS equation results in multiple terms representing a DAS algebra. It is proposed to use the MV adaptive beamformer instead of the existing DAS. MVB-DMAS is evaluated numerically and experimentally. In particular, at the depth of 45 mm MVB-DMAS results in about 31, 18, and 8 dB sidelobes reduction compared to DAS, MV, and DMAS, respectively. The quantitative results of the simulations show that MVB-DMAS leads to improvement in full-width-half-maximum about 96%, 94%, and 45% and signal-to-noise ratio about 89%, 15%, and 35% compared to DAS, DMAS, MV, respectively. In particular, at the depth of 33 mm of the experimental images, MVB-DMAS results in about 20 dB sidelobes reduction in comparison with other beamformers. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Experimental verification of the relativistic fine-structure term of the Klein-Gordon equation in pionic titanium atoms

International Nuclear Information System (INIS)

Delker, L.; Dugan, G.; Wu, C.S.; Lu, D.C.; Caffrey, A.J.; Cheng, Y.T.; Lee, Y.K.

1979-01-01

A newly designed, large-aperture and high-resolution bent-crystal spectrometer has been used to observe high-intensity sources of pionic x rays. The pionic x-ray source was a target of natural titanium which was placed adjacent to a copper pion-production target in the external beam of the Nevis synchrocyclotron. The energy difference between the 5g → 4f and 5f → 4d transitions in pionic titanium was measured to be 87.6 +- 1.8 eV. Comparison with the prediction of the Klein-Gordon equation is made

Rapid PMR determination of hydrogen in titanium hydride and dehydrogenated titanium powders

International Nuclear Information System (INIS)

Il'enko, V.S.; Demidenko, L.M.

1987-01-01

Proton magnetic resonance (PMR) enables determining hydrogen quantitatively in titanium hydride and dehydrogenated titanium powders without destroying the specimen and is also more informative than high-temperature extraction methods. PMR provides data on the electron-nuclear interactions and the activation energies for hydrogen diffusion while also providing conclusions on the forms and positives of the hydrogen in the lattice and the binding to the metal atoms. The authors have developed a rapid method for determining hydrogen in titanium hydride and dehydrogenated titanium powders which reduces the analysis time and improves the metrological characteristics. The authors use a YaMR-5535 spectrometer working at 40 MHz upgraded for use with hydrogen in solids. The authors used specimens of mass about 2 g ground to 0.1 mm powder

Inverse diffusion theory of photoacoustics

International Nuclear Information System (INIS)

Bal, Guillaume; Uhlmann, Gunther

2010-01-01

This paper analyzes the reconstruction of diffusion and absorption parameters in an elliptic equation from knowledge of internal data. In the application of photoacoustics, the internal data are the amount of thermal energy deposited by high frequency radiation propagating inside a domain of interest. These data are obtained by solving an inverse wave equation, which is well studied in the literature. We show that knowledge of two internal data based on well-chosen boundary conditions uniquely determines two constitutive parameters in diffusion and Schrödinger equations. Stability of the reconstruction is guaranteed under additional geometric constraints of strict convexity. No geometric constraints are necessary when 2n internal data for well-chosen boundary conditions are available, where n is spatial dimension. The set of well-chosen boundary conditions is characterized in terms of appropriate complex geometrical optics solutions

Dry coupling for whole-body small-animal photoacoustic computed tomography

OpenAIRE

Yeh, Chenghung; Li, Lei; Zhu, Liren; Xia, Jun; Li, Chiye; Chen, Wanyi; Garcia-Uribe, Alejandro; Maslov, Konstantin I.; Wang, Lihong V.

2017-01-01

We have enhanced photoacoustic computed tomography with dry acoustic coupling that eliminates water immersion anxiety and wrinkling of the animal and facilitates incorporating complementary modalities and procedures. The dry acoustic coupler is made of a tubular elastic membrane enclosed by a closed transparent water tank. The tubular membrane ensures water-free contact with the animal, and the closed water tank allows pressurization for animal stabilization. The dry coupler was tested using ...

Modeling the photoacoustic signal during the porous silicon formation

Science.gov (United States)

Ramirez-Gutierrez, C. F.; Castaño-Yepes, J. D.; Rodriguez-García, M. E.

2017-01-01

Within this work, the kinetics of the growing stage of porous silicon (PS) during the etching process was studied using the photoacoustic technique. A p-type Si with low resistivity was used as a substrate. An extension of the Rosencwaig and Gersho model is proposed in order to analyze the temporary changes that take place in the amplitude of the photoacoustic signal during the PS growth. The solution of the heat equation takes into account the modulated laser beam, the changes in the reflectance of the PS-backing heterostructure, the electrochemical reaction, and the Joule effect as thermal sources. The model includes the time-dependence of the sample thickness during the electrochemical etching of PS. The changes in the reflectance are identified as the laser reflections in the internal layers of the system. The reflectance is modeled by an additional sinusoidal-monochromatic light source and its modulated frequency is related to the velocity of the PS growth. The chemical reaction and the DC components of the heat sources are taken as an average value from the experimental data. The theoretical results are in agreement with the experimental data and hence provided a method to determine variables of the PS growth, such as the etching velocity and the thickness of the porous layer during the growing process.

Detection of melanoma cells suspended in mononuclear cells and blood plasma using photoacoustic generation

Science.gov (United States)

Spradling, Emily M.; Viator, John A.

2009-02-01

Melanoma is the deadliest form of skin cancer. Although the initial malignant cells are removed, it is impossible to determine whether or not the cancer has metastasized until a secondary tumor forms that is large enough to detect with conventional imaging. Photoacoustic detection of circulating melanoma cells in the bloodstream has shown promise for early detection of metastasis that may aid in treatment of this aggressive cancer. When blood is irradiated with energy from an Nd:YAG laser at 532 nm, photoacoustic signals are created and melanoma cells can be differentiated from the surrounding cells based on waveforms produced by an oscilloscope. Before this can be used as a diagnostic technique, however, we needed to investigate several parameters. Specifically, the current technique involves the in vitro separation of blood through centrifugation to isolate and test only the white blood cell layer. Using this method, we have detected a single cultured melanoma cell among a suspension of white blood cells. However, the process could be made simpler if the plasma layer were used for detection instead of the white blood cell layer. This layer is easier to obtain after blood separation, the optical difference between plasma and melanoma cells is more pronounced in this layer than in the white blood cell layer, and the possibility that any stray red blood cells could distort the results is eliminated. Using the photoacoustic apparatus, we detected no melanoma cells within the plasma of whole blood samples spiked with cultured melanoma cells.

Development of a photoacoustic sensor system for the measurement of atmospheric soot aerosols. Final report; Weiterentwicklung und Charakterisierung des photoakustischen Russsensors. Schlussbericht

Energy Technology Data Exchange (ETDEWEB)

Kraemer, L.; Bozoki, Z.; Niessner, R.

2001-03-01

The photoacoustic soot sensor (PASS) has been optimised and characterised in this work to enable online atmospheric black carbon (BC) monitoring. The mobility of the sensor suited for outdoor measurements was already achieved by a former setup. The major technical modifications include the use of a new diode laser with an emission wavelength of 680 nm and an output power of 250 mW and the redesign of the photoacoustic resonance cell and all optical components. Additionally, most of the electronic compounds have been exchanged, e.g. function generator, microphone preamplifier, lock-in amplifier. Due to these modifications, the increase in the sensitivity of the system led to a detection limit in the order of 100 ng per m{sup 3}. The selectivity has been enhanced by the use of a magnetic valve, which enables the independent determination of particular and gaseous compounds of the sample. Cross-sensitivities to water vapor or nitrogen dioxide can be excluded by differential measurement. Any influence by other airborne atmospheric particles like scattering salt aerosols, desert dust or humic acid is negligable under atmospheric conditions as has been shown in laboratory experiments. For the determination of low atmospheric BC concentrations, the time resolution of the entire setup by employing a software controlled, automated measurement cycle equals {proportional_to}5 minutes. The PASS was tested in various field campaigns at different measurement sites to determine atmospheric BC (Munich-Grosshadern, Kleiner Feldberg) and diesel soot (AIDA, FZ Karlsruhe; diesel engine, DaimlerChrysler). (orig.)

Observation of martensitic structure evolution in Cu-Al-Ni single crystals with shape memory effect under external load using photoacoustic microscopy

International Nuclear Information System (INIS)

Muratikov, K.L.; Glazov, A.L.; Nikolaev, V.I.; Pul'nev, S.A.

2006-01-01

Photoacoustic microscopy is applied to observe the surface structure of Cu-Al-Ni shape-memory single crystals in both the loaded and unloaded states. Visualizing the early stages of the loading-induced martensitic transformation in Cu-Al-Ni single crystals is demonstrated to be feasible. The photoacoustic images are distinguished to advantage from the corresponding optical images by a higher contrast between different phases of the Cu-Al-Ni shape-memory alloy [ru

The effect of ageing on YBa2Cu3O7-x obtained by the photoacoustic method

Directory of Open Access Journals (Sweden)

Nikolić Pantelija M.

2003-01-01

Full Text Available Thermal diffusivity and electric transport properties of fourteen years old superconducting YBa2Cu3O7-x pellets were obtained using the photoacoustic transmission technique and then compared with freshly made superconducting samples. The theoretical model for photoacoustic (PA detection configuration is given. The measured amplitude and phase PA signals, as a function of the modulation frequency, were numerically analyzed. The thermal diffusivity, the coefficient of the carrier diffusion, optical absorption coefficient and the excess carrier lifetime were calculated. The thermal diffusivity of freshly produced samples decreased, after ageing, from about 1.3·10-6 to about 6.1·10-7 m2/s.

Investigation of a dual modal method for bone pathologies using quantitative ultrasound and photoacoustics

Science.gov (United States)

Steinberg, Idan; Gannot, Israel; Eyal, Avishay

2015-03-01

Osteoporosis is a widespread disease that has a catastrophic impact on patient's lives and overwhelming related healthcare costs. In recent works, we have developed a multi-spectral, frequency domain photoacoustic method for the evaluation of bone pathologies. This method has great advantages over pure ultrasonic or optical methods as it provides both molecular information from the bone absorption spectrum and bone mechanical status from the characteristics of the ultrasound propagation. These characteristics include both the Speed of Sound (SOS) and Broadband Ultrasonic Attenuation (BUA). To test the method's quantitative predictions, we have constructed a combined ultrasound and photoacoustic setup. Here, we experimentally present a dual modality system, and compares between the methods on bone samples in-vitro. The differences between the two modalities are shown to provide valuable insight into the bone structure and functional status.

Double Minimum Variance Beamforming Method to Enhance Photoacoustic Imaging

OpenAIRE

Paridar, Roya; Mozaffarzadeh, Moein; Nasiriavanaki, Mohammadreza; Orooji, Mahdi

2018-01-01

One of the common algorithms used to reconstruct photoacoustic (PA) images is the non-adaptive Delay-and-Sum (DAS) beamformer. However, the quality of the reconstructed PA images obtained by DAS is not satisfying due to its high level of sidelobes and wide mainlobe. In contrast, adaptive beamformers, such as minimum variance (MV), result in an improved image compared to DAS. In this paper, a novel beamforming method, called Double MV (D-MV) is proposed to enhance the image quality compared to...

Chemical changes of titanium and titanium dioxide under electron bombardment

Directory of Open Access Journals (Sweden)

Romins Brasca

2007-09-01

Full Text Available The electron induced effect on the first stages of the titanium (Ti0 oxidation and titanium dioxide (Ti4+ chemical reduction processes has been studied by means of Auger electron spectroscopy. Using factor analysis we found that both processes are characterized by the appearance of an intermediate Ti oxidation state, Ti2O3 (Ti3+.

Osseointegration is improved by coating titanium implants with a nanostructured thin film with titanium carbide and titanium oxides clustered around graphitic carbon

International Nuclear Information System (INIS)

Veronesi, Francesca; Giavaresi, Gianluca; Fini, Milena; Longo, Giovanni; Ioannidu, Caterina Alexandra; Scotto d'Abusco, Anna; Superti, Fabiana; Panzini, Gianluca; Misiano, Carlo; Palattella, Alberto; Selleri, Paolo; Di Girolamo, Nicola; Garbarino, Viola; Politi, Laura; Scandurra, Roberto

2017-01-01

Titanium implants coated with a 500 nm nanostructured layer, deposited by the Ion Plating Plasma Assisted (IPPA) technology, composed of 60% graphitic carbon, 25% titanium oxides and 15% titanium carbide were implanted into rabbit femurs whilst into the controlateral femurs uncoated titanium implants were inserted as control. At four time points the animals were injected with calcein green, xylenol orange, oxytetracycline and alizarin. After 2, 4 and 8 weeks femurs were removed and processed for histology and static and dynamic histomorphometry for undecalcified bone processing into methylmethacrylate, sectioned, thinned, polished and stained with Toluidine blue and Fast green. The overall bone-implant contacts rate (percentage of bone-implant contacts/weeks) of the TiC coated implant was 1.6 fold than that of the uncoated titanium implant. The histomorphometric analyses confirmed the histological evaluations. More precisely, higher Mineral Apposition Rate (MAR, μm/day) (p < 0.005) and Bone Formation Rate (BFR, μm 2 /μm/day) (p < 0.0005) as well as Bone Implant Contact (Bic) and Bone Ingrowth values (p < 0.0005) were observed for the TiC coated implants compared to uncoated implants. In conclusion the hard nanostructured TiC layer protects the bulk titanium implant against the harsh conditions of biological tissues and in the same time, stimulating adhesion, proliferation and activity of osteoblasts, induces a better bone-implant contacts of the implant compared to the uncoated titanium implant. - Highlights: • Ti implants were coated with a nanostructured film composed of C gr , TiC and TiO x . • The TiC layer stimulates adhesion, proliferation and activity of osteoblasts. • Uncoated and TiC coated titanium implants were implanted in rabbit femurs. • Bone-implant contacts of TiC coated implants were higher than that of uncoated. • Mineral Apposition Rate of TiC coated implants were higher than that of uncoated.

Assessment of the added value of the Twente Photoacoustic Mammoscope in breast cancer diagnosis

NARCIS (Netherlands)

Hilgerink, Marjolein P.; Hummel, J. Marjan; Manohar, Srirang; Vaartjes, Simon R.; IJzerman, Maarten Joost

2011-01-01

Purpose: Photoacoustic (PA) imaging is a recently developed breast cancer imaging technique. In order to enhance successful clinical implementation, we quantified the potential clinical value of different scenarios incorporating PA imaging by means of multi-criteria analysis. From this analysis, the

Titanium fasteners. [for aircraft industry

Science.gov (United States)

Phillips, J. L.

1972-01-01

Titanium fasteners are used in large quantities throughout the aircraft industry. Most of this usage is in aluminum structure; where titanium structure exists, titanium fasteners are logically used as well. Titanium fasteners offer potential weight savings to the designer at a cost of approximately $30 per pound of weight saved. Proper and least cost usage must take into consideration type of fastener per application, galvanic couples and installation characteristics of protective coatings, cosmetic appearance, paint adhesion, installation forces and methods available and fatigue performance required.

Titanium for salt water service

International Nuclear Information System (INIS)

Gadiyar, H.S.; Shibad, P.R.

1980-01-01

Titanium has potential as major material of construction in desalination plants, in condensers and heat exchangers, in view of its excellent corrosion resistance to salt water upto at least 120deg C. The advantages of titanium in such applications are brought out. The various specific problems such as pitting, crevice and galvanic corrosion and the preventive methods, for adopting titanium have been discussed. The hydriding problem can be overcome by suitably controlling the operating parameters such as temperature and surface preparation. A case has been made to prove the economic viability of titanium in comparison to Al-brass and Cu-Ni alloy. The future of titanium seems to be very promising in view of the negligible tube failures and outages. (auth.)

[The surface roughness analysis of the titanium casting founding by a new titanium casting investment material].

Science.gov (United States)

Liang, Qin-ye; Wu, Xia-yi; Lin, Xue-feng

2012-04-01

To investigate the surface roughness property of the titanium castings cast in a new investment for titanium casting. Six wax patterns (20 mm × 20 mm × 0.5 mm) were invested using two investments: three in a new titanium investment material and three in the control material (Rematitan Plus). Six titanium specimens were obtained by conventional casting. After casting, surface roughness of the specimens were evaluated with a surface profilometer. The surface roughness of the specimens cast in new titanium investment material was (1.72 ± 0.08) µm, which was much smaller than that from Rematitan Plus [(1.91 ± 0.15) µm, P cast using these two investment materials are both smooth enough to fulfill the demand of the titanium precision-casting for prosthodontic clinical use.

Laser induced photoacoustic spectroscopy applied to a study on coagulation processes of Tc(IV) colloid

International Nuclear Information System (INIS)

Sekine, T.; Kino, S.; Kino, Y.; Kudo, H.

2001-01-01

Quantitative determination of size and concentration of colloid particles in aqueous solutions was performed by laser induced photoacoustic spectroscopy (LPAS), and this technique was applied to a study on coagulation processes of Tc(IV) colloids. The intensity of photoacoustic signals from colloid particles (polystyrene, gold sols) was successfully calculated as a product of the number of particles and the absorption cross section per particle based on the Mie's light scattering theory. With this technique, the coagulation of Tc(IV) colloids prepared by the reduction of TcO 4 with Sn(II) was observed. The observed growth rate of colloid particles was successfully analyzed by a newly developed collision model, in which both the distribution of the kinetic energy of particles and the potential barrier between the two particles played significant roles. (author)

Characterization of Maize Grains with Different Pigmentation Investigated by Photoacoustic Spectroscopy

Science.gov (United States)

Rico Molina, R.; Hernández Aguilar, C.; Dominguez Pacheco, A.; Cruz-Orea, A.; López Bonilla, J. L.

2014-10-01

A knowledge of grains' optical parameters is of great relevance in the maize grain technology practice. Such parameters provide information about its absorption and reflectance, which in turn is related to its color. In the dough and tortilla industries, it is important to characterize this attribute of the corn kernel, as it is one of the attributes that directly affects the quality of the food product. Thus, it is important to have techniques that contribute to the characterization of this raw material. It is traditionally characterized by conventional methods, which usually destroy the grain and involve a laborious preparation of material plus they are expensive. The objective of this study was to determine the optical absorption coefficient for maize grains ( Zea mays L.) with different pigmentations by means of photoacoustic spectroscopy (PAS). The genotype A had bluish coloration and genotype B had yellowish coloration. In addition, the photoacoustic signal obtained by two methods was analyzed mathematically: the standard deviation and the first derivative; both results were compared (Fig. 1). In combination with mathematical analysis, PAS may be considered as a potential diagnostic tool for the characterization of the grains. [Figure not available: see fulltext.

CO2 laser photoacoustic detection of ammonia emitted by ceramic industries.

Science.gov (United States)

Sthel, M S; Schramm, D U; Lima, G R; Carneiro, L; Faria, R T; Castro, M P P; Alexandre, J; Toledo, R; Silva, M G; Vargas, H

2011-01-01

A homemade photoacoustic spectrometer has been constructed for monitoring gas emission from several sources. Numerous air pollutant gases are emitted exhaust of industries, vehicles and power plants. The photoacoustic technique is extremely sensitive and selective in detecting various gases. This work focuses on the gas emitted by the ceramic industry in northern Rio de Janeiro State in Brazil, the ceramic industry plays a remarkable role in the economy activity of this region, in recent years, this region developed into a significant red ceramic complex. The potential impact on the atmospheric environment of the region due to gaseous pollutant emissions from these anthropogenic sources needs to be evaluated. In this work we identified NH3 present in the samples collected in the kiln of a ceramic plant, in the concentration range of 33-52 ppmV. The ammonia gas present in our collected samples might come from the excess nitrogen in the manure soil from where the ceramic material was extracted. This soil was used for the sugarcane culture which is another important economic activity of this region. Copyright © 2010 Elsevier B.V. All rights reserved.

X-ray diffraction, Raman, and photoacoustic studies of ZnTe nanocrystals

Science.gov (United States)

Ersching, K.; Campos, C. E. M.; de Lima, J. C.; Grandi, T. A.; Souza, S. M.; da Silva, D. L.; Pizani, P. S.

2009-06-01

Nanocrystalline ZnTe was prepared by mechanical alloying. X-ray diffraction (XRD), energy dispersive spectroscopy, Raman spectroscopy, and photoacoustic absorption spectroscopy techniques were used to study the structural, chemical, optical, and thermal properties of the as-milled powder. An annealing of the mechanical alloyed sample at 590 °C for 6 h was done to investigate the optical properties in a defect-free sample (close to bulk form). The main crystalline phase formed was the zinc-blende ZnTe, but residual trigonal tellurium and hexagonal ZnO phases were also observed for both as-milled and annealed samples. The structural parameters, phase fractions, average crystallite sizes, and microstrains of all crystalline phases were obtained from Rietveld analyses of the X-ray patterns. Raman results corroborate the XRD results, showing the longitudinal optical phonons of ZnTe (even at third order) and those modes of trigonal Te. Nonradiative surface recombination and thermal bending heat transfer mechanisms were proposed from photoacoustic analysis. An increase in effective thermal diffusivity coefficient was observed after annealing and the carrier diffusion coefficient, the surface recombination velocity, and the recombination time parameters remained the same.

Numerical assessment of bone remodeling around conventionally and early loaded titanium and titanium-zirconium alloy dental implants.

Science.gov (United States)

Akça, Kıvanç; Eser, Atılım; Çavuşoğlu, Yeliz; Sağırkaya, Elçin; Çehreli, Murat Cavit

2015-05-01

The aim of this study was to investigate conventionally and early loaded titanium and titanium-zirconium alloy implants by three-dimensional finite element stress analysis. Three-dimensional model of a dental implant was created and a thread area was established as a region of interest in trabecular bone to study a localized part of the global model with a refined mesh. The peri-implant tissues around conventionally loaded (model 1) and early loaded (model 2) implants were implemented and were used to explore principal stresses, displacement values, and equivalent strains in the peri-implant region of titanium and titanium-zirconium implants under static load of 300 N with or without 30° inclination applied on top of the abutment surface. Under axial loading, principal stresses in both models were comparable for both implants and models. Under oblique loading, principal stresses around titanium-zirconium implants were slightly higher in both models. Comparable stress magnitudes were observed in both models. The displacement values and equivalent strain amplitudes around both implants and models were similar. Peri-implant bone around titanium and titanium-zirconium implants experiences similar stress magnitudes coupled with intraosseous implant displacement values under conventional loading and early loading simulations. Titanium-zirconium implants have biomechanical outcome comparable to conventional titanium implants under conventional loading and early loading.

Efficient high-resolution X-ray emission spectrometry using synchrotron radiation

International Nuclear Information System (INIS)

Unterumsberger, Rainer

2015-01-01

The aim of the present work is to get access to high-resolution X-Ray Emission Spectrometry (XES) at nanoscaled materials, consisting of light elements and transition metals, by the increase of the sensitivity of a Wavelength-Dispersive Spectrometer (WDS) in the soft X-Ray range. The increase of the sensitivity was achieved by a refocusing of the incident radiation. With the increased sensitivity of the WDS, it was possible to determine the chemical species of different, nominal 100 nm thin titanium oxides. The combination of the refocusing optic and calibrated spectrometer enabled the detection and deconvolution of the L-fluorescence radiation of these nanoscaled titanium oxides. Due to the calibration of the spectrometer, a reliable determination of the transition probabilities of the titanium La- and Ll-fluorescence lines as a function of the chemical state is possible. To the best of my knowledge, the determination of the transition probabilities as a function of the chemical state in the soft X-Ray range has not been investigated yet. The quality of the refocusing was characterized using different diagnostic tools. Vertical full width at half maximum (FWHM) values of the focused beam between 10 μm to 20 μm and horizontal FWHM values between 12 μm and 25 μm could be achieved over an energy range of 180 eV to 1310 eV. Using calibrated photodiodes, it was possible to determine the absolute transmission of the used single bounce monocapillary as well as to monitor the absolute photon flux. By means of the refocusing, it was possible to increase the photon flux by a factor of 4.9 experimentally. The increase of the photon flux enables the analysis of nanoscaled materials with the used spectrometer. This could be shown based on the determination of the lower limit of detection of boron Ka and titanium La. In both cases, the lower limit of detection of 0.4 nm equivalent layer thickness was achieved (about 1.10 -7 g/cm 2 to 2.10 -7 g/cm 2 or 3.10 15 atoms/cm 2 to

Photoacoustic microbeam-oscillator with tunable resonance direction and amplitude

Science.gov (United States)

Wu, Qingjun; Li, Fanghao; Wang, Bo; Yi, Futing; Jiang, J. Z.; Zhang, Dongxian

2018-01-01

We successfully design one photoacoustic microbeam-oscillator actuated by nanosecond laser, which exhibits tunable resonance direction and amplitude. The mechanism of laser induced oscillation is systematically analyzed. Both simulation and experimental results reveal that the laser induced acoustic wave propagates in a multi-reflected mode, resulting in resonance in the oscillator. This newly-fabricated micrometer-sized beam-oscillator has an excellent actuation function, i.e., by tuning the laser frequency, the direction and amplitude of actuation can be efficiently altered, which will have potential industrial applications.

Picosecond absorption relaxation measured with nanosecond laser photoacoustics.

Science.gov (United States)

Danielli, Amos; Favazza, Christopher P; Maslov, Konstantin; Wang, Lihong V

2010-10-18

Picosecond absorption relaxation-central to many disciplines-is typically measured by ultrafast (femtosecond or picosecond) pump-probe techniques, which however are restricted to optically thin and weakly scattering materials or require artificial sample preparation. Here, we developed a reflection-mode relaxation photoacoustic microscope based on a nanosecond laser and measured picosecond absorption relaxation times. The relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, were measured at 576 nm. The added advantages in dispersion susceptibility, laser-wavelength availability, reflection sensing, and expense foster the study of natural-including strongly scattering and nonfluorescent-materials.

Photoacoustic and transmission studies of SiC polytypes

Directory of Open Access Journals (Sweden)

A.C. de Oliveira

2003-01-01

Full Text Available The optical bandgap energies (OBGE of 3C, 15R, 6H and 4H-SiC have been investigate experimentally by transmission and photoacoustic spectroscopies. The measurements were performed on 470 mum thick wafers. The OBGE obtained from both spectroscopies for different polytypes show very good agreement. In order to have a better understanding of these materials calculations of eletronic band structure were performed by the full-potential linearized augmented plane wave (FPLAPW method. For the OBGE the results are compared to the measurements agreeing closely over the energies of those polytypes.

A sulfur hexafluoride sensor using quantum cascade and CO2 laser-based photoacoustic spectroscopy.

Science.gov (United States)

Rocha, Mila; Sthel, Marcelo; Lima, Guilherme; da Silva, Marcelo; Schramm, Delson; Miklós, András; Vargas, Helion

2010-01-01

The increase in greenhouse gas emissions is a serious environmental problem and has stimulated the scientific community to pay attention to the need for detection and monitoring of gases released into the atmosphere. In this regard, the development of sensitive and selective gas sensors has been the subject of several research programs. An important greenhouse gas is sulphur hexafluoride, an almost non-reactive gas widely employed in industrial processes worldwide. Indeed it is estimated that it has a radiative forcing of 0.52 W/m(2). This work compares two photoacoustic spectrometers, one coupled to a CO(2) laser and another one coupled to a Quantum Cascade (QC) laser, for the detection of SF(6). The laser photoacoustic spectrometers described in this work have been developed for gas detection at small concentrations. Detection limits of 20 ppbv for CO(2) laser and 50 ppbv for quantum cascade laser were obtained.

Thermal diffusivity and electron transport properties of NTC samples obtained by the photoacoustic method

International Nuclear Information System (INIS)

Savic, S.M.; Aleksic, O.S.; Nikolic, M.V.; Lukovic, D.T.; Pejovic, V.Z.; Nikolic, P.M.

2006-01-01

Thermal diffusivity and electron transport parameters of sintered NTC samples were determined by the photoacoustic (PA) technique. Powder mixtures composed of MnO, NiO, CoO and Fe 2 O 3 were milled to nanometer particle size. NTC discs were dry powder pressed and sintered at different temperatures in the range from 900 deg. C to 1300 deg. C for 30 min. A second group of NTC discs was sintered at 1200 deg. C with the sintering time varying from 30 min to 360 min. These NTC samples were polished and exposed to a chopped laser beam in order to plot a response in the acoustic range. The thermal diffusivity of sintered NTC layers based on a metal oxide powder mixture was measured at room temperature by the photoacoustic technique. An increase of thermal diffusivity with the sintering temperature and time of sintering was observed

Thermal diffusivity and electron transport properties of NTC samples obtained by the photoacoustic method

Energy Technology Data Exchange (ETDEWEB)

Savic, S.M. [Institute of Technical Sciences of SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Aleksic, O.S. [Center for Multidisciplinary Studies of the University of Belgrade, Kneza Viseslava 1, 11000 Belgrade (Serbia); Nikolic, M.V. [Center for Multidisciplinary Studies of the University of Belgrade, Kneza Viseslava 1, 11000 Belgrade (Serbia); Lukovic, D.T. [Institute of Technical Sciences of SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Pejovic, V.Z. [Center for Multidisciplinary Studies of the University of Belgrade, Kneza Viseslava 1, 11000 Belgrade (Serbia); Nikolic, P.M. [Institute of Technical Sciences of SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia)]. E-mail: nikolic@sanu.ac.yu

2006-07-15

Thermal diffusivity and electron transport parameters of sintered NTC samples were determined by the photoacoustic (PA) technique. Powder mixtures composed of MnO, NiO, CoO and Fe{sub 2}O{sub 3} were milled to nanometer particle size. NTC discs were dry powder pressed and sintered at different temperatures in the range from 900 deg. C to 1300 deg. C for 30 min. A second group of NTC discs was sintered at 1200 deg. C with the sintering time varying from 30 min to 360 min. These NTC samples were polished and exposed to a chopped laser beam in order to plot a response in the acoustic range. The thermal diffusivity of sintered NTC layers based on a metal oxide powder mixture was measured at room temperature by the photoacoustic technique. An increase of thermal diffusivity with the sintering temperature and time of sintering was observed.

Anodic growth of titanium dioxide nanostructures

DEFF Research Database (Denmark)

2010-01-01

Disclosed is a method of producing nanostructures of titanium dioxide (TiO 2 ) by anodisation of titanium (Ti) in an electrochemical cell, comprising the steps of: immersing a non-conducting substrate coated with a layer of titanium, defined as the anode, in an electrolyte solution...... an electrical contact to the layer of titanium on the anode, where the electrical contact is made in the electrolyte solution...

Opticofiber photoacoustic spectrometry in single-ray two-cell grouping for analytical determination of actinoids in solutions of reprocessing

International Nuclear Information System (INIS)

Yin'kov, S.I.; Myasoedov, B.F.; Kikhara, T.; Fuine, S.; Maeda, M.

1996-01-01

Single-ray two-cell version of photoacoustic spectrometry with laser excitation (Laser Induced Photoacoustic Spectroscopy, LIPAS) for remote determination of actinoids ions in solutions is developed. The spectrometer characteristics were specified by means of uranium-containing solutions, including a great number of non-radioactive ions, the absorption bonds where of imitated the absorption of Pu(3) and Pu(4). The possibilities of the LIPAS technique were studied by analysis of ions, imitating plutonium within the range of 650-724 nm on synthetic solutions with high uranium(6) content and a great number of nonradioactive isotopes of fragmentation-type elements. 8 refs., 9 figs., 1 tab

Testing fruit quality by photoacoustic spectroscopy assay

International Nuclear Information System (INIS)

Popa, C; Dumitras, D C; Patachia, M; Banita, S

2014-01-01

This study was conducted with the aim of testing the hypothesis that raspberry and strawberry fruits from nonorganic farming release more ethylene gas compounds compared to organic ones. At the same time, the experiments focused on evaluation of the potential and capabilities of the laser photoacoustic spectroscopy (LPAS) method in the assessment of fruit quality related to the effects of nitrogen. Ethylene gas can be harmful and carcinogenic, because it can accelerate the natural ripening process of physiologically mature fruits and makes the fruits more consistent in size. With the advantages of LPAS, we demonstrate that the concentration of ethylene from nonorganic raspberry and strawberry fruits is greater than from organic ones. (paper)

Photoacoustic-Based-Close-Loop Temperature Control for Nanoparticle Hyperthermia.

Science.gov (United States)

Xiaohua, Feng; Fei, Gao; Yuanjin, Zheng

2015-07-01

Hyperthermia therapy requires tight temperature control to achieve selective killing of cancerous tissue with minimal damage on surrounding healthy tissues. To this end, accurate temperature monitoring and subsequent heating control are critical. However, an economic, portable, and real-time temperature control solution is currently lacking. To bridge this gap, we present a novel portable close-loop system for hyperthermia temperature control, in which photoacoustic technique is proposed for noninvasive real-time temperature measurement. Exploiting the high sensitivity of photoacoustics, the temperature is monitored with an accuracy of around 0.18 °C and then fed back to a controller implemented on field programmable gate array (FPGA) for temperature control. Dubbed as portable hyperthermia feedback controller (pHFC), it stabilizes the temperature at preset values by regulating the hyperthermia power with a proportional-integral-derivative (PID) algorithm; and to facilitate digital implementation, the pHFC further converts the PID output into switching values (0 and 1) with the pulse width modulation (PWM) algorithm. Proof-of-concept hyperthermia experiments demonstrate that the pHFC system is able to bring the temperature from baseline to predetermined value with an accuracy of 0.3° and a negligible temperature overshoot. The pHFC can potentially be translated to clinical applications with customized hyperthermia system design. This paper can facilitate future efforts in seamless integration of close-loop temperature control solution and various clinical hyperthermia systems.

Time reversal method with stabilizing boundary conditions for Photoacoustic tomography

International Nuclear Information System (INIS)

Chervova, Olga; Oksanen, Lauri

2016-01-01

We study an inverse initial source problem that models photoacoustic tomography measurements with array detectors, and introduce a method that can be viewed as a modification of the so called back and forth nudging method. We show that the method converges at an exponential rate under a natural visibility condition, with data given only on a part of the boundary of the domain of wave propagation. In this paper we consider the case of noiseless measurements. (paper)

Diffuse Urticarial Reaction Associated with Titanium Dioxide Following Laser Tattoo Removal Treatments.

Science.gov (United States)

Willardson, Hal Bret; Kobayashi, Todd T; Arnold, Jason G; Hivnor, Chad M; Bowen, Casey D

2017-03-01

Local and generalized allergic reactions following laser tattoo removal have been documented, but are rare. To our knowledge, this is the fourth documented case of widespread urticarial eruptions following laser tattoo removal treatment. Unlike previously documented cases, this patient's reaction was found to be associated with titanium dioxide within the tattoo and her symptoms were recalcitrant to medical therapy. A 46-year-old female experienced diffuse urticarial plaques, erythema, and pruritis following multiple laser tattoo removal treatments with an Nd:YAG laser. The systemic allergic reaction was recalcitrant to increasing doses of antihistamines and corticosteroids. The tattoo was finally surgically excised. The excised tissue was analyzed by scanning electron microscopy and energy-dispersive X-ray analysis and contained high levels of titanium dioxide. Two weeks following the excision, and without the use of medical therapy, the patient had complete resolution of her generalized urticaria. Ours is the first documented case of a diffuse urticarial reaction following laser tattoo removal treatments that shows a strong association to titanium dioxide within the tattoo pigment. Herein, we describe a novel surgical approach to treat recalcitrant generalized allergic reaction to tattoo pigment.

Osseointegration is improved by coating titanium implants with a nanostructured thin film with titanium carbide and titanium oxides clustered around graphitic carbon

Energy Technology Data Exchange (ETDEWEB)

Veronesi, Francesca [Laboratory of Preclinical and Surgical Studies, Rizzoli Orthopedic Institute, Via Di Barbiano 1/10, Bologna 40136 (Italy); Giavaresi, Gianluca; Fini, Milena [Laboratory of Preclinical and Surgical Studies, Rizzoli Orthopedic Institute, Via Di Barbiano 1/10, Bologna 40136 (Italy); Laboratory of Biocompatibility, Innovative Technologies and Advanced Therapies, Department Rizzoli RIT, Via Di Barbiano 1/10, Bologna 40136 (Italy); Longo, Giovanni [CNR Istituto di Struttura della Materia, CNR, Via del Fosso del Cavaliere 100, 00133 Roma (Italy); Ioannidu, Caterina Alexandra; Scotto d' Abusco, Anna [Dept. of Biochemical Sciences, Sapienza University of Roma, Ple A. Moro 5, 00185 Roma (Italy); Superti, Fabiana; Panzini, Gianluca [Dept. of Technologies and Health, Istituto Superiore di Sanità, Viale Regina Elena, 299 Roma (Italy); Misiano, Carlo [Romana Film Sottili, Anzio, Roma (Italy); Palattella, Alberto [Dept. of Clinical Sciences and Translational Medicine, Tor Vergata University, Via Montpellier 1, 00133 Roma (Italy); Selleri, Paolo; Di Girolamo, Nicola [Exotic Animals Clinic, Via S. Giovannini 53, 00137 Roma (Italy); Garbarino, Viola [Dept. of Radiology, S.M. Goretti Hospital, Via G. Reni 2, 04100 Latina (Italy); Politi, Laura [Dept. of Biochemical Sciences, Sapienza University of Roma, Ple A. Moro 5, 00185 Roma (Italy); Scandurra, Roberto, E-mail: roberto.scandurra@uniroma1.it [Dept. of Biochemical Sciences, Sapienza University of Roma, Ple A. Moro 5, 00185 Roma (Italy)

2017-01-01

Titanium implants coated with a 500 nm nanostructured layer, deposited by the Ion Plating Plasma Assisted (IPPA) technology, composed of 60% graphitic carbon, 25% titanium oxides and 15% titanium carbide were implanted into rabbit femurs whilst into the controlateral femurs uncoated titanium implants were inserted as control. At four time points the animals were injected with calcein green, xylenol orange, oxytetracycline and alizarin. After 2, 4 and 8 weeks femurs were removed and processed for histology and static and dynamic histomorphometry for undecalcified bone processing into methylmethacrylate, sectioned, thinned, polished and stained with Toluidine blue and Fast green. The overall bone-implant contacts rate (percentage of bone-implant contacts/weeks) of the TiC coated implant was 1.6 fold than that of the uncoated titanium implant. The histomorphometric analyses confirmed the histological evaluations. More precisely, higher Mineral Apposition Rate (MAR, μm/day) (p < 0.005) and Bone Formation Rate (BFR, μm{sup 2}/μm/day) (p < 0.0005) as well as Bone Implant Contact (Bic) and Bone Ingrowth values (p < 0.0005) were observed for the TiC coated implants compared to uncoated implants. In conclusion the hard nanostructured TiC layer protects the bulk titanium implant against the harsh conditions of biological tissues and in the same time, stimulating adhesion, proliferation and activity of osteoblasts, induces a better bone-implant contacts of the implant compared to the uncoated titanium implant. - Highlights: • Ti implants were coated with a nanostructured film composed of C{sub gr}, TiC and TiO{sub x}. • The TiC layer stimulates adhesion, proliferation and activity of osteoblasts. • Uncoated and TiC coated titanium implants were implanted in rabbit femurs. • Bone-implant contacts of TiC coated implants were higher than that of uncoated. • Mineral Apposition Rate of TiC coated implants were higher than that of uncoated.

The vapour phase deposition of boron on titanium by the reaction between gaseous boron trichloride and titanium metal. Final report

International Nuclear Information System (INIS)

Cameron, D.J.; Shelton, R.A.J.

1965-03-01

The reaction, between boron trichloride vapour and titanium has been investigated in the temperature range 200 - 1350 deg. C. It has been found that an initial reaction leads to the formation of titanium tetrachloride and the deposition of boron on titanium, but that except for reactions between 900 and 1000 deg. C, the system is complicated by the formation of lower titanium chlorides due to secondary reactions between the titanium and titanium tetrachloride

Synthesis and structural characterisation using Rietveld and pair distribution function analysis of layered mixed titanium-zirconium phosphates

International Nuclear Information System (INIS)

Burnell, Victoria A.; Readman, Jennifer E.; Tang, Chiu C.; Parker, Julia E.; Thompson, Stephen P.; Hriljac, Joseph A.

2010-01-01

Crystalline metal (IV) phosphates with variable zirconium-to-titanium molar ratios of general formula (Ti 1-x Zr x )(HPO 4 ) 2 .H 2 O have been prepared by precipitation of soluble salts of the metals with phosphoric acid and heating the amorphous solids in 12 M H 3 PO 4 in an autoclave. The new materials are structurally characterised by Rietveld analysis of synchrotron X-ray powder diffraction data and pair distribution function (PDF) analysis of high energy synchrotron X-ray total scattering data. A broad range of zirconium-titanium phosphate solid solutions were formed showing isomorphous substitution of titanium by zirconium in the α-titanium phosphate lattice and vice versa for titanium substitution into the α-zirconium phosphate lattice. In both cases the solubility is partial with the coexistence of two substituted phases observed in samples with nominal compositions between the solubility limits. - Graphical abstract: Layered phosphates of general formula (Ti 1-x Zr x )(HPO 4 ).H 2 O have been prepared by the hydrothermal treatment of amorphous gels in phosphoric acid and characterised by Rietveld analysis of high resolution synchrotron X-ray powder diffraction data and pair distribution function analysis of high energy synchrotron X-ray total scattering data.

Light and ultrasound activated microbubbles around gold nanorods for photoacoustic microsurgery

Science.gov (United States)

Cavigli, Lucia; Centi, Sonia; Lai, Sarah; Borri, Claudia; Micheletti, Filippo; Tortoli, Paolo; Panettieri, Ilaria; Streit, Ingolf; Rossi, Francesca; Ratto, Fulvio; Pini, Roberto

2017-07-01

Photoacoustic imaging and microsurgery have recently attracted attention for applications in oncology. Here, we present a versatile set-up to trigger vapor microbubbles around plasmonic nanoparticles by a combined light-ultrasound excitation. This system enables the detection and parametrization of bubbles as a function of several variables, such us optical fluence, ultrasound intensity, nanoparticles concentration, thus providing useful directions to the development of new strategies for treatments based on optical cavitation.

The extent of unwanted infrared photoacoustic signals from polymer sampling tubings exposed to ultraviolet radiation

NARCIS (Netherlands)

Bicanic, D.; Solyom, A.; Angeli, G.; Wegh, H.; Postumus, M.; Jalink, H.

1995-01-01

The extent of unwanted photoacoustic (PA) signals due to volatiles released from various polymer tubing materials [transparent, red and black polyethylene (PE), polymer of tetrafluorethylene (PTFE) and copolymer of tetrafluorethylene and hexafluorethylene (FEP)] when exposed to 245 nm radiation was

Assaying total carotenoids in flours of corn and sweet potato flours by laser photoacoustic spectroscopy

NARCIS (Netherlands)

Luterotti, S.; Bicanic, D.D.; Kijak, K.; Grbesa, D.; Martinez, E.; Spruijt, R.B.

2011-01-01

This study describes the application of the laser photoacoustic spectroscopy (PAS) for quantification of total carotenoids (TC) in corn flours and sweetpotato flours. Overall, thirty-three different corn flours and nine sweetpotato flours were investigated. All PAS measurements were performed at

Studies on selected polymeric materials using the photoacoustic spectroscopic technique

International Nuclear Information System (INIS)

Singh, Hukum

2011-01-01

Polymethylmethacrylate—graft—polybisphenol—A-carbonate (PMMA-G-PC) with 50% grafting is synthesized. The graft co-polymerization of methylmethacrylate (0.036 mol · lit −1 ) onto polybisphenol—A-carbonate (0.5 g) in the presence of a redox couple formed from potassium persulphate (40 mol · lit −1 ) and thio-urea (30 mmol · lit −1 ) in aqueous nitric acid (0.18 M, 100 ml) in air at (45±2) °C for 3.0 h. Condensation of (PMMA-G-PC) with N- [p-(carboxyl phenyl amino acetic acid)] hydrazide (PCPH) affords polybisphenol-A-carbonate-graft-polymethylmethacrylate hydrazide (PCGH). The photoacoustic (PA) spectra of (PCGH) are recorded in a wavelength range from 200 nm to 800 nm at a modulation frequency of 22 Hz, and compared with those of pure polybisphenol-A-carbonate (PC), (PMMA-G-PC) and (PCPH). In the present work, a non-destructive and non-contact analytical method, namely the photoacoustic technique, is successfully implemented for optical and thermal characterization of selected polymeric materials. The indigenous PA spectrometer used in the present study consists of a 300-W xenon arc lamp, a lock-in amplifier, a chopper, a (1/8)-m monochromator controlled by computer and a home-made PA cell. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Detection of circulating breast cancer cells using photoacoustic flow cytometry

Science.gov (United States)

Bhattacharyya, Kiran

According to the American Cancer Society, more than 200,000 new cases of breast cancer are expected to be diagnosed this year. Moreover, about 40,000 women died from breast cancer last year alone. As breast cancer progresses in an individual, it can transform from a localized state to a metastatic one with multiple tumors distributed through the body, not necessarily contained within the breast. Metastasis is the spread of cancer through the body by circulating tumor cells (CTCs) which can be found in the blood and lymph of the diagnosed patient. Diagnosis of a metastatic state by the discovery of a secondary tumor can often come too late and hence, significantly reduce the patient's chance of survival. There is a current need for a CTC detection method which would diagnose metastasis before the secondary tumor occurs or reaches a size resolvable by current imaging systems. Since earlier detection would improve prognosis, this study proposes a method of labeling of breast cancer cells for detection with a photoacoustic flow cytometry system as a model for CTC detection in human blood. Gold nanoparticles and fluorescent polystyrene nanoparticles are proposed as contrast agents for T47D, the breast cancer cell line of choice. The labeling, photoacoustic detection limit, and sensitivity are first characterized and then applied to a study to show detection from human blood.

Application of micro beam PIXE to detection of titanium ion release from dental and orthopaedic implants

International Nuclear Information System (INIS)

Ektessabi, A.M.; Otsuka, T.; Tsuboi, Y.; Yokoyama, K.; Albrektsson, T.; Sennerby, L.; Johansson, C.

1994-01-01

In the past two decades the utilization of dental and orthopaedic implants in reconstructive surgery has been spread widely. Most of these implants are inserted in the corrosive environment of the human body for long periods of time. The level of dissolution, release, and transport of metal ions as a result of corrosion of these materials are not fully known at present. We report the results of application of micro ion beam PIXE spectroscopy to detect release of titanium from titanium and titanium alloy implants inserted in the tibiae of rabbits for three months. It was found that titanium ions could be detected in the surrounding tissues, with high precision, as a gradient from the implant surface and in higher amounts in the bone tissue as compared with the soft tissues. It is concluded that application of micro ion beam PIXE spectroscopy for detection of metal ion release, and distribution of the released material around the implants with high special resolution and accuracy may be used to further investigate the mechanism of metal release, and the relation between surface micromorphology and corrosion resistance of the implant materials. (author)

Process for making a titanium diboride-chromium diboride-yttrium titanium oxide ceramic composition

Science.gov (United States)

Holcombe, C.E.; Dykes, N.L.

1992-04-28

A ceramic composition is described. The ceramic composition consists essentially of from about 84 to 96 w/o titanium diboride, from about 1 to 9 w/o chromium diboride, and from about 3 to about 15 w/o yttrium-titanium-oxide. A method of making the ceramic composition is also described. The method of making the ceramic composition comprises the following steps: Step 1--A consolidated body containing stoichiometric quantities of titanium diboride and chromium diboride is provided. Step 2--The consolidated body is enclosed in and in contact with a thermally insulated package of yttria granules having a thickness of at least 0.5 inches. Step 3--The consolidated body enclosed in the thermally insulated package of yttria granules is heated in a microwave oven with microwave energy to a temperature equal to or greater than 1,900 degrees centigrade to sinter and uniformly disperse yttria particles having a size range from about 1 to about 12 microns throughout the consolidated body forming a densified body consisting essentially of titanium diboride, chromium diboride, and yttrium-titanium-oxide. The resulting densified body has enhanced fracture toughness and hardness. No Drawings

40 CFR 180.1195 - Titanium dioxide.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Titanium dioxide. 180.1195 Section 180.1195 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS... Titanium dioxide. Titanium dioxide is exempted from the requirement of a tolerance for residues in or on...

Advances in cost effective processing of titanium

International Nuclear Information System (INIS)

Nelson, O.E.

1993-01-01

Recently an industry expert pointed out that one of the greatest hindrances to the growth of titanium usage has been the low percentage of material usable in the final product. Due to the extensive processing, forming, and machining operations typically performed on titanium, yield losses are high. This is especially true in aerospace applications where most titanium is used. In engine components, the start to finish ratio, known as the buy to fly ratio, is often as high as 7 to 1. This can be illustrated by looking at the use of titanium in Pratt and Whitney engines. In the JT-8D-217 used on Boeing's 737-200, the titanium buyweight is 5,385 pounds, whereas the finished titanium, flyweight is just 758 pounds. This start to finish ratio is 7.1:1, giving titanium 17.0% of total engine weight. (orig.)

Low-cost Photoacoustic-based Measurement System for Carbon Dioxide Fluxes with the Potential for large-scale Monitoring

Science.gov (United States)

Scholz, L. T.; Bierer, B.; Ortiz Perez, A.; Woellenstein, J.; Sachs, T.; Palzer, S.

2016-12-01

The determination of carbon dioxide (CO2) fluxes between ecosystems and the atmosphere is crucial for understanding ecological processes on regional and global scales. High quality data sets with full uncertainty estimates are needed to evaluate model simulations. However, current flux monitoring techniques are unsuitable to provide reliable data of a large area at both a detailed level and an appropriate resolution, at best in combination with a high sampling rate. Currently used sensing technologies, such as non-dispersive infrared (NDIR) gas analyzers, cannot be deployed in large numbers to provide high spatial resolution due to their costs and complex maintenance requirements. Here, we propose a novel CO2 measurement system, whose gas sensing unit is made up of low-cost, low-power consuming components only, such as an IR-LED and a photoacoustic detector. The sensor offers a resolution of sensor response of just a few seconds. Since the sensor can be applied in-situ without special precautions, it allows for environmental monitoring in a non-invasive way. Its low energy consumption enables long-term measurements. The low overall costs favor the manufacturing in large quantities. This allows the operation of multiple sensors at a reasonable price and thus provides concentration measurements at any desired spatial coverage and at high temporal resolution. With appropriate 3D configuration of the units, vertical and horizontal fluxes can be determined. By applying a closely meshed wireless sensor network, inhomogeneities as well as CO2 sources and sinks in the lower atmosphere can be monitored. In combination with sensors for temperature, pressure and humidity, our sensor paves the way towards the reliable and extensive monitoring of ecosystem-atmosphere exchange rates. The technique can also be easily adapted to other relevant greenhouse gases.

Resonant Absorption in GaAs-Based Nanowires by Means of Photo-Acoustic Spectroscopy

Science.gov (United States)

Petronijevic, E.; Leahu, G.; Belardini, A.; Centini, M.; Li Voti, R.; Hakkarainen, T.; Koivusalo, E.; Guina, M.; Sibilia, C.

2018-03-01

Semiconductor nanowires made of high refractive index materials can couple the incoming light to specific waveguide modes that offer resonant absorption enhancement under the bandgap wavelength, essential for light harvesting, lasing and detection applications. Moreover, the non-trivial ellipticity of such modes can offer near field interactions with chiral molecules, governed by near chiral field. These modes are therefore very important to detect. Here, we present the photo-acoustic spectroscopy as a low-cost, reliable, sensitive and scattering-free tool to measure the spectral position and absorption efficiency of these modes. The investigated samples are hexagonal nanowires with GaAs core; the fabrication by means of lithography-free molecular beam epitaxy provides controllable and uniform dimensions that allow for the excitation of the fundamental resonant mode around 800 nm. We show that the modulation frequency increase leads to the discrimination of the resonant mode absorption from the overall absorption of the substrate. As the experimental data are in great agreement with numerical simulations, the design can be optimized and followed by photo-acoustic characterization for a specific application.

Electron beam melting of sponge titanium

International Nuclear Information System (INIS)

Kanayama, Hiroshi; Kusamichi, Tatsuhiko; Muraoka, Tetsuhiro; Onouye, Toshio; Nishimura, Takashi

1991-01-01

Fundamental investigations were done on electron beam (EB) melting of sponge titanium by using 80 kW EB melting furnace. Results obtained are as follows: (1) To increase the melting yield of titanium in EB melting of sponge titanium, it is important to recover splashed metal by installation of water-cooled copper wall around the hearth and to decrease evaporation loss of titanium by keeping the surface temperature of molten metal just above the melting temperature of titanium without local heating. (2) Specific power consumption of drip melting of pressed sponge titanium bar and hearth melting of sponge titanium are approximately 0.9 kWh/kg-Ti and 0.5-0.7 kWh/kg-Ti, respectively. (3) Ratios of the heat conducted to water-cooled mould in the drip melting and to water-cooled hearth in the hearth melting to the electron beam input power are 50-65% and 60-65%, respectively. (4) Surface defects of EB-melted ingots include rap which occurs when the EB output is excessively great, and transverse cracks when the EB output is excessively small. To prevent surface defects, the up-down withdrawal method is effective. (author)

High-resolution neutron-diffraction measurements to 8 kbar

Science.gov (United States)

Bull, C. L.; Fortes, A. D.; Ridley, C. J.; Wood, I. G.; Dobson, D. P.; Funnell, N. P.; Gibbs, A. S.; Goodway, C. M.; Sadykov, R.; Knight, K. S.

2017-10-01

We describe the capability to measure high-resolution neutron powder diffraction data to a pressure of at least 8 kbar. We have used the HRPD instrument at the ISIS neutron source and a piston-cylinder design of pressure cell machined from a null-scattering titanium zirconium alloy. Data were collected under hydrostatic conditions from an elpasolite perovskite La?NiMnO?; by virtue of a thinner cell wall on the incident-beam side of the cell, it was possible to obtain data in the instrument's highest resolution back-scattering detector banks up to a maximum pressure of 8.5 kbar.

Depth Profiles in Maize ( Zea mays L.) Seeds Studied by Photoacoustic Spectroscopy

Science.gov (United States)

Hernández-Aguilar, C.; Domínguez-Pacheco, A.; Cruz-Orea, A.; Zepeda-Bautista, R.

2015-06-01

Photoacoustic spectroscopy (PAS) has been used to analyze agricultural seeds and can be applied to the study of seed depth profiles of these complex samples composed of different structures. The sample depth profile can be obtained through the photoacoustic (PA) signal, amplitude, and phase at different light modulation frequencies. The PA signal phase is more sensitive to changes of thermal properties in layered samples than the PA signal amplitude. Hence, the PA signal phase can also be used to characterize layers at different depths. Thus, the objective of the present study was to obtain the optical absorption spectra of maize seeds ( Zea mays L.) by means of PAS at different light modulation frequencies (17 Hz, 30 Hz, and 50 Hz) and comparing these spectra with the ones obtained from the phase-resolved method in order to separate the optical absorption spectra of seed pericarp and endosperm. The results suggest the possibility of using the phase-resolved method to obtain optical absorption spectra of different seed structures, at different depths, without damaging the seed. Thus, PAS could be a nondestructive method for characterization of agricultural seeds and thus improve quality control in the food industry.

Application of high resolution synchrotron micro-CT radiation in dental implant osseointegration

DEFF Research Database (Denmark)

Neldam, Camilla Albeck; Lauridsen, Torsten; Rack, Alexander

2015-01-01

The purpose of this study was to describe a refined method using high-resolution synchrotron radiation microtomography (SRmicro-CT) to evaluate osseointegration and peri-implant bone volume fraction after titanium dental implant insertion. SRmicro-CT is considered gold standard evaluating bone...... microarchitecture. Its high resolution, high contrast, and excellent high signal-to-noise-ratio all contribute to the highest spatial resolutions achievable today. Using SRmicro-CT at a voxel size of 5 μm in an experimental goat mandible model, the peri-implant bone volume fraction was found to quickly increase...

Detection of Photoacoustic Transients Originating from Microstructures in Optically Diffuse Media such as Biological Tissue

NARCIS (Netherlands)

Hoelen, C.G.A.; Dekker, Andre; de Mul, F.F.M.

2001-01-01

The generation and detection of broadband photoacoustic (PA) transients may be used for on-axis monitoring or for imaging of optically different structures in the interior of diffuse bodies such as biological tissue. Various piezoelectric sensors are characterized and compared in terms of

Detection, mapping, and quantification of single walled carbon nanotubes in histological specimens with photoacoustic microscopy.

NARCIS (Netherlands)

Avti, P.K.; Hu, S.; Favazza, C.; Mikos, A.G.; Jansen, J.A.; Shroyer, K.R.; Wang, L.V.; Sitharaman, B.

2012-01-01

AIMS: In the present study, the efficacy of multi-scale photoacoustic microscopy (PAM) was investigated to detect, map, and quantify trace amounts [nanograms (ng) to micrograms (microg)] of SWCNTs in a variety of histological tissue specimens consisting of cancer and benign tissue biopsies

Production of titanium tetrachloride

International Nuclear Information System (INIS)

Perillo, P.M.; Botbol, O.

1990-01-01

This report presents a summary of results from theoperation of a laboratory scale for the production in batches of approximately 100 gs of titanium tetrachloride by chlorination with chloroform and carbon tetrachloride between 340 deg C and 540 deg C. Chlorination agent vapors were passed through a quartz column reacting with titanium oxide powder agglomerated in little spheres. Obtained titanium tetrachloride was condensed in a condenser, taken in a ballon and then purified by fractional distillation. Optimun temperature for chloroform was 400 deg C with 74 % yield and for carbon tetrachloride was 500 deg C with 69 % yield. (Author) [es

Uranium fluorides analysis. Titanium spectrophotometric determination

International Nuclear Information System (INIS)

Anon.

Titanium determination in uranium hexafluoride in the range 0.7 to 100 microgrammes after transformation of uranium fluoride in sulfate. Titanium is separated by extraction with N-benzoylphenylhydroxylamine, reextracted by hydrochloric-hydrofluoric acid. The complex titanium-N-benzoylphenylhydroxylamine is extracted by chloroform. Spectrophotometric determination at 400 nm [fr

21 CFR 73.2575 - Titanium dioxide.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Titanium dioxide. 73.2575 Section 73.2575 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2575 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide shall conform in identity and specifications to the requirements...

Titanium oxide nanocoating on a titanium thin film deposited on a glass substrate

Energy Technology Data Exchange (ETDEWEB)

Kotsedi, L., E-mail: kotsedi@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS, National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS, National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Cummings, F.R. [University of the Western Cape, Electron Microscopy Unit, Physics Department, Bellville 7535, Cape Town (South Africa); Turco, S. Lo; Ntwaeaborwa, O.M. [Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Milano, Italy Via Giovanni Pascoli, 70/3, 20133 Milano (Italy); Ramponi, R. [Institute for Photonics and Nanotechnologies (IFN)-CNR, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS, National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa)

2016-03-31

Thin films of titanium were deposited on a glass substrate using electron beam evaporator. Femtosecond laser pulses were focused on the surface of the films, and the samples were scanned while mounted on the motorized computer-controlled motion stage to produce an areal modification of the films. X-ray diffraction of the laser-patterned samples showed evidence of the formation of a γ-Ti{sub 3}O{sub 5} with a monoclinic phase. Rutherford backscattering spectrometry simulation showed that there is an increase in the oxygen concentration as the average laser fluence is increased. Time of flight secondary ions mass spectrometry analysis showed an even distribution of the titanium and oxygen ions on the sample and also ionized molecules of the oxides of titanium were observed. The formation of the oxide of titanium was further supported using the UV–Vis-NIR spectroscopy, which showed that for 0.1 J/cm{sup 2} fluence, the laser-exposed film showed the electron transfer band and the d–d transition peak of titanium was observed at lower wavelengths. - Highlights: • γ-Ti{sub 3}O{sub 5} formed using femtosecond laser. • Fluence and oxygen relation were studied. • Nanoflakes of γ-Ti{sub 3}O{sub 5} were observed under HRSEM.

One-pot synthesis of gold nanostars using plant polyphenols for cancer photoacoustic imaging and photothermal therapy

International Nuclear Information System (INIS)

Zhang, Xiao-Long; Zheng, Cheng; Zhang, Yun; Yang, Huang-Hao; Liu, Xiaolong; Liu, Jingfeng

2016-01-01

Branched plasmonic nanostructures have been found to exhibit strong enhancement of the electromagnetic field surrounding their multi-branched petals. This feature endows them with improved performance in catalysis, surface-enhanced Raman scattering, photoacoustic imaging, and photothermal therapy. Albeit several synthesis techniques have been developed, the precisely controlled growth of highly branched nanostructures with a one-pot surfactant-free procedure is still challenging. Herein, we present a simple seedless route to synthesize gold nanostars (AuNSs) using a natural plant polyphenol, gallic acid (GA), as a reducing and stabilizing agent. The size and shape of AuNSs can be tuned by simply adjusting the amount of added GA. Under the optimum condition, the as-prepared AuNSs with diameters about 100 nm exhibit strong near-infrared absorption, good photothermal efficiency, and high biocompatibility. We demonstrate that AuNSs can be utilized for simultaneous photoacoustic imaging and photothermal therapy in living cancer cells. This study highlights facile synthesized AuNSs could serve as a promising platform for cancer diagnosis and therapy.Graphical AbstractGold nanostars (AuNSs) are synthesized by a simple seedless route using a natural plant polyphenol, gallic acid (GA), as a reducing and stabilizing agent. The AuNSs can be utilized for simultaneous photoacoustic imaging and photothermal therapy in living cancer cells. This study highlights facile synthesized AuNSs could serve as a promising platform for cancer diagnosis and therapy.

One-pot synthesis of gold nanostars using plant polyphenols for cancer photoacoustic imaging and photothermal therapy

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiao-Long [Mengchao Hepatobiliary Hospital of Fujian Medical University, The United Innovation of Mengchao Hepatobiliary Technology Key Laboratory of Fujian Province (China); Zheng, Cheng [Fuzhou University, The Key Lab of Analysis and Detection Technology for Food Safety of the MOE, College of Chemistry (China); Zhang, Yun [Chinese Academy of Sciences, Xiamen Institute of Rare Earth Materials, Haixi Institute (China); Yang, Huang-Hao [Fuzhou University, The Key Lab of Analysis and Detection Technology for Food Safety of the MOE, College of Chemistry (China); Liu, Xiaolong, E-mail: xiaoloong.liu@gmail.com; Liu, Jingfeng, E-mail: drjingfeng@126.com [Mengchao Hepatobiliary Hospital of Fujian Medical University, The United Innovation of Mengchao Hepatobiliary Technology Key Laboratory of Fujian Province (China)

2016-07-15

Branched plasmonic nanostructures have been found to exhibit strong enhancement of the electromagnetic field surrounding their multi-branched petals. This feature endows them with improved performance in catalysis, surface-enhanced Raman scattering, photoacoustic imaging, and photothermal therapy. Albeit several synthesis techniques have been developed, the precisely controlled growth of highly branched nanostructures with a one-pot surfactant-free procedure is still challenging. Herein, we present a simple seedless route to synthesize gold nanostars (AuNSs) using a natural plant polyphenol, gallic acid (GA), as a reducing and stabilizing agent. The size and shape of AuNSs can be tuned by simply adjusting the amount of added GA. Under the optimum condition, the as-prepared AuNSs with diameters about 100 nm exhibit strong near-infrared absorption, good photothermal efficiency, and high biocompatibility. We demonstrate that AuNSs can be utilized for simultaneous photoacoustic imaging and photothermal therapy in living cancer cells. This study highlights facile synthesized AuNSs could serve as a promising platform for cancer diagnosis and therapy.Graphical AbstractGold nanostars (AuNSs) are synthesized by a simple seedless route using a natural plant polyphenol, gallic acid (GA), as a reducing and stabilizing agent. The AuNSs can be utilized for simultaneous photoacoustic imaging and photothermal therapy in living cancer cells. This study highlights facile synthesized AuNSs could serve as a promising platform for cancer diagnosis and therapy.

21 CFR 73.1575 - Titanium dioxide.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Titanium dioxide. 73.1575 Section 73.1575 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1575 Titanium dioxide. (a) Identity and specifications. (1) The color additive titanium dioxide shall conform in identity and specifications to the requirements...

Adhesive-Bonded Tab Attaches Thermocouples to Titanium

Science.gov (United States)

Cook, C. F.

1982-01-01

Mechanical strength of titanium-alloy structures that support thermocouples is preserved by first spotwelding thermocouples to titanium tabs and then attaching tabs to titanium with a thermosetting adhesive. In contrast to spot welding, a technique previously used for thermocouples, fatigue strength of the titanium is unaffected by adhesive bonding. Technique is also gentler than soldering or attaching thermocouples with a tap screw.

Criterion of titanium aviation alloy application

International Nuclear Information System (INIS)

Stasyunas, O.P.

1976-01-01

The most significant statistic mechanical characteristics are presented of titanium as compared with those of aluminium and steel. Based on these data one can draw conclusions as to the advantages and disadvantages of titanium. High chemical activity and diffusivity of titanium place limitations on the use of its alloys. Despite the promising features of a needle-like structure, specifications still keep relying on a globular structure, which is explained by the easeiness of the production. Titanium is expensive, sometimes its cost may by a factor of 20 exceed that of other aviation materials

Enhanced near-infrared photoacoustic imaging of silica-coated rare-earth doped nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Sheng, Yang [Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372 (Singapore); School of Materials Science and Engineering, Changzhou University, Changzhou, Jiangsu 213164 (China); Liao, Lun-De [Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, 35 Keyan Rd., Zhunan Town, Miaoli County 35053, Taiwan, ROC (China); Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456 (Singapore); Bandla, Aishwarya [Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456 (Singapore); Department of Biomedical Engineering, National University of Singapore, 21 Lower Kent Ridge Rd, Singapore 119077 (Singapore); Liu, Yu-Hang [Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 21 Lower Kent Ridge Rd, Singapore 119077 (Singapore); Yuan, Jun [Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456 (Singapore); Thakor, Nitish [Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456 (Singapore); Department of Biomedical Engineering, National University of Singapore, 21 Lower Kent Ridge Rd, Singapore 119077 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 21 Lower Kent Ridge Rd, Singapore 119077 (Singapore); Tan, Mei Chee, E-mail: meichee.tan@sutd.edu.sg [Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372 (Singapore)

2017-01-01

Near-infrared photoacoustic (PA) imaging is an emerging diagnostic technology that utilizes the tissue transparent window to achieve improved contrast and spatial resolution for deep tissue imaging. In this study, we investigated the enhancement effect of the SiO{sub 2} shell on the PA property of our core/shell rare-earth nanoparticles (REs) consisting of an active rare-earth doped core of NaYF{sub 4}:Yb,Er (REDNPs) and an undoped NaYF{sub 4} shell. We observed that the PA signal amplitude increased with SiO{sub 2} shell thickness. Although the SiO{sub 2} shell caused an observed decrease in the integrated fluorescence intensity due to the dilution effect, fluorescence quenching of the rare earth emitting ions within the REDNPs cores was successfully prevented by the undoped NaYF{sub 4} shell. Therefore, our multilayer structure consisting of an active core with successive functional layers was demonstrated to be an effective design for dual-modal fluorescence and PA imaging probes with improved PA property. The result from this work addresses a critical need for the development of dual-modal contrast agent that advances deep tissue imaging with high resolution and signal-to-noise ratio. - Graphical abstract: Illustration of multilayer structured imaging probe with REDNPs as active core, undoped NaYF{sub 4} as intermediate layer and SiO{sub 2} as outer shell. The PA signal amplitude of REs/SiO{sub 2} was increased with the SiO{sub 2} shell thickness. - Highlights: • Silica coating was demonstrated to be much more effective in enhancing the PA signal amplitude comparing to soft polymer. • PA enhancement was attributed to the increased phonon modes and phonon energy with the introduction of the SiO{sub 2} coating. • Multilayer structure was an effective design for dual-modal fluorescence and PA imaging probes with improved PA property.

Study of nanodispersed aluminum and iron alcosols by photoacoustic spectroscopy

Science.gov (United States)

An, Vladimir; de Izarra, Charles; Saveliev, Gennady

2011-06-01

Nanodispersed aluminum and iron alcosols were prepared by ultrasonic dispersion of nanodispersed aluminum and iron powders in absolute ethanol. The photoacoustic signal (PAS) produced in modulated CO2 laser irradiation (1.026 and 1.096 kHz) of alcosols depends on the nature and method of nanoparticle fabrication and does not depend on their concentration in ethanol (within 1-5 g/l). Chemical interaction between metal nanoparticles and ethanol activated by laser irradiation or/and ultrasound is considered as the cause of the PAS.

21 CFR 73.575 - Titanium dioxide.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Titanium dioxide. 73.575 Section 73.575 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Foods § 73.575 Titanium dioxide. (a) Identity. (1) The color additive titanium dioxide is synthetically prepared TiO2, free from admixture with other substances. (2) Color...

21 CFR 73.3126 - Titanium dioxide.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Titanium dioxide. 73.3126 Section 73.3126 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3126 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide (CAS Reg. No. 13463-67-7), Color Index No. 77891, shall...

Welding and Joining of Titanium Aluminides

Science.gov (United States)

Cao, Jian; Qi, Junlei; Song, Xiaoguo; Feng, Jicai

2014-01-01

Welding and joining of titanium aluminides is the key to making them more attractive in industrial fields. The purpose of this review is to provide a comprehensive overview of recent progress in welding and joining of titanium aluminides, as well as to introduce current research and application. The possible methods available for titanium aluminides involve brazing, diffusion bonding, fusion welding, friction welding and reactive joining. Of the numerous methods, solid-state diffusion bonding and vacuum brazing have been most heavily investigated for producing reliable joints. The current state of understanding and development of every welding and joining method for titanium aluminides is addressed respectively. The focus is on the fundamental understanding of microstructure characteristics and processing–microstructure–property relationships in the welding and joining of titanium aluminides to themselves and to other materials. PMID:28788113

Correlation of Critical Temperatures and Electrical Properties in Titanium Films

Science.gov (United States)

Gandini, C.; Lacquaniti, V.; Monticone, E.; Portesi, C.; Rajteri, M.; Rastello, M. L.; Pasca, E.; Ventura, G.

Recently transition-edge sensors (TES) have obtained an increasing interest as light detectors due to their high energy resolution and broadband response. Titanium (Ti), with transition temperature up to 0.5 K, is among the suitable materials for TES application. In this work we investigate Ti films obtained from two materials of different purity deposited by e-gun on silicon nitride. Films with different thickness and deposition substrate temperature have been measured. Critical temperatures, electrical resistivities and structural properties obtained from x-ray are related to each other.

Fabrication of naphthalocyanine nanoparticles by laser ablation in liquid and application to contrast agents for photoacoustic imaging

Science.gov (United States)

Yanagihara, Ryuga; Asahi, Tsuyoshi; Ishibashi, Yukihide; Odawara, Osamu; Wada, Hiroyuki

2018-03-01

Naphthalocyanine nanoparticles were prepared by laser ablation in liquid using second-harmonics of nanosecond Nd:YAG laser as an excitation light sauce at various laser fluence, and the properties of naphthalocyanine nanoparticles, such as shape, size, zeta potential, chemical structure and optical absorption were examined. The scanning electron microscopy (SEM) and dynamic light scattering (DLS) measurements showed that the particle size of the nanoparticles could be controlled by the laser fluence. The IR spectra of the nanoparticles indicated the formation of carboxylate anion species at laser fluences above 100 mJ/cm2, which will result the zeta potential of the nanoparticles depending on the laser fluence. We also examined the potential application to contrast agents for photoacoustic, and confirmed that the naphthalocyanine nanoparticles generated a strong photoacoustic signal.

Application of laser-based photoacoustic spectroscopy and colorimetry for quantification of anthocyanin in hard boiled candy

NARCIS (Netherlands)

Kovács, Mihály; Dóka, Ottó; Bicanic, Dane; Ajtony, Zsolt

2017-01-01

The analytical performance of the newly proposed laser-based photoacoustic spectroscopy (LPAS) and colorimetric method for quantification of anthocyanin (E163) in commercially available hard boiled candies are compared to that of the spectrophotometry (SP). Both LPAS and colorimetry are direct

High speed intravascular photoacoustic imaging of atherosclerotic arteries (Conference Presentation)

Science.gov (United States)

Piao, Zhonglie; Ma, Teng; Qu, Yueqiao; Li, Jiawen; Yu, Mingyue; He, Youmin; Shung, K. Kirk; Zhou, Qifa; Kim, Chang-Seok; Chen, Zhongping

2016-02-01

Cardiovascular disease is the leading cause of death in the industrialized nations. Accurate quantification of both the morphology and composition of lipid-rich vulnerable atherosclerotic plaque are essential for early detection and optimal treatment in clinics. In previous works, intravascular photoacoustic (IVPA) imaging for detection of lipid-rich plaque within coronary artery walls has been demonstrated in ex vivo, but the imaging speed is still limited. In order to increase the imaging speed, a high repetition rate laser is needed. In this work, we present a high speed integrated IVPA/US imaging system with a 500 Hz optical parametric oscillator laser at 1725 nm. A miniature catheter with 1.0 mm outer diameter was designed with a 200 μm multimode fiber and an ultrasound transducer with 45 MHz center frequency. The fiber was polished at 38 degree and enclosed in a glass capillary for total internal reflection. An optical/electrical rotary junction and pull-back mechanism was applied for rotating and linearly scanning the catheter to obtain three-dimensional imaging. Atherosclerotic rabbit abdominal aorta was imaged as two frame/second at 1725 nm. Furthermore, by wide tuning range of the laser wavelength from 1680 nm to 1770 nm, spectroscopic photoacoustic analysis of lipid-mimicking phantom and an human atherosclerotic artery was performed ex vivo. The results demonstrated that the developed IVPA/US imaging system is capable for high speed intravascular imaging for plaque detection.

Determination of iron and titanium in kaolins by the method of non-dispersive X-ray fluorescence

International Nuclear Information System (INIS)

Bialy, N.; Kierzek, J.; Parus, J.

1976-01-01

The possibility of application of the radioactive source excited X-ray fluorescence analysis for titanium and iron determination in kaolins to the routine test of the refinement process has been studied. The iron content can be determined with a simple counting system using a single-channel pulse height analyser, argon filled proportional counter and 109 Cd source of 3 mCi for the excitation of K Fe rays. The samples were analyzed both as pellets and powders. The iron content ranged from 0.2-2.5% and titanium from 0.1-0.64%. The best values of precision and determination limit have been achieved for iron with 238 Pu and for titanium with 55 Fe. The precision and accuracy of the X-ray fluorescence method of iron and titanium determination in kaolins are comparable to those of the chemical method. For the simultaneous iron and titanium determination in the discussed region of concentration it is the most advantageous to use the plutonium source with the activity of several tens of mCi and Si(Li) detector with a moderate resolution (250-300 eV for 5.9 keV). The time of the analysis carried out by the described method is several times shorter than the chemical method. The apparatus used in this method is relatively simple, the sample preparation does not require any chemical treatment and the cost of labour of the sample preparation is minimal. (T.G.)

Welding and Joining of Titanium Aluminides

Directory of Open Access Journals (Sweden)

Jian Cao

2014-06-01

Full Text Available Welding and joining of titanium aluminides is the key to making them more attractive in industrial fields. The purpose of this review is to provide a comprehensive overview of recent progress in welding and joining of titanium aluminides, as well as to introduce current research and application. The possible methods available for titanium aluminides involve brazing, diffusion bonding, fusion welding, friction welding and reactive joining. Of the numerous methods, solid-state diffusion bonding and vacuum brazing have been most heavily investigated for producing reliable joints. The current state of understanding and development of every welding and joining method for titanium aluminides is addressed respectively. The focus is on the fundamental understanding of microstructure characteristics and processing–microstructure–property relationships in the welding and joining of titanium aluminides to themselves and to other materials.

Analysis of titanium content in titanium tetrachloride solution

Science.gov (United States)

Bi, Xiaoguo; Dong, Yingnan; Li, Shanshan; Guan, Duojiao; Wang, Jianyu; Tang, Meiling

2018-03-01

Strontium titanate, barium titan and lead titanate are new type of functional ceramic materials with good prospect, and titanium tetrachloride is a commonly in the production such products. Which excellent electrochemical performance of ferroelectric tempreature coefficient effect.In this article, three methods are used to calibrate the samples of titanium tetrachloride solution by back titration method, replacement titration method and gravimetric analysis method. The results show that the back titration method has many good points, for example, relatively simple operation, easy to judgment the titration end point, better accuracy and precision of analytical results, the relative standard deviation not less than 0.2%. So, it is the ideal of conventional analysis methods in the mass production.

Ultrasonic effects on titanium tanning of leather.

Science.gov (United States)

Peng, Biyu; Shi, Bi; Sun, Danhong; Chen, Yaowen; Shelly, Dennis C

2007-03-01

The effects of ultrasound on titanium tanning of leather were investigated. Either 20 or 40 kHz ultrasound was applied to the titanium tanning of pigskins. Five different treatment conditions were carried out and the effects were examined, such as leather shrinkage temperature (T(s)), titanium content and titanium distribution in the leather. Overall heat loading was carefully controlled. Results showed that 20 kHz ultrasound effectively improves titanium agent penetration into the hide and increases the leather's shrinkage temperature. Doubling the frequency to 40 kHz produced negligible enhancements. An impressive 105.6 degrees C T(s) was achieved using 20 kHz ultrasound pretreatment of the tanning liquor followed by 20 kHz ultrasound in the tanning mixture (liquor plus pigskins) in a special salt-free medium. Finally, using a unique ultrasonic tanning drum with 26.5 kHz ultrasound, the T(s) reached a record level of 106.5 degrees C, a value not achieved in conventional (no ultrasound) titanium tanning. The ultrasonic effects on titanium tanning of leather are judged to make a superior mineral tanned leather.

Applications of laser-photoacoustic gas analysis method; Fotoakustisen kaasuanalyysin sovelluksia. Fotoakustiset mittaukset paineistetussa poelyvirtausreaktorissa

Energy Technology Data Exchange (ETDEWEB)

Hernberg, R.; Stenberg, J. [Tampere Univ. of Technology (Finland). Lab. of Plasma Technology

1997-10-01

Laser induced photoacoustic spectroscopy has been developed in LIEKKI and LIEKKI 2 research programs. The method is intended for In-Situ analysis of gaseous components in hot and reactive environments such as combustion conditions. The method and the instrumentation developed in this project have been calibrated for SO{sub 2}, NO, NO{sub 2}, NH{sub 3}, N{sub 2}O, and H{sub 2}S between 20 and 860 deg C at atmospheric pressure. Calibrations at elevated pressures have been performed for NO{sub 2}, NO, SO{sub 2}, NH{sub 3} and N{sub 2}O. Calibration for OH radical has also been performed. A known concentration of OH was generated by thermally decomposing H{sub 2}O at temperatures between 900 and 1050 deg C. The photoacoustic method has earlier been applied to the chemical analysis of burning CH{sub 4}/HCN/O{sub 2}/N{sub 2} flame at pressures between 1 and 6 bar. The formation of NO and NH{sub 3} measured in post-flame conditions. The relative concentration of OH in the reactive zone of the flame was measured between 1 and 6 bar pressures. The method was also applied to measurements in circulating fluidized bed (CFB). Time resolved gas concentrations were measured at three different heights above the air distributor with a specialized probe. In this project the photoacoustic method is applied in studies regarding the effect of chlorine (Cl) on combustion chemistry. The second goal of this project is to make In-Situ measurements of the formation of NO{sub 2} in combustion. The formation of NO{sub 2} increases strongly at elevated pressures. Due to the instability of NO{sub 2} the analysis is prone to errors with conventional gas sampling probes