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<i>In vivo</i> blood viscosity characterization based on frequency-resolved photoacoustic measurement
摘要： In this letter, we proposed a photoacoustic (PA) method for noninvasively detecting blood viscosity in subcutaneous microvasculature with the frequency-resolved measurement. The influence of viscosity on PA generation was investigated theoretically, and a negative correlation was shown between the viscosity and the full width at half maximum (FWHM) of the PA frequency spectrum, which can be utilized to reflect the viscosity distribution. To test the feasibility and accuracy of this method, water mixed with different concentrations of glycerol was measured. FWHM of the PA frequency spectrum was also obtained in vivo in the mouse ear to characterize the blood viscosity from different vessel bifurcations, and the metabolism-induced viscosity changes were dynamically monitored in the microvasculature. Experimental results demonstrate that this technique has future potential clinical applications for real-time monitoring the viscosity changes in subcutaneous microvasculature.
关键词： in vivo,microvasculature,frequency-resolved measurement,photoacoustic,blood viscosity
更新于2025-09-23 15:21:01
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Advances in Mid-Infrared Spectroscopy-Based Sensing Techniques for Exhaled Breath Diagnostics
摘要： Human exhaled breath consists of more than 3000 volatile organic compounds, many of which are relevant biomarkers for various diseases. Although gas chromatography has been the gold standard for volatile organic compound (VOC) detection in exhaled breath, recent developments in mid-infrared (MIR) laser spectroscopy have led to the promise of compact point-of-care (POC) optical instruments enabling even single breath diagnostics. In this review, we discuss the evolution of MIR sensing technologies with a special focus on photoacoustic spectroscopy, and its application in exhaled breath biomarker detection. While mid-infrared point-of-care instrumentation promises high sensitivity and inherent molecular selectivity, the lack of standardization of the various techniques has to be overcome for translating these techniques into more widespread real-time clinical use.
关键词： point-of-care (POC),infrared lasers,MIR,photoacoustic spectroscopy,biomarkers,exhaled breath analysis,non-invasive diagnostics,QCL,quantum cascade lasers,mid-infrared
更新于2025-09-23 15:21:01
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Wavelength Optimization in the Multispectral Photoacoustic Tomography of the Lymphatic Drainage in Mice
摘要： Multispectral photoacoustic tomography provides mapping of tissue chromophore distributions using sets of tunable laser wavelengths. With the overall goal of studying the dynamics of cerebrospinal fluid in mice in vivo, our work aims to minimize the number of wavelengths to reduce scanning time, improve the temporal resolution, reduce the energy deposition and avoid the tracer photobleaching while maintaining high image quality. To select small sets of wavelengths we directly searched for the combinations of wavelengths providing the best and worst image quality in comparison with a reference image obtained using 131 closely spaced wavelengths between 680 and 940 nm in terms of the peak signal-to-noise ratio (PSNR). We have shown that using the PSNR optimization method, additional improvements could be achieved over the wavelength set selected using the method of the minimization of the extinction matrix condition number.
关键词： photoacoustic,lymphatic drainage,fluorescent dye,multispectral
更新于2025-09-23 15:21:01
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Photoacoustic imaging for monitoring periodontal health: A first human study
摘要： The gold-standard periodontal probe is an aging tool that can detect periodontitis and monitor gingival health but is highly error-prone, does not fully characterize the periodontal pocket, and causes pain. Photoacoustic imaging is a noninvasive technique that can address these limitations. Here, a range of ultrasound frequencies between 16-40 MHz were used to image the periodontium and a contrast medium based on cuttlefish ink was used to label the pockets. A 40 MHz ultrasound frequency could spatially resolve the periodontal anatomy, including tooth, gum, gingival margin, and gingival thickness of tooth numbers 7-10 and 22-27. The photoacoustic-ultrasound measurements were more precise (0.01 mm) than those taken with physical probes by a dental hygienist. Furthermore, the full geometry of the pockets could be visualized with relative standard deviations of 10% (n = 5). This study shows the potential for non-invasive monitoring of periodontal health with photoacoustic-ultrasound imaging in the dental clinic.
关键词： periodontal disease,gingival thickness,periodontal charting,Photoacoustic imaging,melanin nanoparticles,diagnosis,pocket depth
更新于2025-09-23 15:21:01
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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI, USA (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Evaluation of Bone Conduction Vibration System Using Photoacoustic Effect
摘要： This article proposes a novel bone conduction vibrator based on an interesting phenomenon where audible sound can be perceived when a vibration is produced using a laser beam that is synchronized to the sound and this vibration is transmitted to an auricular cartilage. To study this phenomenon, we measured the effect using a rubber sheet with similar properties to those of soft tissue, together with an acceleration sensor, and found that audible sound was produced in the sample. We also calculated the force level based on the mechanical impedance and the acceleration in the proposed system. It is expected that a force level equal to the reference equivalent threshold force level can be achieved at a light intensity below the safety limit for human skin exposure by choosing an irradiation wavelength at which a larger degree of optical absorption occurs. This novel application of the photoacoustic effect is promising for bone conduction hearing aids.
关键词： bone conduction,hearing aids,laser,vibration,photoacoustic effect
更新于2025-09-23 15:21:01
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Quality improvement of acoustic-resolution photoacoustic imaging of skin vasculature based on practical synthetic-aperture focusing and bandpass filtering
摘要： We previously developed a compact acoustic-resolution photoacoustic (PA) imaging system with optical ?ber-based illumination, by which blood vessels in the rat skin were visualized in vivo. However, there were issues to be improved in the imaging characteristics: blurring in the out-of-focus region of the ultrasound sensor and degraded resolution due to low-frequency components in the PA signals. These are common limitations in acoustic-resolution PA imaging methods. In this study, we attempted to solve these problems by introducing signal processing methods based both on the synthetic-aperture focusing technique, which was applied only to signals in the detection zone of the sensor in the horizontal direction that was determined in advance in a phantom study, and on digital acoustic signal ?ltering with three speci?c frequency bands. Ex vivo and in vivo PA imaging of blood vessels in the rat skin and subcutaneous tissue showed the validity of the present signal processing methods.
关键词： photoacoustic imaging,bandpass ?ltering,skin vasculature,synthetic-aperture focusing
更新于2025-09-23 15:21:01
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Photoacoustic Energy Sensor for Nanosecond Optical Pulse Measurement
摘要： We demonstrate a photoacoustic sensor capable of measuring high-energy nanosecond optical pulses in terms of temporal width and energy fluence per pulse. This was achieved by using a hybrid combination of a carbon nanotube-polydimethylsiloxane (CNT-PDMS)-based photoacoustic transmitter (i.e., light-to-sound converter) and a piezoelectric receiver (i.e., sound detector). In this photoacoustic energy sensor (PES), input pulsed optical energy is heavily absorbed by the CNT-PDMS composite film and then efficiently converted into an ultrasonic output. The output ultrasonic pulse is then measured and analyzed to retrieve the input optical characteristics. We quantitatively compared the PES performance with that of a commercial thermal energy meter. Due to the efficient energy transduction and sensing mechanism of the hybrid structure, the minimum-measurable pulsed optical energy was significantly lowered, ~157 nJ/cm2, corresponding to 1/760 of the reference pyroelectric detector. Moreover, despite the limited acoustic frequency bandwidth of the piezoelectric receiver, laser pulse widths over a range of 6–130 ns could be measured with a linear relationship to the ultrasound pulse width of 22–153 ns. As CNT has a wide electromagnetic absorption spectrum, the proposed pulsed sensor system can be extensively applied to high-energy pulse measurement over visible through terahertz spectral ranges.
关键词： photoacoustic sensor,ultrasound sensor,nanosecond optical pulse,CNT-PDMS,optical energy meter
更新于2025-09-23 15:21:01
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Light-controlled detachment of van der Waals adhered particles in solution with photoacoustic resonator
摘要： This letter investigates a method to control the detachment of van der Waals adhered particles via multi-mode photoacoustic resonance. By varying the coupling repetition frequency of the pumping light, we detach adhered particles and reverse the direction of their motion at will. Additionally, the centrifugal acceleration of the resonator increases linearly with the laser energy within the elastic limit with a maximum value of 1.89×106 m/s2, which corresponds to the smallest diameter (3 μm) of glass particles that can be detached. This research can be widely used for the separation, fixation, and collection of cells, large molecules, dust particulates, etc. in the fields of physics, biochemistry, and clinical medicine.
关键词： Particle detachment,Photoacoustic resonance,Optomechanical resonator
更新于2025-09-23 15:19:57
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Heterodyned photoacoustic effect generated by irradiation of single particles by two laser beams modulated at different frequencies
摘要： When a modulated light beam is absorbed by an incompressible particle, the photoacoustic e?ect can take place through heat di?usion into the surrounding ?uid followed by thermal expansion and the generation of sound. When two laser beams modulated at di?erent frequencies irradiate a particle in aqueous solution, the e?ect of one laser is to modulate the thermal expansion coe?cient of the solution in the proximity of the particle at its modulation frequency. Heat di?usion into the same region of ?uid from absorption of radiation from the second laser takes place in ?uid where the thermal expansion coe?cient is modulated so that the photoacoustic e?ect is produced at the sum and di?erence frequencies of the two lasers. Here, a theory for the photoacoustic e?ect at the heterodyne frequency for a single particle and the corresponding experiments with carbon particles of di?erent sizes are reported.
关键词： Heterodyne measurement,Heterodyned photoacoustic e?ect,Modulation of thermal expansion coe?cient
更新于2025-09-23 15:19:57
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Lanthanide-based Nanocomposites for Photothermal Therapy under Near Infrared Laser: Relationship between Light and Heat, Bio-stability and Reaction Temperature
摘要： In this research, typical organic/inorganic photothermal therapy (PTT) agents were designed with combination of up-conversion luminescent (UCL) or NIR II imaging rare earth nanomaterials for photoacoustic (PA)/UCL/NIR II imaging-guided PTT under NIR laser irradiation. The results show that: (1) PTT effect mainly comes from NIR absorption and partly from the UCL light conversion. (2) The visible UCL emission is mainly quenched by the NIR absorption of the coated PTT agent and partly quenched by the visible absorption, indicating the excitation may play a more important role than in the UCL emission process. (3) The bio-stability of the composite might be decided by the synthesized reaction temperature. Among the five inorganic/organic nanocomposite, UCNP@MnO2 is the most suitable candidate for cancer diagnosis and treatment due to its stimuli-response ability to the micro-acid environment of tumor cells and highest bio-stability. The composites generate heat for PTT after entering the tumour cells, and then the visible light emission gradually regains as MnO2 is reduced to colorless Mn2+ ions, thereby illuminating the cancer cells after the therapy.
关键词： Photothermal therapy,Upconversion luminescence imaging,Mito-tracker,Photoacoustic imaging,Inorganic/organic nanocomposite
更新于2025-09-23 15:19:57