Study of erythrocyte sedimentation in human blood through the photoacoustic signals analysis.

Introduction: In this study, we utilized the pulsed photoacoustic (PA) technique to analyze globular sedimentation in whole human blood, with a focus on distinguishing between healthy individuals and those with hemolytic anemia. Methods: Blood samples were collected from both healthy individuals (women and men) and those with hemolytic anemia, and temporal and spectral parameters of PA signals were employed for analysis. Results: Significant differences (p < 0.05) were observed in PA metrics between the two groups. The proposed spectral analysis allowed significant differentiation within a 25-minute measurement window. Anemic blood samples exhibited higher erythrocyte sedimentation rate (ESR) values, indicating increased erythrocyte aggregation. Discussion: This study underscores the potential of PA signal analysis in ESR assessment as an efficient method for distinguishing between healthy and anemic blood, surpassing traditional approaches. It represents a promising contribution to the development of precise and sensitive techniques for analyzing human blood samples in clinical settings.

Image reconstruction algorithm for laser-induced ultrasonic imaging: The single sensor scanning synthetic aperture focusing technique.

This paper aims to implement a laser-induced ultrasound imaging reconstruction method based on the delay-and-sum beamforming through the synthetic aperture focusing technique (SAFT) for a circular scanning, performed with a tomograph that had one acoustic sensor and a system that rotates the sample around a fixed axis. The proposed method, called the Single-sensor Scanning Synthetic Aperture Focusing Technique, considers the size of the sensor and the detection procedure inside the SAFT's algebra. This image reconstruction method was evaluated numerically, using the Green function for the laser-induced ultrasound wave equation to generate a forward problem, and experimentally, using a solid object of polylactic acid, and a Sprague-Dawley rat heart located in a tissue-mimicking phantom. The resulting images were compared to those obtained from the time reversal and the conventional delay-and-sum reconstruction algorithms. The presented method removes the sidelobe artifacts and the comet tail sign, which produces a more distinguishable target on the image. In addition, the proposed method has a faster performance and lower computational load. The implementation of this method in photoacoustic microscopy techniques for image reconstruction is discussed.

Laser-induced sound pinging for the rapid determination of total sugar or sweetener content in commercial beverages.

We recently reported on fixed-path length laser-induced sound pinging (FPL-LISP) as a rapid photoacoustic technique employing an inexpensive benchtop tattoo-removal laser for reliably determining the speed of sound in low-volume fluids. In this contribution, we demonstrate the capacity of FPL-LISP to analyze representative commercial beverages for their natural or artificial sweetener contents. As a benchmark, the speed of sound was determined for solutions of sugars (glucose, fructose, sucrose), mock high fructose corn syrup (HFCS-55), and 12 household sweeteners (culinary sugars, syrups, honey, molasses) across the concentration range of 1-20% w/v in water, simulating the typical sweetener range found in commercial soft drinks. The setup was then employed to estimate sweetener contents of 26 popular commercial beverages using the HFCS-55 standard curve as a training data set. Our results are remarkably consistent with the label values for these representative commercial beverages, in spite of the fact that some beverages clearly employ a sweetener other than HFCS-55 or a proprietary blend, suggesting the excellent potential of the FPL-LISP setup as a quick screening tool well-suited to quality control and real-time assessment in the beverage and fermentation industrial sectors. The proposed approach represents a significant improvement over many existing methods on the basis of measurement time (down to 1 s, which can be considered real time for many applications), lenient sample requirements (tens of microliters to 1 mL), robust and user-friendly analysis, practical considerations (e.g., economical, minimal service and maintenance concerns), and prospects for advancing both online monitoring and fully portable versions of this instrumentation.

Quantitative Photoacoustic Method for the Measurement of Absorption Coefficients of Highly Absorbing Samples.

In this study, we present a quantitative photoacoustic (PA) method for performing absorption measurements on highly absorbing samples. Based on the thermoelastic mechanism, the relative changes in PA signal amplitude allowed the determination of absorption coefficients of materials in the 0.19-2500-cm-1 range, with no prior knowledge of the material's optoacoustic properties required. We have tested our new methodology by performing absorption measurements on a series of planar liquid samples as well as gelatinized spherical samples. In this approach, laser-induced ultrasound waves were detected in transmission mode. With the model presented herein and a measurement of the relative change in amplitude of the PA signal at two different known concentrations, the absorption coefficient of the sample can be straightforwardly extracted. Three important advantages are highlighted by this analytical approach. First, no previous knowledge of the optical or acoustic properties of the sample is necessary. Second, only a small quantity of sample is required. Finally, our methodology includes both short- and long-pulse regimes, validating its use for any laser pulse duration so long as the requirement for thermal confinement is fulfilled. Remarkably, this new methodology performs best for thick, highly absorbing samples where traditional spectrophotometry is most challenging and unreliable, offering a promising alternative for quantification of the absorption properties of a range of diverse liquid, and gelatinous-state materials not amenable to conventional methods.

Spectrophotometric analysis at the single-cell level: elucidating dispersity within melanic immortalized cell populations.

It is widely held that the melanosome is an exemplar of the absorption features of melanin-containing cells, which are assumed to be uniform in both size and optical characteristics. In recent years, however, it has become increasingly apparent that this is a strikingly poor assumption. Indeed, melanin extracted from natural sources and synthetic melanin both show wide variability in their degree of polymerization (molecular weight) and spectroscopic characteristics. In the current study, imaging spectrophotometry performed on individual cells of immortalized melanin-producing cell lines revealed broad distributions in their sizes: 9.5-36.2 µm for Hs936 human melanoma cells, 10.9-20.8 µm for T47D human breast cancer cells, 5.3-43.5 µm for B16F1 mouse melanoma cells, and 6.4-54.2 µm for B16F10 mouse melanoma cells. The color appearance (from translucent to yellow to nearly black), absorption spectrum, and absorption (extinction) coefficient at 532 nm (28.73 to 364.75, 0.01 to 40.17, 5.88 to 977.19, and 0.01 to 1120 cm-1 for Hs936, T47D, B16F1, and B16F10 cells, respectively) of an individual cell also vary widely and cannot be adequately described by a 'typical' value. In comparison, human red blood cells are much more uniform in size (6.0-8.1 µm diameter; 1.9-3.2 µm thickness), although they too show a broad range of absorptivities, with extinction coefficients in the range of 65 to 370 cm-1 when measured at 532 nm. To further evaluate the impact of these findings on photoacoustic bioanalysis, we performed simulations of the generation of photoacoustic signals expected from these cell types. These simulations revealed that their variation in optical features exerts a pronounced effect on the amplitude and shape of the photoacoustic signals generated from these cell types. Finally, we compared the photoacoustic signal generated from these cells under ideal conditions (i.e., a single cell in isolation) versus a heterogeneous real-world sample, demonstrating that when a single or few cancer cells are present within a blood droplet, the photoacoustic signal is indistinguishable from that measured from blood alone. These outcomes have important ramifications for the early photoacoustic detection of cancer cells and circulating tumor emboli, while pointing to the potential of single-cell imaging spectrophotometry to assess heterogeneity within cell populations in more quantitative terms.

Detection of melanoma cells in vitro using an optical detector of photoacoustic waves.

BACKGROUND AND OBJECTIVE: Circulating tumor cells have been shown to correlate positively with metastatic disease state in patients with advanced cancer. We have demonstrated the ability to detect melanoma cells in a flow system by generating and detecting photoacoustic waves in melanoma cells. This method is similar to flow cytometry, although using photoacoustics rather than fluorescence. Previously, we used piezoelectric films as our acoustic sensors. However, such films have indicated false-positive signals due to unwanted direct interactions between photons from the high laser fluence in the flow system and the film itself. We have adapted an optical detection scheme that obviates the need for piezoelectric films. STUDY DESIGN/MATERIALS AND METHODS: Our photoacoustic system comprised a tunable laser system with an output of 410-710 nm with a pulse duration of 5 nanoseconds. The light was delivered by optical fiber to a glass microcuvette that contained saline buffer suspensions of melanoma and white blood cells. We used a continuous HeNe laser to provide a probe beam that reflected off of a glass and water interface in close proximity to the microcuvette. The beam was detected by a high-speed photodiode. When a photoacoustic wave was generated in the microcuvette, the wave propagated and changed the reflectance of the beam due to index of refraction change in the water. This perturbation was used to detect the presence of melanoma cells. RESULTS: We determined a detection threshold of about one individual melanoma cell with no pyroelectric noise indicated in the signals. CONCLUSIONS: The optical reflectance method provides sensitivity to detect small numbers of melanoma cells without created false-positive signals from pyroelectric interference, showing promise as a means to perform tests for circulating melanoma cells in blood samples.