Probe organization of photoacoustic devices using low-cost laser diodes

Photoacoustic technology provides a non-invasive method for detecting biological tissues, but its clinical application is limited, partly due to the large volume and high cost of laser sources. A compact PA sensing instrument powered by laser diodes for biomedical tissue diagnosis can provide clinical doctors with a practical and effective tool for evaluating breast diseases.

By providing a cost-effective organizational diagnostic approach, compact PA sensing instruments can bridge the gap between PA research and its practical applications. This instrument is the work of a research group at the Indian Institute of Technology Indore.

Researchers integrated multiple laser diodes for PA excitation in a compact housing and developed a pulse current supply unit that can induce the laser diode to generate 25 ns of current pulses at a frequency of 20 kHz. They characterize the optical semiconductor laser tube casing and power supply unit based on pulse width, laser intensity, and repeatability of multiple laser diodes.

In order to improve signal strength, the team concentrated the laser diodes in the casing at one point. This enhances the amplitude of the PA signal and improves the signal-to-noise ratio. The amplitude of the time-domain PA signal indicates that as the number of laser diodes increases, the light energy increases.

Researchers compared laser diode based PA systems with traditional Nd: YAG laser based PA systems and found that these systems exhibited similar PA responses. The amplitude of the acoustic spectrum indicates that the new PA sensing instrument is effective for traditional PA settings.
The team used a compact PA sensing system to study fibrocystic changes in the breast in vitro. Researchers analyzed the spectrum of PA signals to quantitatively evaluate tissue characteristics.

The system distinguishes tissue types based on quantitative spectral parameters. The PA spectral response reveals different spectral patterns corresponding to different tissue types. Compared with normal breast tissue, fibrocystic breast disease tissue exhibits higher dominant frequency peaks and energy.

Fibrocystic breast disease samples exhibit dominant frequency peaks around 1.60 MHz, indicating an increase in tissue density due to increased glandular and stromal elements. In contrast, normal breast tissue shows a lower peak frequency of 0.26 MHz, reflecting its fiber and fat composition. The histopathological examination confirmed these findings and confirmed the correlation between spectral response and tissue characteristics. Researchers also used the system to associate PA spectral parameters with the elastic properties of fibrocystic breast disease tissue compared to normal breast parenchymal tissue samples.

Ultrasound and mammography are currently the most common diagnostic methods for breast diseases, followed by fine needle aspiration cytology. Due to the accuracy issues of these imaging methods, an alternative screening technique is needed to enable clinical doctors to have a deeper understanding of disease diagnosis than traditional methods.

The experimental results indicate that PA sensing instruments can provide a fast, reliable, and non-invasive method to evaluate tissue density and identify pathological changes in breast tissue, thereby enabling more timely intervention and improving results.

The use of advanced signal processing technology and high-frequency transducers can enhance the real-time and in vivo research capabilities of the system, thereby expanding its clinical practicality. In the future, laser diodes of different wavelengths can be merged into the same optical shell to study biological tissues of various wavelengths.
The study was published in the Journal of Biomedical Optics.

Source: Laser Net