Multidirectional reception of photoacoustic signals for higher resolution imaging

In this study, the authors prepared a thin silicone tube filled with a mixture of red ink and olive oil as a model that mimics arteriosclerosis. The tube was embedded in a soft phantom. Photoacoustic measurements were performed using 405 nm and 520 nm laser diodes. As a result, the 405 nm laser produced a higher photoacoustic signal as the oil concentration in the mixture increased, whereas the 520 nm laser produced lower photoacoustic signals as the oil concentration increased. By focusing on the difference in the optical absorption at different wavelengths between the red ink and oil, it was shown that there was a possibility of estimation of the oil concentration from the ratio of photoacoustic signals between different wavelengths.

Section: Introductionmentioning

confidence: 99%

Estimation of the composition ratio of two contents filled in an elastic thin tube through laser-diode-based photoacoustic measurements

Wang,

Wada,

Nakamura

2024

“…Then, the tissue temporarily undergoes thermoelastic volume expansion, and pressure waves are generated and detected with a piezoelectric ultrasonic transducer. [20][21][22] Thus, the imaging depth exceeds the optical diffusion limit (;1 mm). 23) X-ray CT and MRI 24) are other modalities that provide better spatial resolution than ultrasonic imaging.…”

Section: Introductionmentioning

confidence: 99%

Directivity of photoacoustically generated ultrasound from a thin tube embedded in the soft phantom

Wang

Wada

Nakamura

2023

Authors’ previous study has revealed that the acoustic resonances had non-negligible effects on the photoacoustic signal for liquid sample confined in a thin tube. This paper presents numerical and experimental studies on the effects of tube’s hardness on the directivity of the generated photoacoustic signal. Thin glass capillary and silicone tube of 1 mm in diameter were tested with a pulsed light of 637 nm in wavelength. Black ink was confined in the capillary and tube as photoacoustic sample material. In the glass capillary, acoustic resonance modes in the tube was efficiently excited, and clear directivity was observed in the photoacoustic signals. On the other hand, little resonance was stimulated in the silicon tube because of the acoustic impedance matching between the sample and surrounding media, which resulted in weak confinement of acoustic waves. The results suggested a possibility of characterization of the physical properties of thin tube.

“…In this imaging technique, an optical absorber such as biological tissue is irradiated with a pulsed laser, the tissue temporarily undergoes thermoelastic volume expansion, and the generated pressure wave (PA wave) is acquired with an ultrasonic detector. [1][2][3] One of the features of PA imaging is deeper penetration in comparison with the optical imaging modality. Pure optical imaging has optical scattering that is two to three orders of magnitude greater than ultrasonic scattering, which significantly limits the imaging depth in living tissue.…”

Section: Introductionmentioning

confidence: 99%

Development of optical resolution photoacoustic microscopy with sub-micron lateral resolution for visualization of cells and their structures

Shintate

Morino

Kawaguchi

et al. 2020

Photoacoustic (PA) imaging is a hybrid imaging technique with light-dependent contrast and ultrasound-dependent depth. In previous studies, the interest of PA imaging was mainly clinical research. However, in recent years, PA imaging that targets cells also has attracted attention. Cells are the smallest unit in our body, and cell abnormalities cause various diseases. Therefore, PA imaging of cells is important for elucidating the relationship between diseases and PA properties and linking the results to the clinical application of PA imaging. For PA imaging of cells and its internal structures, sub-micron lateral resolution is required. In this study, we have developed an optical resolution photoacoustic microscopy (OR-PAM) system using a high NA objective lens and a single-mode fiber to achieve sub-micron lateral resolution. With the OR-PAM, it was confirmed that the lateral resolution was better than 700 nm, and the characteristic shapes of red blood cells and melanoma cells could be visualized.