Multispectral photoacoustic holography of elastomers from a bright background

Abstract

Photoacoustic imaging of elastomers has important biomedical value. However, a bright background, e.g., blood vessels in living tissue, brings a challenge for photoacoustic elastography. In this study, we predicted that the spectrum of photoacoustic signals from elastomers with high elasticity could appear as narrow peaks at the eigen-frequencies of elastomers, but the signals from a bright background, e.g., blood vessel, show flat broadband spectrum for their low-quality factor. Even when the two kinds of signals are mixed together, the signals from elastomers can be identified from the spectrum since they present as convex narrow peaks on a wide base. Based on this factor, we propose a multispectral photoacoustic holography to realize selective imaging of tiny elastomers. This method recovers the image only using several frequency components in photoacoustic signals, instead of the whole-band signal. Since these narrow peaks in the spectrum correspond to the eigen-vibration of elastomers, the proposed method can highlight the elastomers with high elasticity from a bright background with low elasticity. The method was validated by experiments. This study might be helpful to localize elastic anomalous areas in the tissue, such as calcification in the vascular network, microcalcification in a tumor, and implants.

Temperature difference effect of biological tissues induced by low-intensity unfocused ultrasound

“…It is important to consider how to achieve photoacoustic imaging of other components under these bright backgrounds produced by high light absorption components. 7,8) Some researchers have found that the photoacoustic signal amplitude increased by about 5% when the temperature of biological light absorbers increased by 1 °C, and this effect was nearly linear. 9,10) If there is a way to effectively raise the temperature of components other than those with high light absorption coefficients, it is anticipated that the temperature rise of various components will be used to weight their respective photoacoustic signals, thereby reducing the impact of strong photoacoustic signals on imaging.…”