Abstract
In photoacoustic computed tomography, the limited directivity of the detectors may cause deformation of off-center targets and lead to an imbalanced resolution in the imaging area. To improve the directivity of the acoustic detectors, several negative acoustic lenses have been proposed. In this study, we develop a new compound acoustic lens fabricated by integrating a concave polydimethylsiloxane (PDMS) lens and a convex epoxy lens. Both theoretical simulations and experimental evaluations demonstrate that the compound lens provides a larger directivity compared to single lenses made of PDMS, epoxy, and liquid. The measured acceptance angles of a 6-mm piezoelectric acoustic transducer equipped with the compound, epoxy, liquid, and PDMS lenses are 55°, 36°, 25°, and 20°, respectively. No deformation is observed in the off-center targets by using compound lens. However, serious deformation appears in the cases using single lenses.
Highlights
Over the past decade, there has been considerable interest in photoacoustic imaging (PAI) due to its rich optical contrast, high acoustic resolution, and relatively deep penetration [1]
We report a new compound acoustic lens made by integrating a convex lens fabricated with epoxy and a concave lens made of PDMS, and further compared it with three single acoustic lenses made of epoxy, PDMS, and liquid
We find that the edge spread functions (ESFs) of target 2 and 3 with compound lens have steeper edges compared to the case using the flat transducer
Summary
There has been considerable interest in photoacoustic imaging (PAI) due to its rich optical contrast, high acoustic resolution, and relatively deep penetration [1]. There will be degradation in the tangential resolution leading to serious deformation of the off-center targets To solve this problem, point detectors with an extra small active area, such as hydrophone, are always employed [15]; the sensitivity is relatively low and causes a low signal to noise ratio (SNR) of the raw signals. Point detectors with an extra small active area, such as hydrophone, are always employed [15]; the sensitivity is relatively low and causes a low signal to noise ratio (SNR) of the raw signals Another method is to integrate flat transducers and negative acoustic lenses [16]. Both the simulation and experimental results indicate that the compound lens offers the best directivity enlargement, and there is no deformation in the phantom experiments
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