Abstract
Although linear transducer arrays have been intensely used in photoacoustic imaging, their geometrical shape constrains light illumination. Today, most linear array based photoacoustic systems utilize side-illumination geometry, which consists of two line fiber bundles attached to the side of the probe. The angled light illumination increases the light travel distance in deep tissue, consequently limiting the imaging depth. This issue was partially addressed by adding a right angle prism in front of the transducer. While this design makes the light illumination and acoustic detection co-axial, the transducer and the fiber bundles are orthogonal to each other, making the system inconvenient for handheld use. To overcome this limitation, here we propose a double-reflector design, in which the second reflector redirects the acoustic signals by another 90°, so that the transducer and the fiber bundle are now parallel to each other. In this design, both the transducer and fiber bundle output are fitted into a compact housing for convenient handheld imaging. To evaluate the efficiency of our design, we performed various phantom and human in vivo experiments. Our results demonstrate that the double-reflector design indeed provides deeper imaging depth and it also allows for easy imaging of objects with uneven surfaces.
Highlights
Photoacoustic (PA) imaging (PAI) is a promising modality for high-resolution imaging of optical absorption in deep tissue
Compared to that of perpendicular illumination, photons in the side-illumination geometry will need to travel over a longer distance before reaching the object, resulting in weaker fluence
Multiple groups have used the Monte Carlo (MC) simulation to investigate this issue[15,16]. All their results demonstrated that the smaller the light incident angle, the higher the light fluence in deep tissue
Summary
Photoacoustic (PA) imaging (PAI) is a promising modality for high-resolution imaging of optical absorption in deep tissue. The prism is transparent to light, whereas the acoustic waves will be reflected by 90°, achieving co-axially illumination and detection. This design is inconvenient for handheld operation because the transducer and fiber bundle are orthogonal to each other. Reflects the light beam two times and is permeable to acoustic waves[18] This design achieves coaxial light delivery and acoustic detection with the optical fiber bundle and transducer probe parallel to each other. Compared to the single-reflector design, we added one additional glass to reflect acoustic waves by another 90 degrees Both the transducer array and fiber bundle are parallel to each other. Compared to the design by Li et al, we reflect acoustic waves instead of propagating them through two different mediums, eliminating impedance mismatch
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