Photoacoustic imaging probe for detecting lymph nodes and spreading of cancer at various depths

Abstract

We propose a compact and easy to use photoacoustic imaging (PAI) probe structure using a single strand of optical fiber and a beam combiner doubly reflecting acoustic waves for convenient detection of lymph nodes and cancers. Conventional PAI probes have difficulty detecting lymph nodes just beneath the skin or simultaneously investigating lymph nodes located in shallow as well as deep regions from skin without any supplementary material because the light and acoustic beams are intersecting obliquely in the probe. To overcome the limitations and improve their convenience, we propose a probe structure in which the illuminated light beam axis coincides with the axis of the ultrasound. The developed PAI probe was able to simultaneously achieve a wide range of images positioned from shallow to deep regions without the use of any supplementary material. Moreover, the proposed probe had low transmission losses for the light and acoustic beams. Therefore, the proposed PAI probe will be useful to easily detect lymph nodes and cancers in real clinical fields.

Effective photoacoustic absorption spectrum for collagen-based tissue imaging

“…8 Additionally, to delineate transparent organs such as lymph nodes, gastrointestinal tracts, and bladders, labeled imaging has also been performed using several contrast agents, such as indocyanine green or methylene blue. [9][10][11][12] The second window of the NIR (NIR-II) region, also called short-wave infrared region (SWIR, defined here as 1100 to 2000 nm), is of current interest due to the relative low levels of scattering and the high-maximum permissible exposure compared with the NIR-I region. [12][13][14][15] Additionally, in the SWIR band, we find the optical absorption peaks of water, collagen, and lipids, three major molecules of human tissues.…”

In vivo Microscopic Photoacoustic Spectroscopy for Non-Invasive Glucose Monitoring Invulnerable to Skin Secretion Products

“…A signal from a shallow depth (<100 µm) may create difficulties in locating an acoustic detector because the detector is supposed to be located close to the region of incidence of the laser light in the perpendicular direction of the acoustic wave propagation. In order to overcome these challenges, researchers reported on an optical-acoustic beam combiner or photoacoustic cavity to guide the ultrasound to the acoustic detector 22 , 49 , 50 . We chose the latter case, as reported previously 21 , 29 , 30 , 32 .…”

Review of methods to improve the performance of linear array-based photoacoustic tomography

“…Lee et al proposed a handheld probe in which the illuminated light beam axis coincides with the axis of the ultrasound through a beam combiner. 44 The beam combiner doubly re°ects the acoustic waves to the linear array transducer and the transmission losses of the light and acoustic beams are low. Moreover, the laser output was shaped to a line beam by three cylindrical lenses (Fig.…”

“…In their small animal experiments, the lymph nodes near the skin could be detected without the need for any supplementary material. 44 Li et al proposed a similar handheld probe design, utilizing polymethyl methacrylate (PMMA) as an optical/acoustic coupler. 27 The optical/acoustic coupler re°ects the light beam two times and is permeable to acoustic waves, achieving coaxial light delivery and acoustic detection with the optical ber bundle and transducer probe parallel to each other.…”

“…Schemes of a handheld probe with the illuminated light beam axis coincides with the axis of the ultrasound through a beam combiner. 44 detection with the minimal wave aberration, however, it is inconvenient for handheld operation. The double-re°ector system represents the most compact design among the three.…”