Peripheral vascular disease (PVD) is a narrowing of the arteries in the extremities that might result in amputation when left untreated. The conventional ways to diagnose PVD are vascular imaging techniques such as ultrasound (US) Doppler, computed tomography (CT) angiography, and magnetic resonance angiography, which generally can only visualize large vessels or require contrast agents. Photoacoustic (PA) imaging could be a promising agent-free, highresolution modality to visualize vessels and be applied in various clinical studies. We have previously demonstrated an agent-free multi-structural photoacoustic (PA) and US peripheral angiography technique using contour scanning. To reduce the effect of the optical fluence, we compensated the PA images using the background PA signals that represent optical attenuation in the tissue. To evaluate its capability to provide functional information of the vasculature, we demonstrated an intentional blood flow occlusion with a pressure cuff and observed the changes in the quantification metrics. From the experiments, we confirmed the potential of the technique for providing a diagnostic evaluation of the peripheral vasculature.
Recently, 3D photoacoustic (PA) and ultrasound (US) technologies have been developed in various forms. There are roughly two main streams to obtain a 3D image; an 1D array US transducer with motorized scanner and a 2D matrix array US transducer. The former has limitations such as longer time to obtain a single 3D image, bulky design with the scanner that degrades portability, and anisotropic resolution. In contrast, the latter acquires and generates a 3D image at once, which enables real-time imaging, compact design, and isotropic resolution. In this study, we demonstrate dual-modal PA and US imaging using a 2D matrix array transducer scanner. The resolution was measured through a phantom experiment, and the methylene blue signal was verified through a rat SLN experiment.
Clinical PA (photoacoustic) /US (ultrasound) imaging has been widely explored and in most cases is performed in 2D. However, 2D PA/US imaging technology has problems of low reproducibility and high operator dependency. For these reasons, we developed a clinical handheld 3D PA/US scanner using an 1D linear array US transducer and a compact mechanical scanner, which is managed by a Scotch yoke mechanism. The total weight, overall size and the field of view (FOV) of the scanner are 950 g, 100 × 80 × 100 mm3 and 38 × 40 mm2, respectively. We have successfully evaluated the feasibility of clinical use by acquiring various images of the human body parts such as face, neck and calf. We believe that the hand-held scanner can be used for a variety of clinical applications.
Cutaneous melanoma accounts for only 5% of skin cancer, but it is as dangerous as it is associated with 75% skincancer- related deaths. Clinical decision-making and prognosis is the thickness of melanoma into the tissue. Another feature is that the cancer that can occur anywhere on the body, including the face, chest, thigh, soles, and groin, and its size is also very diverse. Here, we developed a hand-held scanner and obtained 3D photoacoustic images of in vivo human melanoma by using multispectral real-time clinical photoacoustic and ultrasound imaging system with the scanner. The scanner allowed wide-field scanning of 3.8 cm (transducer aperture size) × 3 cm (scanning range). Four patients were recruited to obtain photoacoustic melanoma images of various sites (thigh, sole, etc.), types (in situ, invasive, etc.) and sizes (sub-mm to cm). Five wavelengths were used to perform spectral unmixing. The penetration depth of melanoma was successfully confirmed by the multispectral photoacoustic images. The melanoma depth measured by photoacoustic imaging was significantly similar to histopathologic results obtained after excision (mean absolute error = 0.6 mm). In this study, we acquired small-to-large size and various types of melanoma multispectral photoacoustic images in vivo. We hope that this study will be an additional criterion for histopathological results that may have a positive impact on the diagnosis, treatment, and prognosis of melanomas.
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