Benefiting from the high imaging resolution and deep penetration depth, Optical coherence tomography (OCT) is extensively applicable in ophthalmology, dermatology, and other clinical fields. However, the imaging quality is usually compromised by some noises such as horizontal coherence stripes, periodic background noise, and speckle noise. This paper proposes a multi-noise removal algorithm that combines spatial and transform-domain methods with optimized wavelet threshold denoising. This algorithm eliminates horizontal coherence stripes by generating a denoising mask through image segmentation and connected-domain filtering of superimposed B-scan images, utilizing the mask to remove these stripes. Besides, the periodic noise is removed by using frequency domain filters, while the speckle noise is also suppressed with the optimized wavelet threshold denoising method. We performed skin imaging using the SS-OCT system, processed the images, and evaluated the algorithm by quantifying the parameters such as signal-to-noise ratio, contrastto-noise ratio, and equivalent number of looks. Results demonstrate that the proposed algorithm can effectively suppress multiple noises while retaining the original detailed information. This study offers an ideal solution for OCT image denoising, potentially extending its clinical applications.
Angiogenesis is essential for bone homeostasis and repair. Newly formed vessels convey osteogenic progenitors during bone regeneration. However, the lack of continuous and label-free visualization of the bone microvasculature has resulted in little understanding of the neovascular dynamics. Here, we take advantage of optical-resolution photoacoustic microscopy (ORPAM) for label-free, intravital, long-term observation of the bone vascular dynamics. We quantify the angiogenic effect of locally-applied vascular endothelial growth factor (VEGF) in the mouse tibia defect model. VEGF treatment increased the concentration of total hemoglobin, vascular branching, and vascular density, which increased bone formation within the defect. These data demonstrated ORPAM as a useful imaging tool understand bone angiogenesis, and revealed the effectiveness of locally delivered therapeutic agents with sufficient sensitivity, contributing to the studying the bone regeneration in the future.
Photoacoustic microscopy (PAM) is an emerging technique extensively used to study brain activities. However, limited by the size and performance of optical/acoustic scanners, existing ORPAMs are still bulky, heavy, and suffer from low imaging quality/speed. Here, we develop a wearable ORPAM probe featuring small, light, fast, and cellular imaging capability. To evaluate the probe, we monitored the cerebral vascular network within two hours and demonstrated that the microscope was stable enough to study long-term brain hemodynamics in a freely moving rat.
Hemorrhagic shock, as an important clinical issue, is regarding as a critical disease with a high mortality rate. Unfortunately, existing clinical technologies are inaccessible to assess the hemorrhagic shock via hemodynamics in microcirculation. Here, we proposed an ultracompact photoacoustic microscope to assess hemorrhagic shock by using a rat model. In animal study, hemodynamic features of the microvascular network including concentration of total hemoglobin (CHbT) and small vascular density (SVD) were derived to assess the microvascular hemodynamics of different organs, assessing the hemorrhagic shock via microcirculation. On the other hand, in vivo oral imaging of healthy volunteers also indicates the translational possibility of this technique for clinical evaluation of hemorrhagic shock.
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