Photoacoustic Microscopy (PAM) has emerged as a rapidly advancing non-invasive medical imaging method in recent years. However, slow imaging speed has impeded its widespread adoption in clinical applications. In certain scenarios, sparse spatial sampling is essential for PAM so there is a trade-off between spatial resolution and imaging speed. To address this limitation, we propose a frequency domain index based on Cumulative Power Difference (CPD) to determine rapidly the optimal down-sampling factors. In this study, the structural images of mice ears were acquired by the PAM system. Subsequently, the optimal down-sampling factor was determined through CPD analysis of these images via interpolation. Finally, the correlation between cumulative power difference and the image quality loss curve were analyzed. The results indicate that the quality of the reconstructed images decreases with the increasing down-sampling factor. Moreover, the cumulative power difference is an effective tool for rapid assessment of reconstruction image quality degradation due to varying down-sampling factors.
Pressure ulcer is a common condition for patients who are bedridden or have limited mobility. In this study, two models of pressure ulcer on mouse ears were established, and the blood flow after pressure ulcers was monitored using a Laser Speckle Contrast Imaging (LSCI) system. Maps of blood flow revealed that after a single 1.5-hour pressure ulcer on the mouse ear, the blood flow perfusion at the compressed area gradually recovered over time and essentially returned to normal by the fifth day. Conversely, with continuous daily pressure ulcers for 1.5 hours, the compressed area showed almost no perfusion by the fourth day, and the ulceration was fully formed by the 5th day. Compared to white light imaging, LSCI offers more precise monitoring of blood flow at pressure ulcer sites. The research solves the problem of dynamic functional monitoring of the blood flow velocity changes at spatial resolution. It provides a new technology for dynamic assessment of pressure ulcers and offers a new method for the care and treatment of clinical patients.
Striae gravidarum is a kind of striae atrophicae commonly observed in primigravid women. Striae gravidarum appear irregular purple or light red at the beginning of pregnancy, and gradually fade to silver bright stripes in the late pregnancy or postpartum. Currently, laser therapy can help with striae gravidarum, so it is crucial to know how to effectively assess striae gravidarum both during and after treatment. This research proposed a feature enhanced U-net architecture model for identifying severity of stretch marks. This approach initially extracts the single-channel grayscale from RGB images of striae gravidarum and enhances their contrast and saturation by using optimal adjustment parameters. Subsequently, a U-net model is employed to perform striae gravidarum extraction based on the enhanced images. The train dataset is 848 frames, and the test dataset is 95 frames. Compared to the traditional threshold segmentation methods, the proposed approach achieves higher accuracy in segmenting stretch marks across different pregnancies. Compared to the full-connection model method, the proposed approach not only demonstrates faster calculation speed and reduced data requirements but also achieves superior results in terms of segmentation and classification accuracy, which is of great significance for the construction of auxiliary diagnostic instrument for striae gravidarum treatment.
Currently, intracranial pressure (ICP) is the primary clinical monitoring parameter for traumatic brain injury (TBI). However, during the hyperacute phase of TBI, ICP value lags behind changes of brain temperature (BT) and neurometabolic activity. This is due to the compensatory capacity of the intracranial space. Here, we explored BT changes and concentration changes of cytochrome c (∆Ccytc) during the hyper-acute phase of TBI. Nine mice were randomly divided into control group, mild TBI group, and severe TBI group. The mouse TBI model is created by using various levels of striking force. The strike device is designed and improved based on Feeney's free fall model. BT can be measured by a minimally invasive measurement probe, allowing for the observation of changes in both time and spatial distribution. ∆Ccytc was calculated using an intrinsic optical signal imaging system (IOSI). The relationship between BT and ∆Ccytc was analyzed during the development of mice TBI models.
Photoacoustic Microscopy (PAM) is a novel medical imaging technique developed rapidly in recent years with the advantages of high resolution, high contrast, and no ionizing radiation. In this study, we developed a One-Shot functional Photoacoustic Microscopy (OS-fPAM) system for assessing Traumatic Brain Injury (TBI). The OS-fPAM system only employed a single 532 nm nanosecond pulse laser with Raman delay optical path control, which can produce both 532 nm and 553 nm laser beams. The dual-wavelength beams were then coupled via a dichroic mirror and focused on the surface of the experimental sample. Then, the photoacoustic signal was collected and amplified in the ultrasonic signal acquisition module, and the blood oxygen saturation (sO2) image was calculated by two wavelength photoacoustic images. The feasibility of the OS-fPAM system was performed through the calibration experiments with different ratios of red ink and blue ink. Meanwhile, the OS-fPAM system can monitor microvascular structures and sO2 in the TBI model on mice for 96 hours in vivo with a spatial resolution of ~40 μm, demonstrating the potential to evaluate rehabilitation and cerebral vascular damage.
Cerebral edema is a potentially fatal disorder and divided into several types. The accurately identifying the type of cerebral edema is vital for the precise treatment. Previous studies have been devoted the multi-model parameters to access the feature cerebral edema. However, few research focused on the models to distinguish the types of cerebral edema. Here, a multi-parameter joint imaging system was developed, which combined laser speckle contrast imaging system (LSCI) and intrinsic optical signals imaging system (IOS). Several parameters such as relative cerebral blood flow (rCBF), concentration changes of oxy-hemoglobin (HbO), deoxy-hemoglobin (HbR), and blood oxygen saturation (sO2) were recorded at the same region of interest (ROI). Vasogenic and cytotoxic cerebral edema models were induced by phenylephrine hydrochloride and vasopressin, respectively. The mice were randomly assigned to 2 groups and 10 individuals in each group. After drug injection, the parameters were collected every 20 minutes within 2 h in vivo. The rCBF in both groups increased gradually within 2 hours throughout the whole process, but the rCBF in the vasogenic group grew substantially faster than it in the cytotoxic group within the first 80 minutes. In the vasogenic group, the concentration changes of HbO and HbR were more pronounced. The data was analyzed by the t-test of an independent sample, and there were significant differences between the parameters of the two types of cerebral edema. It has potential for achieving a classification of cerebral edema.
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