Multispectral indices for real-time and non-invasive tissue ischemia monitoring using snapshot cameras

An adequate supply of oxygen-rich blood is vital to maintain cell homeostasis, cellular metabolism, and overall tissue health. While classical methods of measuring tissue ischemia are often invasive, localized and require skin contact or contrast agents, spectral imaging shows promise as a non-invasive, wide field, and contrast-free approach. We evaluate three novel reflectance-based spectral indices from the 460 - 840 nm spectral range. With the aim of enabling real time visualization of tissue ischemia, information is extracted from only 2-3 spectral bands. Video-rate spectral data was acquired from arm occlusion experiments in 27 healthy volunteers. The performance of the indices was evaluated against binary Support Vector Machine (SVM) classification of healthy versus ischemic skin tissue, two other indices from literature, and tissue oxygenation estimated using spectral unmixing. Robustness was tested by evaluating these under various lighting conditions and on both the dorsal and palmar sides of the hand. A novel index with real-time capabilities using reflectance information only from 547 nm and 556 nm achieves an average classification accuracy of 88.48, compared to 92.65 using an SVM trained on all available wavelengths. Furthermore, the index has a higher accuracy compared to reference methods and its time dynamics compare well against the expected clinical responses. This holds promise for robust real-time detection of tissue ischemia, possibly contributing to improved patient care and clinical outcomes.

MicroCT Can Characterize Clots Retrieved With Mechanical Thrombectomy From Acute Ischemic Stroke Patients–A Preliminary Report

Background

Characterization of the clot occluding the arteries in acute ischemic stroke received ample attention, in terms of elucidating the relationship between the clot composition, its etiology and its amenability for pharmacological treatment and mechanical thrombectomy approaches. Traditional analytical techniques such as conventional 2D histopathology or electron microscopy sample only small parts of the clot. Visualization and analysis in 3D are necessary to depict and comprehend the overall organization of the clot. The aim of this study is to investigate the potential of microCT for characterizing the clot composition, structure, and organization.

Methods

In a pilot study, we analyzed with microCT clots retrieved from 14 patients with acute ischemic stroke. The following parameters were analyzed: overall clot density, clot segmentation with various density thresholds, clot volume.

Results

Our findings show that human clots are heterogeneous in terms of CT intra-clot density distribution. After fixation in formalin, the clots display a shift toward negative values. On average, we found the mean HU values of red clots retrieved from patients to be −153 HU, with SD = 23.8 HU, for the intermediate clots retrieved from patients −193 HU, SD = 23.7 HU, and for the white clots retrieved from patients −229 HU, SD = 64.8 HU.

Conclusion

Our study shows that volumetric and density analysis of the clot opens new perspectives for clot characterization and for a better understanding of thrombus structure and composition.

Appropriateness criteria for treatment of osteoporotic vertebral compression fractures

The purpose of this study was to review and summarise the literature on appropriateness criteria for treatment of osteoporotic vertebral compression fractures (OVCF), with appropriateness defined as a treatment where the expected benefits outweigh the expected harms, confirmed by available evidence and expert opinion. A comprehensive search of peer-reviewed publications (PubMed, EMBASE) and grey literature was performed. To be included for analysis, documents had to be a review article (e.g. clinical guideline or meta-analysis), focus on OVCF and make a statement on treatment appropriateness. Eleven publications fulfilled the eligibility criteria. Among the five publications that made recommendations about non-surgical management (NSM), there is agreement that conservative methods are appropriate in OVCF patients who have low level of pain, and that the majority of patients should be treated with conservative methods before other treatments are initiated. All publications made recommendations about vertebral augmentation procedures (VAP), i.e. vertebroplasty (VP) and/or balloon kyphoplasty (BKP). VAP are mostly considered appropriate in patients with high level of pain who do not respond to NSM. However, results cannot be generalised due to heterogeneity of treatment recommendations and patient selection. Although there is a consensus that NSM should be considered as the first-line treatment, there is more heterogeneity in treatment recommendations for VAP. This could most likely be explained by an insufficient clinical evidence base for VAP and heterogeneity of OVCF patients, leading to greater reliance on expert opinion affecting the quality of evidence in the primary sources.