Hyperspectral imaging has been explored for clinical applications in various medical disciplines. Based on our experiences, the potential of this versatile imaging method as well as pitfalls and limitations of current approaches are discussed. The use of reference samples and simple image modeling strategies are suggested to avoid misinterpretation and achieve a more conclusive image interpretation.
Hyperspectral imaging (HSI) is a new emerging modality for noncontact assessement of tissue perfusion parameters. This study includes investigations on monitoring perfusion changes of the hand during a modified Allen test and cuff occlusion test, on the influence of the skin tones during HSI-measurements and the feasibility of HSI monitoring of intraoral free flaps
The perfusion in cutaneous flap transplants needs to be monitored in order to detect vascular problems as early as possible. This can avoid tissue hypoxia and therefore, necrosis of the transplant. Since free flap transplant failures tend to happen more commonly during surgery than at a later onset, a non-contact real-time imaging device would be most advantageous. As hyperspectral imaging (HSI) is a new emerging modality to asses free flap perfusion contactless, this study aimed to investigate whether perfusion data can be interpreted appropriately using HSI, especially in regard to the individual skin tone. Further factors that might alter these HSI-interpretations, such as aging, BMI, different sexes or smoking habits, were also considered. Therefore, a prospective feasibility study was conducted, including 101 volunteers from whom images were taken on 16 different body sites. Skin pigmentation classification was performed using the Fitzpatrick skin type classification questionnaire and the individual typology angle (ITA) acquired from the images. Perfusion indices provided by the camera software were correlated to the possible influencing factors. The results show that a dark skin tone related to a high amount of melanin may influence the HSI-measurements and thus changes the HSI-derived perfusion indices. In addition, certain physiological influencing factors such as age, BMI and sex alter the tissue composition and qualities, thus showing measurement peculiarities within these groups. In conclusion, hyperspectral imaging can be used for perfusion assessment for people with lighter skin tone levels. Further developments are appreciated especially regarding skin pigmentation and the interpretation of indices of greater skin tone levels.
Hyperspectral imaging to monitor perfusion parameters during the Allen test was performed in 20 volunteers. Clear differences in tissue oxygenation and hemoglobin index during rest, occlusion and reperfusion were visually and computationally evident.
Convolutional neural networks were trained to determine four perfusion parameters from HSI recordings. The false-color images generated in this process show slight differences from the corresponding references, but can be reproduced meaningfully by visual assessment.
Detection of an early stage of subglottic edema is vital for airway management and prevention of stenosis, a life-threatening condition in critically ill neonates. As an observer for the task of diagnosing edema in vivo, we investigated spatiotemporal correlation (STC) of full-range optical coherence tomography (OCT) images acquired in the rabbit airway with experimentally simulated edema. Operating the STC observer on OCT images generates STC coefficients as test statistics for the statistical decision task. Resulting from this, the receiver operating characteristic (ROC) curves for the diagnosis of airway edema with full-range OCT in-vivo images were extracted and areas under ROC curves were calculated. These statistically quantified results demonstrated the potential clinical feasibility of the STC method as a means to identify early airway edema.
Recently, full-range optical coherence tomography (OCT) systems have been developed to image the human airway.
These novel systems utilize a fiber-based OCT probe which acquires three-dimensional (3-D) images with micrometer
resolution. Following an airway injury, mucosal edema is the first step in the body’s inflammatory response, which
occasionally leads to airway stenosis, a life-threatening condition for critically ill newborns. Therefore, early detection of
edema is vital for airway management and prevention of stenosis. In order to examine the potential of the full-range
OCT to diagnose edema, we investigated temporal correlation of OCT images obtained from the subglottic airway of
live rabbits. Temporally correlated OCT images were acquired at fixed locations in the rabbit subglottis of either
artificially induced edema or normal tissues. Edematous tissue was experimentally modeled by injecting saline beneath
the epithelial layer of the subglottic mucosa. The calculated cross temporal correlations between OCT images of normal
airway regions show periodicity that correlates with the respiratory motion of the airway. However, the temporal
correlation functions calculated from OCT images of the edematous regions show randomness without the periodic
characteristic. These in-vivo experimental results of temporal correlations between OCT images show the potential of a
computer-based or -aided diagnosis of edema in the human respiratory mucosa with a full-range OCT system.
Background: Malignancies of the upper aerodigestive tract (UADT) are conventionally diagnosed by white light endoscopy, biopsy and histopathology. Probe-based Confocal Laser Endomicroscopy (pCLE) is a novel non-invasive technique which offers in vivo surface and sub-surface imaging of tissue. It produces pictures of cellular architecture comparable to histology without the need for biopsy. It has already been successfully used in different clinical subspecialties to help in the diagnosis and treatment planning of inflammatory and neoplastic diseases. PCLE needs to be used in combination with specific or non-specific contrast agents. In this study we evaluated the potential use of pCLE in combination with non-specific and specific contrast agents to distinguish between healthy mucosa and invasive carcinoma. Methods: Tissue samples from healthy mucosa and squamous cell carcinoma of the head and neck were taken during surgery. After topical application of three different contrast agents, samples were examined using different pCLE-probes and a Confocal Laser Scanning Microscope (CLSM). Images were then compared to the corresponding histological slides and cryosections. Results: Initial results show that pCLE in combination with fluorophores allows visualization of cellular and structural components. Imaging of different layers was possible using three distinct pCLEprobes. Conclusion: pCLE is a promising non-invasive technique that may be a useful adjunct in the evaluation, diagnosis and treatment planning of head and neck malignancies.
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