Detection of cutaneous oxygen saturation using a novel snapshot hyperspectral camera: a feasibility study.

BACKGROUND: Tissue necrosis, a consequence of inadequate tissue oxygenation, is a common post-operative complication. As current surgical assessments are often limited to visual and tactile feedback, additional techniques that can aid in the interrogation of tissue viability are needed to improve patient outcomes. In this bi-institutional pilot study, the performance of a novel snapshot hyperspectral imaging camera to detect superficial cutaneous oxygen saturation (StO2) was evaluated. METHODS: Healthy human volunteers were recruited at two participating centers. Cutaneous StO2 of the forearm was determined by a snapshot hyperspectral camera on two separate study days during occlusion-reperfusion of the brachial artery and after induction of local vasodilation. To calculate the blood StO2 at each pixel in the multispectral image, spectra were selected, and fitting was performed over wavelengths ranging from 470 to 950 nm. RESULTS: Quantitative detection of physiological changes in cutaneous StO2 levels was feasible in all sixteen volunteers. A significant (P<0.001) decrease in cutaneous StO2 levels from 78.3% (SD: 15.3) at baseline to 60.6% (SD: 19.8) at the end of occlusion phase was observed, although StO2 levels returned to baseline after five minutes. Mean cutaneous StO2 values were similar in the same subjects on separate study days (Pearson R2: 0.92 and 0.77, respectively) at both centers. Local vasodilation did not yield significant changes in cutaneous StO2 values. CONCLUSIONS: This pilot study demonstrated the feasibility of a snapshot hyperspectral camera for detecting quantitative physiological changes in cutaneous StO2 in normal human volunteers, and serves as a precursor for further validation in perioperative studies.

Tissue characterization with depth-resolved attenuation coefficient and backscatter term in intravascular optical coherence tomography images.

An important application of intravascular optical coherence tomography (IVOCT) for atherosclerotic tissue analysis is using it to estimate attenuation and backscatter coefficients. This work aims at exploring the potential of the attenuation coefficient, a proposed backscatter term, and image intensities in distinguishing different atherosclerotic tissue types with a robust implementation of depth-resolved (DR) approach. Therefore, the DR model is introduced to estimate the attenuation coefficient and further extended to estimate the backscatter-related term in IVOCT images, such that values can be estimated per pixel without predefining any delineation for the estimation. In order to exclude noisy regions with a weak signal, an automated algorithm is implemented to determine the cut-off border in IVOCT images. The attenuation coefficient, backscatter term, and the image intensity are further analyzed in regions of interest, which have been delineated referring to their pathology counterparts. Local statistical values were reported and their distributions were further compared with a two-sample t-test to evaluate the potential for distinguishing six types of tissues. Results show that the IVOCT intensity, DR attenuation coefficient, and backscatter term extracted with the reported implementation are complementary to each other on characterizing six tissue types: mixed, calcification, fibrous, lipid-rich, macrophages, and necrotic core.

Validation of full-field optical coherence tomography in distinguishing malignant and benign tissue in resected pancreatic cancer specimens.

BACKGROUND: Pancreatic cancer is the fourth leading cause of cancer-related mortality in the United States. The minority of patients can undergo curative-intended surgical therapy due to progressive disease stage at time of diagnosis. Nonetheless, tumor involvement of surgical margins is seen in up to 70% of resections, being a strong negative prognostic factor. Real-time intraoperative imaging modalities may aid surgeons to obtain tumor-free resection margins. Full-field optical coherence tomography (FF-OCT) is a promising diagnostic tool using high-resolution white-light interference microscopy without tissue processing. Therefore, we composed an atlas of FF-OCT images of malignant and benign pancreatic tissue, and investigated the accuracy with which the pathologists could distinguish these. MATERIALS AND METHODS: One hundred FF-OCT images were collected from specimens of 29 patients who underwent pancreatic resection for various indications between 2014 and 2016. One experienced gastrointestinal pathologist and one pathologist in training scored independently the FF-OCT images as malignant or benign blinded to the final pathology conclusion. Results were compared to those obtained with standard hematoxylin and eosin (H&E) slides. RESULTS: Overall, combined test characteristics of both pathologists showed a sensitivity of 72%, specificity of 74%, positive predictive value of 69%, negative predictive value of 79% and an overall accuracy of 73%. In the subset of pancreatic ductal adenocarcinoma patients, 97% of the FF-OCT images (n = 35) were interpreted as tumor by at least one pathologist. Moreover, normal pancreatic tissue was recognised in all cases by at least one pathologist. However, atrophy and fibrosis, serous cystadenoma and neuroendocrine tumors were more often wrongly scored, in 63%, 100% and 25% respectively. CONCLUSION: FF-OCT could distinguish normal pancreatic tissue from pathologic pancreatic tissue in both processed as non-processed specimens using architectural features. The accuracy in pancreatic ductal adenocarcinoma is promising and warrants further evaluation using improved assessment criteria.

Noninvasive Detection of Metastases and Follicle Density in Ovarian Tissue Using Full-Field Optical Coherence Tomography.

PURPOSE: Autotransplantation of ovarian tissue can be used to restore fertility in patients with cancer following gonadotoxic treatment. Whether this procedure is safe remains unclear, as current tumor detection methods render the ovarian tissue unsuitable for transplantation. Full-field optical coherence tomography (FF-OCT) is an imaging modality that rapidly produces high-resolution histology-like images without the need to fix, freeze, or stain the tissue. In this proof-of-concept study, we investigated whether FF-OCT can be used to detect metastases in ovarian tissue, thereby increasing the safety of ovarian tissue autotransplantation. We also evaluated whether cortical ovarian tissue and follicles remain viable following FF-OCT imaging. EXPERIMENTAL DESIGN: Formalin-fixed, paraffin-embedded tissue samples were obtained from seven normal ovaries and fourteen ovaries containing metastases and/or micrometastases. These samples were deparaffinized and imaged using FF-OCT. The FF-OCT images were then compared with corresponding hematoxylin and eosin-stained tissue sections. Finally, we examined the effect of FF-OCT imaging on the viability of ovarian tissues and follicles in fresh bovine ovarian tissue using a glucose uptake and neutral red staining, respectively. RESULTS: FF-OCT illustrated both normal structures and metastases in ovarian tissue within minutes. Primordial follicles were readily identifiable. Finally, tissues and follicles remained viable following FF-OCT imaging for up to 180 and 60 minutes, respectively. CONCLUSIONS: FF-OCT imaging is a promising method for the noninvasive detection of metastases, including micrometastases, in ovarian tissue. Moreover, this method facilitates the selection of cortical ovarian tissue with the highest density of primordial follicles, potentially increasing the likelihood of restoring ovarian function following ovarian tissue autotransplantation. Clin Cancer Res; 22(22); 5506-13. ©2016 AACR.

3D assessment of stent cell size and side branch access in intravascular optical coherence tomographic pullback runs.

We present a semi-automatic approach to assess the maximum circular unsupported surface area (MCUSA) of selected stent cells and the side branch access through stent cells in intravascular optical coherence tomography (IVOCT) pullback runs. Such 3D information may influence coronary interventions, stent design, blood flow analysis or prognostic evaluation. First, the stent struts are detected automatically and stent cells are reconstructed with users' assistance. Using cylinder fitting, a 2D approximation of the stent cell is generated for MCUSA detection and measurement. Next, a stent surface is reconstructed and stent-covered side branches are detected. Both the stent cell contours and side branch lumen contours are projected onto the stent surface to indicate their areas, and the overlapping regions are measured as the side branch access through these stent cells. The method was evaluated on phantom data sets and the accuracy of the MCUSA and side branch access was found to be 95% and 91%, respectively. The usability of this approach for clinical research was proved on 12 in vivo IVOCT pullback runs.