G.C. Langhout

Detection of melanoma metastases in resected human lymph nodes by noninvasive multispectral photoacoustic imaging

Objective. Sentinel node biopsy in patients with cutaneous melanoma improves staging, provides prognostic information, and leads to an increased survival in node-positive patients. However, frozen section analysis of the sentinel node is not reliable and definitive histopathology evaluation requires days, preventing intraoperative decision-making and immediate therapy. Photoacoustic imaging can evaluate intact lymph nodes, but specificity can be hampered by other absorbers such as hemoglobin. Near infrared multispectral photoacoustic imaging is a new approach that has the potential to selectively detect melanin. The purpose of the present study is to examine the potential of multispectral photoacoustic imaging to identify melanoma metastasis in human lymph nodes. Methods. Three metastatic and nine benign lymph nodes from eight melanoma patients were scanned ex vivo using a Vevo LAZR© multispectral photoacoustic imager and were spectrally analyzed per pixel. The results were compared to histopathology as gold standard. Results. The nodal volume could be scanned within 20 minutes. An unmixing procedure was proposed to identify melanoma metastases with multispectral photoacoustic imaging. Ultrasound overlay enabled anatomical correlation. The penetration depth of the photoacoustic signal was up to 2 cm. Conclusion. Multispectral three-dimensional photoacoustic imaging allowed for selective identification of melanoma metastases in human lymph nodes.

Differentiation of healthy and malignant tissue in colon cancer patients using optical spectroscopy: A tool for image-guided surgery

Surgery for colorectal cancer aims for complete tumor resection. Optical‐based techniques can identify tumor and surrounding tissue through the tissue specific optical properties, absorption and scattering, which are both influenced by the biochemical and morphological composition of the tissue.

Nerve detection using optical spectroscopy, an evaluation in four different models: In human and swine, in-vivo, and post mortem

Identification of peripheral nerve tissue is crucial in both surgery and regional anesthesia. Recently, optical tissue identification methods are presented to facilitate nerve identification in transcutaneous procedures and surgery. Optimization and validation of such techniques require large datasets. The use of alternative models to human in vivo, like human post mortem, or swine may be suitable to test, optimize and validate new optical techniques. However, differences in tissue characteristics and thus optical properties, like oxygen saturation and tissue perfusion are to be expected. This requires a structured comparison between the models.

In vivo nerve identification in head and neck surgery using diffuse reflectance spectroscopy: Optical intra-operative nerve identification

Careful identification of nerves during head and neck surgery is essential to prevent nerve damage. Currently, nerves are identified based on anatomy and appearance, optionally combined with electromyography (EMG). In challenging cases, nerve damage is reported in up to 50%. Recently, optical techniques, like diffuse reflectance spectroscopy (DRS) and fluorescence spectroscopy (FS) show potential to improve nerve identification.

Optimal endobronchial tool sizes for targeting lung lesions based on 3D modeling

Background For patients with suspicious lung lesions found on chest x-ray or CT, endo/trans- bronchial biopsy of the lung is the preferred method for obtaining a diagnosis. With the addition of new screening programs, a higher number of patients will require diagnostic biopsy which will prove even more challenging due to the small size of lesions found with screening. There are many endobronchial tools available on the market today and a wide range of new tools under investigation to improve diagnostic yield. However, there is little information available about the optimal tool size required to reach the majority of lesions, especially peripheral ones. In this manuscript we investigate the percentage of lesions that can be reached for various diameter tools if the tools remain inside the airways (i.e. endobronchial biopsy) and the distance a tool must travel “off-road” (or outside of the airways) to reach all lesions. Methods and findings To further understand the distribution of lung lesions with respect to airway sizes and distances from the airways, six 3D models of the lung were generated. The airways were modeled at two different respiratory phases (inspiration and expiration). Three sets of 1,000 lesions were randomly distributed throughout the lung for each respiratory phase. The simulations showed that the percentage of reachable lesions decreases with increasing tool diameter and decreasing lesion diameter. A 1mm diameter tool will reach <25% of 1cm lesions if it remains inside the airways. To reach all 1cm lesions this 1mm tool would have to navigate through the parenchyma up to 8.5mm. CT scans of 21 patient lesions confirm these results reasonably well. Conclusions The smaller the tool diameter the more likely it will be able to reach a lung lesion, whether it be for diagnostic biopsy, ablation, or resection. However, even a 1mm tool is not small enough to reach the majority of small (1-2cm) lesions. Therefore, it is necessary for endobronchial tools to be able to navigate through the parenchyma to reach the majority of lesions.

605PCOLORECTAL CANCER IDENTIFIED USING OPTICAL SPECTROSCOPY

ABSTRACT Aim: Complete tumor resection is essential to improve the outcome and quality of life after surgery for colorectal cancer. The identification of tumor and healthy surrounding tissue could facilitate complete tumor resection. Optical based techniques can identify tumor and surrounding tissue through a tissue specific “optical fingerprint”. Dual-modality Diffuse Reflectance Spectroscopy–Fluorescence Spectroscopy (DRS-FS) was evaluated for discrimination between healthy and malignant tissue in colon surgery with ultimate application implementation into surgical instruments. Methods: Differences in tissue composition and structure were measured through a fiber-optic needle using dual-modality DRS-FS. Resection specimens of colon cancer patients were investigated immediately after resection. Multiple optical parameters were derived from the measurements, including volume concentration of familiar optical absorbers like hemoglobin, b-carotene, water and lipids. Furthermore, scattering- and absorption coefficients were assessed, as well as sources of intrinsic fluorescence. The optical based parameters were cross-validated with the results of histopathological analysis using a classification and regression tree (CART) algorithm. Results: A total of 1273 measurements was performed on 21 specimens. Spectral characteristics of b-carotene, hemoglobin, lipids and water could be identified in the measured spectra. Differentiation of tumor from surrounding tissue was possible with a sensitivity and specificity of 95% and 88%, respectively. In 10 specimens optical data were collected along a needle path towards the tumor. Both DRS and FS spectra showed significant spectral changes when the needle tip was guided from healthy tissue into tumor. Conclusions: This study demonstrates that dual-modality DRS-FS allows accurate identification of colon cancer based on optical detection of differences in tissue composition and structure. The technique, here demonstrated in a needle like probe, may be incorporated into surgical instruments for optical guided surgery or combined in other devices. Disclosure: B.H.W. Hendriks: The author who is affiliated with Philips Research (B.H.) is an employee of Philips. The prototype system described in this article is a research prototype, not a commercial product. All other authors have declared no conflicts of interest.