Publications by authors named "Benno H W Hendriks"

51 Publications

Imaging PPG for In Vivo Human Tissue Perfusion Assessment during Surgery.

J Imaging 2022 Mar 31;8(4). Epub 2022 Mar 31.

IGT & US Devices & Systems, Philips Research, High Tech, Campus 34, 5656 AE Eindhoven, The Netherlands.

Surgical excision is the golden standard for treatment of intestinal tumors. In this surgical procedure, inadequate perfusion of the anastomosis can lead to postoperative complications, such as anastomotic leakages. Imaging photoplethysmography (iPPG) can potentially provide objective and real-time feedback of the perfusion status of tissues. This feasibility study aims to evaluate an iPPG acquisition system during intestinal surgeries to detect the perfusion levels of the microvasculature tissue bed in different perfusion conditions. This feasibility study assesses three patients that underwent resection of a portion of the small intestine. Data was acquired from fully perfused, non-perfused and anastomosis parts of the intestine during different phases of the surgical procedure. Strategies for limiting motion and noise during acquisition were implemented. iPPG perfusion maps were successfully extracted from the intestine microvasculature, demonstrating that iPPG can be successfully used for detecting perturbations and perfusion changes in intestinal tissues during surgery. This study provides proof of concept for iPPG to detect changes in organ perfusion levels.
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http://dx.doi.org/10.3390/jimaging8040094DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9031653PMC
March 2022

Hyperspectral Imaging for Tissue Classification after Advanced Stage Ovarian Cancer Surgery-A Pilot Study.

Cancers (Basel) 2022 Mar 10;14(6). Epub 2022 Mar 10.

Department of Gynecological Oncology, Erasmus MC Cancer Institute, University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands.

The most important prognostic factor for the survival of advanced-stage epithelial ovarian cancer (EOC) is the completeness of cytoreductive surgery (CRS). Therefore, an intraoperative technique to detect microscopic tumors would be of great value. The aim of this pilot study is to assess the feasibility of near-infrared hyperspectral imaging (HSI) for EOC detection in ex vivo tissue samples. Images were collected during CRS in 11 patients in the wavelength range of 665-975 nm, and processed by calibration, normalization, and noise filtering. A linear support vector machine (SVM) was employed to classify healthy and tumorous tissue (defined as >50% tumor cells). Classifier performance was evaluated using leave-one-out cross-validation. Images of 26 tissue samples from 10 patients were included, containing 26,446 data points that were matched to histopathology. Tumorous tissue could be classified with an area under the curve of 0.83, a sensitivity of 0.81, a specificity of 0.70, and Matthew's correlation coefficient of 0.41. This study paves the way to in vivo and intraoperative use of HSI during CRS. Hyperspectral imaging can scan a whole tissue surface in a fast and non-contact way. Our pilot study demonstrates that HSI and SVM learning can be used to discriminate EOC from surrounding tissue.
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http://dx.doi.org/10.3390/cancers14061422DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8946803PMC
March 2022

Steering light in fiber-optic medical devices: a patent review.

Expert Rev Med Devices 2022 Mar 17;19(3):259-271. Epub 2022 Mar 17.

Department of Biomechanical Engineering, Delft University of Technology, Delft, The Netherlands.

Introduction: Steering light is relevant to many medical applications that require tissue illumination, sensing, or modification. To control the propagation direction of light beams, a great variety of innovative fiber-optic medical devices have been designed.

Areas Covered: This review provides a comprehensive overview of the patent literature on light beam control in fiber-optic medical devices. The Web of Science Derwent Innovation Index database was scanned, and 81 patents on fiber-optic devices published in the last 20 years (2001-2021) were retrieved and categorized based on the working principle to steer light (refraction/reflection, scattering, diffraction) and the design strategy that was employed (within fiber, at fiber end, outside fiber).

Expert Opinion: Patents describing medical devices were found for all categories, except for generating diffraction at the fiber end surface. The insight in the different designs reveals that there are still several opportunities to design innovative devices that can collect light at an angle off-axis, reduce the angular distribution of light, or split light into multiple beams.
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http://dx.doi.org/10.1080/17434440.2022.2054334DOI Listing
March 2022

Layer thickness prediction and tissue classification in two-layered tissue structures using diffuse reflectance spectroscopy.

Sci Rep 2022 02 1;12(1):1698. Epub 2022 Feb 1.

Department of Surgery, Netherlands Cancer Institute, 1066 CX, Amsterdam, The Netherlands.

During oncological surgery, it can be challenging to identify the tumor and establish adequate resection margins. This study proposes a new two-layer approach in which diffuse reflectance spectroscopy (DRS) is used to predict the top layer thickness and classify the layers in two-layered phantom and animal tissue. Using wavelet-based and peak-based DRS spectral features, the proposed method could predict the top layer thickness with an accuracy of up to 0.35 mm. In addition, the tissue types of the first and second layers were classified with an accuracy of 0.95 and 0.99. Distinguishing multiple tissue layers during spectral analyses results in a better understanding of more complex tissue structures encountered in surgical practice.
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http://dx.doi.org/10.1038/s41598-022-05751-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8807816PMC
February 2022

Augmented reality navigation for cranial biopsy and external ventricular drain insertion.

Neurosurg Focus 2021 08;51(2):E7

1Department of Neurosurgery, Karolinska University Hospital, and Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.

Objective: The aim of this study was to evaluate the accuracy (deviation from the target or intended path) and efficacy (insertion time) of an augmented reality surgical navigation (ARSN) system for insertion of biopsy needles and external ventricular drains (EVDs), two common neurosurgical procedures that require high precision.

Methods: The hybrid operating room-based ARSN system, comprising a robotic C-arm with intraoperative cone-beam CT (CBCT) and integrated video tracking of the patient and instruments using nonobtrusive adhesive optical markers, was used. A 3D-printed skull phantom with a realistic gelatinous brain model containing air-filled ventricles and 2-mm spherical biopsy targets was obtained. After initial CBCT acquisition for target registration and planning, ARSN was used for 30 cranial biopsies and 10 EVD insertions. Needle positions were verified by CBCT.

Results: The mean accuracy of the biopsy needle insertions (n = 30) was 0.8 mm ± 0.43 mm. The median path length was 39 mm (range 16-104 mm) and did not correlate to accuracy (p = 0.15). The median device insertion time was 149 seconds (range 87-233 seconds). The mean accuracy for the EVD insertions (n = 10) was 2.9 mm ± 0.8 mm at the tip with a 0.7° ± 0.5° angular deviation compared with the planned path, and the median insertion time was 188 seconds (range 135-400 seconds).

Conclusions: This study demonstrated that ARSN can be used for navigation of percutaneous cranial biopsies and EVDs with high accuracy and efficacy.
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http://dx.doi.org/10.3171/2021.5.FOCUS20813DOI Listing
August 2021

Optical tissue measurements of invasive carcinoma and ductal carcinoma in situ for surgical guidance.

Breast Cancer Res 2021 05 22;23(1):59. Epub 2021 May 22.

Department of Surgery, Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Postbus 90203, 1006, Amsterdam, BE, Netherlands.

Background: Although the incidence of positive resection margins in breast-conserving surgery has decreased, both incomplete resection and unnecessary large resections still occur. This is especially the case in the surgical treatment of ductal carcinoma in situ (DCIS). Diffuse reflectance spectroscopy (DRS), an optical technology based on light tissue interactions, can potentially characterize tissue during surgery thereby guiding the surgeon intraoperatively. DRS has shown to be able to discriminate pure healthy breast tissue from pure invasive carcinoma (IC) but limited research has been done on (1) the actual optical characteristics of DCIS and (2) the ability of DRS to characterize measurements that are a mixture of tissue types.

Methods: In this study, DRS spectra were acquired from 107 breast specimens from 107 patients with proven IC and/or DCIS (1488 measurement locations). With a generalized estimating equation model, the differences between the DRS spectra of locations with DCIS and IC and only healthy tissue were compared to see if there were significant differences between these spectra. Subsequently, different classification models were developed to be able to predict if the DRS spectrum of a measurement location represented a measurement location with "healthy" or "malignant" tissue. In the development and testing of the models, different definitions for "healthy" and "malignant" were used. This allowed varying the level of homogeneity in the train and test data.

Results: It was found that the optical characteristics of IC and DCIS were similar. Regarding the classification of tissue with a mixture of tissue types, it was found that using mixed measurement locations in the development of the classification models did not tremendously improve the accuracy of the classification of other measurement locations with a mixture of tissue types. The evaluated classification models were able to classify measurement locations with > 5% malignant cells with a Matthews correlation coefficient of 0.41 or 0.40. Some models showed better sensitivity whereas others had better specificity.

Conclusion: The results suggest that DRS has the potential to detect malignant tissue, including DCIS, in healthy breast tissue and could thus be helpful for surgical guidance.
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http://dx.doi.org/10.1186/s13058-021-01436-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8141169PMC
May 2021

Proton density fat fraction of the spinal column: an MRI cadaver study.

Biomed Eng Online 2021 Jan 7;20(1). Epub 2021 Jan 7.

Department of Biomechanical Engineering, Delft University of Technology, Delft, The Netherlands.

Background: The increased popularity of minimally invasive spinal surgery calls for a revision of guidance techniques to prevent injuries of nearby neural and vascular structures. Lipid content has previously been proposed as a distinguishing criterion for different bone tissues to provide guidance along the interface of cancellous and cortical bone. This study aims to investigate how fat is distributed throughout the spinal column to confirm or refute the suitability of lipid content for guidance purposes.

Results: Proton density fat fraction (PDFF) was assessed over all vertebral levels for six human cadavers between 53 and 92 years of age, based on fat and water MR images. According to their distance to the vertebra contour, the data points were grouped in five regions of interest (ROIs): cortical bone (-1 mm to 0 mm), pre-cortical zone (PCZ) 1-3 (0-1 mm; 1-2 mm; 2-3 mm), and cancellous bone ([Formula: see text] 3 mm). For PCZ1 vs. PCZ2, a significant difference in mean PDFF of between -7.59 pp and -4.39 pp on average was found. For cortical bone vs. PCZ1, a significant difference in mean PDFF of between -27.09 pp and -18.96 pp on average was found.

Conclusion: A relationship between distance from the cortical bone boundary and lipid content could be established, paving the way for guidance techniques based on fat fraction detection for spinal surgery.
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http://dx.doi.org/10.1186/s12938-020-00846-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7792224PMC
January 2021

Diffuse reflectance spectroscopy for breach detection during pedicle screw placement: a first in vivo investigation in a porcine model.

Biomed Eng Online 2020 Jun 12;19(1):47. Epub 2020 Jun 12.

Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 2, 2628 CD, Delft, The Netherlands.

Background: The safe and accurate placement of pedicle screws remains a critical step in open and minimally invasive spine surgery, emphasizing the need for intraoperative guidance techniques. Diffuse reflectance spectroscopy (DRS) is an optical sensing technology that may provide intraoperative guidance in pedicle screw placement.

Purpose: The study presents the first in vivo minimally invasive procedure using DRS sensing at the tip of a Jamshidi needle with an integrated optical K-wire. We investigate the effect of tissue perfusion and probe-handling conditions on the reliability of fat fraction measurements for breach detection in vivo.

Methods: A Jamshidi needle with an integrated fiber-optic K-wire was gradually inserted into the vertebrae under intraoperative image guidance. The fiber-optic K-wire consisted of two optical fibers with a fiber-to-fiber distance of 1.024 mm. DRS spectra in the wavelength range of 450 to 1600 nm were acquired at several positions along the path inside the vertebrae. Probe-handling conditions were varied by changing the amount of pressure exerted on the probe within the vertebrae. Continuous spectra were recorded as the probe was placed in the center of the vertebral body while the porcine specimen was sacrificed via a lethal injection.

Results: A typical insertion of the fiber-optic K-wire showed a drop in fat fraction during an anterior breach as the probe transitioned from cancellous to cortical bone. Fat fraction measurements were found to be similar irrespective of the amount of pressure exerted on the probe (p = 0.65). The 95% confidence interval of fat fraction determination was found in the narrow range of 1.5-3.6% under various probe-handling conditions. The fat fraction measurements remained stable during 70 min of decreased blood flow after the animal was sacrificed.

Discussions: These findings indicate that changes in tissue perfusion and probe-handling conditions have a relatively low measureable effect on the DRS signal quality and thereby on the determination of fat fraction as a breach detection signal.

Conclusions: Fat fraction quantification for intraoperative pedicle screw breach detection is reliable, irrespective of changes in tissue perfusion and probe-handling conditions.
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http://dx.doi.org/10.1186/s12938-020-00791-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7291697PMC
June 2020

Intraoperative tumor margin assessment using diffuse reflectance spectroscopy: the effect of electrosurgery on tissue discrimination using ex vivo animal tissue models.

Biomed Opt Express 2020 May 7;11(5):2402-2415. Epub 2020 Apr 7.

Delft University of Technology, Biomechanical Engineering Department, Delft, The Netherlands.

Using an intraoperative margin assessment technique during breast-conserving surgery (BCS) helps surgeons to decrease the risk of positive margin occurrence. Diffuse reflectance spectroscopy (DRS) has the potential to discriminate healthy breast tissue from cancerous tissue. We investigated the performance of an electrosurgical knife integrated with a DRS on porcine muscle and adipose tissue. Characterization of the formed debris on the optical fibers after electrosurgery revealed that the contamination is mostly burned tissue. Even with contaminated optical fibers, both tissues could still be discriminated with DRS based on fat/water ratio. Therefore, an electrosurgical knife integrated with DRS may be a promising technology to provide the surgeon with real-time guidance during BCS.
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http://dx.doi.org/10.1364/BOE.385621DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7249845PMC
May 2020

Fusion of augmented reality imaging with the endoscopic view for endonasal skull base surgery; a novel application for surgical navigation based on intraoperative cone beam computed tomography and optical tracking.

PLoS One 2020 16;15(1):e0227312. Epub 2020 Jan 16.

Eindhoven University of Technology (TU/e), Eindhoven, The Netherlands.

Objective: Surgical navigation is a well-established tool in endoscopic skull base surgery. However, navigational and endoscopic views are usually displayed on separate monitors, forcing the surgeon to focus on one or the other. Aiming to provide real-time integration of endoscopic and diagnostic imaging information, we present a new navigation technique based on augmented reality with fusion of intraoperative cone beam computed tomography (CBCT) on the endoscopic view. The aim of this study was to evaluate the accuracy of the method.

Material And Methods: An augmented reality surgical navigation system (ARSN) with 3D CBCT capability was used. The navigation system incorporates an optical tracking system (OTS) with four video cameras embedded in the flat detector of the motorized C-arm. Intra-operative CBCT images were fused with the view of the surgical field obtained by the endoscope's camera. Accuracy of CBCT image co-registration was tested using a custom-made grid with incorporated 3D spheres.

Results: Co-registration of the CBCT image on the endoscopic view was performed. Accuracy of the overlay, measured as mean target registration error (TRE), was 0.55 mm with a standard deviation of 0.24 mm and with a median value of 0.51mm and interquartile range of 0.39--0.68 mm.

Conclusion: We present a novel augmented reality surgical navigation system, with fusion of intraoperative CBCT on the endoscopic view. The system shows sub-millimeter accuracy.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0227312PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6964902PMC
May 2020

Diffuse reflectance spectroscopy accurately identifies the pre-cortical zone to avoid impending pedicle screw breach in spinal fixation surgery.

Biomed Opt Express 2019 Nov 24;10(11):5905-5920. Epub 2019 Oct 24.

Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.

Pedicle screw placement accuracy during spinal fixation surgery varies greatly and severe misplacement has been reported in 1-6.5% of screws. Diffuse reflectance (DR) spectroscopy has previously been shown to reliably discriminate between tissues in the human body. We postulate that it could be used to discriminate between cancellous and cortical bone. Therefore, the purpose of this study is to validate DR spectroscopy as a warning system to detect impending pedicle screw breach in a cadaveric surgical setting using typical clinical breach scenarios. DR spectroscopy was incorporated at the tip of an integrated pedicle screw and screw driver used for tissue probing during pedicle screw insertions on six cadavers. Measurements were collected in the wavelength range of 400-1600 nm and each insertion was planned to result in a breach. Measurements were labelled as cancellous, cortical or representing a pre-cortical zone (PCZ) in between, based on information from cone beam computed tomographies at corresponding positions. In addition, DR spectroscopy data was recorded after breach. Four typical pedicle breach types were performed, and a total of 45 pedicle breaches were recorded. For each breach direction, the technology was able to detect the transition of the screw tip from the cancellous bone to the PCZ (P < 0.001), to cortical bone (P < 0.001), and to a subsequent breach (P < 0.001). Using support vector machine (SVM) classification, breach could reliably be detected with a sensitivity of 98.3 % [94.3-100 %] and a specificity of 97.7 % [91.0-100 %]. We conclude that DR spectroscopy reliably identifies the area of transition from cancellous to cortical bone in typical breach scenarios and can warn the surgeon of impending pedicle breach, thereby resulting in safer spinal fixation surgeries.
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http://dx.doi.org/10.1364/BOE.10.005905DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6865097PMC
November 2019

Using Diffuse Reflectance Spectroscopy to Distinguish Tumor Tissue From Fibrosis in Rectal Cancer Patients as a Guide to Surgery.

Lasers Surg Med 2020 09 3;52(7):604-611. Epub 2019 Dec 3.

Department of Surgery, Antoni van Leeuwenhoek Hospital, The Netherlands Cancer Institute, Amsterdam, 1066 CX, The Netherlands.

Background And Objectives: In patients with rectal cancer who received neoadjuvant (chemo)radiotherapy, fibrosis is induced in and around the tumor area. As tumors and fibrosis have similar visual and tactile feedback, they are hard to distinguish during surgery. To prevent positive resection margins during surgery and spare healthy tissue, it would be of great benefit to have a real-time tissue classification technology that can be used in vivo.

Study Design/materials And Methods: In this study diffuse reflectance spectroscopy (DRS) was evaluated for real-time tissue classification of tumor and fibrosis. DRS spectra of fibrosis and tumor were obtained on excised rectal specimens. After normalization using the area under the curve, a support vector machine was trained using a 10-fold cross-validation.

Results: Using spectra of pure tumor tissue and pure fibrosis tissue, we obtained a mean accuracy of 0.88. This decreased to a mean accuracy of 0.61 when tumor measurements were used in which a layer of healthy tissue, mainly fibrosis, was present between the tumor and the measurement surface.

Conclusion: It is possible to distinguish pure fibrosis from pure tumor. However, when the measurements on tumor also involve fibrotic tissue, the classification accuracy decreases. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/lsm.23196DOI Listing
September 2020

Toward assessment of resection margins using hyperspectral diffuse reflection imaging (400-1,700 nm) during tongue cancer surgery.

Lasers Surg Med 2020 07 15;52(6):496-502. Epub 2019 Sep 15.

Department of Surgery, Netherlands Cancer Institute, Antoni van Leeuwenhoek, Amsterdam, The Netherlands.

Background And Objectives: There is a clinical need to assess the resection margins of tongue cancer specimens, intraoperatively. In the current ex vivo study, we evaluated the feasibility of hyperspectral diffuse reflectance imaging (HSI) for distinguishing tumor from the healthy tongue tissue.

Study Design/materials And Methods: Fresh surgical specimens (n = 14) of squamous cell carcinoma of the tongue were scanned with two hyperspectral cameras that cover the visible and near-infrared spectrum (400-1,700 nm). Each pixel of the hyperspectral image represents a measure of the diffuse optical reflectance. A neural network was used for tissue-type prediction of the hyperspectral images of the visual and near-infrared data sets separately as well as both data sets combined.

Results: HSI was able to distinguish tumor from muscle with a good accuracy. The diagnostic performance of both wavelength ranges (sensitivity/specificity of visual and near-infrared were 84%/80% and 77%/77%, respectively) appears to be comparable and there is no additional benefit of combining the two wavelength ranges (sensitivity and specificity were 83%/76%).

Conclusions: HSI has a strong potential for intra-operative assessment of tumor resection margins of squamous cell carcinoma of the tongue. This may optimize surgery, as the entire resection surface can be scanned in a single run and the results can be readily available. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/lsm.23161DOI Listing
July 2020

Validation of diffuse reflectance spectroscopy with magnetic resonance imaging for accurate vertebral bone fat fraction quantification.

Biomed Opt Express 2019 Aug 1;10(8):4316-4328. Epub 2019 Aug 1.

Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 2, 2628 CD, Delft, the Netherlands.

Safe and accurate placement of pedicle screws remains a critical step in open and minimally invasive spine surgery. The diffuse reflectance spectroscopy (DRS) technique may offer the possibility of intra-operative guidance for pedicle screw placement. Currently, Magnetic Resonance Imaging (MRI) is one of the most accurate techniques used to measure fat concentration in tissues. Therefore, the purpose of this study is to compare the accuracy of fat content measured invasively in vertebrae using DRS and validate it against the Proton density fat fraction (PDFF) derived via MRI. Chemical shift-encoding-based water-fat imaging of the spine was first performed on six cadavers. PDFF images were computed and manually segmented. 23 insertions using a custom-made screw probe with integrated optical fibers were then performed under cone beam computer tomography (CBCT). DR spectra were recorded at several positions along the trajectory as the optical screw probe was inserted turn by turn into the vertebral body. Fat fractions determined via DRS and MRI techniques were compared by spatially correlating the optical screw probe position within the vertebrae on CBCT images with respect to the PDFF images. The fat fraction determined by DRS was found to have a high correlation with those determined by MRI, with a Pearson coefficient of 0.950 (P< 0.001) as compared with PDFF measurements calculated from the MRI technique. Additionally, the two techniques were found to be comparable for fat fraction quantification within vertebral bodies (R = 0.905).
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http://dx.doi.org/10.1364/BOE.10.004316DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6701522PMC
August 2019

Diffuse reflectance spectroscopy, a potential optical sensing technology for the detection of cortical breaches during spinal screw placement.

J Biomed Opt 2019 01;24(1):1-11

Delft University of Technology, Department of Biomechanical Engineering, Delft, Netherlands.

Safe and accurate placement of screws remains a critical issue in open and minimally invasive spine surgery. We propose to use diffuse reflectance (DR) spectroscopy as a sensing technology at the tip of a surgical instrument to ensure a safe path of the instrument through the cancellous bone of the vertebrae. This approach could potentially reduce the rate of cortical bone breaches, thereby resulting in fewer neural and vascular injuries during spinal fusion surgery. In our study, DR spectra in the wavelength ranges of 400 to 1600 nm were acquired from cancellous and cortical bone from three human cadavers. First, it was investigated whether these spectra can be used to distinguish between the two bone types based on fat, water, and blood content along with photon scattering. Subsequently, the penetration of the bone by an optical probe was simulated using the Monte-Carlo (MC) method, to study if the changes in fat content along the probe path would still enable distinction between the bone types. Finally, the simulation findings were validated via an experimental insertion of an optical screw probe into the vertebra aided by x-ray image guidance. The DR spectra indicate that the amount of fat, blood, and photon scattering is significantly higher in cancellous bone than in cortical bone (p  <  0.01), which allows distinction between the bone types. The MC simulations showed a change in fat content more than 1 mm before the optical probe came in contact with the cortical bone. The experimental insertion of the optical screw probe gave similar results. This study shows that spectral tissue sensing, based on DR spectroscopy at the instrument tip, is a promising technology to identify the transition zone from cancellous to cortical vertebral bone. The technology therefore has the potential to improve the safety and accuracy of spinal screw placement procedures.
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http://dx.doi.org/10.1117/1.JBO.24.1.017002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6985697PMC
January 2019

Towards the use of diffuse reflectance spectroscopy for real-time in vivo detection of breast cancer during surgery.

J Transl Med 2018 12 19;16(1):367. Epub 2018 Dec 19.

Department of Surgery, the Netherlands Cancer Institute-Antoni van Leeuwenhoek, Plesmanlaan 121, Postbus 90203, 1066 CX, Amsterdam, The Netherlands.

Background: Breast cancer surgeons struggle with differentiating healthy tissue from cancer at the resection margin during surgery. We report on the feasibility of using diffuse reflectance spectroscopy (DRS) for real-time in vivo tissue characterization.

Methods: Evaluating feasibility of the technology requires a setting in which measurements, imaging and pathology have the best possible correlation. For this purpose an optical biopsy needle was used that had integrated optical fibers at the tip of the needle. This approach enabled the best possible correlation between optical measurement volume and tissue histology. With this optical biopsy needle we acquired real-time DRS data of normal tissue and tumor tissue in 27 patients that underwent an ultrasound guided breast biopsy procedure. Five additional patients were measured in continuous mode in which we obtained DRS measurements along the entire biopsy needle trajectory. We developed and compared three different support vector machine based classification models to classify the DRS measurements.

Results: With DRS malignant tissue could be discriminated from healthy tissue. The classification model that was based on eight selected wavelengths had the highest accuracy and Matthews Correlation Coefficient (MCC) of 0.93 and 0.87, respectively. In three patients that were measured in continuous mode and had malignant tissue in their biopsy specimen, a clear transition was seen in the classified DRS measurements going from healthy tissue to tumor tissue. This transition was not seen in the other two continuously measured patients that had benign tissue in their biopsy specimen.

Conclusions: It was concluded that DRS is feasible for integration in a surgical tool that could assist the breast surgeon in detecting positive resection margins during breast surgery. Trail registration NIH US National Library of Medicine-clinicaltrails.gov, NCT01730365. Registered: 10/04/2012 https://clinicaltrials.gov/ct2/show/study/NCT01730365.
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http://dx.doi.org/10.1186/s12967-018-1747-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6299954PMC
December 2018

Real-time oncological guidance using diffuse reflectance spectroscopy in electrosurgery: the effect of coagulation on tissue discrimination.

J Biomed Opt 2018 11;23(11):1-10

Delft University of Technology, Biomechanical Engineering Department, Delft, The Netherlands.

In breast surgery, a lack of knowledge about what is below the tissue surface may lead to positive tumor margins and iatrogenic damage. Diffuse reflectance spectroscopy (DRS) is a spectroscopic technique that can distinguish between healthy and tumor tissue making it a suitable technology for intraoperative guidance. However, because tumor surgeries are often performed with an electrosurgical knife, the effect of a coagulated tissue layer on DRS measurements must be taken into account. It is evaluated whether real-time DRS measurements obtained with a photonic electrosurgical knife could provide useful information of tissue properties also when tissue is coagulated and cut. The size of the coagulated area is determined and the effect of its presence on DR spectra is studied using ex vivo porcine adipose and muscle tissue. A coagulated tissue layer with a depth of 0.1 to 0.4 mm is observed after coagulating muscle with an electrosurgical knife. The results show that the effect of coagulating adipose tissue is negligible. Using the fat/water ratio's calculated from the measured spectra of the photonic electrosurgical knife, it was possible to determine the distance from the instrument tip to a tissue transition during cutting. In conclusion, the photonic electrosurgical knife can determine tissue properties of coagulated and cut tissue and has, therefore, the potential to provide real-time feedback about the presence of breast tumor margins during cutting, helping surgeons to establish negative margins and improve patient outcome.
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http://dx.doi.org/10.1117/1.JBO.23.11.115004DOI Listing
November 2018

In vivo nerve identification in head and neck surgery using diffuse reflectance spectroscopy.

Laryngoscope Investig Otolaryngol 2018 Oct 9;3(5):349-355. Epub 2018 Aug 9.

Department of Surgery The Netherlands Cancer Institute-Antoni van Leeuwenhoek Amsterdam the Netherlands.

Background: 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.

Methods: 212 intra-operative DRS/FS measurements were performed. Small nerve branches (1-3 mm), on near-nerve adipose tissue, muscle and subcutaneous fat were measured during 11 surgical procedures. Tissue identification was based on quantified concentrations of optical absorbers and scattering parameters.

Results: Clinically comprehensive parameters showed significant differences (<0.05) between the tissues. Classification using k-Nearest Neighbor resulted in 100% sensitivity and a specificity of 83% (accuracy 91%), for the identification of nerve against surrounding tissues.

Conclusions: DRS/FS is a potentially useful intraoperative tool for identification of nerves from adjacent tissues.

Level Of Evidence: Observational proof of principle study.
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http://dx.doi.org/10.1002/lio2.174DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6209613PMC
October 2018

Toward complete oral cavity cancer resection using a handheld diffuse reflectance spectroscopy probe.

J Biomed Opt 2018 10;23(12):1-8

Netherlands Cancer Institute, Antoni van Leeuwenhoek, Department of Surgery, Amsterdam, The Netherlands.

This ex-vivo study evaluates the feasibility of diffuse reflectance spectroscopy (DRS) for discriminating tumor from healthy tissue, with the aim to develop a technology that can assess resection margins for the presence of tumor cells during oral cavity cancer surgery. Diffuse reflectance spectra were acquired on fresh surgical specimens from 28 patients with oral cavity squamous cell carcinoma. The spectra (400 to 1600 nm) were detected after illuminating tissue with a source fiber at 0.3-, 0.7-, 1.0-, and 2.0-mm distances from a detection fiber, obtaining spectral information from different sampling depths. The spectra were correlated with histopathology. A total of 76 spectra were obtained from tumor tissue and 110 spectra from healthy muscle tissue. The first- and second-order derivatives of the spectra were calculated and a classification algorithm was developed using fivefold cross validation with a linear support vector machine. The best results were obtained by the reflectance measured with a 1-mm source-detector distance (sensitivity, specificity, and accuracy are 89%, 82%, and 86%, respectively). DRS can accurately discriminate tumor from healthy tissue in an ex-vivo setting using a 1-mm source-detector distance. Accurate validation methods are warranted for larger sampling depths to allow for guidance during oral cavity cancer excision.
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http://dx.doi.org/10.1117/1.JBO.23.12.121611DOI Listing
October 2018

Optical signature of nerve tissue-Exploratory ex vivo study comparing optical, histological, and molecular characteristics of different adipose and nerve tissues.

Lasers Surg Med 2018 09 14;50(9):948-960. Epub 2018 May 14.

Department of Anatomy and Embryology, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, The Netherlands.

Background: During several anesthesiological procedures, needles are inserted through the skin of a patient to target nerves. In most cases, the needle traverses several tissues-skin, subcutaneous adipose tissue, muscles, nerves, and blood vessels-to reach the target nerve. A clear identification of the target nerve can improve the success of the nerve block and reduce the rate of complications. This may be accomplished with diffuse reflectance spectroscopy (DRS) which can provide a quantitative measure of the tissue composition. The goal of the current study was to further explore the morphological, biological, chemical, and optical characteristics of the tissues encountered during needle insertion to improve future DRS classification algorithms.

Methods: To compare characteristics of nerve tissue (sciatic nerve) and adipose tissues, the following techniques were used: histology, DRS, absorption spectrophotometry, high-resolution magic-angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy, and solution 2D C- H heteronuclear single-quantum coherence spectroscopy. Tissues from five human freshly frozen cadavers were examined.

Results: Histology clearly highlights a higher density of cellular nuclei, collagen, and cytoplasm in fascicular nerve tissue (IFAS). IFAS showed lower absorption of light around 1200 nm and 1750 nm, higher absorption around 1500 nm and 2000 nm, and a shift in the peak observed around 1000 nm. DRS measurements showed a higher water percentage and collagen concentration in IFAS and a lower fat percentage compared to all other tissues. The scattering parameter (b) was highest in IFAS. The HR-MAS NMR data showed three extra chemical peak shifts in IFAS tissue.

Conclusion: Collagen, water, and cellular nuclei concentration are clearly different between nerve fascicular tissue and other adipose tissue and explain some of the differences observed in the optical absorption, DRS, and HR-NMR spectra of these tissues. Some differences observed between fascicular nerve tissue and adipose tissues cannot yet be explained but may be helpful in improving the discriminatory capabilities of DRS in anesthesiology procedures. Lasers Surg. Med. 50:948-960, 2018. © 2018 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/lsm.22938DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6220981PMC
September 2018

Nerve detection during surgery: optical spectroscopy for peripheral nerve localization.

Lasers Med Sci 2018 Apr 2;33(3):619-625. Epub 2018 Feb 2.

Department of Surgery, The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands.

Precise nerve localization is of major importance in both surgery and regional anesthesia. Optically based techniques can identify tissue through differences in optical properties, like absorption and scattering. The aim of this study was to evaluate the potential of optical spectroscopy (diffuse reflectance spectroscopy) for clinical nerve identification in vivo. Eighteen patients (8 male, 10 female, age 53 ± 13 years) undergoing inguinal lymph node resection or resection or a soft tissue tumor in the groin were included to measure the femoral or sciatic nerve and the surrounding tissues. In vivo optical measurements were performed using Diffuse Reflectance Spectroscopy (400-1600 nm) on nerve, near nerve adipose tissue, muscle, and subcutaneous fat using a needle-shaped probe. Model-based analyses were used to derive verified quantitative parameters as concentrations of optical absorbers and several parameters describing scattering. A total of 628 optical spectra were recorded. Measured spectra reveal noticeable tissue specific characteristics. Optical absorption of water, fat, and oxy- and deoxyhemoglobin was manifested in the measured spectra. The parameters water and fat content showed significant differences (P < 0.005) between nerve and all surrounding tissues. Classification using k-Nearest Neighbor based on the derived parameters revealed a sensitivity of 85% and a specificity of 79%, for identifying nerve from surrounding tissues. Diffuse Reflectance Spectroscopy identifies peripheral nerve bundles. The differences found between tissue groups are assignable to the tissue composition and structure.
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http://dx.doi.org/10.1007/s10103-017-2433-1DOI Listing
April 2018

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

PLoS One 2017 19;12(12):e0189963. Epub 2017 Dec 19.

Department of Surgery, Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, CX Amsterdam, The Netherlands.

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.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0189963PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5736231PMC
January 2018

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

Lasers Surg Med 2018 03 21;50(3):253-261. Epub 2017 Nov 21.

Department of Surgery, The Netherlands Cancer Institute-Antoni van Leeuwenhoek, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.

Objective: 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.

Study Design: Comparative observational study.

Methods: Nerve and surrounding tissues in human (in vivo and post mortem) and swine (in vivo and post mortem) were structurally compared macroscopically, histologically, and spectroscopically. Diffuse reflective spectra were acquired (400-1,600 nm) after illumination with a broad band halogen light. An analytical model was used to quantify optical parameters including concentrations of optical absorbers.

Results: Several differences were found histologically and in the optical parameters. Histologically nerve and adipose tissue (subcutaneous fat and sliding fat) showed clear similarities between human and swine while human muscle enclosed more adipocytes and endomysial collagen. Optical parameters revealed model dependent differences in concentrations of β-carotene, water, fat, and oxygen saturation. The similarity between optical parameters is, however, sufficient to yield a strong positive correlation after cross model classification.

Conclusion: This study shows and discusses similarities and differences in nerve and surrounding tissues between human in vivo and post mortem, and swine in vivo and post mortem; this could support the discussion to use an alternative model to optimize and validate optical techniques for clinical nerve identification. Lasers Surg. Med. 50:253-261, 2018. © 2017 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/lsm.22755DOI Listing
March 2018

Diffuse reflectance spectroscopy as a tool for real-time tissue assessment during colorectal cancer surgery.

J Biomed Opt 2017 Oct;22(10):1-6

Antoni van Leeuwenhoek Hospital-The Netherlands Cancer Institute, Department of Surgery, Amsterdam, The Netherlands.

Colorectal surgery is the standard treatment for patients with colorectal cancer. To overcome two of the main challenges, the circumferential resection margin and postoperative complications, real-time tissue assessment could be of great benefit during surgery. In this ex vivo study, diffuse reflectance spectroscopy (DRS) was used to differentiate tumor tissue from healthy surrounding tissues in patients with colorectal neoplasia. DRS spectra were obtained from tumor tissue, healthy colon, or rectal wall and fat tissue, for every patient. Data were randomly divided into training (80%) and test (20%) sets. After spectral band selection, the spectra were classified using a quadratic classifier and a linear support vector machine. Of the 38 included patients, 36 had colorectal cancer and 2 had an adenoma. When the classifiers were applied to the test set, colorectal cancer could be discriminated from healthy tissue with an overall accuracy of 0.95 (±0.03). This study demonstrates the possibility to separate colorectal cancer from healthy surrounding tissue by applying DRS. High classification accuracies were obtained both in homogeneous and inhomogeneous tissues. This is a fundamental step toward the development of a tool for real-time in vivo tissue assessment during colorectal surgery.
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http://dx.doi.org/10.1117/1.JBO.22.10.106014DOI Listing
October 2017

Using DRS during breast conserving surgery: identifying robust optical parameters and influence of inter-patient variation.

Biomed Opt Express 2016 Dec 17;7(12):5188-5200. Epub 2016 Nov 17.

Netherlands Cancer Institute - Antoni van Leeuwenhoek, Amsterdam The Netherlands; MIRA Institute, University Twente, The Netherlands.

Successful breast conserving surgery consists of complete removal of the tumor while sparing healthy surrounding tissue. Despite currently available imaging and margin assessment tools, recognizing tumor tissue at a resection margin during surgery is challenging. Diffuse reflectance spectroscopy (DRS), which uses light for tissue characterization, can potentially guide surgeons to prevent tumor positive margins. However, inter-patient variation and changes in tissue physiology occurring during the resection might hamper this light-based technology. Here we investigate how inter-patient variation and tissue status ( vs ) affect the performance of the DRS optical parameters. and measurements of 45 breast cancer patients were obtained and quantified with an analytical model to acquire the optical parameters. The optical parameter representing the ratio between fat and water provided the best discrimination between normal and tumor tissue, with an area under the receiver operating characteristic curve of 0.94. There was no substantial influence of other patient factors such as menopausal status on optical measurements. Contrary to expectations, normalization of the optical parameters did not improve the discriminative power. Furthermore, measurements taken were not significantly different from the measurements taken . These findings indicate that DRS is a robust technology for the detection of tumor tissue during breast conserving surgery.
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http://dx.doi.org/10.1364/BOE.7.005188DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5175562PMC
December 2016

In vivo tumor identification of colorectal liver metastases with diffuse reflectance and fluorescence spectroscopy.

Lasers Surg Med 2016 11 8;48(9):820-827. Epub 2016 Sep 8.

Department of Surgery, The Netherlands Cancer Institute, Amsterdam, The Netherlands.

Background And Objective: Over the last decade, an increasing effort has been put towards the implementation of optical guidance techniques to aid surgeons during cancer surgery. Diffuse reflectance spectroscopy (DRS) and fluorescence spectroscopy (FS) are two of these new techniques. The objective of this study is to investigate whether in vivo optical spectroscopy is able to accurately discriminate colorectal liver metastases (CRLM) from normal liver tissue in vivo.

Materials And Methods: DRS and FS were incorporated at the tip of a needle and were used for in vivo tissue differentiation during resection of CRLM. Measurements were taken in and around the tumor lesions and measurement sites were marked and correlated to histology (i.e., normal liver tissue or tumor tissue). Patients with and without neoadjuvant systemic chemotherapy were included into the study.

Results: Four hundred and eighty-four measurements were taken in and near 19 liver lesions prior to resection. Overall sensitivity and specificity for DRS was 95% and 92%, respectively. Bile was the most discriminative parameter. The addition of FS did not improve the overall accuracy. Sensitivity and specificity was not hampered by neo-adjuvant chemotherapy; sensitivity and specificity after neo-adjuvant chemotherapy were 92% and 100%, respectively.

Conclusion: We have successfully integrated spectroscopy technology into a disposable 15 Gauge optical needle and we have shown that DRS and FS can accurately discriminate CRLM from normal liver tissue in the in vivo setting regardless of whether the patient was pre-treated with systemic therapy. This technique makes in vivo guidance accessible for common surgical practice. Lasers Surg. Med. 48:820-827, 2016. © 2016 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/lsm.22581DOI Listing
November 2016

In vivo characterization of colorectal metastases in human liver using diffuse reflectance spectroscopy: toward guidance in oncological procedures.

J Biomed Opt 2016 09;21(9):97004

Netherlands Cancer Institute, Department of Surgery, Plesmanlaan 121, 1066CX Amsterdam, The NetherlandsfUniversity of Twente, MIRA Institute, Drienerlolaan 5, Zuidhorst ZH116, 7522 NB Enschede, The Netherlands.

There is a strong need to develop clinical instruments that can perform rapid tissue assessment at the tip of smart clinical instruments for a variety of oncological applications. This study presents the first in vivo real-time tissue characterization during 24 liver biopsy procedures using diffuse reflectance (DR) spectroscopy at the tip of a core biopsy needle with integrated optical fibers. DR measurements were performed along each needle path, followed by biopsy of the target lesion using the same needle. Interventional imaging was coregistered with the DR spectra. Pathology results were compared with the DR spectroscopy data at the final measurement position. Bile was the primary discriminator between normal liver tissue and tumor tissue. Relative differences in bile content matched with the tissue diagnosis based on histopathological analysis in all 24 clinical cases. Continuous DR measurements during needle insertion in three patients showed that the method can also be applied for biopsy guidance or tumor recognition during surgery. This study provides an important validation step for DR spectroscopy-based tissue characterization in the liver. Given the feasibility of the outlined approach, it is also conceivable to make integrated fiber-optic tools for other clinical procedures that rely on accurate instrument positioning.
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http://dx.doi.org/10.1117/1.JBO.21.9.097004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8357329PMC
September 2016

Spectral sensing for tissue diagnosis during lung biopsy procedures: The importance of an adequate internal reference and real-time feedback.

Lung Cancer 2016 08 26;98:62-68. Epub 2016 May 26.

Department of Surgery, Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, Netherlands; MIRA Institute, University of Twente, Building Zuidhorst, Room ZH 116, Enschede, Netherlands.

Objectives: Difficulties in obtaining a representative tissue sample are a major obstacle in timely selecting the optimal treatment for patients with lung cancer or other malignancies. Having a modality to provide needle guidance and confirm the biopsy site selection could be of great clinical benefit, especially when small masses are targeted. The objective of this study was to evaluate whether diffuse reflectance spectroscopy (DRS) at the tip of a core biopsy needle can be used for biopsy site confirmation in real time, thereby enabling optimized biopsy acquisition and improving diagnostic capability.

Materials And Methods: We included a total of 23 patients undergoing a routine computed tomography (CT) guided transthoracic needle biopsy of a lesion suspected for lung cancer or metastatic disease. DRS measurements were acquired during needle insertion and clinically relevant parameters were extracted from the spectral data along the needle paths. Histopathology results were compared with the DRS data at the final measurement position.

Results: Analysis of the collective data acquired from all enrolled subjects showed significant differences (p<0.01) for blood content, stO2, water content, and scattering amplitude. The identified spectral contrast matched the final pathology in 20 out of 22 clinical cases that could be used for analysis, which corresponds with an overall diagnostic performance of 91%. Three cases underlined the importance of adequate reference measurements and the need for real time diagnostic feedback. Continuous real time DRS measurements performed during a biopsy procedure in one patient provided clear information with respect to the variation in tissue and allowed identification of the tumour boundary.

Conclusions: The presented technology creates a basis for the design and clinical implementation of integrated fibre-optic tools for a variety of minimal invasive applications.
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http://dx.doi.org/10.1016/j.lungcan.2016.05.019DOI Listing
August 2016

Nerve detection with optical spectroscopy for regional anesthesia procedures.

J Transl Med 2015 Dec 15;13:380. Epub 2015 Dec 15.

Department of Anesthesiology, University Medical Center St. Radboud, Nijmegen, The Netherlands.

Background: Regional anesthesia has several advantages over general anesthesia but requires accurate needle placement to be effective. To achieve accurate placement, a needle equipped with optical fibers that allows tissue discrimination at the needle tip based on optical spectroscopy is proposed. This study investigates the sensitivity and specificity with which this optical needle can discriminate nerves from the surrounding tissues making use of different classification methods.

Methods: Diffuse reflectance spectra were acquired from 1563 different locations from 19 human cadavers in the wavelength range of 400-1710 nm; measured tissue types included fascicular tissue of the nerve, muscle, sliding fat and subcutaneous fat. Physiological parameters of the tissues were derived from the measured spectra and part of the data was directly compared to histology. Various classification methods were then applied to the derived parameter dataset to determine the accuracy with which fascicular tissue of the nerve can be discriminated from the surrounding tissues.

Results: From the parameters determined from the measured spectra of the various tissues surrounding the nerve, fat content, blood content, beta-carotene content and scattering were most distinctive when comparing fascicular and non-fascicular tissue. Support Vector Machine classification with a combination of feature selections performed best in discriminating fascicular nerve tissue from the surrounding tissues with a sensitivity and specificity around 90 %.

Conclusions: This study showed that spectral tissue sensing, based on diffuse reflectance spectroscopy at the needle tip, is a promising technique to discriminate fascicular tissue of the nerve from the surrounding tissues. The technique may therefore improve accurate needle placement near the nerve which is necessary for effective nerve blocks in regional anesthesia.
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http://dx.doi.org/10.1186/s12967-015-0739-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4678621PMC
December 2015
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