Coherent anti-Stokes Raman metrology of phonons powered by photonic-crystal fibers (original) (raw)
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Shining light on neurosurgery diagnostics using Raman spectroscopy
Journal of Neuro-Oncology, 2016
Surgical excision of brain tumors provides a means of cytoreduction and diagnosis while minimizing neurologic deficit and improving overall survival. Despite advances in functional and three-dimensional stereotactic navigation and intraoperative magnetic resonance imaging, delineating tissue in real time with physiological confirmation is challenging. Raman spectroscopy is a promising investigative and diagnostic tool for neurosurgery, which provides rapid, nondestructive molecular characterization in vivo or in vitro for biopsy, margin assessment, or laboratory uses. The Raman Effect occurs when light temporarily changes a bond's polarizability, causing change in the vibrational frequency, with a corresponding change in energy/wavelength of the scattered photon. The recorded inelastic scattering results in a "fingerprint" or Raman spectrum of the constituent under investigation. The amount, location, and intensity of peaks in the fingerprint vary based on the amount of vibrational bonds in a molecule and their ensemble interactions with each other. Distinct differences between various pathologic conditions are shown as different intensities of the same peak, or shifting of a peak based on the binding conformation. Raman spectroscopy has potential for integration into clinical practice, particularly in distinguishing normal and diseased tissue as an adjunct to standard pathologic diagnosis. Further, development of fiber-optic Raman probes that fit through the instrument port of a standard endoscope now allows researchers and clinicians to utilize spectroscopic information for evaluation of in vivo tissue. This review highlights the need for such an instrument, Steven N. Kalkanis, skalkan1@hfhs.org. Brandy Broadbent and James Tseng have contributed equally to the work.
Oxygenation Monitoring of Tissue Vasculature by Resonance Raman Spectroscopy
Analytical Chemistry, 2007
Resonance Raman spectroscopy offers a mechanism for the non-invasive measurement of in vivo and in situ hemoglobin oxygen saturation (HbO 2 Sat) in living tissue. Clinically informative signals can be provided by resonance enhancement with deep violet excitation. It is notable that fluorescence does not significantly degrade the quality of the signals. During the controlled hemorrhage and resuscitation of rats, signal intensity ratios of oxy-vs deoxyhemoglobin from sublingual mucosa correlated with co-oximetry values of blood withdrawn from a central venous catheter. The spectroscopic application described here has potential as a non-invasive method for the diagnosis of clinical shock and guidance of its therapy.
Optical Access to Arteriovenous Cerebral Microcirculation Through a Transparent Cranial Implant
Lasers in Surgery and Medicine, 2019
Background and Objective: Microcirculation plays a critical role in physiologic processes and several disease states. Laser speckle imaging (LSI) is a full-field, real-time imaging technique capable of mapping microvessel networks and providing relative flow velocity within the vessels. In this study, we demonstrate that LSI combine with multispectral reflectance imaging (MSRI), which allows for distinction between veins and arteries in the vascular flow maps produced by LSI. We apply this combined technique to mouse cerebral vascular network in vivo, comparing imaging through the skull, to the dura mater and brain directly through a craniectomy, and through a transparent cranial "Window to the Brain" (WttB) implant. Study Design/Materials and Methods: The WttB implant used in this study is made of a nanocrystalline Yttria-Stabilized-Zirconia ceramic. MSRI was conducted using white-light illumination and filtering the reflected light for 560, 570, 580, 590, 600, and 610 nm. LSI was conducted using an 810 nm continuous wave near-infrared laser with incident power of 100 mW, and the reflected speckle pattern was captured by a complementary metal-oxide-semiconductor (CMOS) camera. Results: Seven vessel branches were analyzed and comparison was made between imaging through the skull, craniectomy, and WttB implant. Through the skull, MSRI did not detect any vessels, and LSI could not image microvessels. Imaging through the WttB implant, MSRI was able to identify veins versus arteries, and LSI was able to image microvessels with only slightly higher signal-to-noise ratio and lower sharpness than imaging the brain through a craniectomy. Conclusions: This study demonstrates the ability to perform MSRI-LSI across a transparent cranial implant, to allow for cerebral vascular networks to be mapped, including microvessels. These images contain additional information such as vein-artery separation and relative blood flow velocities, information which is of value scientifically and medically. The WttB implant provides substantial improvements over imaging through the murine cranial bone, where microvessels are not visible and MSRI cannot be performed. Lasers Surg. Med.
Resonance Raman spectroscopy: A new technology for tissue oxygenation monitoring
Critical Care Medicine, 2006
Objective: To evaluate resonance Raman spectroscopy for the detection of changes in sublingual mucosal hemoglobin oxygen saturation (SmO 2 ) in response to hemorrhage and resuscitation, and to compare SmO 2 with other indicators of tissue oxygenation including central venous oxygen saturation (ScvO 2 ), lactate, base excess, and shed blood volume.
Proceedings SPIE, 2020
We recently reported the first noninvasive, label free measurement of pH in a bodily fluid in vivo using only Raman spectra i.e. in vivo rat model measurements probing the immediate vicinity of a contusive spinal cord injury (SCI) in the first minutes and hours after injury. Calibrated and assigned using Raman spectra of authentic materials, in the rat model we were not able to sample the cerebrospinal fluid (CSF) to allow comparison with an independent measurement of the pH. Swine presents a better model because they allow physical sampling of CSF, although still not ideal for our purposes. We were only able to physically sample CSF from the fourth cerebral ventricle of 2 different animals, before and after all spectral measurements on cords were completed. One measurement each for 2 different animals on physically sampled CSF averaged a pH of 7.001±0.106 (N=2) as per standard laboratory instrumentation. Using a dynamic analysis and the Henderson-Hasselbalch equation, the average o...
Cerebral Arterial Oxygen Saturation Measurements Using a Fiber-Optic Pulse Oximeter
Background A pilot investigation was undertaken to assess the performance of a novel fiber-optic cerebral pulse oximetry system. A fiber-optic probe designed to pass through the lumen of a cranial bolt of the type used to make intracranial pressure measurements was used to obtain optical reflectance signals directly from brain tissue. Methods Short-duration measurements were made in six patients undergoing neurosurgery. These were followed by a longer duration measurement in a patient recovering from an intracerebral hematoma. Estimations of cerebral arterial oxygen saturation derived from a frequency domain-based algorithm are compared with simultaneous pulse oximetry (SpO 2) and hemoximeter (SaO 2) blood samples. Results The short-duration measurements showed that reliable photoplethysmographic signals could be obtained from the brain tissue. In the long-duration study, the mean (±SD) difference between cerebral oxygen saturation (ScaO 2) and finger SpO 2 (in saturation units) was-7.47(±3.4)%. The mean (±SD) difference between ScaO 2 and blood SaO 2 was-7.37(±2.8)%. Conclusions This pilot study demonstrated that arterial oxygen saturation may be estimated from brain tissue via a fiber-optic pulse oximeter used in conjunction with a cranial bolt. Further studies are needed to confirm the clinical utility of the technique.
Measurements of cerebral arterial oxygen saturation using a fiber-optic pulse oximeter
2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2009
This pilot investigation was undertaken to assess the performance of a novel fiber-optic cerebral pulse oximetry system. A fiber-optic probe designed to pass through the lumen of a cranial bolt of the type used to make intracranial pressure measurements was used to obtain optical reflectance signals directly from the brain tissue. Preliminary results from seven patients measured in the operating theatre and ITU are presented. Estimations of cerebral arterial oxygen saturation derived from a frequency domain-based algorithm are compared with pulse oximetry (SpO 2) and hemoximeter (SaO 2) blood samples. The mean (±SD) difference between cerebral oxygen saturation (ScaO 2) and finger SpO 2 (in saturation units) was-7.47(±3.4)%. The mean (±SD) difference between ScaO 2 and blood SaO 2 was-7.37(±2.8)%.
Neurophotonics, 2016
Advances in image-guided therapy enable physicians to obtain real-time information on neurological disorders such as brain tumors to improve resection accuracy. Image guidance data include the location, size, shape, type, and extent of tumors. Recent technological advances in neurophotonic engineering have enabled the development of techniques for minimally invasive neurosurgery. Incorporation of these methods in intraoperative imaging decreases surgical procedure time and allows neurosurgeons to find remaining or hidden tumor or epileptic lesions. This facilitates more complete resection and improved topology information for postsurgical therapy (i.e., radiation). We review the clinical application of recent advances in neurophotonic technologies including Raman spectroscopy, thermal imaging, optical coherence tomography, and fluorescence spectroscopy, highlighting the importance of these technologies in live intraoperative tissue mapping during neurosurgery. While these technologies need further validation in larger clinical trials, they show remarkable promise in their ability to help surgeons to better visualize the areas of abnormality and enable safe and successful removal of malignancies.