Endoscopic Raman Spectroscopy Research Articles

Ferrofluid-enabled micro rotary-linear actuator for endoscopic three-dimensional imaging and spectroscopy

This work develops the first tubular microactuator functionalized by ferrofluid that enables both rotational and axial motions in a simultaneous or selective manner for endoscopic imaging and spectroscopy catheter applications. A layer of ferrofluid attracted on the magnetic rotor/slider lifts it off the inner walls of the catheter tube, offering a near friction-less electromagnetic revolution of the rotor and/or its sliding motion along the catheter’s axis controlled by a fluidic pressure. A device prototype coupled with a prism mirror is microfabricated and evaluated to verify the effectiveness of the device design for 3-dimesnional (3D) scanning of a probing laser beam. Measurements show a superior revolving stability along its axis compared to the preceding design without axial motion function. An application of angle-resolved endoscopic Raman spectroscopy is experimentally demonstrated through an ex-vivo test using mouse tissue. The study suggests a promising potential of the microactuator for 3D endoscopic applications with Raman spectroscopy and likely with other modalities including ultrasound and optical coherence tomography.

Side‐Viewing Endoscopic Raman Spectroscopy for Angle‐Resolved Analysis of Luminal Organs

AbstractThere are many medical applications requiring angle‐resolved analysis of luminal organs. One example is lung cancer detection. Early diagnosis is the most effective way to tackle this disease. This, however, remains a challenge due to the lack of accurate detection technology. The problem is exacerbated in cases of peripheral lung cancer growing on narrow bronchi that are difficult to probe. Here, an endoscopic Raman spectroscopy device is demonstrated with a side‐viewing functionality that enables circumferential scanning spectral measurements inside thin conduits. A tubular micro rotary stepping actuator is custom‐designed and integrated with a Raman probe, for the first time, to scan a probing laser beam sideways for angle‐resolved local Raman analysis with no aid of tissue labeling, toward enabling detection of lesion‐induced biochemical changes in vivo and in real time. A microfabricated prototype is evaluated using test chemicals, harvested animal lung tissue ex vivo, as well as a murine colon model in situ and human skin in vivo. All the test results show excellent agreements with reported reference data while revealing >99% wavenumber accuracies. The study indicates that microactuator‐assisted endoscopic Raman spectroscopy is a promising technology for luminal tissue analysis and encourages further studies of its sensitivity in lesion detection.

In vivo analysis of mucosal lipids reveals histological disease activity in ulcerative colitis using endoscope-coupled Raman spectroscopy.

The goal of this study is to evaluate endoscopic Raman spectroscopy as a noninvasive technique to determine histological inflammatory status of colitis. Colon mucosal composition was investigated in vivo from patients with ulcerative colitis (UC) and from age- and body mass index (BMI) matched controls using endoscope-coupled Raman spectroscopy. The results were co-registered with histological assessment of inflammatory status at the same locations. Substantial decreases (50-60%) in the content of phosphotidylcholines (PCs) and total lipids were observed in inflamed colon tissue (histology grade 1, 2 and 3) compared to those from the quiescent (histology grade 0) and from the controls. No significant difference was observed in lipids or PC contents between control and grade 0, or among grades 1 - 3. The degree of lipid unsaturation increased in the inflamed tissue regardless of disease severity. The inflammation-associated alterations in lipids and PC are observed independent of BMI or the anatomical locations for data collection. Multivariate analysis using support vector machine (SVM) algorithm classified the spectra of the controls or the inactive colitis from those of inflamed tissue with a sensitivity of 83.5% and 97.1% respectively. Our results showed that mucosal lipid content is related to the microscopic disease activity, and thus could serve as a valuable spectral marker to differentiate active colitis from the quiescent.

Disposable sheath that facilitates endoscopic Raman spectroscopy.

In vivo endoscopic Raman spectroscopy of human tissue using a fiber optic probe has been previously demonstrated. However, there remain several technical challenges, such as a robust control over the laser radiation dose and measurement repeatability during endoscopy. A decrease in the signal to noise was also observed due to aging of Raman probe after repeated cycles of harsh reprocessing procedures. To address these issues, we designed and tested a disposable, biocompatible, and sterile sheath for use with a fiber optic endoscopic Raman probe. The sheath effectively controls contamination of Raman probes between procedures, greatly reduces turnaround time, and slows down the aging of the Raman probes. A small optical window fitted at the sheath cap maintained the measurement distance between Raman probe end and tissue surface. To ensure that the sheath caused a minimal amount of fluorescence and Raman interference, the optical properties of materials for the sheath, optical window, and bonding agent were studied. The easy-to-use sheath can be manufactured at a moderate cost. The sheath strictly enforced a maximum permissible exposure standard of the tissue by the laser and reduced the spectral variability by 1.5 to 8.5 times within the spectral measurement range.

Development and in vivo testing of a high frequency endoscopic Raman spectroscopy system for potential applications in the detection of early colonic neoplasia.

The objective of this study was to build and test an adjunct system to a colonoscope for in vivo measurement of Raman spectra from colon tissue for potentially improving the detection of early cancers. The novelty of this system was that low cost fibre optic probes were used, without the addition of expensive optical filters. Good quality in vivo Raman spectra were successfully obtained with a 1 s integration time in the high frequency (HF) range from normal tissue and polyps of patients during a colonoscopy. The polyps were subsequently removed, and their pathology determined. The acquired in vivo Raman spectra showed clear changes between tissue with normal and tubular adenoma pathology. Further clinical study with this low cost HF Raman probe is warranted to fully test its clinical utility.

Endoscopic Raman Spectroscopy for Molecular Fingerprinting of Gastric Cancer: Principle to Implementation.

Currently, positive endoscopic biopsy is the standard criterion for gastric cancer diagnosis but is invasive, often inconsistent, and delayed although early detection and early treatment is the most important policy. Raman spectroscopy is a spectroscopic technique based on inelastic scattering of monochromatic light. Raman spectrum represents molecular composition of the interrogated volume providing a direct molecular fingerprint. Several investigations revealed that Raman spectroscopy can differentiate normal, dysplastic, and adenocarcinoma gastric tissue with high sensitivity and specificity. Moreover, this technique can indentify malignant ulcer and showed the capability to analyze the carcinogenesis process. Automated on-line Raman spectral diagnostic system raised possibility to use Raman spectroscopy in clinical field. Raman spectroscopy can be applied in many fields such as guiding a target biopsy, optical biopsy in bleeding prone situation, and delineating the margin of the lesion. With wide field technology, Raman spectroscopy is expected to have specific role in our future clinical field.

Endoscopic Raman spectroscopy enables objective diagnosis of dysplasia in Barrett's esophagus

Early detection and targeted endoscopic resection of Barrett's esophagus-associated high-grade dysplasia (HGD) can prevent progression to invasive esophageal malignancy. Raman spectroscopy, a highly sophisticated analytical technique, has been translated into an endoscopic tool to facilitate rapid, objective diagnosis of dysplasia in the esophagus. To evaluate the ability of endoscopic Raman spectroscopy (ERS) to objectively detect esophageal HGD and adenocarcinoma. A total of 798 one-second spectra were measured from 673 ex vivo esophageal tissue samples, collected from patients with Barrett's esophagus by using a novel endoscopic Raman probe. Spectra were correlated with consensus histopathology. Multivariate analysis was used to evaluate the classification accuracy of ERS ex vivo. Probe measurements were conducted in the laboratory. Tissue specimens were collected from the operating theatre and endoscopy unit. Tissue from 62 patients was included in the study. Endoscopic biopsy/resection or esophagectomy was performed where indicated clinically. Diagnostic performance of ERS for detection of HGD and esophageal adenocarcinoma. ERS demonstrated a sensitivity of 86% and a specificity of 88% for detecting HGD and adenocarcinoma. The ability to grade dysplasia and differentiate intestinal metaplasia from nonintestinal metaplasia columnar-lined esophagus was also demonstrated. Diagnostic classification was based on objective measurement of the biochemical profile of different tissue types. The potential for combination ERS and narrow-band imaging was also demonstrated. Measurements were taken from ex vivo tissue. ERS enables rapid, accurate, objective diagnosis of superficial esophageal disease (metaplasia, dysplasia, intramucosal cancer) in clinically applicable time scales.

Mo1516 Development of an Endoscopic Raman Spectroscopy System for the Improving Detection of Early Colonic Neoplasias

Mo1516 Development of an Endoscopic Raman Spectroscopy System for the Improving Detection of Early Colonic Neoplasias

In Vivo Characterization of Lung Cancers Using Endoscopic Raman Spectroscopy: A Pilot Study

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In vivo endoscopic Raman spectroscopy for the differentiation of dysplasia (low-grade versus high-grade) within Barrett's esophagus

In vivo endoscopic Raman spectroscopy for the differentiation of dysplasia (low-grade versus high-grade) within Barrett's esophagus