Catherine Kendall

The use of Raman spectroscopy to identify and grade prostatic adenocarcinoma in vitro.

Raman spectroscopy is an optical technique, which provides a measure of the molecular composition of tissue. Raman spectra were recorded in vitro from both benign and malignant prostate biopsies, and used to construct a diagnostic algorithm. The algorithm was able to correctly identify each pathological group studied with an overall accuracy of 89%. The technique shows promise as a method for objectively grading prostate cancer.

Advances in the clinical application of Raman spectroscopy for cancer diagnostics.

Light interacts with tissue in a number of ways including, elastic and inelastic scattering, reflection and absorption, leading to fluorescence and phosphorescence. These interactions can be used to measure abnormal changes in tissue. Initial optical biopsy systems have potential to be used as an adjunct to current investigative techniques to improve the targeting of blind biopsy. Future prospects with molecular-specific techniques may enable objective optical detection providing a real-time, highly sensitive and specific measurement of the histological state of the tissue. Raman spectroscopy has the potential to identify markers associated with malignant change and could be used as diagnostic tool for the early detection of precancerous and cancerous lesions in vivo. The clinical requirements for an objective, non-invasive, real-time probe for the accurate and repeatable measurement of pathological state of the tissue are overwhelming. This paper discusses some of the recent advances in the field.

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

BACKGROUND Early detection and targeted endoscopic resection of Barretts 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. OBJECTIVE To evaluate the ability of endoscopic Raman spectroscopy (ERS) to objectively detect esophageal HGD and adenocarcinoma. DESIGN A total of 798 one-second spectra were measured from 673 ex vivo esophageal tissue samples, collected from patients with Barretts 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. SETTING Probe measurements were conducted in the laboratory. Tissue specimens were collected from the operating theatre and endoscopy unit. PATIENTS Tissue from 62 patients was included in the study. INTERVENTIONS Endoscopic biopsy/resection or esophagectomy was performed where indicated clinically. MAIN OUTCOME MEASUREMENT Diagnostic performance of ERS for detection of HGD and esophageal adenocarcinoma. RESULTS 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. LIMITATIONS Measurements were taken from ex vivo tissue. CONCLUSION ERS enables rapid, accurate, objective diagnosis of superficial esophageal disease (metaplasia, dysplasia, intramucosal cancer) in clinically applicable time scales.

Raman spectroscopy of parathyroid tissue pathology.

Primary hyperparathyroidism (HPT) in 80% of patients is due to a solitary parathyroid adenoma, while in 20% multigland pathology exists, usually hyperplasia [Scott-Coombes, Surgery, 21(12):309–312, 2003]. Despite recent advances in minimally invasive parathyroidectomy, better preoperative localisation techniques and intraoperative parathyroid hormone (PTH) monitoring, a 4% failure rate [Grant CS, Thompson G, Farley D, Arch Surg, 140:47–479, 2005] persists making accurate differentiation between adenomas and hyperplasia of prime importance. We investigated the ability of Raman spectroscopy to accurately differentiate between parathyroid adenomas and hyperplasia. Raman spectra were measured at defined points on the parathyroid tissue sections using a bench-top microscopy system. Multivariate analysis of the spectra was carried out to construct a diagnostic algorithm correlating spectral results with the histopathological diagnosis. A total of 698 spectra were analysed. Principal-component (PCA)-fed linear discriminant analysis (LDA) used to construct a diagnostic algorithm. Detection sensitivity for parathyroid adenomas was 95% and hyperplasia was 93%. These preliminary results indicate that Raman spectroscopy is potentially an excellent tool to differentiate between parathyroid adenomas and hyperplasia.

Raman spectroscopy: a potential tool for early objective diagnosis of neoplasia in the oesophagus.

There is a profound clinical need for a diagnostic tool that will enable clinicians to identify early neoplastic change in the oesophagus. Raman Spectroscopy (RS) has demonstrated the potential to provide non-invasive, rapid, objective diagnosis of endoscopically invisible precancerous oesophageal dysplasia in vitro. RS analyses biological material to identify highly specific biochemical information that can be used to influence clinical care. Raman spectroscopic mapping could provide automated assessment of tissue biopsies to aid histopathological diagnosis in vitro. Furthermore, the recent development of fibre-optic Raman probes has enabled endoscopic assessment of oesophageal mucosa in vivo. Accurate identification of dysplasia will enable targeted endoscopic resection of early lesions preventing the development of oesophageal cancer. This review summarises the development of Raman systems for use as laboratory based analytical adjuncts and endoscopic diagnostic tools in the distal oesophagus.

Vibrational spectroscopy for cancer diagnostics

The vibrational spectroscopy techniques of Raman spectroscopy and Fourier-transform infrared spectroscopy offer a number of potential advantages as tools for clinical diagnosis. The ability of these methods to detect subtle biochemical changes relating to pathology opens the possibility of their use in tissue diagnosis. Potential applications include use as an ‘optical biopsy’ technique for in vivo tissue diagnosis or to guide therapy, as a ‘digital staining’ method to assist a histopathologist in analysing a sample, or as an entirely automated process for histopathology classification. To date, much work has been undertaken in applying these spectroscopic methods to discriminate between disease states across a wide range of pathologies and organ systems, but as yet none have entered routine clinical practice. There is a pressing clinical need for real-time, accurate tissue diagnosis, especially in malignant conditions for which rapid diagnosis and comprehensive identification and treatment of diseased tissue are of paramount importance. Cancer diagnostics remains reliant on analysis of tissue samples by histopathologists to confirm malignancy, based on morphological tissue changes and immunohistochemical staining techniques. There is increasing evidence that vibrational spectroscopy, in combination with chemometric data analysis, is a powerful and accurate technique for detecting cancerous and pre-cancerous biochemical changes both in vitro and in vivo, for a range of malignant conditions. This review examines the progress of vibrational spectroscopy towards selected clinical applications, with a particular focus on cancer diagnostics.

Assessment of a custom-built Raman spectroscopic probe for diagnosis of early oesophageal neoplasia

We evaluate the potential of a custom-built fiber-optic Raman probe, suitable for in vivo use, to differentiate between benign, metaplastic (Barretts oesophagus), and neoplastic (dysplastic and malignant) oesophageal tissue ex vivo on short timescales. We measured 337 Raman spectra (λ(ex)=830 nm; P(ex)=60 mW; t=1 s) using a confocal probe from fresh (298) and snap-frozen (39) oesophageal tissue collected during surgery or endoscopy from 28 patients. Spectra were correlated with histopathology and used to construct a multivariate classification model which was tested using leave one tissue site out cross-validation in order to evaluate the diagnostic accuracy of the probe system. The Raman probe system was able to differentiate, when tested with leave one site out cross-validation, between normal squamous oesophagus, Barretts oesophagus and neoplasia with sensitivities of (838% to 6%) and specificities of (89% to 99%). Analysis of a two group model to differentiate Barretts oesophagus and neoplasia demonstrated a sensitivity of 88% and a specificity of 87% for classification of neoplastic disease. This fiber-optic Raman system can provide rapid, objective, and accurate diagnosis of oesophageal pathology ex vivo. The confocal design of this probe enables superficial mucosal abnormalities (metaplasia and dysplasia) to be classified in clinically applicable timescales paving the way for an in vivo trial.

Raman spectroscopy – A potential new method for the intra-operative assessment of axillary lymph nodes

Sentinel Lymph Node Biopsy has become the standard surgical procedure for the sampling of axillary lymph nodes in breast cancer. Intra-operative node assessment of these nodes would allow definitive axillary surgery to take place immediately with associated benefits for patient management. Our experimental study aims to demonstrate that a Raman spectroscopy probe system could overcome many of the disadvantages of current intra-operative methods. 59 axillary lymph nodes, 43 negative and 16 positive from 58 patients undergoing breast surgery at our district general hospital were mapped using Raman micro-spectroscopy. These maps were then used to model the effect of using a Raman spectroscopic probe by selecting 5 and 10 probe points across the mapped images and evaluating the impact on disease detection. Results demonstrated sensitivities of up to 81% and specificities of up to 97% when differentiating between positive and negative lymph nodes, dependent on the number of probe points included. The results would have concurred with histopathology assessment in 89% and 91% of cases in the 5 and 10 point models respectively. Using Raman spectroscopy in this way could allow lymph node assessment within a time-frame suitable for intra-operative use.

Evaluation of linear discriminant analysis for automated Raman histological mapping of esophageal high-grade dysplasia

Rapid Raman mapping has the potential to be used for automated histopathology diagnosis, providing an adjunct technique to histology diagnosis. The aim of this work is to evaluate the feasibility of automated and objective pathology classification of Raman maps using linear discriminant analysis. Raman maps of esophageal tissue sections are acquired. Principal component (PC)-fed linear discriminant analysis (LDA) is carried out using subsets of the Raman map data (6483 spectra). An overall (validated) training classification model performance of 97.7% (sensitivity 95.0 to 100% and specificity 98.6 to 100%) is obtained. The remainder of the map spectra (131,672 spectra) are projected onto the classification model resulting in Raman images, demonstrating good correlation with contiguous hematoxylin and eosin (HE) sections. Initial results suggest that LDA has the potential to automate pathology diagnosis of esophageal Raman images, but since the classification of test spectra is forced into existing training groups, further work is required to optimize the training model. A small pixel size is advantageous for developing the training datasets using mapping data, despite lengthy mapping times, due to additional morphological information gained, and could facilitate differentiation of further tissue groups, such as the basal cells∕lamina propria, in the future, but larger pixels sizes (and faster mapping) may be more feasible for clinical application.

Optical adjuncts for enhanced colonoscopic diagnosis

Optical techniques using previously unexploited properties of light interaction with tissue may be valuable in the detection, diagnosis and staging of colorectal neoplasia.