T. C. Bakker Schut

Use of fibre optic probes for detection of Barrett’s epithelium in the rat oesophagus by Raman spectroscopy

In the last decades, there has been a dramatic increase in the incidence of Barretts oesophagus and the associated oesophageal adenocarcinoma. Therefore, patients with a Barretts oesophagus undergo regular endoscopic surveillance with randomly taken biopsies to detect the presence of high-grade dysplasia or carcinoma. Sampling errors and observer variation, inherent to such a surveillance protocol warrant other detection methods. Raman spectroscopy is a non-invasive optical spectroscopic technique that provides detailed information about the molecular composition and structure of tissues. Changes in molecular composition in tissues as a consequence of pathologic processes, can thus be recognised. For clinical application of Raman spectroscopy, thin and flexible fibre optic probes can be used that fit in the auxiliary channel of an endoscope. In this study, a multivariate classification model was developed for detection of Barretts epithelium, based on ex vivo Raman spectra of the rat oesophagus. The spectra were collected with three different fibre optic probes and on 11 different days. This mimics the way a database is collected in a clinical situation, including all instrument calibration, probe-to-probe and day-to-day variation. After elimination of interfering background signal contributions from the different probes using a vector-correction procedure, we could discriminate between Barretts and normal epithelium with accuracy higher than 93%. The model yields a spectral discriminant that best separates the two groups. To facilitate interpretation of this discriminant, we obtained Raman spectra from tissue sections of normal oesophageal epithelium, keratin and muscle layer using a confocal Raman microscope.

Discrimination between oral cancer and healthy tissue based on water content determined by Raman spectroscopy.

Tumor-positive resection margins are a major problem in oral cancer surgery. High-wavenumber Raman spectroscopy is a reliable technique to determine the water content of tissues, which may contribute to differentiate between tumor and healthy tissue. The aim of this study was to examine the use of Raman spectroscopy to differentiate tumor from surrounding healthy tissue in oral squamous cell carcinoma. From 14 patients undergoing tongue resection for squamous cell carcinoma, the water content was determined at 170 locations on freshly excised tongue specimens using the Raman bands of the OH-stretching vibrations (3350-3550 cm(-1)) and of the CH-stretching vibrations (2910-2965 cm(-1)). The results were correlated with histopathological assessment of hematoxylin and eosin stained thin tissue sections obtained from the Raman measurement locations. The water content values from squamous cell carcinoma measurements were significantly higher than from surrounding healthy tissue (p-value < 0.0001). Tumor tissue could be detected with a sensitivity of 99% and a specificity of 92% using a cutoff water content value of 69%. Because the Raman measurements are fast and can be carried out on freshly excised tissue without any tissue preparation, this finding signifies an important step toward the development of an intraoperative tool for tumor resection guidance with the aim of enabling oncological radical surgery and improvement of patient outcome.

On-line detection of cholesterol and calcification by catheter based Raman spectroscopy in human atherosclerotic plaque ex vivo

Background: Raman spectroscopy has the unique potential to detect and quantify cholesterol and calcification in an atherosclerotic plaque in vivo. Objective: To evaluate the sensitivity and specificity of this technique for detecting cholesterol or calcification in human coronary artery and aorta specimens ex vivo, using a compact clinical fibreoptic based Raman system developed for in vivo applications. Design: From nine coronary arteries and four aorta specimens, 114 sites were evaluated for the presence of cholesterol and calcification by Raman spectroscopy and standard histology. Raman spectra were acquired and evaluated on-line in around five seconds. Results: The correlation between Raman spectroscopy and histology was r = 0.68 for cholesterol and r = 0.71 calcification in the plaque (p < 0.0001). Sensitivity and specificity for detecting cholesterol and calcification were excellent: receiver operating characteristic (ROC) analysis for each of the components revealed areas under the curves of > 0.92 (p < 0.0001). At the optimal cut-off values determined by ROC analysis, positive predictive values of > 80% and negative predictive values of > 90% were obtained. Conclusions: On-line real time catheter based Raman spectroscopy detects accumulation of cholesterol and calcification in atherosclerotic plaque with high sensitivity and specificity.

Identification of Bladder Wall Layers by Raman Spectroscopy

PURPOSE We explored the applicability of Raman spectroscopy to in situ investigation of bladder wall tissue. MATERIALS AND METHODS Bladder wall tissue was obtained from a guinea pig model and frozen sections were used for Raman spectroscopic investigations. From each section 500 to 700 spectra were obtained in a 2-dimensional grid spanning the urothelium, lamina propria and muscle layer. The data set of spectra was subdivided into groups of similar spectra by a cluster analysis algorithm. With each group assigned a different color Raman maps of frozen sections were constructed based on group membership of measured spectra. These maps were then compared with histological and histochemical data obtained from hematoxylin and eosin and immunohistochemical staining for collagen I and III and for smooth muscle actin to correlate Raman spectral features with bladder wall structure and molecular composition. RESULTS Urothelium, lamina propria and muscle layers could be clearly distinguished based on Raman spectra. Lamina propria spectra were dominated by signal contributions of collagen and the smooth muscle layer showed strong signal contributions of actin. The urothelium had a relatively strong lipid signal contribution. CONCLUSIONS These results and the fact that Raman spectroscopy is rapidly evolving into a technology that can be applied in vivo by thin, flexible fiberoptic catheters indicate that prospects are good for in vivo analysis of the molecular composition of the normal and pathological bladder without biopsies.

Raman spectroscopic detection of changes in molecular composition of bladder muscle tissue caused by outlet obstruction

Bladder outlet obstruction leads to loss of bladder function as a result of structural damage. Functional parameters of an obstructed bladder do not enable a prediction of the clinical outcome of removal of the obstruction. Therefore, other diagnostic methods are needed. This study presents first results of an approach based on Raman spectroscopy, which aims to detect changes in molecular composition of the bladder wall that may have diagnostic value. Raman spectroscopic mapping of unfixed sections of damaged and undamaged bladder wall from a guinea pig model of bladder obstruction was used to detect changes in composition of bladder muscle tissue. Collagen infiltration in muscle fibers was clearly visualized. Other compositional changes that are revealed include the accumulation of glycogen in obstructed bladder wall as well as an apparent but as yet unknown change in protein composition. In vivo Raman spectroscopic application may enable determination of bladder structure without the need for biopsies. These initial findings show that Raman spectroscopy can be a valuable diagnostic tool for evaluation of the extent of bladder structure loss.

NIR Raman Spectroscopy of Healthy and Diseased Esophagus

Due to chronic duodeno-gastro-esophageal reflux, the epithelial lining of the esophagus can undergo a change to a more intestinal like type of epithelium. This condition, referred to as Barrett’s esophagus, markedly increases the risk of developing esophageal adenocarcinoma [1]. This type of cancer is rapidly increasing in western society and shows a very high mortality, primarily due to late detection. Early detection of malignancy can significantly increase survival rates. Most detection methods depend on histological examination from endoscopically collected biopsies. However, there are no endoscopically clearly observable differences between healthy tissue, metaplasia and severe displasia. Therefore it is necessary to randomly collect biopsies, with a significant risk of missing malignant degenerations.

Evaluation of bone resection margins of segmental mandibulectomy for oral squamous cell carcinoma

Resection margins are frequently studied in patients with oral squamous cell carcinoma and are accepted as a constant prognostic factor. While most evidence is based on soft tissue margins, reported data for bone resection margins are scarce. The aim of this retrospective study was to evaluate and determine the utility of surgical margins in bone resections for oral cavity squamous cell carcinoma (OCSCC). The status of bone resection margins and their impact on survival was investigated in patients who had undergone segmental mandibulectomy for OCSCC. Medical records were retrieved for the years 2000-2012; 127 patients were identified and included in the study. Tumour-positive bone resection margins were found in 21% of the patients. The 5-year overall survival was significantly lower in this group (P<0.005). Therefore, there is a need for intraoperative feedback on the status of bone resection margins to enable immediate additional resection where necessary. Although the lack of intraoperative methods for the evaluation of bone tissue has been addressed by many authors, there is still no reliable method for widespread use. Future research should focus on an objective, accurate, and rapid method of intraoperative assessment for the entire bone resection margin to optimize patient outcomes.