FTIR-spectroscopy is a powerful and reliable non-destructive optical analytical tool. Neither micro-FTIR-spectrometry nor fiberoptic evanescent wave spectroscopy (FEWS), which is the combination of FTIR and fiber optics techniques using a spectrometer as radiation source, are used so far in a routine mode for diagnosis or therapeutics purposes in clinical applications. However in the past few years lots of attempts using the potential of IR-spectroscopy have been improved in order to analyze human tissues of various origin. This was leading to classifications. Diseased and healthy tissue could be distinguished. Hereby the state of disease is reflected by its "microheterogenous" composition based on the biomolecular structure and/or the content of biologically active molecular components and compounds.
In modern clinical fields, preference is given to non-invasive techniques to avoid or reduce the pain of patients. New techniques are not acceptable unless they are efficient and secure for medical diagnostics on a higher level. Therefore the aim of this project is to develop a method for minimal invasive surgery. This has to be implemented on an endoscopic device including a visual imaging system. The device is based on MIR fiberoptic technique and consists of tunable infrared diode lasers. For detection an IR-sensitive focal plane array will be used.
At first we used micro-FTIR-spectroscopy in transmission mode to probe thin unfixed cryosections of air dried human soft tissue. Stressed and unstressed native specimens of adenocarcinoma of the colon, mammacarcinoma and human melanoma were investigated. In the first step standard parameters for the measurement and the procedure of tissue handling were optimized in order to evaluate distinct wavenumbers for tissue diagnostics. All spectroscopic results were compared to the pathological finding. Additional investigations on specimen at a microscopic scale were performed in contact and non-contact using the ATR and remission mode.
Attempts were made to confirm these results under conditions similar to the IR-microscopic investigations using a fiberoptic experimental set up in ATR and reflectance mode.
The FTIR-ATR-technique is limited by the penetration depth to biological tissue. So we focused our interest to the remission of infrared radiation. In respect to humidity and temperature a designed specimen container was used for these FTIR-microspectroscopic measurements.
Results will be presented which where obtained by using flexible infrared waveguides for mapping experiments in reflectance mode under physiological like conditions and also by using tunable diode lasers. Further, details of the experimental set up will be described.
New applications for the Fiberoptic Evanescent Wave Fourier Transform Infrared (FEW-FTIR) method have been developed for the diagnostics of skin, breast and colon tissue. Our technique allows for the detection of inconsistencies in the molecular structure of normal tissues noninvasively and in vivo. This FET-FTIR method is direct, nondestructive, and fast (seconds). Our optical fibers for the middle infrared (MIR) range are nontoxic, nonhygroscopic, flexible, and characterized by extremely low losses. This combination of traditional Fourier Transform Infrared (FTIR) spectroscopy and advanced fiber technology in the MIR range has opened the door for new powerful diagnostic tools for investigations of tissue and phenomena including normal skin, process of aging allergies, and precancerous conditions. This method could be extended to applications involving the detection of the influence of environmental factors (sun, water, pollution, and weather) on the skin surfaces of children and adults. We are in a process to apply our method also to studies of colon tissue in vivo and in vitro with a combination of FTIR microscopy and microimaging. In this study, we have also noninvasively investigated more than 100 cases of normal skin and several acupuncture points in vivo in the range of 1450 to 1800 cm-1. The results of our analysis of body tissue and body fluids are discussed in terms of structural similarities and differences on a molecular level.
In this study, Fourier transform infrared microspectroscopy is used to analyze formalin fixed, paraffin embedded, sections of liver tissue. The goal of this work is to further characterize the infrared spectral signatures of the various biochemical and cellular components found in benign and diseased tissue. The relatively homogenous cellular composition and uniform anatomic organization makes the liver uniquely suited for this purpose. Hepatocytes constitute approximately 80% of the total cellular mass of the liver. The remainder is extracellular matrix, vascular epithelium and hematopoietic cells. The infrared spectra collected from benign (post-mortem), inactive cirrhosis and hepatocellular carcinoma are presented. These spectra are evaluated in terms of the major biochemical and histological components present within the liver parenchyma. This is achieved by correlating the spectral data with histochemical staining methods that give an indication of the contributions of various structural and cellular elements.
Under normal circumstances the liver contains an abundant but short lived glycogen supply. In the benign (post-mortem) sample, the glycogen has been consumed metabolically revealing spectral features associated with proteins and nucleic acids. Normal liver contains a fine network of connective tissue fibers interspersed among the liver cell population; however, in the spectra of the post-mortem sample, the spectral features commonly associated with connective tissue proteins are absent.
In contrast, the cirrhotic liver contains course and abundant connective tissue fibers arising from chronic liver disease. Measurements from fibrous areas in cirrhosis display infrared features similar to those observed in other connective tissues. Despite this, there is no indication that fibers found among the hepatocytes in cirrhosis contribute significantly to the overall spectra. The hepatocytes in cirrhosis contain abundant glycogen which can vary significantly in intensity. These spectra would be extremely difficult to differentiate from those of other glycogen rich epithelial tissues.
In hepatocellular carcinoma, there are no connective tissue fibers, and the hepatocytes do not contain glycogen. Instead, the liver parenchyma is composed of sheets of neoplastic hepatocytes that can appear morphologically similar to normal hepatocytes. However, the infrared spectra obtained form neoplastic hepatocytes are easily distinguishable from the spectra of hepatocytes of the other two conditions reported here. The spectral changes observed for the neoplastic hepatocytes are dominated by features that agree with neoplastic changes observed in other tissues.
This presentation will discuss a number of infrared spectroscopic experiments performed with (on) human and animal hearts and lungs.
Microcirculatory compromise remains a serious complication in many facets of surgery. In plastic surgery, compromised blood flow in transplanted tissue can arise from vascular thrombosis or failure of anastomosis. Clinical signs of poor perfusion, based on observations of skin color, temperature and capillary refill, become evident only after several hours of compromised perfusion. Late intervention threatens the viability of the transplanted tissue. Near infrared diffuse reflectance spectroscopy and spectroscopic imaging can determine the degree of tissue ischemia at the time of surgery as well as during post-operative recovery. This study uses the reverse McFarlane dorsal skin flap model to demonstrate the potential of near infrared spectroscopy and imaging to detect poorly oxygenated tissues as well as determining tissue edema and dehydration. Near infrared spectra and images (650 – 1100 nm) of the rat dorsum were taken prior to surgery, immediately following surgical elevation of the flap, as well as over 48 hours following surgery. Regional variations in tissue oxygenation and hydration can be visualized in a rapid and noninvasive manner using these techniques. Significant changes in tissue oxygenation and hydration were observed upon surgical elevation of the skin flap and a significant regional variation along the skin flap was also observed. Ischemia – reperfusion injury induced by vascular clamping at the base of the pedicle flap was easily detectable using near infrared spectroscopy and imaging. The spectroscopic data are compared to laser Doppler measurements of skin flap perfusion. The study indicates the potential of near infrared spectroscopy and imaging to monitor tissue oxygenation and water content during surgery and post-operatively.
Keywords: near infrared spectroscopy; near infrared multispectral
imaging; tissue oxygenation; tissue edema; ischemia - reperfusion injury;