Sune Montan

Multispectral system for medical fluorescence imaging

The principles of a powerful multicolor imaging system for tissue fluorescence diagnostics are discussed. Four individually spectrally filtered images are formed on a matrix detector by means of a split-mirror arrangement. The four images are processed in a computer, pixel by pixel, by means of mathematical operations, leading to an optimized contrast image, which enhances a selected feature. The system is being developed primarily for medical fluorescence imaging, but has wide applications in fluorescence, reflectance, and transmission monitoring related to a wide range of industrial and environmental problems. The system operation is described for the case of linear imaging on a diode array detector. Laser-induced fluorescence is used for cancer tumor and atherosclerotic plaque demarcation using the contrast enhancement capabilities of this imaging system. Further examples of applications include fluorescing minerals and flames.

Multicolor imaging and contrast enhancement in cancer-tumor localization using laser-induced fluorescence in hematoporphyrin-derivative-bearing tissue

Simultaneous imaging of laser-induced fluorescence in three selected wavelength bands from hematoporphyrin-derivative-bearing tissue has been performed, permitting considerable contrast enhancement for cancer-tumor localization.

Clinical multi-colour fluorescence imaging of malignant tumours - initial experience

Purpose: the detection of malignant tumours relies on a variety of diagnostic procedures including X-ray images and, for hollow organs, endoscopy. the purpose of this study was to present a new technique for non-invasive tumour detection based on tissue fluorescence imaging Material and Methods: A clinically adapted multi-colour fluorescence system was employed in the real-time imaging of malignant tumours of the skin, breast, head and neck region, and urinary bladder. Tumour detection was based on the contrast displayed in fluorescence between normal and malignant tissue, related to the selective uptake of tumour-marking agents, such as haematoporphyrin derivative (HPD) and δ-amino levulinic acid (ALA), and natural chromophore differences between various tissues. in order to demarcate basal cell carcinomas of the skin, ALA was applied topically 4–6 h before the fluorescence investigation. for urinary bladder tumour visualisation (transitional cell carcinoma of different stages including carcinoma in situ), ALA was instilled into the bladder 1–2 h prior to the study. Malignant and premalignant lesions in the head and neck region were imaged after i.v. injection of HPD (Photofrin). Finally, the extent of in situ and invasive carcinomas of the breast was investigated in surgically excised specimens from patients that received a low-dose injection of HPD 24 h prior to the study. the tumour imaging system was coupled to an endoscope. Fluorescence light emission from the tissue surface was induced with 100-nslong optical pulses at 390 nm, generated from a frequency-doubled alexandrite laser. with the use of special image-splitting optics, the tumour fluorescence, intensified in a micro-channel plate, was imaged in 3 selected wavelength bands. These 3 images were processed together to form a new optimised-contrast image of the tumour. This image, updated at a rate of about 3 frames/s, was mixed with a normal colour video image of the tissue Results: A clear demarcation from normal surrounding tissue was found during in vivo measurements of superficial bladder carcinoma, basal cell carcinoma of the skin, and leukoplakia with dysplasia of the lip, and in in vitro investigations of resected breast cancer Conclusions: the initial clinical experience of using multi-colour fluorescence imaging has shown that the technique has the potential to reveal malignant tumour tissue, including non-invasive early carcinoma and also precancerous tissue. Further investigations are needed to fully develop the method

Clinical spectral characterisation of colonic mucosal lesions using autofluorescence and delta aminolevulinic acid sensitisation

BACKGROUND AND AIMS Laser induced fluorescence (LIF) from colonic mucosa was measured in vivo with and without δ aminolevulinic acid (ALA) in an attempt to differentiate between neoplasia and non-neoplasia in real time during colonoscopy. METHODS Spectra from 32 adenomas, 68 normal sites, and 14 hyperplastic polyps in 41 patients were obtained with a point monitoring system. Twenty one of the patients had been given a low dose of ALA as a photosensitiser before the examination. Light of 337, 405, or 436 nm wavelength was used as excitation. Stepwise multivariate linear regression analysis was performed. RESULTS With 337 nm excitation, 100% sensitivity and 96% specificity was obtained between normal mucosa and adenomas. Seventy seven per cent of the hyperplastic polyps were classified as non-neoplastic. When exciting with 405 and 436 nm, the possibility of distinguishing different types of tissue was considerably better in the ALA patients than in the non-ALA patients. CONCLUSIONS The in vivo point measurements imply that a good discrimination between normal tissue and adenomatous polyps can be obtained using the LIF technique. Excitation at 337 nm and at 405 nm or 436 nm using ALA gives good results. LIF also shows potential for distinguishing adenomatous from hyperplastic polyps. The number of detection wavelengths could be reduced if chosen properly.

Laser-Induced Fluorescence Studies of Hematoporphyrin Derivative (HPD) in Normal and Tumor Tissue of Rat

Fluorescence studies of hematoporphyrin derivative (HPD) in normal and tumor tissue of rat were performed with nitrogen laser excitation and optical multi-channel detection. Fifteen types of tissue including inoculated tumor were investigated for rats at different delays after HPD injection. Optimum contrast functions and other criteria for discriminating tumor tissue from normal tissue are discussed. The results should have implications for practical human HPD endoscopy.

Fluorescence Endoscopy Instrumentation For Improved Tissue Characterization

An endoscopic instrument for normal optical inspection and simultaneous fluorescence characterization is described. The equipment is primarily intended for early cancer detection using characteristic fluorescence from the tumor-seeking agent hematoporphyrin derivative. A dimensionless ratio of two fluorescence intensities is monitored making the equipment insensitive to target distance and surface topography. A measurement example is given and possible improvements are discussed.

Fluorescence diagnostics and kinetic studies in the head and neck region utilizing low-dose δ-aminolevulinic acid sensitization

Diagnostic measurements and pharmacokinetic studies were performed in 17 patients with various kinds of malignant, premalignant and benign lesions in the head and neck region by means of point monitoring laser-induced fluorescence. For marking different types of tissue, delta-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) was used. The ALA-induced PpIX synthesis was monitored at different time intervals after oral administration of ALA in low doses, 5 and 15 mg/kg b.w. Besides the porphyrin-related signal the tissue endogenous fluorescence was also recorded. The fluorescence spectra were evaluated at two different wavelengths corresponding to the specific drug-related fluorescence peak and the endogenous tissue fluorescence emission at 635 and 490 nm, respectively. The evaluated fluorescence data were correlated to the histopathological tissue investigation. A fall-off in the overall fluorescence intensity at 490 nm was obtained for all the malignant and premalignant areas, as well as an increased red fluorescence. A ratio between the red and the blue/green fluorescence intensity was formed for each time interval after the ALA administration. The lower drug dose seems to be sufficient to obtain a useful demarcation ratio between normal and diseased tissue with a very low PpIX fluorescence intensity in the normal tissue. A PpIX fluorescence maximum seems to occur between 3 and 4 h in normal tissues, whereas malignant tumour tissue shows a higher level for a longer period of time.

Aspects of Tumour Demarcation In Rats By Means of Laser-induced Fluorescence and Hematoporphyrin Derivatives

The effects of different parameters of interest for the localization of malignant tumours in situ by means of laser-induced fluorescence and haematoporphyrin derivatives were investigated. Such parameters are drug composition, drug concentration, laser pulse energy and excitation wavelength. In order to assess the relative merits of the two tumor-seeking agents Photofrin (haematoporphyrin derivative) and Photofrin II (dihaematoporphyrin ether) we have performed a comparative study on rat tissues. The results suggest that Photofrin is at least as good as the therapeutically more potent agent Photofrin II. A linear relation between drug dose and recorded porphyrin fluorescence intensity was also found. Using not only the porphyrin fluorescence, but also natural tissue autofluorescence, better tumour demarcation is observed when utilizing an excitation wavelength shorter than the porphyrin excitation peak at 405 nm.

Remote sample characterization based on fluorescence monitoring

The possibilities and limitations of remote sample characterization using induced fluorescence are discussed. General equations for remote sensing of fluorescence are presented and discussed. The implications of different elements of a system for remote fluorescence sensing on different parameters of the equations are treated. Background light influence and signal processing are considered. Pulsed lasers, flashlamps and cw lamps as excitation sources are compared when matched to the proper detection scheme employing boxcar integration or lock-in detection. Model experiments have been performed to demonstrate different measurement strategies. Examples from remote oil-slick characterization are chosen as illustrations.

A system for industrial surface monitoring utilizing laser-induced fluorescence

A system utilizing laser-induced fluorescence for surface monitoring is described. Results of laboratory and industrial measurements of surface films are reported and further applications of the technique are described.