Time-resolved measurements of tissue autofluorescence (AF) excited at 405 nm were carried out with an optical-fiber-based spectrometer in the bronchi of 11 patients. The objectives consisted of assessing the lifetime as a new tumor/normal (T/N) tissue contrast parameter and trying to explain the origin of the contrasts observed when using AF-based cancer detection imaging systems. No significant change in the AF lifetimes was found. AF bronchoscopy performed in parallel with an imaging device revealed both intensity and spectral contrasts. Our results suggest that the spectral contrast might be due to an enhanced blood concentration just below the epithelial layers of the lesion. The intensity contrast probably results from the thickening of the epithelium in the lesions. The absence of T/N lifetime contrast indicates that the quenching is not at the origin of the fluorescence intensity and spectral contrasts. These lifetimes (6.9 ns, 2.0 ns, and 0.2 ns) were consistent for all the examined sites. The fact that these lifetimes are the same for different emission domains ranging between 430 and 680 nm indicates that there is probably only one dominant fluorophore involved. The measured lifetimes suggest that this fluorophore is elastin.
Autofluorescence bronchoscopy (AFB) has been shown to be a highly sensitive tool for the detection of early endobronchial cancers. When excited with blue-violet light, early neoplasia in the bronchi tend to show a decrease of autofluorescence in the green region of the spectrum and a relatively smaller decrease in the red region of the spectrum. Superposing the green foreground image and the red background image creates the resultant autofluorescence image. Our aim was to investigate whether the addition of backscattered red light to the tissue autofluorescence signal could improve the contrast between healthy and diseased tissue. We have performed a clinical study involving 41 lung cancers using modified autofluorescence bronchoscopy systems. The lesions were examined sequentially with conventional violet autofluorescence excitation (430 nm±30 nm) and violet autofluorescence excitation plus backscattered red light (430 nm±40 nm plus 665 nm±15 nm). The contrast between (pre-)neoplastic and healthy tissue was quantified with off-line image analysis. We observed a 2.7 times higher contrast when backscattered red light was added to the violet excitation. In addition, the image quality was improved in terms of the signal-to-noise ratio (SNR) with this spectral design.
Head and neck (H&N) cancer patients have a high incidence of second primary tumours in the tracheobronchial tree. Diagnostic autofluorescence bronchoscopy (DAFE) has shown promising results in the detection of early neoplastic and pre-neoplastic changes in the bronchi. We have investigated the medical impact of DAFE in a population of H&N cancer patients. The bronchoscopies were performed using a modified commercially available DAFE system. Endoscopic imaging of the tissue autofluorescence (AF) was combined with an online image analysis procedure allowing to discriminate between true and false positive results. White light (WL) bronchoscopy was performed as a control. Twenty-one patients with high lung cancer risk factors underwent WL and AF bronchoscopy with this improved system. Forty-one biopsies were taken on macroscopicall suspicious (WL or AF positive) sites. Seven patients were found to have second primary tumours in the bronchi. The sensitivity for the detection of these early lesions with the DAFE was 1.6 times larger than the sensitivity of WL bronchoscopy only. The positive predictive value (PPV) for AF is 79% (33% for WL alone). The PPV of both methods together is 100%. DAFE proved to be efficient for the detection of second primary lesions in H&N cancer patients and can be used as a simple addition to pre-operative work-up or follow-up in this patient population.
Crohn's disease is an inflammatory bowel disease originating from an overwhelming response of the mucosal immune
system. Low dose photodynamic therapy (PDT) may modify the mucosal immune response and thus serve as a therapy
for Crohn's disease. Most patients with Crohn's disease show inflammatory reactions in the terminal ileum or colon
where PDT treatment is feasible by low-invasive endoscopic techniques. However, the tube like geometry of the colon,
it's folding, and the presences of multiple foci of Crohn's lesions along the colon require the development of adequate
light delivery techniques. We present a prototype light delivery system for endoscopic clinical PDT in patients with
Crohn's disease. The system is based on a cylindrical light diffuser inserted into a diffusing balloon catheter.
Homogenous irradiation is performed with a 4 W diode laser at 635 nm. Light dosimetry is performed using a calibrated
integrating sphere. The system can be used with conventional colonoscopes and colonovideoscopes having a 3.8 mm
diameter working channel. The feasibility of PDT in colon with our prototype was demonstrated in first clinical trials.
To detect bronchial carcinoma by autofluorescence, we measured in-vivo, in an in-vivo model, and in-vitro the spectra of tumor and normal tissue by a fiber-optic-spectrometer. The main difference between tumor and bronchial tissue is the intensity of the 505 nm main peak.
Tanja Gabrecht, Pascal Uehlinger, Snezana Andrejevic, Pierre Grosjean, Alexandre Radu, Philippe Monnier, Bernd-Claus Weber, Hubert van den Bergh, Georges Wagnieres
Autofluorescence (AF) bronchoscopy is a useful tool for early cancer detection. However the mechanisms involved in this diagnosis procedure are poorly understood. We present an in vivo autofluorescence imaging study to access the depth of the principal contrast mechanisms within the bronchial tissue comparing a narrow band and broad band violet fluorescence excitation. Knowledge of this parameter is crucial for the optimization of the spectral and optical design of clinical diagnostic AF imaging devices. We observed no differences in the chromatic contrast using the two excitation modes, indicating that the principal contrast mechanisms have a non-superficial character.
The early detection and localization of bronchial cancer remains a challenging task. Autofluorescence bronchoscopy is emerging as a useful diagnostic tool with improved sensitivity and specificity. Evidence exists that the native fluorescence or autofluorescence of bronchial tissues changes when they turn dysplastic or to carcinoma in situ (CIS). Early lesions in the bronchi tend to show a decrease in autofluorescence in the green region of the spectrum when excited with violet light and a relative increase in the red region of the spectrum. Several endoscopic imaging devices relying on these optical properties of bronchial mucosa have been developed. An industrial endoscopic autofluorescence imaging system for the detection of early cancerous lesions in the bronchi has been developed in collaboration with the firm Richard Wolf Endoskope GmbH, Knittlingen (Germany) and its performance has been evaluated in a previous clinical study. A second study, presented in this article, aims to optimize the spectral design of the device. Twenty-four lung cancer or high risk patients were enrolled in this study to assess the influence of additional backscattered red light on the tumor-to-healthy tissue contrast and to compare the effect of a narrow band violet excitation to a large band violet excitation. In our study we observed a three times higher contrast between cancer and healthy tissue, when backscattered red light was added to the violet excitation. The comparison between a narrow and a large band violet excitation indicated an increase of the tumor-to-healthy tissue contrast by the narrow band excitation.
Time-resolved measurements of endogenous tissue autofluorescence were carried out on the bronchial mucosa of 18 patients during endoscopy by the means of a optical fibre-based spectrometer. The objective was to assess the fluorescence lifetime as a new contrast parameter between normal and malignant tissue and to explain the origin of a previously observed contrast in fluorescence intensity. The intra- and interpatient variation of tissue autofluorescence intensity and decay on normal tissue was determined with the outcome that a strong fluctuation in autofluorescence intensity but not in lifetime was observed on the normal tissue. Preliminary results were obtained by comparing fluorescence decays on normal mucosa and dysplasia/carcinoma in situ. No significant change in fluorescence decay nor in spectrum between 510 and 650 nm was found. Measurements in parallel with an endoscopic autofluorescence imaging device, on the other hand, indicated a contrast in intensity and spectrum on the same lesions. This suggests that the spectral contrast might be due to an enhanced blood concentration in deeper lying layers of the lesion the optical fibre-based contact measurements are less sensitive to. The difference in intensity might be due to a lower concentration in fluorophores or to the thickening of the epithelium in the neoplastic mucous membrane. However, no indication for fluorescence quenching in the upper layers of the mucous membrane as the reason for the reduced fluorescence intensity was found. The fluorescence decays showed a quite stable behaviour with three decay times of 6.9 ns, 2.0 ns and 0.2 ns in the spectral range between 430 and 680 nm. This can be an indication that there is one dominant fluorophore involved, the calculated decay times suggest that it might be elastin. However, a slight spectral dependence of the fluorescence decays let presume that there is a contribution from other fluorophores, probably flavins and NADH.
Early detection and localisation of bronchial cancer remains a challenging task. One approach is to exploit the changes in the autofluorescence characteristics of the bronchial tissue as a diagnostic tool with improved sensitivity. Evidence exists that this native fluorescence or autofluorescence of bronchial tissues changes when they turn dysplastic and to carcinoma in situ. There is an agreement in the literature that the lesions display a decrease of autofluorescence in the green region of the spectrum under illumination with violet light and a relative increase in the red region of the spectrum is often reported. Imaging devices rely on this principle to detect early cancerous lesions in the bronchi. Based on a previous spectroscopic study, an industrial imaging prototype has been developed to detect early cancerous lesions in collaboration with the firm 'Richard Wolf Endoskope GmbH'. A preliminary clinical trial involving 20 patients with this spectrally optimised system proved that autofluorescence can detect lesions that would otherwise have remained invisible even to an experienced endoscopist under white light illumination. A systematic analysis of the autofluorescence images pointed out that real-time decisional functions can be defined in order to reduce the number of false positive results. Using this method, a Positive Predictive Value (PPV) of 75% was achieved using autofluorescence only. A PPV of even 100% were obtained when white light mode and autofluorescence mode were combined under the applied conditions. Furthermore, the sensitivity was estimated to be twice as high in AF mode than in WL mode.
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