Detection of bladder urothelial carcinoma using in vivo noncontact, ultraviolet excited autofluorescence measurements converted into simple color coded images: a feasibility study.

PURPOSE: A difficulty in nonmuscle invasive bladder cancers is the diagnosis of flat and small lesions during white light cystoscopy. We assessed a prototype that measures ultraviolet laser induced autofluorescence for endoscopic detection of nonmuscle invasive bladder cancer. MATERIALS AND METHODS: We compared spectroscopic results with histological findings in 3 groups, including normal urothelium, papillary tumors and flat lesions. The developed method is based on exciting the fluorescence of molecules naturally present in tissue using ultraviolet laser pulses. The diagnostic signal was converted into the intensity ratio of the emitted light at approximately 360 and 450 nm. This ratio depends on the histopathological state of the tissue. The signal was converted into a simple color coded image, in which green indicates normal tissue and red indicates neoplasm. RESULTS: A total of 14 patients were included in analysis. At 360 and 450 nm excitation wavelengths the overall fluorescence intensity of bladder tumors was clearly decreased compared to that of normal urothelium regardless of tumor stage or grade. At the 308 nm excitation wavelength the shape of the tumor spectra, including carcinoma in situ, was markedly different from that of normal or nonspecific inflammatory mucosa. The correlation between red images and tumor in the specimen was 100%. No absolute intensity determinations were required since a definite diagnosis was established based on the fluorescence intensity ratio at 360 and 450 nm. CONCLUSIONS: This feasibility study confirms the functionality of our clinical prototype for the noncontact imaging detection of nonmuscle invasive bladder cancer via an endoscope using ultraviolet excited autofluorescence measurements.

Time-resolved diffusing wave spectroscopy with a CCD camera.

We show how time-resolved measurements of the diffuse light transmitted through a thick scattering slab can be performed with a standard CCD camera, thanks to an interferometric protocol. Time-resolved correlations measured at a fixed photon transit time are also presented. The high number of pixels of the camera allows us to attain a quite good sensitivity for a reasonably low acquisition time.

Cerebral hemodynamics and brain oxygen changes related to gravity-induced loss of consciousness in rhesus monkeys.

The aim of the present experiment was to study the influence of +Gz acceleration (head-to-foot inertial forces) onset on cerebral oxygenation changes (cerebral oxy- and deoxy-hemoglobin) and cerebral blood volume (CBV) in order to evaluate the role of cerebral hypoxemia and ischemia in the appearance of +Gz-induced loss of consciousness (G-LOC). We used five rhesus monkeys which were equipped with near infrared spectroscopy optodes fixed onto the parietooccipital cranial bone. G-LOC (isoelectric electrocorticogram) was detected with silver balls electrodes in contact with the dura matter. The animals were centrifuged up to +12 Gz with two onset rates (0.1 and 3 G/s). Cerebral deoxy-hemoglobin increased significantly (max: +30 +/- 6% of control, P < 0.01) only during the 0.1 G/s run. At G-LOC, CBV changes were not related to G-onset rate (P = 0.30; mean change: -32 +/- 6% of control). We conclude that cerebral ischemia is the main mechanism in the occurrence of G-LOC.

Performance assessment of photon migration instruments: the MEDPHOT protocol.

We propose a comprehensive protocol for the performance assessment of photon migration instruments. The protocol has been developed within the European Thematic Network MEDPHOT (optical methods for medical diagnosis and monitoring of diseases) and is based on five criteria: accuracy, linearity, noise, stability, and reproducibility. This protocol was applied to a total of 8 instruments with a set of 32 phantoms, covering a wide range of optical properties.

Asymptotic behavior and inverse problem in layered scattering media.

The main challenge of noninvasive optical biopsy is to obtain an accurate value of the optical coefficients of an encapsulated organ (muscle, brain, etc.). The idea developed by us is that some interesting information could be deduced from the long-time behavior of the reflectance function. This asymptotic behavior is analyzed for layered media in the framework of the diffusion approximation. A new method is derived to obtain accurate values for the optical parameters of the deepest layers. This method is designed to work in a specific long-time regime that is still within the scope of standard time-of-flight experiments but far from being included in the mathematically defined asymptotic region. The limits of this method, linked to the cases where the asymptotic behavior is no longer governed by the deepest layer, are then discussed.