Multispectral autofluorescence imaging for detection of cervical lesions: A preclinical study.

AIM: The aim of this study was to develop a novel optical imaging system for detecting protoporphyrin IX (PpIX) autofluorescence, to prove that PpIX autofluorescence is as useful as 5-aminolevulinic acid (5-ALA)-induced fluorescence for detecting and localizing cervical cancer, and to monitor the change in PpIX autofluorescence or induced PpIX fluorescence before, during, and after photodynamic therapy (PDT). METHODS: TC-1 cells - highly tumorigenic cells immortalized using human papillomavirus type 16 proteins E6 and E7 - were subcutaneously grafted into the thighs of nude mice. The suspected tumor tissues were visualized using autofluorescence imaging and induced fluorescence imaging under 5-ALA administration. When the 5-ALA-induced PpIX was sufficiently accumulated in tumor tissues, PDT was performed using a 635-nm laser. We observed the change in fluorescence intensity during PDT. For 3 weeks after PDT, we monitored tumor remission by using white-light imaging and fluorescence imaging. RESULTS: The transplanted cells were visualized by PpIX autofluorescence, which was induced by heme synthesis. After 5-ALA administration, PpIX could be targeted by using PDT, which decreased PpIX autofluorescence. Photobleaching is useful for monitoring PDT dosimetry and for determining the photodynamic response to therapy. CONCLUSION: PpIX autofluorescence clearly differentiated the tumor from adjacent normal tissues. The results of PpIX autofluorescence imaging and 5-ALA-induced fluorescence imaging were identical. PpIX autofluorescence imaging is a simple and cost-effective cervical cancer screening method that could be performed during or after PDT to ensure effective treatment or remission as a change in fluorescence intensity can be observed in real time without a blinding effect.

A novel imaging platform for non-invasive screening of abnormal glucose tolerance.

Optical measurement of skin auto-fluorescence (SAF), most likely emanating from accumulated advanced glycation end-products (AGEs), has been proposed for the noninvasive diagnosis of glucose intolerance in clinical settings. Here, we developed a novel imaging system with transmission geometry for SAF measurement and compared its diagnostic performance in a Korean population.

Endoscopic Fluorescence Angiography with Indocyanine Green : A Preclinical Study in the Swine.

OBJECTIVE: Microscopic indocyanine green (ICG) angiography is useful for identifying the completeness of aneurysm clipping and the preservation of parent arteries and small perforators. Neuroendoscopy is helpful for visualizing structures beyond the straight line of the microscopic view. We evaluated our prototype of endoscopic ICG fluorescence angiography in swine, which we developed in order to combine the merits of microscopic ICG angiography and endoscopy. METHODS: Our endoscopic ICG system consists of a camera, a light source, a display and software. This system can simultaneously display real-time visible and near infrared fluorescence imaging on the same monitor. A commercially available endoscope was used, which was 4 mm in diameter and had an angle of 30°. A male crossbred swine was used. RESULTS: Under general anesthesia, a small craniotomy was performed and the brain surface of the swine was exposed. ICG was injected via the ear vein with a bolus dose of 0.3 mg/kg. Visible and ICG fluorescence images of cortical vessels were simultaneously observed on the display monitor at high resolution. The real-time merging of the visible and fluorescent images corresponded well. CONCLUSION: Simultaneous visible color and ICG fluorescent imaging of the cortical vessels in the swine brain was satisfactory. Technical improvement and clinical implication are expected.

Chaotic stimulated Brillouin scattering near the threshold in a fiber with feedback.

We investigate a nonlinear dynamical behavior of the stimulated Brillouin scattering (SBS) near the threshold in the presence of feedback. When a cw Nd:YAG laser is injected into a single mode optical fiber, the SBS signal exhibits intermittently appearing irregular self-pulsations near the threshold. By examining the time series of the SBS signals, we verify that spontaneous Brillouin scattering having a stochastic property is dramatically suppressed due to the feedback. We explain the chaotic phenomenon of SBS in the presence of feedback in comparison with that in the absence of feedback.

Phase synchronization of chaotic lasers.

We experimentally investigate phase synchronization between two electronically coupled diode laser pumped Nd:YAG lasers. As the coupling strength increases, the phase of the two chaotic laser outputs develops from a nonsynchronous state to a phase synchronous one through a phase jump state. We find that there are 2pi phase jumps and a pi/2 phase shift between the two laser outputs unlike in optically coupled Nd:YAG lasers. To clarify the transition to phase synchronization with a pi/2 phase shift, we analyze the phenomenon of phase synchronization by using a phase portrait, phase difference dynamics, and frequency variation depending on the coupling strength and obtain the scaling rule of the average phase locking time in the intermittent phase jump state.

Lag synchronization in coupled Nd:YAG lasers pumped by laser diodes.

We experimentally investigate lag synchronization in mutually coupled Nd:YAG lasers. Two laser diode pumped Nd:YAG lasers, when they are electronically coupled, exhibit lag synchronization for a strong coupling strength region. We investigate the synchronous behaviors of the lasers by analyzing error dynamics, phase portraits, and similarity function. We confirm the observation of lag synchronization by obtaining the probability distribution of the intermittent lag synchronization length before lag synchronization.

Periodic phase synchronization in coupled chaotic oscillators.

We investigate the characteristics of temporal phase locking states observed in the route to phase synchronization. It is found that before phase synchronization there is a periodic phase synchronization state characterized by periodic appearance of temporal phase-locking state and that the state leads to local negativeness in one of the vanishing Lyapunov exponents. By taking a statistical measure, we present the evidences of the phenomenon in unidirectionally and mutually coupled chaotic oscillators, respectively. And it is qualitatively discussed that the phenomenon is described by a nonuniform oscillator model in the presence of noise.

Generalized phase synchronization in unidirectionally coupled chaotic oscillators.

We investigate phase synchronization between two identical or detuned response oscillators coupled to a slightly different drive oscillator. Our result is that phase synchronization can occur between response oscillators when they are driven by correlated (but not identical) inputs from the drive oscillator. We call this phenomenon generalized phase synchronization and clarify its characteristics using Lyapunov exponents and phase difference plots.