Development of a Fluorescence Detection System Using Optical Parametric Oscillator (OPO) Laser Excitation for in Vivo Diagnosis

Highly sensitive detection of cancer cells using femtosecond dual-wavelength near-IR two-photon imaging

We describe novel imaging protocols that allow detection of small cancer cell colonies deep inside tissue phantoms with high sensitivity and specificity. We compare fluorescence excited in Styryl-9M molecules by femtosecond pulses at near IR wavelengths, where Styryl-9M shows the largest dependence of the two-photon absorption (2PA) cross section on the local environment. We show that by calculating the normalized ratio of the two-photon excited fluorescence (2PEF) intensity at 1200 nm and 1100 nm excitation wavelengths we can achieve high sensitivity and specificity for determining the location of cancer cells surrounded by normal cells. The 2PEF results showed a positive correlation with the levels of MDR1 proteins expressed by the cells, and, for high MDR1 expressors, as few as ten cancer cells could be detected. Similar high sensitivity is also demonstrated for tumor colonies induced in mouse external ears. This technique could be useful in early cancer detection, and, perhaps, also in monitoring dormant cancer deposits.

Autofluorescence spectroscopy for evaluating dysplasia in colorectal tissues

The aim of this study was to assess the applicability of autofluorescence (AF) spectroscopy as a method for the diagonosis of normal, benign and malignant of dysplasia in colorectal tissues experimentally. By improvement of optical design in laser pulse generator, wavelength-adjustable output was acquired and the optimal wavelength was defined as 380 nm. With 380-nm pulsed laser excitation, AF spectra of normal, benign and malignant colorectal tissues were recorded in the spectra region from 460-570 nm in vitro. The spectral analysis for discrimination among the different types of tissues was carried out using principal component analysis (PCA)-based Neural networks algorithm. The performance of analysis was pretty good with sensitivity, specificity and accuracy found to be 100%,90% and 96.7%, respectively. The AF spectroscopy may serve as an excellent tool for the evaluation of dysplasia in colorectal clinical diagnosis.

Detection and treatment of dysplasia in Barrett's esophagus: a pivotal challenge in translating biophotonics from bench to bedside

Barrett's esophagus (BE) is a condition that poses high risk of developing dysplasia leading to cancer. Detection of dysplasia is a critical element in determining therapy but is extremely challenging, so that standard white-light endoscopy is used only as a means to guide biopsy. Many novel optical techniques have been aimed at this problem, including various forms of improved wide-field white-light (chromoendscopy/magnification and narrow-band) and fluorescence imaging, and "optical biopsy" techniques (diffuse reflectance, elastic light scattering, fluorescence and Raman spectroscopies, confocal microendoscopy, and optical coherence tomography). While promising, either as stand-alone modalities or in combination, to date none has solved this pivotal challenge to the point of clinical adoption. Likewise, minimally invasive treatment of BE patients with dysplasia remains suboptimal, despite recent approval of photodynamic therapy for this indication. This work presents a critique and summary of each of these biophotonic technologies, and discusses the fundamental advantages and limitations of each. The future directions for this field are considered, particularly from the perspective of relying on intrinsic (endogenous) optical signatures compared with the use of exogenous contrast agents.