Multispectral fluorescence imaging of human ovarian and fallopian tube tissue for early-stage cancer detection.

With early detection, 5-year survival rates for ovarian cancer exceed 90%, yet no effective early screening method exists. Emerging consensus suggests over 50% of the most lethal form of the disease originates in the fallopian tube. Twenty-eight women undergoing oophorectomy or debulking surgery provided informed consent for the use of surgical discard tissue samples for multispectral fluorescence imaging. Using multiple ultraviolet and visible excitation wavelengths and emissions bands, 12 fluorescence and 6 reflectance images of 47 ovarian and 31 fallopian tube tissue samples were recorded. After imaging, each sample was fixed, sectioned, and stained for pathological evaluation. Univariate logistic regression showed cancerous tissue samples had significantly lower intensity than noncancerous tissue for 17 image types. The predictive power of multiple image types was evaluated using multivariate logistic regression (MLR) and quadratic discriminant analysis (QDA). Two MLR models each using two image types had receiver operating characteristic curves with area under the curve exceeding 0.9. QDA determined 56 image type combinations with perfect resubstituting using as few as five image types. Adaption of the system for future in vivo fallopian tube and ovary endoscopic imaging is possible, which may enable sensitive detection of ovarian cancer with no exogenous contrast agents.

Ultrahigh resolution all-reflective optical coherence tomography system with a compact fiber-based supercontinuum source.

We report the construction and characterization of an all-reflective optical coherence tomography (OCT) system using a newly developed compact fiber-based broadband supercontinuum source. The use of only reflective optical components has enabled us to avoid chromatic dispersion effects and to obtain ultrahigh resolution OCT images of biological samples. We achieved an axial resolution of 2 µm in air with 87 dB dynamic range at a center wavelength around 1300 nm.

Tissue-engineered vascular grafts as in vitro blood vessel mimics for the evaluation of endothelialization of intravascular devices.

The accelerating use of minimally invasive procedures for the treatment of cardiovascular disease, and the commensurate development of intravascular devices such as stents, has lead to a high demand for preclinical assessment techniques. A 3-dimensional in vitro blood vessel mimic (BVM) would be ideal for device testing before animal or clinical studies. This is possible based on current capabilities for the creation of tissue-engineered vascular grafts (TEVGs). Using an established method of pressure-sodding human endothelial cells onto a polymer scaffold, a BVM was created in an in vitro bioreactor system under flow. Scanning electron microscopy and immunohistochemistry verified a cellular lining and revealed a luminal monolayer of endothelial cells. After BVM development, bare metal stents were deployed. Stented and unstented BVMs were evaluated using fluorescent nuclear staining and optical coherence tomography (OCT). En face and cross-sectional evaluation of bisbenzimide-stained nuclei revealed cellular coverage of the stent surfaces. Cross-sectional evaluation using OCT also illustrated a cellular layer developing over the stent struts. These data support the use of TEVGs as in vitro BVMs for pre-clinical evaluation of the endothelial cell response to stents and endovascular devices.

Mechanistic comparison of blood undergoing laser photocoagulation at 532 and 1,064 nm.

BACKGROUND AND OBJECTIVES: We seek to compare and contrast the mechanisms of blood photocoagulation under 532 and 1,064 nm laser irradiation in vitro in order to better understand the in vivo observations. We also seek to validate a finite element model (FEM) developed to study the thermodynamics of coagulation. STUDY DESIGN/MATERIALS AND METHODS: We study the photocoagulation of whole blood in vitro at 532 and 1,064 nm using time-domain spectroscopic and optical coherence tomography (OCT)-based imaging techniques. We model the coagulation using an FEM program that includes the latent heat of vaporization (LHV) of water, consideration of the pulse shape of the laser, and the bathochromic shift in the hemoglobin absorption spectrum. RESULTS: We find significant similarities in the spectroscopic, chemical, and structural changes occurring in hemoglobin and in the blood matrix during photocoagulation despite the very large difference in the absorption coefficients. The more uniform temperature profile developed by the deeper-penetrating 1,064 nm laser allows us to resolve the structural phase transition in the red blood cells (going from biconcave disc to spherocyte) and the chemical transition creating met-hemoglobin. We find that the RBC morphology transition happens first, and that the met-Hb transition happens at a much higher temperature ( > 90 degrees C) than is found in slow bath heating. The FEM analysis with the LHV constraint and bathochromic shift predicts accurately the imaging results in both cases, and can be used to show that at 1,064 nm there is the potential for a runaway increase in absorption during the laser pulse. CONCLUSIONS: Photothermally mediated processes dominate the in vitro coagulation dynamics in both regimes despite the difference in absorption coefficients. There is a significant risk under 1,064 nm irradiation of vascular lesions in vivo that the dynamic optical properties of blood will cause runaway absorption and heating. This may in turn explain some recent results at this wavelength where full-thickness burns resulted from laser treatment.

Chemical and structural changes in blood undergoing laser photocoagulation.

The treatment of cutaneous vascular lesions (port wine stains etc.) using lasers has been guided by theories based on the "cold" or room-temperature optical properties of the hemoglobin target chromophore. We have recently presented evidence showing that under the influence of laser irradiation, the optical properties of blood in vitro are time and temperature dependent. Such complications are not currently subsumed into the in vivo theory. Here, we study the time-domain optical properties of blood undergoing photocoagulation in vitro using two newly developed time-resolved techniques. We also study the asymptotic effect of laser photocoagulation on the chemical and structural properties of the components of the blood matrix. We present evidence showing that the photocoagulation process involves significant changes in the optical absorption and scattering properties of blood, coupled with photothermally induced chemical and structural changes. We demonstrate the first use of a laser to deliberately generate magnetic resonance imaging contrast in vitro. We show that this technique offers significant potential advantages to in vivo intravenous chemical contrast agent injection.

Dual modality instrument for simultaneous optical coherence tomography imaging and fluorescence spectroscopy.

We develop a dual-modality device that combines the anatomical imaging capabilities of optical coherence tomography (OCT) with the functional capabilities of laser-induced fluorescence (LIF) spectroscopy. OCT provides cross-sectional images of tissue structure to a depth of up to 2 mm with approximately 10-microm resolution. LIF spectroscopy provides histochemical information in the form of emission spectra from a given tissue location. The OCT subsystem utilizes a superluminescent diode with a center wavelength of 1300 nm, whereas a helium cadmium laser provides the LIF excitation source at wavelengths of 325 and 442 nm. Preliminary data are obtained on eight postmortem aorta samples, each 10 mm in length. OCT images and LIF spectra give complementary information from normal and atherosclerotic portions of aorta wall. OCT images show structures such as intima, media, internal elastic lamina, and fibrotic regions. Emission spectra ratios of 520/490 (325-nm excitation) and 595/635 (442-nm excitation) could be used to identify normal and plaque regions with 97 and 91% correct classification rates, respectively. With miniaturization of the delivery probe and improvements in system speed, this dual-modality device could provide a valuable tool for identification and characterization of atherosclerotic plaques.