M. Mustata

Imaging of tumor necroses using full-frame optical coherence imaging

Holographic optical coherence imaging (OCI) has been used to acquire depth resolved images in tumor spheroids. OCI is a coherence-domain imaging technique that uses dynamic holography as the coherence gate. The technique is full-frame (en face) and background free, allowing real-time acquisition to a digital camera without motional reconstruction artifacts. We describe the method of operation of the holographic OCI on highly scattering specimens of tumor spheroids. Because of the sub-resolution structure in the sample, the holograms consist primarily of speckle fields. We present two kinds of volumetric data acquisition. One is uses fly-throughs with a stepping reference delay. Another is static holograms at a fixed reference delay with the coherence gate inside the tumor spheroids. At a fixed reference delay, the holograms consist of time-dependent speckle patterns. The method can be used to study cell motility inside tumor spheroids when metabolic or cross-linking poisons are delivered to the specimens.

Holographic optical coherence imaging of tumor spheroids

We present depth-resolved coherence-domain images of living tissue using a dynamic holographic semiconductor film. An AlGaAs photorefractive quantum-well device is used in an adaptive interferometer that records coherent backscattered (image-bearing) light from inside rat osteogenic sarcoma tumor spheroids up to 1 mm in diameter in vitro. The data consist of sequential holographic image frames at successive depths through the tumor represented as a visual video “fly-through.” The images from the tumor spheroids reveal heterogeneous structures presumably caused by necrosis and microcalcifications characteristic of human tumors in their early avascular growth.

Time-dependent speckle in holographic optical coherence imaging and the health of tumor tissue

Holographic optical coherence imaging acquires en face images from successive depths inside scattering tissue. In a study of multicellular tumor spheroids the holographic features recorded from a fixed depth are observed to be time dependent, and they may be classified as variable or persistent. The ratio of variable to persistent features, as well as speckle correlation times, provides quantitative measures of the health of the tissue. Studies of rat osteogenic sarcoma tumor spheroids that have been subjected to metabolic and cross-polymerizing poisons provide quantitative differentiation among healthy, necrotic, and poisoned tissue. Organelle motility in healthy tissue appears as super-Brownian laser speckle, whereas chemically fixed tissue exhibits static speckle.

Holographic optical coherence imaging of rat osteogenic sarcoma tumor spheroids

Holographic optical coherence imaging is a full-frame variant of coherence-domain imaging. An optoelectronic semiconductor holographic film functions as a coherence filter placed before a conventional digital video camera that passes coherent (structure-bearing) light to the camera during holographic readout while preferentially rejecting scattered light. The data are acquired as a succession of en face images at increasing depth inside the sample in a fly-through acquisition. The samples of living tissue were rat osteogenic sarcoma multicellular tumor spheroids that were grown from a single osteoblast cell line in a bioreactor. Tumor spheroids are nearly spherical and have radial symmetry, presenting a simple geometry for analysis. The tumors investigated ranged in diameter from several hundred micrometers to over 1 mm. Holographic features from the tumors were observed in reflection to depths of 500-600 microm with a total tissue path length of approximately 14 mean free paths. The volumetric data from the tumor spheroids reveal heterogeneous structure, presumably caused by necrosis and microcalcifications characteristic of some human avascular tumors.

Neuronal elasticity as measured by atomic force microscopy

A cells form and function is determined to a great extent by its cellular membrane and the underlying cytoskeleton. Understanding changes in the cellular membrane and cytoskeleton can provide insight into aging and disease of the cell. The atomic force microscope (AFM) allows unparalled resolution for the imaging of these cellular components and the ability to probe their mechanical properties. This report describes our progress toward the use of AFM as a tool in neuroscience applications. Elasticity measurements are reported on living chick embryo dorsal root ganglion and sympathetic neurons in vitro. The neuronal cellular body and growth cones regions are examined for variations in cellular maturity. In addition, cellular changes due to exposure to various environmental conditions and neurotoxins are investigated. This report includes data obtained on different AFM systems, using various AFM techniques and thus also provides knowledge of AFM instruments and methodology.

Optical coherence imaging of rat tumor spheroids

We report the first results of optical coherence imaging (OCI) of rat tumor spheroids. OCI is a full-frame variant of optical coherence tomography (OCT). The coherent image spatially modulates a high-sensitivity dynamic holographic film composed of a photorefractive quantum well (PRQW). Full-frame readout out of the hologram is observed in real time on a video camera. This system may be considered generally as a video camera with a coherence filter on the lens. Tumor spheroids are small (100-1000 m) balls of tumor cells that are cultured in vitro. Larger spheroids have increasingly complex inner structure. Necrosis and calcification form and expand, reminiscent of structure in malignant cysts in human tumors. In addition, rafts of tumor cells become separated by fluid-filled voids. These features are within the resolution limit of the OCI system, and produce highly structured coherent images.

Fourier-domain holographic optical coherence imaging

We demonstrate the first spatial Fourier-domain holographic (FDH) optical coherence flythroughs of rat tumors and mouse corneas. FDH eliminates scattered background in the holographic reconstruction and improves signal-to-noise over previous image-domain holography of tissue

Adaptive optical coherence tomography using photorefractive quantum wells

Summary form only given. In this paper, we report the first demonstration of adaptive OCT using a photorefractive quantum well (PRQW) as an adaptive beam combiner. The coherent light is detected as an adaptive homodyne signal. Depth information is retrieved by using a short-coherence light source and scanning a delay line. The system operates at quadrature for maximum homodyne detection (determined solely by choosing center wavelength), requiring no active feedback. This scheme is robust and insensitive to mechanical vibrations and laser speckle.

Autocorrelation imaging of 3D structures using a femtosecond laser: application to imaging of sandstone

Optical coherence imaging (OCI) is an autocorrelation imaging technique that uses short-coherence light and holographic recording and reconstruction to perform laser-ranging into translucent media. OCI is a full-frame variant of OCT and shares excellent discrimination against scattered light from heterogeneous media. We present the first use of OCI to image into a heterogeneous translucent media: sandstone. There are two motivations for studying sandstone. First, it is an excellent example of a heterogeneous translucent medium on which to study the effects of holographic reconstruction in the presence of static scattered speckle. Second, it is of intrinsic interest for energy production as an excellent example of an oil or gas reservoir rock. Using Optical Coherence Imaging (OCI) we have imaged several layers of grains in a sandstone sample. Information on grain geometry was obtained as deep as 400 microns into the sample.