Simulation of diffuse photon migration in tissue by a Monte Carlo method derived from the optical scattering of spheroids.

A Monte Carlo method was derived from the optical scattering properties of spheroidal particles and used for modeling diffuse photon migration in biological tissue. The spheroidal scattering solution used a separation of variables approach and numerical calculation of the light intensity as a function of the scattering angle. A Monte Carlo algorithm was then developed which utilized the scattering solution to determine successive photon trajectories in a three-dimensional simulation of optical diffusion and resultant scattering intensities in virtual tissue.

Three-dimensional tomographic reconstruction of mesospheric airglow structures using two-station ground-based image measurements.

A new methodology is presented to create two-dimensional (2D) and three-dimensional (3D) tomographic reconstructions of mesospheric airglow layer structure using two-station all-sky image measurements. A fanning technique is presented that produces a series of cross-sectional 2D reconstructions, which are combined to create a 3D mapping of the airglow volume. The imaging configuration is discussed and the inherent challenges of using limited-angle data in tomographic reconstructions have been analyzed using artificially generated imaging objects.

High-frequency ultrasound for intraoperative margin assessments in breast conservation surgery: a feasibility study.

Background: In addition to breast imaging, ultrasound offers the potential for characterizing and distinguishing between benign and malignant breast tissues due to their different microstructures and material properties. The aim of this study was to determine if high-frequency ultrasound (20-80 MHz) can provide pathology sensitive measurements for the ex vivo detection of cancer in margins during breast conservation surgery.

Methods: Ultrasonic tests were performed on resected margins and other tissues obtained from 17 patients, resulting in 34 specimens that were classified into 15 pathology categories.

Ultrasonic differentiation of normal versus malignant breast epithelial cells in monolayer cultures.

Normal and malignant mammary epithelial cells were studied using laboratory measurements, wavelet analysis, and numerical simulations of monolayer cell cultures to determine whether microscopic breast cancer can be detected in vitro with high-frequency ultrasound. Pulse-echo waveforms were acquired by immersing a broadband, unfocused 50-MHz transducer in the growth media of cell culture well plates and collecting the first reflection from the well bottoms. The simulations included a multilayer pulse-reflection model and a model of two-dimensional arrays of spherical cells and nuclei.

Simulation of elastic wave scattering in cells and tissues at the microscopic level.

The scattering of longitudinal and shear waves from spherical, nucleated cells and three-dimensional tissues with simple and hierarchical microstructures was numerically modeled at the microscopic level using an iterative multipole approach. The cells were modeled with a concentric core-shell (nucleus-cytoplasm) structure embedded in an extracellular matrix. Using vector multipole expansions and boundary conditions, scattering solutions were derived for single cells with either solid or fluid properties for each of the cell components.

Histology-based simulations for the ultrasonic detection of microscopic cancer in vivo.

Ultrasonic spectroscopy may offer an alternative to imaging methods for the in vivo detection of microscopic cancer. To investigate this potential, a numerical model that incorporates multiple scattering, wave-mode conversion, and hierarchical microstructures was developed to simulate ultrasonic interactions in biological tissue at the microscopic level. Simulated high-frequency (20-75 MHz) spectra of up to 2137 cells displayed significant correlations to nucleus diameter and malignant cell infiltration, and indicated as few as 300 malignant cells may be detectable in normal tissue.