Alignment Maps of Tissues: II. Fast Harmonic Analysis for Imaging

Abstract

A methodology for generating polarized light retardation and alignment direction images is presented. A rotated quarter-wave plate changes the linear polarized light to a polarized probe with various degrees of ellipticity by which samples are imaged with the use of a circular analyzer. A harmonic representation of image intensity allows simple analysis, requiring only simple image operations and realizing four orders-of-magnitude computational savings for strongly aligned tissues, where linear birefringence is the dominant optical property. The method is demonstrated for a porcine heart valve leaflet.

Engineered Microvessels with Strong Alignment and High Lumen Density Via Cell-Induced Fibrin Gel Compaction and Interstitial Flow

“…28 A custom MATLAB script determined the average birefringence (a measure of fibril alignment) of each construct. Optical density was also measured from these images by averaging the pixel intensity of the region of interest.…”

Vector correlation technique for pixel-wise detection of collagen fiber realignment during injurious tensile loading

“…10,23 The signed harmonic coefficients, B and C, were scaled by pixel intensity and used to calculate the retardation ͑␦͒ and the fiber-alignment direction ͑␣͒ at each pixel using the following equations:…”

“…Although QPLI techniques can define both the mean fiber direction and the strength of the alignment of collagen fibers in soft tissues at every pixel for which polarized light data are acquired, 10,16,23,24 analysis techniques to detect any microstructural damage in ligament tissue using QPLI or any other nondestructive imaging technique remain largely rudimentary. These previous analysis techniques made advances toward the identification of fiber kinematics during loading that were associated with mechanical failure.…”

Planar Biaxial Behavior of Fibrin-Based Tissue-Engineered Heart Valve Leaflets

“…29 Alignment information was recorded at preload and during the last 2 s of each of the relaxation steps. In this method, a mean fiber alignment direction is generated for each pixel in the alignment image (the gauge areas were approximately 200Â200 pixels spanning 5 mm by 5 mm).…”