Intelligent Measurement of Spinal Curvature Using Cascade Gentle AdaBoost Classifier and Region-Based DRLSE

For spinal curvature measurements, because of the anatomical complexity of the spine CT image, developing an automated method to avoid manual landmark is a challenging task. In this study, we propose an intelligent framework that integrates the cascade AdaBoost classifier and region-based distance regularized level set evolution (DRLSE) with the vertebral centroid measurement. First, the histogram-of-oriented-gradients based cascade gentle AdaBoost classifier is used to detect automatically and localize vertebral bodies from computer tomography (CT) spinal images. Considering these vertebral pathological images enables us to produce a diverse training dataset. Then, the DRLSE method introduces the local region information to converge the vertebral boundary quickly. The located bounding box is regarded as an accurate initial contour. This avoids the negative impact of manual initialization. Finally, we perform vertebral centroid extraction and spinal curve fitting. The spinal curvature angle is determined by calculating the angle between two tangents to the curve. We verified the effectiveness of the proposed method on 10 spine CT volumes. Quantitative comparison against the ground-truth centroids yielded a detection accuracy rate of 98.3% and a mean centroid location error of 1.15 mm. The comparative results with existing methods demonstrate that the proposed method can accurately detect and segment vertebral bodies. Furthermore, the spinal curvature can be automatically measured without manual landmark.</jats:p

Shear-horizontal waves in a rotated Y-cut quartz plate with an imperfectly bonded mass layer

We study shear-horizontal (SH) waves in an unbounded plate of rotated Y-cut quartz carrying a thin mass layer imperfectly or nonrigidly bonded to the surface of the quartz plate. The imperfect interface is described by the so-called shear-lag model that allows the displacement to be discontinuous across the interface. A transcendental frequency equation that determines the dispersion relations of the waves is obtained. Exact and approximate solutions to the frequency equation are presented. The effects of the mass layer and the imperfect interface on the dispersion relations are examined. A quantitative criterion is given which distinguishes whether the combined effect of the mass layer and the imperfect interface raises or lowers the wave frequencies