3D identification of trabecular bone fracture zone using an automatic image registration scheme: A validation study

Accurate identification of the local fracture zone is an important step towards the failure assessment of trabecular bone. In previous in-vitro studies, local fracture zones were visually identified in micro-CT images by experienced observers. This is a time-consuming and observer-dependent approach and it prevents any large-scale analysis of local trabecular fracture regions. The scope of this study is the application and validation of a new registration scheme for the automatic identification of trabecular bone fracture zones. Six human trabecular specimens were extracted from different anatomical sites. Five specimens were mechanically tested and scanned using micro-CT. For each specimen pre- and post-failure micro-CT datasets were obtained. The sixth specimen was scanned twice without any mechanical compression and was used to test the accuracy of the proposed scheme. The registration scheme was applied to the acquired datasets for the automatic identification of the fracture zone. The proposed scheme comprises of a three-dimensional (3D) automatic registration method to define the differences between the two datasets, and the application of a criterion for defining slices of the pre-failure dataset as "broken" or "unbroken". Identifications of the fracture zones were qualitatively validated against visual identification of observers. Furthermore, "full 3D" fracture zone identification, based on the presented scheme, was proposed. The proposed scheme proved to be more accurate and significantly faster than the currently used visual process.     

Analysis of relation between skin elasticity and the entropy of skin image using near‐infrared and visible light sources

Skin elasticity has been regarded as one of the main indicators of skin condition. Current measurement devices for skin elasticity are mostly expensive for home‐use and should contact the skin surface. As a first step to develop improved methods, we focus on the relation between skin elasticity and the entropy of skin images. Reduced skin elasticity causes wrinkles. It spreads frequency components and increases their randomness in the frequency domain. The randomness is quantified as entropy, which is a measure of the disorder of a system in physics. Therefore, skin elasticity is expected to have a negative relation with entropy. This tendency can be improved by applying penetration depth characteristics according to the wavelength of light. From cheeks and forehead of 12 Korean adults, skin images are acquired with three different light sources (470 nm, 870 nm and broadband light) and skin elasticity is measured. The root mean square error between the measured data and the fitted model is “0.27” (870 nm), “0.49” (broadband light) and “1.42” (470 nm). Furthermore, the results are analyzed by classifying by sex, age and measurement area. This study demonstrates the possibility of developing noncontact home‐use devices to measure skin elasticity in the future.     

MtreeRing: An R package with graphical user interface for automatic measurement of tree ring widths using image processing techniques

Accurate measurements of ring-width series are essential for dendrochronological analyses. We present an R package MtreeRing for ring-width measurements on scanned digital images. A morphological alternate sequential filter is used for noise reduction in the original image. Ring boundaries are determined by the steepest negative slopes in the light reflectance of latewood-earlywood transitions. To automatically identify tree rings, the package provides three alternative methods (watershed-based segmentation, Canny edge detector, and a linear detection algorithm), each with advantages and disadvantages and suited to different wood anatomical features. The user can also manually mark tree rings on species with complex anatomical structures. The arcs of inner-rings and angles of successive inclined ring boundaries are used to correct ring-width series. Differences in ring-width measurements between MtreeRing and WinDENDRO in a given coniferous species (Larix gmelinii) were assessed, and no significant difference between programs was found. Furthermore, the package provides an R-based web application which was developed using the Shiny framework. This beginner-friendly application allows viewing and interacting with tree ring images. It requires no programming experience and can run on either a local computer or a remote server.