The meaning of graylevels in backscattered electron images of bone

Abstract

Backscattered electron (BSE) imaging is considered to be a useful technique for determining relative differences in bone tissue density. However, it is not clear how graylevel variations seen in BSE images of bone tissue, which are primarily dependent on the tissue's average atomic number, correlate to tissue density (g/cm3) and mineral content. Simulated bone tissues, ranging from 32-50% mineral by volume, were made by mixing synthetic hydroxyapatite with a simulated organic matrix. This technique allowed mineral content to be varied while mineral composition and crystallography remained constant. The densities of the simulated tissues were determined using Archimedes' principle. Average atomic numbers of the simulated tissues were interpolated from a regression of BSE graylevel against average atomic numbers of pure standard materials. A strong positive correlation was found to exist between mineral content and density (r2 = 0.978) as well as between mineral content and atomic number (r2 = 0.965). The average graylevel in the BSE image also exhibited a positive correlation to mineral content (r2 = 0.965) and density (r2 = 0.923). Graylevel variations in BSE images of simulated bone tissue were shown to be strongly correlated to density and mineral content, but only as a coincidence of their association with atomic number.

Experimental confirmation of the sheep model for studying the role of calcified fibrocartilage in hip fractures and tendon attachments

“…The greater trochanters of the rats were sectioned with a smaller diamondimpregnated blade using a water-cooled bone saw (Isomet; Beuler, Lake Bluff, IL). One coronal section from each specimen was used for light histology of the tendon insertion, and the other coronal section was used for quantitative BSE imaging of the calcified fibrocartilage and cortical bone (Skedros et al, 1993a;Bloebaum et al, 1997;Roschger et al, 1998).…”

Age‐Related mineralization heterogeneity changes in trabecular bone of the proximal femur

“…BSE provides a black-and-white image that is brighter in areas with a higher average atomic number and darker in regions of lower average atomic number Skedros et al, 1993a). It is similar to the image obtained from an X-ray or microradiography, but as the backscattered electrons only penetrate a few microns into the surface of the specimen, projection effect is minimal (Bachus and Bloebaum, 1992).…”

“…WMGLs are linearly correlated to ash percent (mineral content independent of porosity) Skedros et al, 1993a;Roschger et al, 1998). The two mineral standards of known ash percent were used to create a linear regression line correlating WMGL to ash percent.…”

Restoration of bone defect and enhancement of bone ingrowth using partially demineralized bone matrix and marrow stromal cells

“…A JSM-5610 scanning electron microscope (JEOL Inc., Tokyo, Japan) equipped with backscattered electron detector with accelerating voltages at 20 kV was used. Images based on gray level distinction were used to identify bone, soft tissues, and implant materials by the criteria that metal appears white, newly formed bone is indicated by darker gray, and soft tissues and marrow appear black [9,21]. The images of bonelimplant interface area of each section were taken at 35x magnification and assembled to reproduce the total bonelimplant interface for analysis (Fig.…”