Materials / A bone sample containing a bone graft substitute analyzed by correlating density information obtained by X-ray micro tomography with compositional information obtained by Raman microscopy

The ability ofbonegraft substitutes to promote newbone formation has been increasingly used in the medical field to repair skeletal defects or to replace missingbonein a broad range of applications in dentistry and orthopedics. A common way to assess such materials is via micro computed tomography (-CT), through the density information content provided by the absorption of X-rays. Information on the chemical composition of a material can be obtained via Raman spectroscopy. By investigating abonesamplefrom miniature pigs containing thebonegraft substitute Bio Oss®, we pursued the target of assessing to what extent the density information gained by -CT imaging matches the chemical information content provided by Raman spectroscopic imaging. Raman images and Raman correlation maps of the investigatedsamplewere used in order to generate a Raman based segmented image by means of an agglomerative, hierarchical cluster analysis. The resulting segments, showing chemically related areas, were subsequently compared with the -CT image by means of a one-way ANOVA. We found out that to a certain extent typical gray-level values (and the related histograms) in the -CT image can be reliably related to specific segments within the image resulting from the cluster analysis