Optical coherence tomography application for assessing variation in bone mineral content: a preclinical study

OBJECTIVE: Optical Coherence Tomography (OCT) is a non-invasive imaging technique that produces cross-sectional imag- es through biological tissues, allowing three-di- mensional reconstruction and analysis. Aim was to evaluate if OCT may discriminate among tis- sues with different bone density and composi- tion, by measuring the depth of light penetration in porcine and rat bone samples. MATERIALS AND METHODS: Two carpal bone samples (2 cm length) were harvested from the porcine forelimb and fixed overnight in 3.7% buffered formal saline. Following fixation, one sample was decalcified in a 1:1 mixture of 8% hydrochloric acid and 8% formic acid solu- tion for three days, with solution changes each day. Samples were imaged using an OCT micro- scope. Furthermore, the calvaria, ulnar, alveolar and basal bone of mandible of 6 male and 6 fe- male rats were cleared of overlying soft tissues and scanned under OCT. The light penetration depth in each sample was measured using the software Image J, and Scattering Attenuation Microscopy. RESULTS: In the mineralized bone the average depth (μm) and standard deviation (SD) of light penetration were 790.1±18.05 and 410.4±21.7 for periosteal and endosteal surface, respective- ly, and 507.3±21.03 for cross-section surfac- es, while it was 858.4±32.03 for periosteal sur- face, 1150±26.9 for endosteal, and 627.3±31.8 for cross-section bone surfaces in demineralized porcine bone. There was a significant difference (p<0.001) in depth of light penetration between normal and de-mineralized bone for all regions evaluated. No systematic significant difference in light penetration depth between-gender was found at any site evaluated, while there were variations between sites (p<0.001). The OCT de- tected differences in bone mineral and porosity among gender (p<0.0001) CONCLUSIONS: This study suggests that OCT may represent a valuable technique to es- timate local variations in bone mineral content.