Trabecular bone morphology from micro-magnetic resonance imaging

Abstract

Micro-magnetic resonance imaging (micro-MRI) is potentially a widely available tool to image and quantify the three-dimensional structure of trabecular bone. However, it has not been demonstrated that the same quantitative measurements can be obtained using micro-MRI as would be obtained from conventional light microscope images. Bovine trabecular bone from several anatomic sites was imaged with both optical and micro-MRI methods. The six faces of approximately cubic trabecular bone specimens were examined with the light microscope, and the volume of bone internal to these faces was then imaged using an 8.6 T 25 mm bore magnet. Three-dimensional measures of bone morphology were calculated from both the optical and micro-MR images using the method of directed secants. Quantitative measures from the two imaging methods were compared by paired f-tests. Volume fractions (BV/TV) measured by micro-MRI were linearly related to (r² = 0.81) and did not differ statistically from (p = 0.96) similar measurements from optical images. The trabecular plate number (Tb.N) measured by micro-MRI also was linearly related to (r² = 0.53) and did not differ statistically from (p = 0.17) similar measurements from optical images. The orientation of trabeculae predicted from micro-MRI was within 6° of that calculated from optical images in 10 out of 16 specimens. The micro-MRI morphology measurements are relatively easy to perform, and since several hundred small-bore high-field strength MRI systems are available, this technique could be used widely to quantify the morphology of trabecular bone.