Abstract: An imaging marker comprised of glass and iron-containing aluminum microspheres in a gel matrix which shows uniformly good contrast with MR, US and X-Ray imaging. The marker is small and can be easily introduced into tissue through a 12-gauge biopsy needle. The concentration of glass microspheres and the size dictate the contrast for US imaging. The contrast seen in MRI resulting from susceptibility losses is dictated by the number of iron-containing aluminum microspheres; while the artifact of the marker also depends on its shape, orientation and echo time. By optimizing the size, iron concentration and gel binding, an implantable tissue marker is created which is clearly visible with all three imaging modalities.

Abstract: The present invention provides an in situ, low dose and noninvasive method and device for estimating bone mineral content of trabecular bones, particularly the calcaneus. The method of estimating bone mineral content involves measuring the intensity of X-rays backscattered from the calcaneus and estimating the calcium content from this intensity. In one embodiment the X-ray source is a small x-ray tube that provides a continuous energy spectrum of X-rays. The intensity of backscattered X-rays from the soft tissue covering the trabecular bone, preferably the calcaneus, is compensated for by directly measuring the thickness of the soft tissue. Alternatively the soft tissue thickness can be measured directly along with the bone mineral content from the backscattered X-rays by measuring intensity over an energy range and correlating these results with a model of backscattering from a trabecular bone covered with a layer of soft tissue.