Characterization of Intra-osseous Vascular Response With Ultrasound Imaging on Healthy Volunteers

Blood circulation within bone is thought to have a key role in bone growth, in fracture healing and in the development of bone diseases like osteoporosis. Current medical imaging techniques such as conventional ultrasonography fail to detect blood circulation within bone. The investigators propose to develop a new type of ultrasonography called intraosseous functional ultrasonography that will enable the detection and the characterization of blood circulation in solid bone tissue, marrow and soft tissues surrounding bone (muscle for instance). Because most soft tissues are essentially made of water, the speed of sound in soft tissues is close to that in water and it varies only a little between different types of soft tissues. For this reason, clinical ultrasound scanners used for ultrasonography assume that the speed of sound in the human body is the same for all types of soft tissues. This assumption is reasonable in soft tissues, but it does not hold in bone because solid bone tissue is much stiffer than soft tissues. Seismologists have extensive experience in producing images of the structure of the Earth based on the analysis of elastic waves which follow the same laws of Physics as ultrasound waves. The subsurface of the Earth contains layers of solid materials and liquids, consequently it is very similar to a region of the human body containing bone and soft tissues. Therefore the investigators will first work on the adaption of time-tested seismic imaging methods to make ultrasonography of bone possible. Once a correct image of bone is obtained, the investigators will use an ultrasound scanner dedicated to research to repeat this image hundreds of times per second, very much like a slow motion video. Because blood is moving while bone is still, the intensity in the image is being slightly changed where blood is moving. Thus the analysis of these changes makes it possible to detect and characterize blood flow within bone. In this way the investigators expect to be able to detect blood flowing with a speed as low as a few millimeters per second. Finally the sensitivity of the technique to detect and characterize blood circulation in bone will be evaluated in patients at the hospital and in healthy volunteers. The success of this work will help gaining knowledge on the role of blood circulation within bone. In the long term, it may help in the diagnosis of bone diseases.