Bone Mineral Density (BMD) is a measure of the density of bone. This is assessed using ultrasound waves or x-rays, primarily to detect osteopenia or osteoporosis, diseases in which the bone’s mineral and density are low and the risk of fractures is increased.
Bone sonometry (CUBAClinical) is a bone scan method introduced in 1992, using ultrasound (sound waves) instead of x-rays radiation. It is an established technique involving the measurement of the linear acoustic parameters of bone (speed of sound, SOS, and broadband attenuation, BUA).
Dual Energy X-ray Absorptiometry (DEXA) uses radiation to determine bone density. The spine and hip are most commonly measured areas.
While both sonometry and x-ray systems are safe and quick, sonometry does not use radiation. X-ray methods measure the density of bone, sonometry also provides information relating to the strength of bone (structure, elasticity) which is important for determining fracture risk.
How is the measurement taken?
To take the measurement, you will need to take off your shoe and stocking and sit down. The nurse or technician will apply a gel to both sides of your heel, then position and strap your foot in the machine. The transducers that send and receive the sound wave will then be put into contact with your heel and takes measurement within a few minutes. You will be given a report about your bone quality, showing your risk of fracture. There is no sensation or noise associated with the measurement procedure.
Why do we measure the heel?
Fractures often happens in the hips. However fats and muscle covering the hips affects ultrasound signal, making it unsuitable for site for sonometry measurement. The heel bone is 95% trabecular bone, which is very similar to the bone in the hip. It is convenient and easily accessible making it an ideal site for bone sonometry measurement.
How does the heel ultrasound work?
TheBone Sonometer (CUBAClinical) sends an ultrasonic sound wave through the heel bone. As the sound wave travels from one side to the other, the wave is changed by the internal structure and content of the bone. The more complex the structure of the bone, the more the sound wave will be absorbed. Therefore, normal bone has a higher measurement than bone with osteoporosis. Likewise, the greater the connectivity in the honeycomb-like structure of the bone, the faster the sound wave will pass through it. As bone becomes osteoporotic, this honeycomb weakens and begins to fail, and the speed of the sound wave slows down. These changes in the absorption and speed of the sound wave are changed into measurements of the strength of the bone, which can be compared to reference (normal) values for your race, age, and sex.
What does the Bone Sonometer measures?
The Bone Sonometer measures two parameters. BUA (Broadband Ultrasound Attenuation) and VOS (Velocity of Sound).
BUA = The attenuation of the ultrasound signal as it passes through the heel
Normal bone has a higher attenuation (BUA) than osteoporotic bone. The stronger the bone the better the BUA results. The more complex the bone structure the more the sound wave is blocked.
Prospective clinical studies have demonstrated that subjects with low BMD are at higher risk of fracture. The risk of fracture increases exponentially with decreasing BMD. Studies have also demonstrated the strong exponential relationship between heel ultrasound and x-ray results, and the ability of the CUBAClinical to predict the risk of future fracture.
Other Bone Scanning Modality include Dexa Scan & Quantitative CT Scan.