Quantitative ultrasound (QUS) is a type of medical technology used to investigate bone density. It involves the use of sound waves at high frequencies. The manner in which the sound waves pass through bones is recorded and this gives an indication of the strength and quality of bone tissue. This type of bone ultrasound has been used in osteoporosis detection and it may be used to assess a patient's risk before another testing procedure, known as dual energy x-ray absorptiometry (DXA), is carried out in order to make a diagnosis. Osteoporosis is a condition in which bones are weakened when the spaces inside them enlarge, making fractures more likely.
Although dual energy x-ray absorptiometry is considered the best method for diagnosing osteoporosis, it is expensive, involves low levels of radiation and must be carried out by a radiographer. For these reasons, it is better used to make a final diagnosis rather than as an initial screening test for a population. Instead, people may be screened first using methods such as questionnaires and quantitative ultrasound before selecting those who seem most at risk of osteoporosis for DXA.
Quantitative ultrasound can be performed using portable scanners. This makes it a suitable osteoporosis test for reaching and assessing large numbers of people. Other advantages of quantitative ultrasound are that it is less expensive than DXA and does not use radiation. The procedure is also relatively quick, with a simple test of the heel bone taking only about 15 minutes to perform.
During a quantitative ultrasound of the heel bone, the patient places the heel inside the portable scanning machine and sound waves are sent from a transducer through the bone and received by another transducer. A transducer converts one form of energy to another, and in this case electrical impulses are converted into sound and back. There is no pain during the procedure and, as the transducers move around the heel, it may feel similar to a massage.
The speed at which sound waves travel through the heel bone and the amount of sound which reaches the second transducer are analyzed and compared with results from the general population. Patients' results give information about their bone structure, density and strength, and these factors are combined into a single score, known as a T-score. A young and healthy adult's T-score would be 0.0, and scores which are lower than -2.5 represent a high risk of osteoporosis, while a score above -1.0 is associated with a low risk.