Ultrasonic tissue characterisation of skeletal muscle

Ultrasound techniques have been used for the non-invasive, quantitative characterisation of muscle tissue in normal subjects and volunteer patients. Radio frequency (RF) echoes from a volume of tissue have been digitised and analysed using computer techniques. Attention has been given to the correct positioning and orientation of the transducer during examination due to the importance of the angle dependence of the interaction of ultrasound with muscle fasciculi. Several different muscles in the leg, arm and back of normal subjects have been examined, whereas patient studies have concentrated on the vastus intermedius. Ultrasonic data from patients with muscular dystrophy have been correlated with measurements of muscle tissue density obtained using X-ray computerised tomography (X-ray CT). The technique shows that ultrasound can be used to differentiate between normal and diseased muscle quantitatively. Results indicate that pathological change can be detected and monitored earlier with ultrasound than with X-ray CT. These quantitative methods are now in use as a guide to the staging and monitoring of pathological change in muscle.