High frequency energy absorption and the measurement of limb muscle

High frequency energy absorption (HFEA) is being developed as a portable, inexpensive, non-invasive procedure for the measurement of muscle mass within cross-sections of limbs. The instrument consists of a flexible coil 2.5 cm wide of which the length can be adjusted over a 10 cm range. A series of coils of different lengths has been constructed that are jointly suitable for limbs with circumferences ranging from 20 to 75 cm. To measure HFEA, a coil of appropriate length is attached to a 9v battery that, through an oscillator, produces a frequency varying from 15 MHz (longest coil) to 40 MHz (shortest coil). Zero readings, with the coil set at the same circumference as the limb, are obtained before and after HFEA is measured and they are used to adjust the observed values. HFEA, in theory, is related to the number of electrolytes deep to the coil and almost all these electrolytes are in muscle. Good precision has been demonstrated and the instrument has been successfully validated against saline solutions. A previous model was validated against magnetic resonance images with good results (r2 about 0.8). Further validation of the present model against magnetic resonance images is almost complete; these findings are presented.