Measurement of the quadriceps femoris muscle using magnetic resonance and ultrasound imaging.

OBJECTIVES To define a method for measurement of the cross sectional area and volume of the quadriceps femoris muscle using magnetic resonance imaging (MRI) in conjunction with stereology, and to compare the results of measurements obtained by the MRI method with those obtained by the conventional method of static B-mode ultrasound in order to evaluate whether MRI is a reliable alternative to ultrasound. METHODS A preliminary MRI study was undertaken on a single female volunteer in order to optimise the scanning technique and sampling design for estimating the muscle volume using the Cavalieri method. Ten healthy volunteers participated in the method comparison study. Each volunteer underwent static B-mode ultrasonography, immediately followed by MRI. The cross sectional area of the quadriceps femoris was estimated at the junction of the proximal one third and distal two thirds of the thigh, and seven systematic sections of the thigh were obtained in order to estimate muscle volume by both modalities. RESULTS Seven sections through the muscle are required to achieve a coefficient of error of 4-5%. There was no significant difference in the cross sectional area estimates or volume estimates when ultrasound and MRI were compared. CONCLUSION Muscle cross sectional area and volume can be measured without bias by MRI in conjunction with stereological methods and the method is a reliable alternative to static B-mode ultrasound for this purpose.