In order to verify the accuracy of the thickness of the rectus femoris muscle and overlying subcutaneous fat as assessed by ultrasound, experiments were conducted on １０ healthy subjects aged over ３０ years to assess the following： １） concordance of measurements made by two different observers； ２） concordance of repeated measurements made by the same observer ; and ３） concordance of repeated measurements made by the same observer with and without an imaging aid（ultrasound gel block）.
Between two observers with varying experience in ultrasound, no significant difference in measured muscle thickness was observed ; however, there was a significant difference in subcutaneous fat thickness. When measurements were made by the same observer on two separate days, a significant positive correlation was evident for muscle and subcutaneous fat thickness between the first and second tests. While use of the imaging aid was associated with higher concordance of measurements between the first and second tests, the measurements themselves were affected.
Although ultrasonic measurement of tissue thickness requires further investigation to minimize intra-observer error and examine correlations with other imaging techniques, the accuracy of the measurements in the present study suggests that clinical application may be possible
