Studies for the Practical Uses of the A-Mode Type Ultrasonic Device

-Stability of measurement at upper-arm posterior-

Abstract

The A -mode ultrasonic skin thickness device newly developed has been tested for practical uses since 1982. In order to approve both sensibility and specificity of ultrasonic measurement, the target waves reflected from interface between subcutaneous fat layer and muscles were identified in comparison with X-ray CT scan picture at thigh in the former report. Through the trial it has become clear that the ultrasonic device is able to measure skin thickness precisely even at thigh where skinfold calipers are unable to fold skin. In this report, the ultrasonic device has been checked also regarding to stability of measurement among inspectors who are 7 medical students in comparison with EIKEN's caliper. The experiment was conducted as follows: 1) Seven students measured each other, so that every students assessed six students except for himself and was measured 6 times by his colleagues with ultrasonic device and EIKEN's skinfold caliper respectively. 2) Their measurement were conducted at first by a student with ultrasonic device successively. Then another student in turn measured his colleagues and this turn of inspector continued until all students finished. 3) When all students had measured their colleagues using ultrasonics, they repeated then measurement with EIKEN's caliper in the same way of turning. 4) Measuring point was keeping marked by black magic ink on upper-arm posterior during the experiment. Results were as follows: 1) Standard deviation of measured values were much smaller in ultrasonic measurement than in EIKEN's measurement, i.e., standard deviations were 0.29mm at minimum and 0.70mm at maxium in ultrasonics and 0.94mm at minimum and 3.20mm at maximum in EIKEN's caliper. 2) As well as sensitivity and specificity in the former report, reproducibility of inter-inspectors was also confirmed here, so that ultrasonic device became much more available for practical uses. 3) As the students were new-comers for the ultrasonic measurement, accuracy of the measurement will be more improved through the intensive training and the establishment of measuring manual in future.