This study aimed to identify factors that strongly influence the reliability of the method used to measure the MT and echo intensity (EI) of the vastus medialis muscle via ultrasound equipment.
Ten healthy young adults participated in the study. The examiners were two physical therapists. The vastus medialis muscle was measured via an ultrasound machine with the participants in an end-sitting position. In this study, the conditions were set for three factors (measurement posture, measurement position, and probe angle). Eight conditions were used for the measurement: one with all three factors fixed, one with all three factors not fixed, three with only two fixed factors, and three with only one fixed factor. Three consecutive imaging sessions were conducted for each condition. Ten participants × eight conditions × three consecutive measurements × two examiners; 480 images were captured. Images were processed blindly for subject information and conditions, and measurements of MT and EI were performed in random order by a single examiner. MT and EI were measured via ImageJ (version 1.54g), and intra- and interrater reliabilities for the eight conditions were calculated via intrarater correlation coefficients (ICCs). Bland–Altman analysis (BAA) was also used to extract systematic errors. The representative value for interrater reliability was the average of the three measurements, and the intrarater BAA was analyzed on the basis of the results of the second and third measurements. The significance level was set at 5%, and R4.4.0 statistical software was used.
The ICC (1, 1) was greater than 0.878, and the ICC (2, 1) was greater than 0.849 under all conditions. The fixed condition for all three factors had the lowest interexaminer error and not systematic error, with an MT of 0.23 cm and an EI of 11.05 au for the minimal detectable change 95% confidence interval (MDC95). BAA results revealed fixation errors under certain conditions.
The image capture phase clearly has high interexaminer reliability and low error when the three factors of posture, measurement position, and probe angle are fixed. The lowest reliability was obtained when only the probe angle was fixed without fixing the posture and measurement position, and a higher reliability was obtained when none of the factors were fixed. Therefore, if the posture and measurement position cannot be fixed, reliability can be ensured by manipulating the probe on the basis of these conditions.
This study is important for measuring intra- and interrater reliability via ultrasonography of the vastus medialis muscle. The results of this study will be useful for developing a highly reliable measurement method for the vastus medialis muscle via ultrasonography.
ultrasound
vastus medialis muscle
