Intra-rater reliability of transversus abdominis measurement by a novice examiner: Comparison of “freehand” to “probe force device” method of real-time ultrasound imaging

Abstract

A “free hand” real-time-ultrasound method is commonly applied to measure transversus abdominis. Potentially, this increases transversus abdominis measurement error due to uncontrolled variability in probe to skin force, inclination, and roll, particularly for novice examiners. This single-group repeated-measures reliability study compared the intra-rater reliability of transversus abdominis thickness and activation measurement by a novice examiner between free hand and a standardized probe force device method. The examiner captured ultrasound videos of transversus abdominis in a single session in healthy participants ( n = 33). Free hand ultrasound featured uncontrolled probe force, inclination, and roll, while probe force device method ultrasound standardized these parameters. Images of transversus abdominis at rest and contracted were measured and transversus abdominis activation calculated. Intraclass correlation coefficient, coefficient of variation, standard error of measurement, and worthwhile differences were calculated. The probe force device method resulted in greater reliability (intraclass correlation coefficient = 0.75–0.96) and lower measurement error (coefficient of variation = 8.89–28.7%) compared to free hand (intraclass correlation coefficient = 0.63–0.93; coefficient of variation = 6.52–29.4%). Reliability was good for all measurements except free hand TrA-C, which was moderate. TrA-C had the lowest reliability, followed by contracted thickness of the transverse abdominis, with resting thickness of the transverse abdominis being highest. Worthwhile differences were lower using a probe force device method versus free hand for resting thickness of the transverse abdominis and contracted thickness of the transverse abdominis and similar for TrA-C. Standardization using probe force device method ultrasound to measure transversus abdominis improved intra-rater reliability in a novice examiner. Use of a probe force device method is recommended to improve reliability through reduced sources of measurement error. Probe force device method intra- and inter-rater reliability in examiners of varying experience, in clinical populations, and to visualize other structures merits exploration.

A Deep Learning Localization Method for Measuring Abdominal Muscle Dimensions in Ultrasound Images

“…A limitation of this study are that all the still images were extracted only from eligible participants, in a single site and with a single acquisition protocol [5]. To avoid overfitting to a single acquisition protocol, exams should be obtained on several sites.…”

“…The false-positive loss (L F ) discourages the model from predicting a blob with no point annotations, in order to reduce the number of false positive predictions, and is described using equation (5).…”

“…The TrA400 dataset consists of 400 2D US images used to measure the thickness and activation changes in the TrA. The US images were captured from abdominal US videos using methods described previously in Kennedy et al [5]. The 400 2D US images are from 56 participants and at least 4 images per participant were captured as detailed below.…”

“…Two-dimensional US imaging is a valid method of measuring abdominal muscle dimensions in patients undergoing physical rehabilitation [4]. Previous literature [5] has demonstrated that the measurement of the Transversus Abdominis (TrA), a broad paired muscular sheet found on the lateral sides of the abdominal wall, can be used to quantitatively express dysfunctional TrA activation. In terms of calculating TrA activation (TrA-C), US measurements of TrA thickness at rest (RTrA), and when fully contracted (CTrA) have been used as a preeminent measurement [5], [6].…”

Intra- and inter-rater reliability of muscle thickness measurement of the tibialis anterior using different inward pressures

“…Recently, there was an interesting study [22] using a probe force device, which was used to examine the intra-rater reliability of the transverse abdominis by a novice examiner in comparison to the freehand method. This study [22] suggested that use of the device and view of real-time force, inclination or roll would be helpful in obtaining reliable values of abdominal muscle parameters during ultrasound imaging than the freehand method. In the same context, the current study showed a higher intra-rater reliability of obtaining TA muscle thickness using a custom-made holder with a oneaxis loadcell through real-time feedback compared to the freehand method.…”