Precision and accuracy of repeat ultrasound image acquisition and analysis of the cross-sectional areas of the equine flexor tendons of the forelimbs for follow-up assessments

Abstract

Ultrasound imaging of the distal limb enables veterinarians to determine morphological characteristics like the size and degree of changes in tissue conformation of the flexor tendons. To date, no study has validated the accuracy and precision of repeat follow-up ultrasound examinations for quantitative measurements of the cross-sectional area (CSA) of both flexor tendons. So this study was perforemed evaluate the accuracy and precision of ultrasound image acquisition and analysis to evaluate the cross-sectional areas of the equine deep and superficial digital flexor tendons of the forelimbs. In 10 consecutively obtained transverse images the CSA of both flexor tendons at 3 levels was examined in 5 horses by one operator. To examine the agreement of repeat image analysis, the CSA of the SDFT and DDFT at 3 levels on the left forelimb of 12 sound warmblood horses was repeatedly measured 10 times in the obtained ultrasound images by the same experienced operator. For all examinations the overall concordance correlation coefficient (OCCC) was calculated. The OCCC of the repeated image acquisition at the SDFT was very high at all levels (≥ 0.98 -≥ 0.99) and at the DDFT, a substantial or modest agreement for level 2A (0.98) and 2B (0.94) and a poorer agreement at level 1B (0.84) was shown. Repeat image analysis of the CSA showed an extremely high agreement between all measurements of the cross-sectional area at all levels of both tendons (≥ 0.99). The results show that the acquisition and analysis of transverse ultrasound images of the SDFT and the DDFT to measure the cross-sectional areas at different levels can be stated as a technique to perform quantitative examinations with high precision and accuracy for scientific purpose or as follow-up examinations of clinical cases.

Correlations between the equine metacarpophalangeal joint angulation and toe conformation in statics

“…The overall concordance correlation coefficient for image acquisition was between 0.84 and 0.98 (CSA DDFT 2A) and > 0.99 (CSA SDFT) (Kojah et al, 2017). The OCCC for the analysis of the CSA was > 0.99 for all zones at each tendon (Kojah et al, 2017). These values and those stated by other authors prove the high accuracy and precision of the ultrasound examination performed in this study (Pickersgill et al, 2001).…”

“…The precision of ultrasound image acquisition and analysis to assess the CSA of both flexor tendons at different levels was tested in advance with the given setup under the same conditions and with the same operator. The overall concordance correlation coefficient for image acquisition was between 0.84 and 0.98 (CSA DDFT 2A) and > 0.99 (CSA SDFT) (Kojah et al, 2017). The OCCC for the analysis of the CSA was > 0.99 for all zones at each tendon (Kojah et al, 2017).…”

Immediate effects of an artificial change in hoof angulation on the dorsal metacarpophalangeal joint angle and cross‐sectional areas of both flexor tendons

“…Reference points in the saved images with a known distance were used for calibration for further analysis in (ImageJ)xi. 21 The CSAs of the SDFT and the DDFT was measured by outlining the structures of interest with a cursor and then calculating the encompassed area. The parameters of interest were measured by the same person, considering standardised references.…”

“…Ultrasound imaging acquisition and analysis was evaluated as a highly accurate and precise method to perform quantitative measurements of the CSA of the SDFT/DDFT in the context of follow-up examinations in a scientific or clinical context. 21 It can be assumed that a decrease in the tendons' CSA is related to stretching caused by higher forces acting on the tendons, while an increased CSA indicates relaxation of the tendons. The present study showed that toe and heel elevation caused a similar response in the CSAs of the SDFT and DDFT.…”

“…All images were analysed using the image processing software (ImageJ)xi. Reference points in the saved images with a known distance were used for calibration for further analysis in (ImageJ)xi 21 . The CSAs of the SDFT and the DDFT was measured by outlining the structures of interest with a cursor and then calculating the encompassed area.…”