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

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.