ULTRASOUND TISSUE CHARACTERISATION, AN INNOVATIVE TECHNIQUE FOR INJURY-PREVENTION AND MONITORING OF TENDINOPATHY

Ultrasonography (US) is used to visualise tendon structure. However, its capacity to detect early disintegration, to reproducibly monitor progress of pathology or repair, and to objectively evaluate effect of therapies and exercise is poor. Furthermore, US is not able to reliably assess tissue integrity as its limits of resolution means that every US image is a mixture of reflections (of relatively large structures like secondary tendon bundles, fasciculi) and interfering echoes (generated by smaller entities like fibrils and cells) that cannot be discriminated by the eye.Therefore, a method for computerised ‘ultrasound tissue characterisation’ (UTC) was created. A high-resolution probe is fixed in a tracking device and moves automatically along a tendon's long axis, collecting transverse images at even distances of 0.2 mm. By compounding contiguous transverse images, a 3-D ultrasound data-block is created that can be used for (A) tomographic visualisation in 3 planes of view plus a 3-D rendered view, and for (B) tissue characterisation and quantification of 3-D architecture of the tendon matrix.Dedicated UTC-Algorithms can discriminate four different echo-types, namely: echo-type I, generated by reflections at intact and aligned tendon bundles, echo-type II, generated by reflections at discontinuous or wavy tendon bundles, echo-type III, generated by interfering echoes from mainly fibrillar components, and echo-type IV, generated by mainly cellular components and fluid in amorphous tissue. Initially, UTC was validated by precisely matching UTC-processed images with corresponding tendon specimens, sampled from isolated flexor tendons in the horse. These four echo-types appeared to be highly correlated with histo-morphological characteristics, showing the discriminative power of UTC for tissue characterisation.Since 2005, UTC is implemented for human Achilles and patellar tendons and has been used in multiple research projects too. Some relevant observations in these studies are:Inter-and intra-observer reproducibility of both data-collection and analysis appeared to be high (ICC over 0.90), indicating an excellent reliability for longitudinal monitoring.Observational studies of UTC parameters related to age revealed that Achilles tendons of young persons (24–30 years of age) are characterised by 80–85% echo-type I, 10–15% echo-type II and only 2–5% type III plus IV echoes. Initial deterioration, mostly asymptomatic, was characterised by increasing percenta