Ultrasound Doppler of the Achilles Tendon before and after Injection of an Ultrasound Contrast Agent - Findings in Asymptomatic Subjects

Abstract

The sensitivity of ultrasound Doppler has now reached a level at which perfusion can be detected even in normal, resting musculoskeletal tissues. To be able to distinguish normal from abnormal flow, the resistive index (RI) determined by spectral Doppler may be of value. Inflammation is associated with low RI values and a value of 1.00 is normal. In tissues with no detectable flow, it has been assumed that RI may be defined as 1.00. This study was performed to test if normal tendinous vessels could be visualised with a contrast agent, and if such vessels had normal RI. Ultrasound (US) was performed with a 14 MHz linear transducer. 22 asymptomatic tendons in 12 subjects were scanned, and only 5 ultrasonically normal tendons in 5 subjects were identified. In these 5 normal tendons, SonoVue was used to make vessels visible. The Achilles tendons and the peritendinous tissues were evaluated clinically. In all 5 ultrasonically normal tendons, arteries could be detected with Doppler after contrast injection and in all cases with normal RI values. All vessels were located in the mid-portion of the tendon. 18 tendons were categorised as normal by the clinician. After administration of a contrast agent, all Achilles tendons could be demonstrated to have arteries present in the mid-portion. The flow profile of these arteries was fully normal without diastolic component and with an RI of 1.00. This finding has implications for criteria of normality of tendons, which cannot be based exclusively on the presence or absence of Doppler activity. The majority of the tendons in this study had ultrasound abnormalities both on gray-scale and colour Doppler. It can be speculated that the abnormalities may be age-related degenerative changes and that age-stratified normal materials are needed to define normality. There was no consistency between US and clinical diagnosis.