Ultrasound Doppler of the Achilles Tendon before and after Injection of an Ultrasound Contrast Agent - Findings in Asymptomatic Subjects - Koenig, M J; Torp-Pedersen, S; Holmich, P; Terslev, L; Nielsen, M B; Boesen, M; Bliddal, H (Ultraschall in der Medizin - European Journal of Ultrasound, 2007)