title: Influence of ultrasound operating parameters on ultrasound-induced thrombolysis in vitro.
abstract: The effect of operating parameters on the thrombolytic potency of ultrasound (US) is important for potential therapeutic applications, but is not fully understood. Fresh human whole-blood thrombi were exposed in vitro to focused US from a diagnostic transducer driven by an impulse generator via an amplifier to vary duration (10 to 60 min), intensity (7 to 90 W/cm(2)), frequency (2 to 4.5 MHz), pulsed wave duty cycle (1:5 to 1:100 and continuous wave mode) and pulse length (100 to 400 micros). Segments of thrombi (498 +/- 73 mg) were submersed and insonated in saline solution. Thrombolytic efficiency was expressed as percentage loss of mass compared with controls (noninsonified thrombi). Ultrasound exposure achieved a significantly higher thrombolysis than no US, 56 +/- 16 % vs. 29 +/- 11 % (n = 232, p < 10(-6)). There was an exponential saturation-type correlation with duration of insonation (r(2) = 0.64) and intensity (r(2) = 0.97), an inverse correlation with US frequency at matched intensities (r(2) = 0.76, p < 10(-5)), a logarithmic relationship with duty cycle in pulsed mode (r(2) = 0.86) and a modest direct effect of pulse length (r(2) = 0.57, p < 10(-5)). Thus, thrombolytic efficiency of US depends directly on duration, intensity, duty cycle and pulse length and inversely, on frequency.
authors.affiliation: Med.Klinik II, Universitätsklinikum Erlangen, Erlangen, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Schäfer
authors.forename: Stefan
authors.initials: S
authors.lastname: Kliner
authors.forename: Lutz
authors.initials: L
authors.lastname: Klinghammer
authors.forename: Hans
authors.initials: H
authors.lastname: Kaarmann
authors.forename: Ivan
authors.initials: I
authors.lastname: Lucic
authors.forename: Uwe
authors.initials: U
authors.lastname: Nixdorff
authors.forename: Uri
authors.initials: U
authors.lastname: Rosenschein
authors.forename: Werner G
authors.initials: WG
authors.lastname: Daniel
authors.forename: Frank A
authors.initials: FA
authors.lastname: Flachskampf
mesh_terms: D016022:Case-Control Studies; D006801:Humans; D015912:Thrombolytic Therapy / Q000379:methods; D013927:Thrombosis / Q000628:therapy*; D014464:Ultrasonic Therapy / Q000379:methods*; D018084:Ultrasonography, Interventional