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Influence of ultrasound operating parameters on ultrasound-induced thrombolysis in vitro

2005; Elsevier BV; Volume: 31; Issue: 6 Linguagem: Inglês

10.1016/j.ultrasmedbio.2005.03.005

1879-291X

Simon Schäfer, Stefan Kliner, Lutz Klinghammer, H. Kaarmann, Ivan Lucic, Uwe Nixdorff, Uri Rosenschein, Werner G. Daniel, Frank A. Flachskampf,

Photoacoustic and Ultrasonic Imaging

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/cm2), 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 μs). 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 (r2 = 0.64) and intensity (r2 = 0.97), an inverse correlation with US frequency at matched intensities (r2 = 0.76, p < 10−5), a logarithmic relationship with duty cycle in pulsed mode (r2 = 0.86) and a modest direct effect of pulse length (r2 = 0.57, p < 10−5). Thus, thrombolytic efficiency of US depends directly on duration, intensity, duty cycle and pulse length and inversely, on frequency. (E-mail: [email protected] )