Investigation of Thrombolysis and Safety of Stand-Alone High-Intensity Focused Ultrasound Therapy in Partially Occluded Ex-Vivo Animal Models.
Stand-alone high-intensity focused ultrasound (HIFU) therapy is a promising non-invasive approach for treating thrombo-occlusive disease. The objective of this study was to investigate the ability of this approach to achieve safe thrombolysis in clinical treatment.
Two types of thrombo-occlusive models, utilizing plastic tubes (model-Ⅰ) and the abdominal aorta of rabbits (model-Ⅱ), were exposed to 1.1-MHz HIFU with a pulse repetition frequency (PRF) of 1-100 Hz and transducer power (Pelect) up to 180 W. A duty cycle of 0.6% was set to maintain tissue temperature below 43℃.
The experimental results from model-I demonstrated that extensive thrombolysis was seen at Pelect ≥ 120 W and PRF ≤ 10 Hz. In the experiments using model-Ⅱ (Pelect = 120-180 W, PRF = 1 Hz) a degree of thrombolysis of over 70% was found with treatment times between 12 and 33 minutes. Under these conditions the arteries appeared to have suffered only minor damage, with slight laceration of the intima/inner media and separation of medial lamellae. The mean damage score did not exceed the threshold for vascular rupture at any power level, with no significant differences observed (n = 3, p > 0.05), but slightly lower values were noted at lower power levels. The maximum diameter of the clot debris was < 8 μm, therefore comparable to that of a typical capillary, minimizing the danger of distal embolization.
The results confirm the potential of stand-alone HIFU as an effective treatment of thrombo-occlusive disease without causing significant vascular damage.
Two types of thrombo-occlusive models, utilizing plastic tubes (model-Ⅰ) and the abdominal aorta of rabbits (model-Ⅱ), were exposed to 1.1-MHz HIFU with a pulse repetition frequency (PRF) of 1-100 Hz and transducer power (Pelect) up to 180 W. A duty cycle of 0.6% was set to maintain tissue temperature below 43℃.
The experimental results from model-I demonstrated that extensive thrombolysis was seen at Pelect ≥ 120 W and PRF ≤ 10 Hz. In the experiments using model-Ⅱ (Pelect = 120-180 W, PRF = 1 Hz) a degree of thrombolysis of over 70% was found with treatment times between 12 and 33 minutes. Under these conditions the arteries appeared to have suffered only minor damage, with slight laceration of the intima/inner media and separation of medial lamellae. The mean damage score did not exceed the threshold for vascular rupture at any power level, with no significant differences observed (n = 3, p > 0.05), but slightly lower values were noted at lower power levels. The maximum diameter of the clot debris was < 8 μm, therefore comparable to that of a typical capillary, minimizing the danger of distal embolization.
The results confirm the potential of stand-alone HIFU as an effective treatment of thrombo-occlusive disease without causing significant vascular damage.
Authors
Ri Ri, Xu Xu, Shang Shang, Yue Yue, Greenwald Greenwald, Mohammed Mohammed, Shen Shen
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