Low-frequency ultrasound penetrates the cranium and enhances thrombolysis in vitro.
OBJECTIVE
Refinements of treatment methods are sought to rapidly reduce the volume of intracranial clots and to decrease patient exposure to possible complications of thrombolytic therapy for intracranial hematomas. We assessed the possibility of adding ultrasonication using model systems including human blood clots and temporal bone in vitro.


METHODS
The transmittance of ultrasound through temporal bone obtained at autopsy was compared between the frequencies 211.5 KHz and 1.03 MHz, using a meter to determine the power delivered. The frequency 211.5 KHz was chosen to assess the ultrasound effect on the weight of 24-hour-old clots prepared from human blood after exposures at 37 degrees C to 2 mg/ml urokinase with no additional treatment, ultrasound, or agitation during an interval of up to 12 hours. At these times, fibrin degradation products also were measured.


RESULTS
The transmittance of low-frequency ultrasound (211.5 KHz) through temporal bone was approximately 40%, which is four times higher than that of high-frequency ultrasound (1.03 MHz). Ultrasound but not agitation significantly increased clot lysis (140% of lysis with urokinase alone), with correspondingly increased fibrin degradation products.


CONCLUSIONS
We conclude that low-frequency ultrasound transmits well through human temporal bone and enhances thrombolysis in vitro. Clinically, this method may be promising for reducing dosages of thrombolytic agents and shortening the period of clot removal.
Akiyama
M
M
Department of Neurosurgery, Jikei University School of Medicine, Tokyo, Japan.
Ishibashi
T
T
Yamada
T
T
Furuhata
H
H
D000368:Aged; D003131:Combined Modality Therapy; D004867:Equipment Design; D005260:Female; D006801:Humans; D002542:Intracranial Embolism and Thrombosis / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D013701:Temporal Bone; D015912:Thrombolytic Therapy / Q000295:instrumentation*; D014464:Ultrasonic Therapy / Q000295:instrumentation*