Development of a Transcranial Ultrasound Thrombolysis System for Stroke Therapy

A custom-designed transducer to the right of the picture exposes a whole blood clot bathing in plasma and rt-PA within the central holder to ultrasound in a temperature-controlled water tank. The clot is then removed and weighed so as to assess percent mass loss relative to its initial mass. The two sound absorvers to the left of the picture are used to prevent the generation of reflections and standing waves during ultrasound exposure.

Experimental setup for assessing the combined thrombolytic action of ultrasound and r-tPA

Experimental validation of a finite-difference model for the prediction of transcranial ultrasound fields based on CT images

Ultrasound enhanced thrombolysis (UET) is a promising technique for the treatment of ischemic stroke. Transcranial 120-kHz unfocused ultrasound allows efficient transmission through the temporal bone and enhances thrombolysis. To predict the transcranial acoustic fields, a finite-difference acoustic model based on CT scans was implemented. The numerical model was first validated using an analytical model. Acoustic fields produced in four human skulls insonified by 60- and 120-kHz pulsed ultrasound were measured in vitro. Corresponding acoustic fields were simulated using coregistered CT scans. Good agreement with hydrophone measurements was found (mean error < 14%). Although a bias due to the conversion of CT data to mechano-acoustic parameters was observed, high correlation between measurement and simulation (Rē>0.88) was found for the amplitude of both the transmitted wave and the reflection from the contralateral bone. A quantitative estimate of 120-kHZ UET ultrasound fields can therefore be obtained by finite-difference simulation using CT data.

Related References:
Bouchoux G. et al. 2012, Physics in Medicine and Biology, 57:8005

Experimental setup for measuring pressure fields within the skull. Also shown is the dual array transducer with an inner transmit element centered at 120kHz and an outer receive element centered at 60 kHz

Comparison of simulated and experimental pressure fields for skull 1

Comparison of simulated and experimental values of peak transmitted and reflected pressure amplitudes for 4 skulls (12 experiments).