Ultrasound bubble excitation for Doppler measurement of cerebrospinal fluid shunt flow

Normal cerebrospinal fluid (CSF) contains few natural scatterers making it difficult to measure the flow by Doppler ultrasound. A new technique is proposed whereby bubbles are generated in a shunt tube by low-frequency (LF) ultrasound (100-300 kHz) at peak pressures of only 0.1 MPa, and their velocity is measured by Doppler ultrasound. Preliminary experimental results using a simple in-vitro model are presented to demonstrate the feasibility of this non-invasive method for measuring flows in a 1.3 mm(ID) shunt.