Magnetic linear actuator for vascular access surveillance

Vascular access (VA) surveillance to guide care is essential for dialysis patients. Non-linear, patient specific formation of stenoses reduce VA efficiency. Various methods are used to monitor blood flow or pressure. However, these are surrogates for stenosis rather than direct measurements. There is also no reimbursement for VA surveillance and measurements consume clinician time, making more frequent measurements difficult. Hemodynamic variability increases the chance of infrequent observations missing stenosis formation. This paper presents a specialized ultrasound system intended to slide between the dialysis needles and provide operator independent VA geometry and volume flow during treatment. Specific attention is paid toward the magnetic design of the Lorentz force linear actuator. Experimental results indicate that the system can successfully collect Doppler flow information across a tissue-mimicking flow phantom vessel.