Non-Invasive Electromagnetic Skin Patch Sensor to Measure Intracranial Fluid–Volume Shifts

Abstract

Elevated intracranial fluid volume can drive intracranial pressure increases, which can potentially result in numerous neurological complications or death. This study’s focus was to develop a passive skin patch sensor for the head that would non-invasively measure cranial fluid volume shifts. The sensor consists of a single baseline component configured into a rectangular planar spiral with a self-resonant frequency response when impinged upon by external radio frequency sweeps. Fluid volume changes (10 mL increments) were detected through cranial bone using the sensor on a dry human skull model. Preliminary human tests utilized two sensors to determine feasibility of detecting fluid volume shifts in the complex environment of the human body. The correlation between fluid volume changes and shifts in the first resonance frequency using the dry human skull was classified as a second order polynomial with R2 = 0.97. During preliminary and secondary human tests, a ≈24 MHz and an average of ≈45.07 MHz shifts in the principal resonant frequency were measured respectively, corresponding to the induced cephalad bio-fluid shifts. This electromagnetic resonant sensor may provide a non-invasive method to monitor shifts in fluid volume and assist with medical scenarios including stroke, cerebral hemorrhage, concussion, or monitoring intracranial pressure.

Passive Self Resonant Skin Patch Sensor to Monitor Cardiac Intraventricular Stroke Volume Using Electromagnetic Properties of Blood

“…Additionally, the penetration depth of the sensor’s electromagnetic field is an important factor. We have conducted some preliminary studies with varying thickness of muscle tissue and bone and have been able to detect usable signals in depths of up to 26 cm [26] , [27] , [49] . Due to the operating principles of the sensor, the penetration depth is substrate specific.…”

“…In summary, this study presents a foundation for the development of a passive skin patch sensor, powered externally by radiofrequency (RF) waves via an antenna, to measure cardiac fluid volume changes. In our previous work, we were able to demonstrate the ability of an RF skin patch sensor to detect intracranial fluid-volume shifts, detect pulsatile blood flow in a human arm phantom, identify hemodynamic waveform features, and measure heart rate [24] – [27] . The patch sensor was designed from a single baseline component comprised of a trace of silver configured into a square planar spiral patch.…”

Blood Pressure Sensors: Materials, Fabrication Methods, Performance Evaluations and Future Perspectives

“…Skin patch sensors based on electromagnetic (EM) detection were built from a conductive trace of copper to measure intravascular stroke volume [124] and intracranial blood pressure [158]. Also, a magnetoelastic skin curvature sensor along with ECG electrodes was used to measure blood pressure in the carotid [159].…”

In-Vivo Microsystems: A Review

“…With skin electrodes, the measurement volume can be just under the epidermis [ 37 ]. Another type of device is to use electromagnetic patches to measure the intracranial fluid-volume shift [ 38 ].…”