Fibre optic sensor for non‐invasive monitoring of blood pressure during MRI scanning

Abstract

This report focuses on designing and implementing a non-invasive blood pressure (NIBP) measuring device capable of being used during magnetic resonance imaging (MRI). Based on measuring pulse wave velocity in arterial blood, the device uses the obtained result to estimate diastolic blood pressure. Pulse transit times are measured by two fibre optical accelerometers placed over the chest and carotid artery. The fabricated accelerometer contains two static fibres and a cantilever beam, whose free end is angled at 90 degrees to act as a reflecting surface. Optical fibres are used for both illuminating the surface and receiving the reflected light. When acceleration is applied to the sensor, it causes a deflection in the beam, thereby changing the amount of reflected light. The sensor's output voltage is proportional to the intensity of the reflected light. Tests conducted on the electronics and sensors inside an MRI room during scanning proved that the device is MR- compatible. No artifacts or distortions were detected.

Synchronous Multiscale Neuroimaging Environment for Critically Sampled Physiological Analysis of Brain Function: Hepta-Scan Concept

“…The completely MRI-compatible measurement method is described more precisely in the following reference (Myllylä et al, 2011a). Cardiovascular pulses induce tiny movements of the skin, especially near the arteries.…”

“…However, also the diameter of the vessel, thickness of the vessel wall, and the density of blood have an effect on PWV. To take this into account, we used a mathematical expression for estimating BP from PWV, described in the following references (Myllylä, 2014;Myllylä et al, 2011a). During artifacts, for example, caused by expectoration, swallowing, and others, the BP is interpolated between successful measurements.…”

“…Vasomotor waves are slow, minute-scale general fluctuations of blood vessel wall tone that modulate blood perfusion pressure from microvasculature to global blood pressure (BP). By measuring the speed of heart pulsation propagation in the blood vessels, one is able to noninvasively monitor the vasomotor waves of BP (Gesche et al, 2012;Gribbin et al, 1976;Myllylä et al, 2011a;Sorvoja, 2006). To the best of our knowledge, a direct time-domain correlation between vasomotor waves and VLFFs of BOLD signals has never been reported previously.…”

Multimodal brain imaging with magnetoencephalography: A method for measuring blood pressure and cardiorespiratory oscillations

“…Developed method to quantify cerebral hemodynamics is based on NIRS 10 and the method to continuously estimate BP oscillations is based on determining pulse propagation between heart and carotid artery, assumed to reflect systemic BP 11 . Further, heart rate (HR) and breathing patterns are determined by measuring chest wall motion.…”

Use of Optoelectronics to Measure Biosignals Concurrently During Functional Magnetic Resonance Imaging of the Brain

“…A recent example of optoelectronics used in fMRI is a system that is able to measure diastolic blood pressure through an fMRI experiment (Myllyla, Elseoud et al 2011). This device uses a fibre optic sensor to measure skin movements associated with blood pressure changes in the underlying blood vessels.…”