Intensity-Modulated Microbend Fiber Optic Sensor for Respiratory Monitoring and Gating During MRI

Abstract

This paper describes a novel microbend fiber optic sensor system for respiratory monitoring and respiratory gating in the MRI environment. The system enables the noninvasive real-time monitoring and measurement of breathing rate and respiratory/body movement pattern of healthy subjects inside the MRI gantry, and has potential application in respiratory-gated image acquisition based on respiratory cues. The working principle behind this sensor is based on the microbending effect of an optical fiber on light transmission. The sensor system comprises of a 1.0-mm-thin graded-index multimode optical fiber-embedded plastic sensor mat, a photoelectronic transceiver, and a computer with a digital signal processing algorithm. In vitro testing showed that our sensor has a typical signal-to-noise ratio better than 28 dB. Clinical MRI trials conducted on 20 healthy human subjects showed good and comparable breathing rate detection (with an accuracy of ±2 bpm) and respiratory-gated image quality produced using the sensor system, with reference to current predicate hospital device/system. The MRI safe, ease of operation characteristics, low fabrication cost, and extra patient comfort offered by this system suggest its good potential in replacing predicate device/system and serve as a dual function in real-time respiratory monitoring and respiratory-gated image acquisition at the same time during MRI.

Fiber-optic sensors for monitoring patient physiological parameters: a review of applicable technologies and relevance to use during magnetic resonance imaging procedures

“…In sensors measuring transmission loss caused by slight (miniscule) deflections of an optical fiber or in fiber bends with a radius of curvature well above the fiber diameter (>10 mm), i.e., in so-called micro- [82][83][84][85][86][87][88] and macrobend [89][90][91][92][93][94][95][96][97][98][99][100][101][102][103][104][105][106][107] sensors, respectively, the intensity of the light reaching the receiver is also measured. As in the cases described above, body movements (caused by respiration and heart function, among other things) are a complicating factor since these movements produce micro-and macrobends of fibers with a variable radius of curvature.…”

“…The measuring system for micro-and macrobend sensors is distinguished by a simple design for the sensors alone as well as for the associated transceiver modules (light source and photodetector). Nevertheless, due to their relatively low sensitivity, the sensors have to be embedded in a special mat 82,83 or cushion, [85][86][87][88] on which the patient lies during monitoring, or in textiles, such as a vest, T-shirt, or belt, which are worn by the monitored person, [89][90][91][92][93][94][95][96][97][98][99][100][101][102][103][104][105][106][107] to ensure immediate proximity to the lungs and heart. An example of a microbend sensor system is shown in Fig.…”

Design of micro bending deformer for optical fiber weight sensor

“…Micro bending fiber has been widely used for displacement sensor, pressure and temperature [2]. Such an optics-based sensor has a sufficiently small size, high sensitivity and not interference by electromagnetic waves [3].…”

Unconstrained pulse pressure monitoring for health management using hetero-core fiber optic sensor

“…However, the raw signals generated using these unconstrained methods were noisy because of the inherent vibrational signals in the sensor output; consequently, an algorithm based on a wavelet transformation or appropriate band-pass filter was needed to be adapted to the raw signal. In the past few decades, several techniques have been developed for monitoring human respiration using optical fiber sensors, such as motion capture and monitoring systems [10][11][12][13][14][15]. This is because optical fiber sensors have several advantages, such as the sensor not needing a power supply, resistance to EMI, flexibility, light weight, and high resistance to moisture.…”

“…However, plastic optical fibers have limited multi-mode stability for bending actions in the transmission line. Other approaches for respiration and heartbeat monitoring were employed, such as using optical interferometers with optical fiber length changes [13], microbend fiber sensors based on intensity modulation [14], and fiber Bragg gratings [15]. Although these techniques utilized an optical fiber, the optical interferometer methods were easily affected by external disturbances along the transmission fiber line because of the focus on the fiber length change owing to external perturbations.…”