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. 2021 Jun 21;21(12):4238.
doi: 10.3390/s21124238.

Photonic Integrated Interrogator for Monitoring the Patient Condition during MRI Diagnosis

Mateusz Słowikowski  1   2 , Andrzej Kaźmierczak  1 , Stanisław Stopiński  1   3 , Mateusz Bieniek  1 , Sławomir Szostak  1 , Krzysztof Matuk  4 , Luc Augustin  5 , Ryszard Piramidowicz  1   3
Affiliations

Photonic Integrated Interrogator for Monitoring the Patient Condition during MRI Diagnosis

Mateusz Słowikowski et al. Sensors (Basel). .

Abstract

In this work, we discuss the idea and practical implementation of an integrated photonic circuit-based interrogator of fiber Bragg grating (FBG) sensors dedicated to monitoring the condition of the patients exposed to Magnetic Resonance Imaging (MRI) diagnosis. The presented solution is based on an Arrayed Waveguide Grating (AWG) demultiplexer fabricated in generic indium phosphide technology. We demonstrate the consecutive steps of development of the device from design to demonstrator version of the system with confirmed functionality of monitoring the respiratory rate of the patient. The results, compared to those obtained using commercially available bulk interrogator, confirmed both the general concept and proper operation of the device.

Keywords: FBG; interrogator; photonic integrated circuit; sensor network.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The general idea of the system for monitoring the vital functions of a patient undergoing an MRI procedure.
Figure 2
Figure 2
Readout system for FBG sensor network: (a) Broadband light source, (b) circulator (c) optical fiber with FBG sensors, (d) spectrometer, (e) array of photodiodes.
Figure 3
Figure 3
(a) Layout of PIC containing two integrated interrogators based on 36-channel AWGs having 75 GHz (top) and 50 GHz (bottom) channel spacing; (b) optical micrograph of a fabricated optical interrogator circuit.
Figure 4
Figure 4
Transmission spectrum of (a) 36-channel; (b) two adjacent channels of 50 GHz channel-spaced AWG based interrogator.
Figure 5
Figure 5
Transmission spectrum of 16 channels of 50 GHz channel-spaced AWG based interrogator with an active SOA.
Figure 6
Figure 6
Schematic representation of the measurement system incorporating PIC-based interrogator.
Figure 7
Figure 7
Comparison of the shape of FBG reflection spectrum collected with optical spectrum analyzer with the response of 14 consecutive photodiodes of the 50 GHz channel-spaced AWG-based interrogator.
Figure 8
Figure 8
(a) Photodiodes names description on layout; (b) photodiode current measured during the experimental two cycles of fiber tensioning and loosening.
Figure 9
Figure 9
(a) Close up on the experiment shown in Figure 8, (b) corresponding reflection spectra recorded with the reference interrogator at given tensions applied.
Figure 10
Figure 10
(a) Functional block diagram of the dedicated electronic driver; (b) assembly of the packaged interrogator chip.
Figure 11
Figure 11
(a) Influence of temperature on FBG and PIC interrogator response; (b) response of the reference Ibsen I-MON 256.
Figure 12
Figure 12
Regular breathing and effect of FBG heating up captured by (a) PIC interrogator; (b) Ibsen I-MON 256 interrogator.
Figure 13
Figure 13
Previous measurement close-up with breath results captured by (a) PIC interrogator; (b) Ibsen I-MON 256 interrogator.
Figure 14
Figure 14
Result of measurement with person lying on the mattress and changing breathing pace: regular breathing (R), apnea (A), fast breathing (F) and regular breathing (R), captured by (a) PIC interrogator; (b) Ibsen I-MON 256 interrogator. Effect of FBG heating up is visible also.
See this image and copyright information in PMC

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