A Novel FBG-Based Triggering System for Cardiac MR Imaging at 3 Tesla: A Pilot Pre-Clinical Study

Abstract

This first-ever study demonstrates the applicability of a fiber Bragg grating (FBG) system for MR cardiac triggering of cardiovascular magnetic resonance at 3 Tesla. The unique patented system senses body movements caused by cardiac activity using a non-invasive ballistocardiography (BCG) sensor. The pilot research compares a novel FBG-based system with clinically used triggering systems based on electrocardiography (ECG) and pulse oximetry (POX). The pilot pre-clinical study was conducted on 8 subjects at a Siemens Prisma 3T MR Scanner. The study compares images from two basic cardiac sequences, TRUE FISP (Free Induction Decay Steady-State Precession) and PSIR (Phase Sensitive Inversion Recovery), using objective methods and subjective evaluation by clinical experts. The study presents original results that confirm the applicability of optical sensors in the field of cardiac triggering having a number of advantages in comparison to conventional solutions, such as no eddy current interference, ease of placement of the sensor on the patient's body, and senor reusability. The proposed FBG-based system achieves comparable results with the most frequently used and most accurate ECG-based and POX-based clinical systems. In terms of subjective evaluation by experts, the FBG system outperformed the POX-based system used in clinical practice.

A Comparison of Alternative Approaches to MR Cardiac Triggering: A Pilot Study at 3 Tesla

“…The gained precision and resistance to artifacts from the MR environment promise the successful usability of FBG sensors in synchronization of MRI. That was proved in our previous study published in [55],…”

“…The use of the proposed sensors can lead to higher image sharpness and noise reduction, thus increasing the quality of acquired images. In general, the study provided additional information on the proposed systems, which have been already the objects of our previous papers, see [18], [48], [51], [54], [55].…”

“…We used improved sensors introduced in [55], [58] with reduced size and weight (30 x 15 mm and 2g, respectively) resulting in simpler implementation and minimal load burden on the patient. For the modified Bragg grating encapsulation, we used the PDMS Sylgard 184 polymer [59], which proved to be advantageous [44], [48].Triggering system utilizing optical FBG sensor is based on virtual instrumentation in combination with FBG interrogator unit FBGuard, as described in detail in [55]. We used a digital output module to generate the MRI sequence triggering pulse.…”

Fiber-Optic Cardiorespiratory Monitoring and Triggering in Magnetic Resonance Imaging

“…In 2020, Nedoma et al performed cardiac triggering using the FBG sensor prototype with PDMS (polydimethylsiloxane polymer) encapsulation and in this time placed on the chest [70]. In this study, the optimal sensor placement was investigated first in laboratory conditions to generate greater BCG signal amplitude and it was found to be dependent on the size of the contact area of the sensor with the patient's body.…”

“…PMMA [74] or FBG [37]), sensors within harness (s2 -FBG, s3 -macro-bending [77]), chest sensor (s4 -e.g. FBG encapsulated in PDMS [70] or fiberglass [78]), pad sensor (s5, e.g. micro-bending pad [79] or FBG springboard [68]).…”