A simple fiber optic monitor of cardiac and respiratory activity for biomedical magnetic resonance applications

SummaryAnaesthetists are increasingly involved in patient care during magnetic resonance imaging and spectroscopy. This paper describes a system which has been developed for the management of critically ill patients and the conduct of anaesthesia in a magnetic resonance unit with a 1.6 tesla whole body magnet. Dificulties which arise from working in a confined space in a high magnetic field are highlighted. Different approaches to anaesthesia, sedation and the modijication of equipment for use in [his environment ure reviewed. The problems associated with patient monitoring within a magnetic field are discussed and some solutions are suggested. A transport system for critically ill patients is described and a protocol for management is outlined.

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“…pulse oximeters: see below). The use of fibreoptic [40] and telemetry systems [41] avoids the hazards of trailing cables.…”

Section: Monitoringmentioning

confidence: 99%

“…This problem can be ameliorated by the use of shielded cables [I]. Another solution is to transmit the ECG data by telemetry [41], lossy transmission lines [46] or a fibreoptic system [40].…”

Section: Ecgmentioning

confidence: 99%

Magnetic resonance for the anaesthetist

et al. 1992

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“…However, such superficial measurements suffer from low sensitivity, particularly in small animals. An optic fiber reflectometer was also successfully used, both invasively (11) and non‐invasively (12), to obtain non‐ECG‐gated cardiac images in rats.…”

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confidence: 99%

Cardiac and respiratory double self‐gated cine MRI in the mouse at 7 T

Hiba

Richard

Janier

et al. 2006

Magnetic Resonance in Med

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ECG-gated cardiac MRI in the mouse is hindered by many technical difficulties in ECG signal recording inside static and variable high magnetic scanner fields. The present study proposes an alternative robust method of acquiring auto-gated cardiac and respiratory cine images in mouse heart. In our approach, a motion synchronization signal is extracted from the echo peak MR signal of a non-triggered radial acquisition. This signal is then used for both cardiac and respiratory retrospective gating before cine image reconstruction. Highly asymmetric echoes were acquired to achieve the radial k-space sampling in order to avoid radial acquisition related artifacts and to increase auto-gating robustness. In vivo experiments demonstrated the feasibility and robustness of self-gated cine-MRI in the mouse heart at 7T. The signal-to-noise and contrast-tonoise ratios of the self-gated and ECG-gated images were comparable, all parameters being equal. Magn Reson Med 55: 506 -513, 2006.

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“…Only a handful of studies pertaining to few invasive or minimally invasive methods unaffected by RF fields and gradient switching can be found in the literature. An invasive miniature optical probe inserted into an artery showed an optical signal resulting from a fluctuating light reflection caused by the pulsatile blood flow [13]. A second study described an optical stethoscope where an optical fiber was carefully introduced into the animal's esophagus and the fiber tip then placed close to the mouse's heart.…”

Section: Introductionmentioning

confidence: 99%

An Optical Fiber-Based Gating Device for Prospective Mouse Cardiac MRI

Sablong

Rengle

Ramgolam

et al. 2014

IEEE Trans. Biomed. Eng.

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Abstract-Prospective synchronization of MRI acquisitions on living organisms involves the monitoring of respiratory and heart motions. The electrocardiogram (ECG) signal is conventionally used to measure the cardiac cycle. However, in some circumstances, obtaining an uncorrupted ECG signal recorded on small animals with RF pulses and gradient switching is challenging. To monitor respiratory motion, an air cushion associated with a pressure sensor is commonly used but the system suffers from bulkiness. For many applications, the physiological gating information can also be derived from an MR navigated-signal. However, a compact device that can simultaneously provide respiratory and cardiac information, for both prospective gating and physiological monitoring, is desirable. This is particularly valid since small volume coils or dedicated cardiac RF coil arrays placed directly against the chest wall are required to maximize measurement sensitivity. An optic-based device designed to synchronize MRI acquisitions on small animal's respiratory and heart motion was developed using a transmit-receive pair of optical fibers. The suitability of the developed device was assessed on mice (n=10) and was based on two sets of experiments with dual cardiac and respiratory synchronization. Images acquired with prospective triggering using the opticalbased signal, ECG and the pressure sensor during the same experiment were compared between themselves in the first set. The second set compared prospective technique using optical-based device and ECG to a retrospective technique. The optical signal which was correlated to both respiratory and heart motion was totally unaffected by radiofrequency pulses or currents induced by the magnetic field gradients used for imaging. Mice heart MR images depict low visible motion artifacts with all sensors or techniques used. No significant SNR differences were found between each series of image. Full fiber optic based signal derived from heart and respiratory motion was suitable for prospective triggering of heart MR imaging. The fiber optic device performed similarly to the ECG and air pressure sensors, while providing an advantage for imaging with dedicated cardiac array coils by reducing bulk. It can be an attractive alternative for small animal MRI in difficult environments such as limited space and strong gradient switching.

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A simple fiber optic monitor of cardiac and respiratory activity for biomedical magnetic resonance applications

Cited by 18 publications

References 4 publications

Magnetic resonance for the anaesthetist

Magnetic resonance for the anaesthetist

Cardiac and respiratory double self‐gated cine MRI in the mouse at 7 T

An Optical Fiber-Based Gating Device for Prospective Mouse Cardiac MRI

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