Circulatory monitoring of children during anaesthesia in low-field magnetic resonance imaging

Accessory equipment considerations with respect to MRI compatibility

The MR Section of The National Electrical Manufacturers Association (NEMA), in response to a request from the Food & Drug Administration (FDA), recently issued a position paper to address generic issues related to the compatibility of accessory equipment produced by third party equipment manufacturers or MR equipment users and intended to be used in conjunction with MR equipment or within the MR scanning room. The recommendations concern scanning accessories, such as radiofrequency (RF) coils, patient monitoring equipment and injectors, as well as patient comfort accessories and positioning devices. The following issues related to safety performance are discussed: (a) the interaction of the equipment with the MR scanner, (b) interactions of the MR scanner with the equipment, and (c) potential safety hazards for patients and staff that can be posed by accessory equipment in the MR scan environment. The recommendations are based on combined input from NEMA member companies who manufacture MR systems and MR accessories and are presented for consideration in the design of MR accessory products and incorporation of these concepts into testing plans to ensure MR compatibility of third party devices.

[Anesthesia for MRI examination]

Magnetic resonance imaging (MRI) requires the patients to stay for 30-45 min in a magnetic closed noisy space. Therefore most children and agitated adults require general anaesthesia or sedation in order to high quality images. Anaesthesia may be given by several routes (TIVA, inhalational or intrarectal administration) using common drugs. However, the magnetic field limits the selection of patients undergoing MRI and the spectrum of anaesthetic and monitoring equipment. The magnetic field may have deleterious effects on implanted ferromagnetic devices. It may attract objects towards the magnet centre at a dangerous speed. Moreover it may disturb the function of monitors and anaesthesia machines which should be tested for a specific magnetic field strength before introducing their use in a given MRI unit.

Sedation, anesthesia, and physiologic monitoring during MR imaging: evaluation of procedures and equipment

The authors developed safe standard sedation and general anesthesia procedures for adults and children, including adequate physiologic monitoring, during magnetic resonance (MR) imaging. Six-year results are reported from one institution; 75% of the 600 patients per year who require sedation or anesthesia are children who require sedation only. Testing was done to determine MR compatibility of various types of equipment essential for monitoring and supporting sedated or anesthetized patients in 1.0- and 1.5-T MR imagers. Use of sedation procedures that include oral chloral hydrate after sleep deprivation resulted in a failure rate of 3.8% in sedating outpatient children. Every physiologic parameter that can be monitored under normal circumstances in the critical care unit or operating room can be monitored during MR imaging. Our experience indicates that with careful consideration of the unique MR environment and with rigorous testing of monitoring equipment, MR imaging can be performed safely in sedated or anesthetized patients.

Magnetic resonance for the anaesthetist. Part II: Anaesthesia and monitoring in MR units

Anaesthetists 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. Difficulties which arise from working in a confined space in a high magnetic field are highlighted. Different approaches to anaesthesia, sedation and the modification of equipment for use in this environment are 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.

Policies, guidelines, and recommendations for MR imaging safety and patient management. SMRI Safety Committee

The following are policies, guidelines, and recommendations from the Safety Committee of the Society for Magnetic Resonance Imaging (SMRI) concerning various issues related to magnetic resonance (MR) imaging safety and patient management. These policies, guidelines, and recommendations were developed to provide standardized and consistent information for use by health practitioners involved in clinical MR imaging.

Remote auscultatory patient monitoring during magnetic resonance imaging

A system for patient monitoring during magnetic resonance imaging (MRI) is described. The system is based on remote auscultation of heart sounds and respiratory sounds using specially developed pickup heads that are positioned on the precordium or at the nostrils and connected to microphones via polymer tubing. The microphones operate in a differential mode outside the strong magnetic field to reduce various sources of interference from the MRI equipment. After amplification, the signal is transmitted as infrared light to a small, battery-operated receiver and a headphone set. Thus, the patient can be simultaneously auscultated both inside and outside the shielded MRI room by infrared transmission through a metal mesh window. Bench tests of the system show that common mode acoustic noise is suppressed by approximately 30 dB in the frequency region of interest (100-1,000 Hz), and that polymer tubing having a diameter of approximately 2 mm can be used for efficient sound transmission. Recordings in situ show satisfactory detection of both heart sounds and respiratory sounds, although the signal is somewhat masked by noise during imaging. A clinical test incorporating 17 sedated or anesthetized patients was also performed. In all but four cases, the quality of the breath and heart sounds was regarded as acceptable or better.

Low field magnetic resonance imaging of the central nervous system in 15 children with autistic disorder

Fifteen children, 10 boys and 5 girls, with autistic disorder, were studied with low field magnetic resonance imaging (MRI). The age ranged from 2.7-13.1 years, with a mean of 8.3 years. All patients but one (who refused) had a normal CT scan of the C.N.S. The MRI investigation was performed during anaesthesia with a low field magnetic resonance imager. The cerebrum, cerebellum, and brain stem were examined. No pathological changes were found in any of the patients studied.