emi filers for mri devices, emi filters for mri scanners

Impact of EMI Noise on MRI Devices and EMI Filters for MRI Scanners

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In continuation with the series of articles analysing the Impact of EMI/RFI on the Medical Industry, our focus area for today is on MRI scanning equipment.

If you are looking for information on EMI impact on Medical Ventilators, you can refer to the below article, as the first part of this series.

Read More: EMI Filters for Medical Ventilators

Importance of MRI Scanners in the current Medical Industry:

Magnetic Resonance Imaging (MRI) is a non-invasive imaging technology that produces 3 dimensional detailed anatomical images of human body parts. It is used for disease detection, diagnosis, and treatment monitoring. MRI scanners are particularly well suited to image the non-bony parts or soft tissues of the body. They differ from Computed Tomography (CT) scans, as they do not use the damaging ionizing radiation of X-rays.

MRIs employ powerful magnets which produce a strong magnetic field that forces protons in the body to align with that field. When an RF pulse is passed through the patient, the protons get stimulated. When the RF field is turned off, the MRI sensors are able to detect the energy released as the protons realign with the magnetic field. Physicians are able to tell the difference between various types of tissues based on these magnetic properties.

MRI Scanners have taken precedence over other scanning and diagnostic techniques in the medical industry, so it becomes increasingly important to ensure the absolute safety and reliability of this critical equipment.

What are the Impacts of Electromagnetic Interference(EMI) Emissions on MRI devices?

Although MRI does not emit any ionizing radiation that is found in X-ray and CT imaging, it does employ a strong magnetic field. This makes the MRI device highly susceptible to EMI impact. EMI can affect equipment functioning, affect accuracy of readings, and result in frequent wear and tear of components. This is apart from the danger to the humans involved.

MRI Scanners are frequently identified by their magnetic field strength, measured in Tesla. Across the MR industry, most scanners are 1.5T or 3.0T, however there are varying strengths below 1.5T and more recently, up to 7.0T. This means the magnet in a 1.5T MRI scanner is 30,000 times stronger than the Earth’s magnetic field!

Source and impact of Electromagnetic radiation on devices is hard to detect. Medical practitioners may go on running diagnostic tests without realizing that EMI is degrading the accuracy of measurements. Even after noticing the impact of EMI, it is difficult to distinguish EMI from other noise sources. Even identifying the actual device which is the EMI source is quite an elaborate task.

Instead of dealing with the impact of EMI emissions after the problem occurs, it is better to take preventive measures during the MRI room / equipment design stage itself. Appropriate power line EMI Filters and shielding solutions are employed during the MRI equipment design to safeguard the equipment and the safety of the patient.

What are the Sources of EMI noise in MRI scanners?

In order to generate images of various body organs, MRI scanners use very strong magnetic fields, gradients, radio waves and RF sensors. The combination of strong magnetic fields and radio waves makes the MRI scanner a source of extremely high level EMI emissions. At the same time, the device is also highly susceptible to interference from external EMI sources.

1. EMI/RFI Emissions from the MRI device – RF emissions from within the MRI chamber may get conducted through electrical / signal cables or even propagate as radiated emission through air. This would cause disturbance in nearby equipment in the lab. This could also affect the patient and device technicians working nearby.

2. Susceptibility to external EMI sources – EMI noise from nearby devices such as mobile phones, Wi-Fi routers, power supplies and other medical equipment could reach the MRI equipment either as conducted or radiated emissions.

3. Components within the MRI scanner – Major components include the main polarizing magnet, shim coils, gradient systems to localise the MR signal, and the RF system to excite and detect the MR signals. EMI emissions from any of these components may affect the functioning of the other components.

All these factors make EMI an important consideration when building an MRI room. Even the lowest levels of noise can impact the MRI machine functionality and image quality.

How to handle EMI noise in MRI Scanners?

  1. Turn off the device which is the source of EMI – Identify the device which is the EMI source, preferably turn it off. Or move it far away to minimise impact.
  2. Isolate EMI source from device – Source of EMI should be isolated from the surrounding environment. This can be accomplished by properly grounding the machinery, constructing a Faraday cage around it, or placing it in a room constructed of conductive material.
  3. Shielded Chambers – Critical testing equipment and machineries are kept inside a shielded chamber which completely eliminates the external interference.
  4. Points of Entry (POE) – The POE (Points Of Entry) of the shielded room which is for power, lighting, signal, telephone and data lines have to be protected against the interferences.
  5. EMI filter in the MRI device – MRI EMI filters provide very high shielding effectiveness to the shielded room. A well designed EMI Filter can provide 100 dB attenuation to the noise throughout the band pass frequencies from 100 KHz to 10 GHz.

EMI Safety and Compliance Standards

Efficient handling of EMI/EMC is critical to the Medical industry. Since the impact of EMI related disturbance/damage can cost human lives, the standards of compliance and testing for medical applications are very stringent.

Extensive EMI testing, especially onsite testing is carried out to certify the compliance levels to EMI/EMC. The primary standard required by the CDRH/ FDA in the US is IEC 60601-1-2: International Electro-technical Commission – Medical Electrical Equipment – Part 1-2: General Requirements for Safety – Collateral standard: Electromagnetic Compatibility – Requirements and Tests.

Medical Grade EMI Filters from EMISINDIA

EMIS is a leading and trusted EMI/EMC solutions provider across several countries the world over. EMIS products and services cater to various industry sectors such as defence, automotive, consumer appliances, power supply and telecommunication sectors.

EMIS specialises in Medical Grade EMI filters and EMI/EMC solutions, with special focus on the needs of the medical industry. These products guarantee high accuracy and comply with the highest international safety standards.

We have a wide range of input filters to reduce conducted and radiated EMI. Our product range also meets requirements concerning EMI susceptibility which support the entire frequency spectrum. We also trade in associated products for adequate grounding, shielding and cabling to manage radiated emissions. Our facility filters comply with the highest international standards of conducted emission tests.

EMIS MRI Filters – Single phase, dual stage EMI filters

Single phase and Dual Stage Filters series of Medical Grade EMI filters from EMIS are specifically designed for MRI scanner applications. The dual stage filtering is suited for applications where more filtering is required to meet the stringent emission and susceptibility limits. They provide superior performance when used in applications with low impedance loads controlling pulsed, continuous, and intermittent interference noise.

These filters also provide good attenuation of incoming interference. The Pig tail arrangement at the output side for the connection provides physical isolation between Input and Output. The Filters are available from 1A to 30A with various Voltage Ratings 250VAC/110VAC/24VDC.

EMIMRI20XX – Product Specifications

  • Single Phase EMI Filters, Dual Stage EMI filters
  • Designed specifically for MRI installations – MRI screened facilities and shielded rooms
  • Designed to meet MRI manufacturer requirements
  • Long lasting shielding of filter elements inside sealed filter compartment
  • Compliant to UL1283, CSA 22.2 No.8-13 and IEC 60939-3 safety standards
  • CE Marking, RoHS compliant filters
  • Easy to Install
  • Compact Design, light weight
  • Customised filters are provided on request
  • Very High Performance Filters are available on request

For more information and technical specifications, please refer to the datasheets.

Dual Stage High Performance Filters

Dual Stage High Performance Filters (Common Mode, Differential Mode)

These EMI Filters guarantee to limit the leakage currents below 0.5 mA in order to meet the requirements of the Medical Standard IEC/EN 60601 for Medical Equipment with Patient Contact or other Medical Environments.

Medical Grade Filters from EMIS comes in a wide range which gives the customer many options to choose in terms of Leakage current and different circuit configuration to fulfil the EMC Requirements as per relevant CISPR standards. The product series is available in different mounting styles. Medical Grade Filters from EMIS meet the requirements of Standard UL 60939-3.

To further explore our product offerings for the healthcare domain, visit our webpage https://www.emisindia.com/industry/healthcare/.

EMI Solutions Pvt Ltd is an ISO 9001-2015 and 14001-2015 certified company that exclusively caters to EMI/EMC Related requirements. We deliver both standard manufactured and custom designed EMI filters and components. We are one of the Largest EMI/RFI Filter manufacturers in India. In addition, our state-of-the art EMI/EMC test facility and technical consultancy services give our customers the convenience of TOTAL SOLUTIONS TO EMI under one roof.

Anuradha c
Author: Anuradha C

An integral part of the content creation team at KWK Resistors, Anuradha is a corporate trainer in the IT/telecom domain with over 18 years of experience. She served in senior technical and management positions in Huawei and TCS for 10+ years

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