Electromagnetic compatibility (EMC) is a property of the device to maintain its compatibility in the electromagnetic environment. The EMC-compatible device is the one that doesn’t emit electromagnetic waves to the level that interferes with the functioning of other devices. Most medical devices that we use today are made EMC compatible. This is because these devices are used for treatment and lifesaving purposes, if electromagnetic interference exists, then they may lead to wrong diagnosis and a host of other problems. Is that all? No, the complications can be much higher. This post analyzes the need for reducing electromagnetic interference, as well as improving electromagnetic compatibility in medical devices.
Types of Electromagnetic Interference That Affect Medical Devices
Every electronic device produces electric and magnetic fields (EMFs), which are invisible areas of energy known as radiation. The radiation can interrupt the working of parts and other devices in the same subsystem. For clarity, EMI is distinguished into three types – Radiated EMI, Coupled EMI, and Conducted EMI.
- Radiated EMI: Some electronic devices produce strong electromagnetic signals in the range of 30 MHz and 1 GHz, which may disturb the working of nearby devices. This type of emission is known as radiated EMI.
- Conducted EMI: Electromagnetic energy may sometimes get coupled with power cables, electrical and electronic devices or other circuits. This type of emission is known as conducted EMI. The conducted EMI is further distinguished into two types:
- Common Mode: The coupling of this type occurs when the two conductors are in the same phase and the noise reflects on them. For instance, it may occur during –positive and negative for power cables and return and out for signals.
- Differential Mode: This type of coupling occurs when the noise reflects on different phases on two conductors.
- Coupled EMI: This type of EMI is usually distinguished into either of these types:
- Magnetic Coupling: This coupling occurs if a varying magnetic field exists between the victim and the source. Sometimes this would occur when two conductors are operated closely. When this happens, the source induces a current in the victim circuit.
- Capacitive Coupling: This coupling occurs when a voltage change occurs in the source. This voltage change will transfer a charge to the victim circuit, thereby causing interference.
EMI and EMC Standards for Medical Devices
All medical devices are designed to comply with IEC 60601-1-2, which are a series of general standards approved by the US Food & Drug Administration (FDA). So, if you wish to submit your device for FDA approval, ensure to get it verified for IEC 60601-1-2 by an accredited laboratory. This standard defines the safety and essential performance expectations of medical equipment or device when subjected to EMI.
- ISO 7637-2
- CISPR 25
- ISO 7137
- EUROCAE ED-14
- RTCA DO-160
In addition to IEC 60601-1-2, medical equipment manufacturers must comply with other EMI standard requirements for using the devices or equipment in vehicles such as medical helicopters, air ambulances, mobile clinics, and railway environments. The following are some standards that they need to adhere to.
Sources of Electromagnetic Interference in Medical Devices
There are many sources of electromagnetic interference in medical devices. The following are a few common ones among them:
- Service Radios/ Emergency Vehicles: Service radios used in emergency vehicles are one of the primary sources radiation. Many new emergency services network (ESN) utilize 4G technology, which helps minimize the risks presented by service radios and mobile phones.
- Diathermy: This surgical technique utilizes an alternate polarity electrical current of high frequency to coagulate or cut tissue during surgery. Diathermy is distinguished into two types – monopolar and bipolar. In monopolar diathermy, the current is directed to the the targeted area of the patient’s body through an active electrode. This current finally exits through the return electrode. In bipolar diathermy, the current is made to pass through two active electrodes to the affected area of the body. Both these types of surgery are known to produce interference in sensitive devices such as implanted pacemakers, cochlear implants, and cardioverter defibrillators.
- Radiofrequency Identification Systems (RFID): They are used in healthcare facilities to track various types of equipment. These systems are known to cause interference in sensitive medical devices such as monitors and pacemakers.
How electromagnetic interference affects medical devices and human lives?
The effects of electromagnetic interference on human lives and medical devices can be more severe than expected. The following are a few possible EMI scenarios:
- The EMI in the ambient system can affect the functioning of active devices such as pacemakers, which may cause death in worst-case scenarios.
- EMI from mobiles and any of the aforementioned sources are known to create unwanted scenarios such as false readings on patient monitors, temporary malfunctioning of implantable devices or false movements of wheelchairs.
- Many emergency devices used in ambulances, such as cochlear implants, implantable pacemakers, neurostimulators, and cerebral spinal fluid (CSF) shunt systems have been found to get affected by radio signals.
Multi-Cavity Shielding Solution to Reduce Electromagnetic Interference in Medical Devices
Today, medical device designers and manufacturers are keen to use multi-cavity shielding solutions to reduce electromagnetic interference in medical devices. This is because these shielding solutions can easily solve many problems associated with regular shields. XGR Technologies Snapshot multi-cavity shield has gained immense prominence in this prospect. These shields are available in various flexible design shapes and can easily conform to device shape. These shielding devices are attached to the PCB after SMT reflow process and allows for easy inspection or rework if necessary.
Metal cans and metal shields were used to reduce electromagnetic interference in medical devices for many years. However, these metal shielding solutions have their drawbacks. Many medical devices such as MRI machines are sensitive to magnets or magnetic materials, which may interfere with metal cans or metal shields. However, SnapShot is made from polymer-based material, which is non-magnetic in nature, and doesn’t cause any interference. This leads to better results of equipment. Feel free to contact the team at XGR Technologies to discuss more about SnapShot multi-cavity shielding solutions for medical devices.
