Overview of Medical Electronics
Electronic products are used extensively in the medical field. Some applications of medical devices in hospitals include diagnostics, treatment, patient monitoring and life support. Reliability and accuracy are the most important factors in medical product design. Further, these devices should be robust enough to recover in the event of a failure and must not cause harm to the patient under any circumstance. Hence, the design and sale of these devices are governed by various standards and regulations.
What are the standards and regulations that govern medical devices?
The ISO has recommended several standards for the design and manufacture of electronic product for medical use. The ISO9001 is a general purpose standard that regulates the design of any new product. In addition, the ISO 13485 published in 2003 governs the quality of medical devices. The ISO 14971 regulates risk management in medical devices. The design of electronic hardware is governed by the IEC 60601-1 standard. The software for medical applications is regulated by the IEC 62304 standard. In addition to these standard regulations, each country imposes stringent requirements on the manufacture of medical devices.
How long does it take to certify a medical device?
It is common for the certification process of medical electronic devices to take months or even years. If the device is used in extremely critical applications, such as in life-support systems, the duration for certification can be longer, sometimes 3 to 5 years. After the certification is obtained, follow up studies must be conducted to ensure the safety of the marketed device.
Different classes of medical equipment
Medical equipment are broadly classified depending on the risk they can pose to a patient in the case of failure. For instance, the United States classifies all medical devices into three classes. Though the actual classification may vary from country to country, the general principles are similar. The more the risk to a patient, the more stringent certification requirements are.
Class I (Low Risk)
Class I medical devices include equipment like bed-patient monitors, battery lights and ultrasonic cleaners that are used for support functions. They do not cause any catastrophic effects in the case of failure. Hence, no special premarket approvals are required for these devices.
Class II (Medium Risk)
Class II medical devices include equipment that are capable of moderate risk to the person in the case of malfunction. Devices such as electronic thermometers, IV lines, infusion pumps and wheeler stretchers fall in this category. These are governed by special controls and may require premarket approvals.
Class III (High Risk)
Class III medical devices are critical devices such as external and internal pacemakers, external defibrillators and heart valves. Failure of these devices can result in severe consequences, including death. These devices are governed by special controls and require premarket approval. In many cases, follow-up of these devices is necessary to ensure that there are no safety issues.
Hardware and software design
Commonly used electronic circuits in medical devices include microcontrollers, timing generators and Analog and Digital converters. In addition, there are several supportive devices like image and video processors and monitoring sensors.
How is the hardware chosen for medical applications?
The architecture for the microprocessors and chipsets used focus on reliability and performance. These devices are fabricated in a process technology node that is reliable and not prone to errors. Further, these devices have strict EMC (ElectroMagnetic Compatibility) requirements and must not radiate significant energy. Implantable devices that run on a battery must have a low power consumption to prolong the life of the device. The most important factor is to ensure that the user is not harmed in the case of a hardware failure.
Are there any materials that are prohibited?
In general, any material that can cause harm to the patient is prohibited. If controlled materials are absolutely needed, such as radioactive materials for treatment, strict conditions are placed on the handling and usage. Materials that are toxic or perishable are avoided. Implantable devices such as pacemakers or heart valves must be built with materials that are bio-compatible, long lasting and non-toxic.
How is the software for medical devices written?
Software is an important part of medical devices. General purpose operating systems such as windows and linux that are found in our home computers are not used in medical devices. Custom built RTOS (Real Time Operating Systems) software is used for these critical applications. The software is written to provide robustness and reliability. If there is a malfunction in a part of the software, the system is capable of recovering from the fault without causing malfunction in other areas.