Your cardiologist hooks you up to an ECG machine with the intent of figuring out what’s going on with your heart. You had hoped that steps have been taken to minimize noise so as to guarantee the best possible signal. Why? Because noise interference can make it difficult for your doctor to figure out what’s going on. Noise in the arena of medical diagnostics signal processing can be downright bad for your health.
All sorts of modern diagnostic equipment are subject to noise. At Rock West Solutions in Southern California, one of the things they do is work with partners to improve signal processing by eliminating noise. Rock West engineers define noise as any kind of signal that interferes with the ability to receive and understand the right information.
In the world of medical diagnostics, noise can come from a variety of different sources. It is up to companies like Rock West Solutions to devise methods to eliminate it where possible and reduce it where it cannot be completely eliminated. To illustrate the point, let us take a look at common sources of noise encountered when using an ECG machine.
Also known as ‘baseline wander’, low-frequency noise is noise generated by the ECG machine itself. The noise is the result of offset voltages, respiration, and patient movement. The main problem with low-frequency noise is that it limits the use of instrumentation amplification. The more amplification introduced to the testing environment, the more troublesome low-frequency noise becomes.
Most biological noise is unavoidable in medical diagnostics. After all, you are dealing with human bodies that make all sorts of noise without end. Where the ECG is concerned, a common source of this noise is muscle movement. Muscles generate electrical signals as they expand and contract. And guess what? The heart is a muscle. The ECG picks up signals from the heart, but it also picks up signals from arms, shoulders and even the muscles surrounding the rib cage.
Noise from Power Lines
Given that ECG machines run on electricity, doctors and technicians also have to deal with power line noise. This noise exists generally in the range of 50Hz to 60Hz. It is present throughout a medical facility regardless of any diagnostics that might be taking place. What’s the solution? Implementing software filters that target those specified frequencies.
Other Sources of Noise
Finally, there are a variety of other sources of noise that must be analyzed on a case-by-case basis. For example, a patient undergoing an ECG test may have an implanted pacemaker generating high-frequency noise via its operation. Additional noise might be generated by electrical equipment in the same room or, in the case of surgery, various pieces of monitoring equipment. Sources of noise have to be isolated in order to be properly dealt with.
How Noise Is Eliminated
Improving signal processing by removing noise is critical to proper diagnostics. However, doing so is easier said than done. Technicians have two ways of attacking the problem: mechanical solutions and software solutions.
Mechanical solutions would involve things like insulating leads, isolating front-end ground electronics, shielding diagnostic equipment, and even changing the way a piece of diagnostic equipment is attached to or directed at the patient. Mechanical solutions are effective but unavoidably limited.
Software solutions generally revolve around using a series of filters that target specific frequencies. The software arena is where the heavy lifting of signal processing is taking place in the modern era. The more advanced software becomes, the better it gets at eliminating noise from multiple sources, thus resulting in better and more accurate diagnostics.