How Noise Affects Medical Imaging Equipment and How to Solve It With a Low Noise Power Supply
Electronic equipment of any kind is affected by noise, the fluctuations in the power supply induced by a number of sources. There are many standard solutions, but most are unable to meet the strict standards for medical imaging equipment. Instead, the best solution is the use of a low noise power supply that implements soft switching technology. This reduces these types of noise compared with hard switching.
The constant fluctuations in voltage inherent to AC power sources are called ripple noise. Sensitive medical equipment like X-ray generators requires a drastic reduction in ripple noise for their DC power supplies. Ripple must be reduced to less than one percent going from AC to DC to maintain X-ray beam quality.
Increasing gain might address ripple noise in some applications but isn’t feasible for medical imaging applications. Instead, the most prudent design choice is to use a low noise power supply. This reduces ripple noise below the strict thresholds required.
Subcircuits and even other devices can transmit conducted emissions to other circuits. Medical resonance imagining (MRI) is strongly affected by conducted emissions, which will rapidly degrade image quality.
This presents a significant challenge given the number of circuits present in support and auxiliary equipment in MRI rooms. There are stringent standards on all of these devices, but they still cause interference. Integrating a low noise power supply is the most effective method for eliminating conducted emissions.
The electromagnetic interference of electrical devices in hospitals is one of their most pressing design concerns. Radiated emissions travel without cables, making isolation unviable. MRI is particularly susceptible to radiated emissions, but numerous other imaging technologies are as well.
The complex interplay of multiple devices and components makes designing around radiated emissions practically impossible. There’s no way to consider every interaction and resonance value ahead of time. The only viable solution for radiated emissions is implementing a low noise power supply.
Common-mode noise occurs when there are voltage surges between lines and grounds. They are particularly challenging to address because they can bypass noise filters. This noise isn’t just an issue for imaging quality but can also damage circuits when severe enough.
There are many intermediate solutions for common-mode noise that fail to address the problem fully. These are generally achieved by shortening cable lengths and decreasing loop areas. This just isn’t viable in many cases and can’t match the effectiveness of a low noise power supply.
Avoid Noise and Leakage Current With a Low Noise Power Supply
Hospitals must carefully plan to minimize leakage current for many types of equipment. Leakage current should flow through the ground connection, but issues can lead to short-circuiting and even dangerous shocks. Medical equipment has much stricter standards for leakage current than most other applications.
The risk of leakage current is often increased by the application of certain noise filtering methods. Like most noise mitigation measures, they introduce as many problems as they solve. A low noise power supply prevents all types of noise while reducing leakage current as well.