Low Noise Power Supply
Mitigating signal noise in MRI scanners with a low noise power supply
Magnetic resonance imaging (MRI) is a modern imaging technique that has revolutionized research, diagnosis, and other aspects of medicine since its inception.
However, the nature of the MRI scanner itself raises numerous engineering and design problems, particularly when it comes to electromagnetic interference. In general, the most effective means for controlling this interference is through the use of a low noise power supply.
Signal-to-Noise Ratio in MRI Scanners
There are many metrics for evaluating the performance of an MRI scanner, and the signal-to-noise ratio is among the most important. The stream of information from the scanner consists of two components. The signal itself is the actual information derived from the scan, and the noise is a result of interference.
When the signal-to-noise ratio is too low, useful information cannot be obtained from the scan. It affects the resolution of the image generated by the MRI scanner, with noise potentially obscuring vital information.
In order to mitigate the effect of noise to some degree, scans can be performed for longer periods of time. This, however, consumes hospital resources and takes up the time of numerous skilled professionals. Instead, a low noise power supply can mitigate the issue at the source.
Increasing Magnetic Field Strength to Mitigate Signal-to-Noise Ratio
Another trend in the design and implementation of MRI scanners has been the increase in the power of the static magnetic fields used. The majority of MRI scanners use field strengths of 1.5 T, with a number of models available in 3 T as well.
However, in order to improve resolution without succumbing to noise degrading the signal, many hospitals are beginning to use 7 T scanners. Some special applications are using upwards of 10 T, approaching ten times the baseline strength.
These machines are more expensive to design, produce, and operate. Effective mitigation of noise as the source could be better achieved by implementing a low noise power supply.
Sources of Noise in MRI Signals
MRI scanners are among the most sensitive machines in common use. They are affected by even minute interference. This includes both conducted and radiated emissions from other circuits within the vicinity. MRI rooms within hospitals are heavily shielded, but that doesn’t address all sources of noise.
The machines can still be affected by ripple noise from the power supply. These fluctuations arise from the transition from the AC power source to a DC signal. Common-mode noise also presents a design challenge for MRI machines, creating a voltage between lines and grounds that can’t be addressed with conventional noise filters. In most cases, a low noise power supply is the only effective means to face these design challenges.
Low Noise Power Supply to Improve MRI Performance
A low noise power supply protects the sensitive MRI signal from ripple noise, conducted and radiated emissions, common-mode noise, and current leakage. This enables the scanner to deliver high-resolution images without resorting to excessive magnetic field strengths or longer scan times.
One major source of noise is that hard switching that produces ripple noise when converting power from AC to DC.
A low noise power supply that integrates soft switching technology can buffers this pattern, delivering the highest quality signal for these essential medical devices.
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