MRI

The magnetic field homogeneity – the measure of field uniformity within the area of the magnet – is a very important parameter, to generate distortion free images and with a maximum signal-to-noise ratio. As the MRI signal is relatively weak, any small external potential RF interference could degrade the image quality. In addition to the shielding of the examination room or the MRI scanner as such, any power supply used inside the examination room requires minimal RF emissions.    

Advanced Energy offers the broadest medical power portfolio to meet all the system power needs for this application. AE's recognized cutting-edge technologies offer highly reliable, precision power as well as modified or customized solutions to meet the necessary requirements.
 

Although the majority of MRI systems use magnetic field strengths of 1,5 and 3 tesla, there are two clearly visible trends from a hardware and economic perspective:

The first involves going to higher field strengths (5T, 7T and even higher) mainly for very dedicated clinical questions and in the field of neurology. At the same time there’s a shift from superconducting magnets, cooled with hundreds of litres of liquid Helium – which is a scarce and limited resource – towards sealed magnets which only need a few litres of liquid Helium. Another emerging alternative technology related to the higher field strength is high temperature superconductivity (HTS), which does not need any Helium at all.   

The other direction is low-field MRI systems, around 0.5T or even lower. These low field strengths still enable a good enough clinical diagnostic image quality, at the expense of a slightly longer examination duration. These low fields are comparably easily achievable with permanent magnets or electromagnets, which avoid the need for liquid Helium and therefore make MRI systems more affordable and accessible to a big part of the world’s population and offers the potential of MRI systems becoming “portable”.  
 

Since MRI systems are complex and require multiple power supplies, there’s no simple answer and it ultimately depends on where the power supply is used in the system. For example, the PSU for a fixed patient support is typically in a range starting from 0.6 to 3 kW, with a 12 or 24 V output, shielded and screwed to the floor. Whereas for an ultra-low field, portable mobile MRI systems, a configurable medical PSU like the CoolX18M with 1.8 kW of power, a very compact size, high efficiency and up to 6 different configurable outputs could be more useful. 

Another example would be the power needs for the external coils (for example, head, knee or ankle coil). To prevent any unwanted coupling and transfer which would mean loss of energy between the transmitting and the receiving coil and to protect the preamplifier of the receiving coil, these external coils are detuned during the RF excitation. The detuning could be achieved actively via a resonant circuit. In this case a pin diode and a forward DC bias is applied and the parallel resonant circuit inserts a high impedance and therefore blocks the current flow during the RF excitation. Depending on the coil size as well as the frequency, there can be more than one clocking network used per coil. 

The UltraVolt high Voltage DC-DC range offers compact, reliable solutions for the pin diode switching providing tightly regulated output power and featuring fast rise-times. They’re suitable for high-energy pulsers, amplifiers, and discharge devices with large capacitance, fast repetition rates, and high current loads.

MRI is a non-invasive imaging technology, which does not need any ionizing radiation, but just uses the nature of some specific nuclei inside the body to absorb precise radio frequency energy. The MRI image represents the relative response of these nuclei measured by analyzing density distribution of the observed nuclei. 
The image contrast in MRI is strongly influenced by other physical factors, including the re-emittance of the absorbed radio-frequency signal and fluid flow inside the body. Therefore, the image information content of an MRI image is very different to an X-ray or Ultrasound image. MRI is not only used for diagnostic imaging but also for functional imaging. 
 

Advanced Energy has partnered with the world’s leading medical device companies to power the future of MRI.
Our proven and highly reliable medical power supply solutions can help minimize development time and reduce risk with proven technology blocks.  Our solutions have allowed our customers to quickly go to market with power platforms that keep them ahead of the curve.  

AE has the broadest medical power portfolio, highest performance and unsurpassed quality with best-in-class QMS (Quality Management System). Our dedicated medical engineering and customer support teams have extensive application knowledge and regulatory expertise with deep system safety knowledge. We can also offer standard off the shelf products or full custom solutions based on the application requirements.