Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic
technology that produces physiologic images based on the use of
magnetic and radio frequency (RF) fields. The MRI system uses powerful
magnets to create a magnetic field which forces hydrogen atoms
in the body into a particular alignment (resonance). Radio frequency
energy is then distributed over the patient, which is disrupted by body
tissue. The disruptions correspond to varying return signals which,
when processed, create the image.
The accurate processing of these signals is key to obtaining high
quality images. A key system consideration for the receive channel
is high SNR. The return signals have narrow bandwidths with an IF
location directly dependent on the main magnet s strength. Some
systems use high-speed pipeline ADCs with wideband amplifiers to
directly sample the IF, leaving large headroom for post-processing
gain by a digital down converter or FPGA. Other systems mix the IF to
baseband where lower-speed, higher-resolution SAR and delta-sigma
ADCs can be used.
For controlling the magnetic and RF energy in the MRI, high-resolution,
high-speed DACs are needed. High resolution is required to accurately
define the area of the patient to be scanned. High-speed is necessary
to match the high IFs being generated by the main magnet.
DSPs can be used to provide gradient processor control used for properly
controlling the magnets in the MRI system. A DSP can also take
care of preprocessing the signal before it reaches the image reconstruction
engine.
A wide variety of TI products are available for MRI systems and
equipment manufacturers, including op amps, DSPs, multi-channel
high- and low-speed data converters, clocking distribution, interface,
and power management.
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