Phased array coil

Last revised by Matt A. Morgan on 22 May 2021

Phased array coils are an example of a receive-only radiofrequency coil system which receives the radiofrequency signal in MRI. It involves the collection of multiple surface coils into a larger array whose individual signals are combined to create one image. As signal coils detect signal based on proximity, they have good signal reception over only a small area. The combination of multiple surface coils into an array allows for a good signal-to-noise ratio over a larger field of view. An example of this is in spine imaging, where single surface coils might provide quite good signal for the adjacent small section of vertebra (which is close to the body surface) but are too small to image the entire longitudinal length of the spine. By aligning multiple surface coils together, the entire spine can be imaged in good quality.

Early array coils came in the form of switchable arrays, with 3 coil segments being positioned and switchable across the cervical, thoracic and lumbar spinal segments. Modern array coils (e.g. phased arrays) combine a larger number of smaller coils into separate receiver chains. Phased array coils overlap and have low input impedance preamplifiers to control coupling between neighboring coils. This has a synergistic effect resulting in a significantly greater signal-to-noise ratio than for a single coil.

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