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Correct Answer: they are receiving coils only.
multichannel coils, commonly utilized in mri systems, are specifically designed to act as receiving coils rather than transmitting ones. this means that their primary function is to receive the magnetic resonance signal emitted by the body's tissues, rather than to generate the initial magnetic field required for mri imaging. the specialized structure of multichannel coils allows them to capture signals with higher sensitivity and from different spatial orientations, significantly enhancing image quality by providing clearer and more detailed images.
the term "multichannel" refers to the coil having multiple individual coil elements or channels, each capable of independently receiving mri signals. this configuration enables parallel imaging techniques, which can accelerate the imaging process and improve the signal-to-noise ratio. by using an array of smaller coils or elements, each tuned to a specific part of the anatomy, multichannel coils can cover larger areas or provide more focused, high-resolution imaging of smaller regions.
it is important to note that while multichannel coils are predominantly used as receivers, the mri system also includes separate coils responsible for transmitting the radiofrequency (rf) pulses that excite the hydrogen nuclei in the body's tissues. these transmitting coils are typically designed differently from receiving coils, often being larger and capable of encompassing a larger area of the body to create a uniform excitation field.
contrary to what might be suggested, multichannel coils are not limited to head imaging; they can be used for various parts of the body, including extremities, the spine, the abdominal area, and the chest, among others. their usage is determined by the specific diagnostic requirements and the part of the body being examined. the flexibility and enhanced capability of multichannel coils make them a crucial component in modern mri technology, facilitating faster and more precise diagnostics.
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