MRI is unique in its ability to move beyond anatomical imaging, as it allows visualizing metabolic functions and chemical processes via spectroscopic imaging, and offers advanced methods to measure physiologic properties such as tissue oxygenation, flow, diffusion, and perfusion. MRI offers excellent soft‐tissue contrast at high spatial and temporal resolutions, with the ability to have a 3D tomographic representation of the subject of interest. Starting with the initial studies by Lauterbur 1 and Mansfield and Grannell, 2 magnetic resonance imaging (MRI) has seen a tremendous growth as a diagnostic and research imaging modality. This review looks at the fundamental principles of an MRI RF coil from the perspective of clinicians and MR technicians and summarizes the current advances and developments in technology. Transmit and receive functionality can be combined in one RF Coil (Tx/Rx Coils). This signal is “picked‐up” by an antenna and preamplified, usually mixed down to a lower frequency, digitized, and processed by a computer to finally reconstruct an image or a spectrum. Due to the precession around the static main magnetic field, the magnetic flux in the receive RF Coil (ī 1 −) changes, which generates a current I. Transmit RF Coils emit magnetic field pulses (ī 1 +) to rotate the net magnetization away from its alignment with the main magnetic field (B 0), resulting in a transverse precessing magnetization. RF coils are the “antennas” of the MRI system and have two functions: first, to excite the magnetization by broadcasting the RF power (Tx‐Coil) and second to receive the signal from the excited spins (Rx‐Coil). Advances in RF hardware have resulted in a variety of designs optimized for specific clinical applications. They directly impact the spatial and temporal resolution, sensitivity, and uniformity in MRI. Radiofrequency (RF) coils are an essential MRI hardware component.
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