Magnetic resonance coil Introduction

The transmitting/receiving Coil (T/R Coil), as its name implies, integrates the transmitting and receiving Coil together, which can both transmit rf pulses and receive RF pulses. The common transmitting/receiving Coil in our daily use has the body Coil embedded inside the aperture of the magnet. It is called q-body coil or QBC coil), head coil (transmitting/receiving coil), and knee coil. This kind of magnetizer coil does not work at the same time, but through the electronic circuit in the transmission and reception of the rapid switch in order to achieve the transmission of radio frequency pulse and the role of receiving signals.

Receiving coils are only used to receive MAGNETIC resonance signals. These coils are common in soft surface coils, body phased coils and some limb coils. In the case of such coils, the task of firing and excitation is entrusted to the body coil, which is installed inside the aperture of the magnet.

If according to the scope of application to classify, according to the scope of use of the coil can be divided into the following five categories, full volume coil, partial volume coil, surface coil, body cavity coil, phased front coil.

Full-volume coil generally refers to the columnar coil that can wrap the whole or a certain position. This kind of coil is mainly used for transmitting RF pulses and receiving MR signals of tissues, such as head coil and body coil. The full volume coil of the head is generally called the cage coil, which has two functions: transmitting/receiving. Because of the large space, this coil can be used for head positioning and gamma knife positioning.

Partial volume coil is formed by the combination of full volume coil and surface coil. This kind of coil generally has two or more than two imaging planes.

Surface coil, receiving coil can be placed on the surface of the imaging body. The surface coils are of various shapes, common flat rectangles and circles. Because the coil is close to the imaging site, it has a high degree of freedom when the coil is placed, and is generally used in superficial tissues or organs. Due to the single number of surface coil channels at the beginning, parallel acquisition technology cannot be used to accelerate scanning. In order to improve the function of surface coil and expand its application range, some new surface coils, such as phased front coil, have been developed.

A phased front coil is a coil array composed of more than two coil units, which are connected to each other to form a larger imaging range. The coil units can be separated from each other, and each coil unit can be visually used as an independent coil. Since each coil unit can transmit signal through a single channel and then constitute a multi-channel transmission, the parallel acquisition technology is compatible in imaging, which greatly improves the efficiency of scanning. The acceleration multiple of parallel acquisition is related to the number of coil channels in this direction. If the number of coil channels in a certain direction is 5, the limit of parallel acquisition factor in this direction is 5.