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|Volume Coil|| |
• View the DATABASE results for 'Volume Coil' (5).
|Bird Cage Coil|| |
|A RF coil, often a transmit receive coil with a number of wires running along the z-direction, arranged to give a cosine current variation around the circumference of the coil, which looks like a bird cage.
The bird cage coil works on a different principle to conventionally tuned local and surround coils in that it behaves like a tuned transmission line with one complete cycle of standing wave around the circumference. The frequency supply is generated by an oscillator, which is modulated to form a shaped pulse by a product detector controlled by the waveform generator. The signal must be amplified to 1000's of watts. This can be done using either solid state electronics, valves or a combination of both.|
The bird cage coil design provides the best field homogeneity of all RF imaging coils.
One advantage is that it is simple to produce an exceedingly uniform B1 radio frequency field over most of the coil's volume, with the result of images with a high degree of uniformity.
A second advantage is that nodes with zero voltage occur 90° away from the driven part of the coil, thus facilitating the introduction of a second signal in quadrature, which produces a circularly polarized radio frequency field.
This type of volume coil is used for brain (head) MRI, or MR imaging of joints, such as the wrist or knees.
See also the related poll result: '3rd party coils are better than the original manufacturer coils'
• View the DATABASE results for 'Bird Cage Coil' (4).
|Crossed Coil|| |
|RF coil pair arranged with their magnetic fields at right angles to each other in such a way as to minimize their mutual magnetic interaction.|
• View the DATABASE results for 'Crossed Coil' (2).
|Helmholtz Pair Coil|| |
|A Helmholtz pair consists of two identical circular magnetic coils that are placed symmetrically one on each side of the experimental area along a common axis, and separated by a distance equal to the radius of the coil. Actually, a slightly larger separation improves the field uniformity. Each coil carries an equal electrical current flowing in the same direction. A cylindrical region extending between the centers of the two coils and approximately 1/5 of their diameter will have a nearly spatially uniform magnetic field.|
In MRI, the Helmholtz pair coils are used as z-gradient coils to produce linear variations in the main magnetic field along the z-axis. Also in use as z-gradient coils are the Maxwell coils (three coils in a slightly more complicated geometry than the Helmholtz configuration). These coils are only occasionally used as RF coils for imaging.
• View the DATABASE results for 'Helmholtz Pair Coil' (2).
|Paired Saddle Coil|| |
• View the DATABASE results for 'Paired Saddle Coil' (2).
|Quadrature Coil|| |
• View the DATABASE results for 'Quadrature Coil' (2).
|Single Turn Solenoid|| |
• View the DATABASE results for 'Single Turn Solenoid' (3).
| [last update: 2018-03-08 05:11:00]|