Gradient coils

The compact MRI system has an advantage for rf coil design because solenoid coils can be used in most applications. The solenoid coil has about three times better SNR than that of the saddle-shaped coil (14). Even if the saddle-shaped or birdcage coil is used in the quadrature mode, the solenoid coil will still have better SNR because an SNR gain of only about 1.4 times is obtained in that mode. 

---

The probe, situated between the field gradient coils in the bore of the magnet, consists of a cylindrical metal tube that transmits the pulses to the... 

Small signal unit Magnet Gradient coil RF coil... 

Figure 2.2.7 shows planar gradient coils designed and manufactured using the... 

Fig. 2.2.7 Planar gradient coils designed and manufactured using the target field method and genetic algorithm [18]. Left Cx or Gy coil. Middle Gz coil. Right three axis gradient coil set made by accumulating three flat gradient coils.

R. Turner 1993, (Gradient coil design a review of methods), Magn. Reson. Imag. 11, 903-920. 

S. Handa, F. Okada, K. Kose 2005, (Effects of Magnetic Circuits on Magnetic Field Gradients Produced by Planar Gradient Coils, Proc 13th ISMRM, 851). 

Fig. 2.6.10 Specialized experimental set-up for microfluidic flow dispersion measurements. Fluid is supplied from the top, flows via a capillary through the microfluidic device to be profiled and exits at the bottom. The whole apparatus is inserted into the bore of a superconducting magnet. Spatial information is encoded by MRI techniques, using rf and imaging gradient coils that surround the microfluidic device. They are symbolized by the hollow cylinder in the figure. After the fluid has exited the device, it is led through a capillary to a microcoil, which is used to read the encoded information in a time-resolved manner. The flow rate is controlled by a laboratory-built flow controller at the outlet [59, 60].

Probe Region of the spectrometer where the sample is held during the acquisition of a spectrum. It contains the transmitter and receiver coils and gradient coils (if fitted). 

An ESRI system can be built with small modifications of commercial spectrometers by, for example, gradient coils fixed on the poles of the spectrometer magnet, regulated direct current (DC) power supplies, and required computer connections [40,53,55]. Gradients can be applied in the three spatial dimensions, and a spectral dimension can be added by the method of stepped gradients. The spectral dimension is important when the spatial variation of ESR line shapes (as a function of sample depth) is of interest this situation will be described below, in the ESRI studies of heterophasic polymers. In most systems, the software for image reconstruction in ESRI experiments must be developed in-house. 

---