# Gradient and rf coil issues in magnetic resonance imaging

## Abstract

Techniques are presented for new analysis of coils in magnetic resonance imaging that should lead to faster and more accurate pictures of humans. Insertable planar, cylindrical or elliptical gradient coils offer the potential for significant performance increases in magnetic resonance imaging. Using variational methods to minimize inductance and thereby optimize switching speeds, the authors has analyzed coils with these three geometries. In the interest of improving image quality by reducing eddy current artifacts, the same methods are used to design a set of self-shielded gradient coils. In the cylindrical and planar cases, scale models of the new coils have been constructed and tested. In the elliptical case, the theory and mathematics necessary to design elliptic gradient coils is presented. This includes the development of a Green function expansion in elliptic cylinder coordinates. The expansion is in terms of cosine-elliptic and Mathieu functions. Improvements in the field uniformity of rf coils results in improved image quality in magnetic resonance imaging. Using a waveguide structure instead of traditional coil designs leads to the possibility of generating more uniform fields at higher frequencies. A new conformal transformation is developed in order to analyze TEM excitations of microstrips and coupled microstrips with circular andmore »

- Authors:

- Publication Date:

- Research Org.:
- Case Western Reserve Univ., Cleveland, OH (United States)

- OSTI Identifier:
- 5231615

- Resource Type:
- Miscellaneous

- Resource Relation:
- Other Information: Thesis (Ph.D.)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 47 OTHER INSTRUMENTATION; MAGNET COILS; DESIGN; MAGNETIC RESONANCE; MEASURING INSTRUMENTS; EDDY CURRENTS; IMAGES; MAGNETIC FIELDS; MATHEMATICS; OPTIMIZATION; PERFORMANCE; VARIATIONAL METHODS; WAVEGUIDES; CURRENTS; ELECTRIC COILS; ELECTRIC CURRENTS; ELECTRICAL EQUIPMENT; EQUIPMENT; RESONANCE; 440800* - Miscellaneous Instrumentation- (1990-)

### Citation Formats

```
Martens, M A.
```*Gradient and rf coil issues in magnetic resonance imaging*. United States: N. p., 1991.
Web.

```
Martens, M A.
```*Gradient and rf coil issues in magnetic resonance imaging*. United States.

```
Martens, M A. Tue .
"Gradient and rf coil issues in magnetic resonance imaging". United States.
```

```
@article{osti_5231615,
```

title = {Gradient and rf coil issues in magnetic resonance imaging},

author = {Martens, M A},

abstractNote = {Techniques are presented for new analysis of coils in magnetic resonance imaging that should lead to faster and more accurate pictures of humans. Insertable planar, cylindrical or elliptical gradient coils offer the potential for significant performance increases in magnetic resonance imaging. Using variational methods to minimize inductance and thereby optimize switching speeds, the authors has analyzed coils with these three geometries. In the interest of improving image quality by reducing eddy current artifacts, the same methods are used to design a set of self-shielded gradient coils. In the cylindrical and planar cases, scale models of the new coils have been constructed and tested. In the elliptical case, the theory and mathematics necessary to design elliptic gradient coils is presented. This includes the development of a Green function expansion in elliptic cylinder coordinates. The expansion is in terms of cosine-elliptic and Mathieu functions. Improvements in the field uniformity of rf coils results in improved image quality in magnetic resonance imaging. Using a waveguide structure instead of traditional coil designs leads to the possibility of generating more uniform fields at higher frequencies. A new conformal transformation is developed in order to analyze TEM excitations of microstrips and coupled microstrips with circular and elliptical cross-sections. This new transformation is derived by expressing a Schwarz-Christoffel transformation in terms of elliptic integrals of the first and third kind. Exact solutions for the complex potential of these geometries are presented for the first time. The uniformity of the magnetic field inside slotted tube transmission lines is examined using the newly developed conformal mapping technique.},

doi = {},

journal = {},

number = ,

volume = ,

place = {United States},

year = {1991},

month = {1}

}