A method to create an optimum current distribution and homogeneous B1 field for elliptical birdcage coils
✍ Scribed by Shizhe Li; Christopher M. Collins; Bernard J. Dardzinski; Chih-Liang Chin; Michael B. Smith
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 918 KB
- Volume
- 37
- Category
- Article
- ISSN
- 0740-3194
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✦ Synopsis
Abstract
For a birdcage coil with elliptical cross‐section, a sinusoidal current pattern does not provide a homogeneous B~1~ field. A simple theory was developed to create an optimized current distribution for elliptical birdcage coils. This optimized current pattern can create a perfectly homogeneous B~1~ field inside any elliptical shape. To verify the theory, a 16‐element high‐pass elliptical birdcage coil was built inside a circular RF shield. The current was optimized by using the inductance characteristics of the coil components to calculate the endring capacitances. The B~1~ field was theoretically calculated and experimentally mapped for the optimized elliptical birdcage coil and a nonoptimized coil. The results demonstrate that by optimizing the current distribution, a very homogeneous B~1~ field is produced. This method can be directly applied in design and construction of elliptical birdcage coils for imaging of the naturally occurring elliptical cross‐sectional geometries in the human body.