Precision electrical adjustment of quadrature coil isolation
US4879516A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 26, 1988 |
| Grant date | Nov 7, 1989 |
| Priority date | — |
| Expiry date | May 26, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R33/3628
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A magnetic resonance imager includes a quadrature coil assembly (20) for transmitting radio frequency signals into and receiving magnetic resonance signal from an examination region. The quadrature coils assembly includes a first coil (22) and a second coil (24). A shunt path (32, 64, 74, 84, 94, 98, 100, 112, 114, 122) provides a current path by shunting at least a portion of one of the coils. A variable impedance (34, 66, 76, 86, 96, 110, 120) adjusts the amount of current flow through the shunt path and the current flow through the bypassed coil portion. More specifically, adjusting the impedance changes the magnetization vector generated by the coil assembly in a transmit mode and adjusts their relative isolation in a receive mode. The quadrature coils are mounted such that they are offset by about, but not quite, 90.degree.. The variable impedance is adjusted until the offset is brought precisely to 90.degree.. In this manner, the quadrature coils are adjusted electronically after assembly to insure the precision of their isolation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.