| 摘要 |
<p>A detunable coil assembly for an NMR imaging system has a cylindrical cage coil (12) comprising two spaced-apart conductive end loops (15,16) with a plurality of conductive segments (21-28) extending between the loops. A grounded shield (14) is disposed around the cage coil. Each of the end loops is coupled to the shield by four switchable impedance circuits (41-48) that are equidistantly spaced around the loop. Each impedance means includes a coaxial cable (50) having a length equal to one-quarter the wavelength of the resonant frequency of the cage coil with the central conductor coupled at one end (51) to the cage coil and the other conductor connected to the shield. A PIN diode (53) terminates the other end (52) of the coaxial cable. A voltage supply (55) provides potentials for alternately forward and reverse biasing the PIN diode.</p> |
