Performance evaluation of whole‐body NMR scanner antenna systems

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Abstract
Whole‐body NMR imaging antennas (probes) are strongly affected by the inevitable magnetic and controllable dielectric losses. Using a convenient parallelepiped model, the magnetic losses are evaluated. By introducing the “ideal power gain,” the best possible antenna performance is delimited as a function of the frequency and the patient examined. By using a cylindrical model and introducing the “electrostatic quality factor” (EQF), the dielectric loss of any antenna can be estimated. With the help of the wideband field measurer described, a simple experimental arrangement, and the analysis developed, the performance of whole‐body NMR antennas can be compared and/or evaluated. An example is given for the application of this model at 6.4, 21, and 64 MHz for three typical patients.