In this work, the concept of mechanically adjustable MR receiver coil arrays is proposed and implemented for the specific case of human wrist imaging. An eight-channel wrist array for proton MRI at 3 Tesla was constructed and evaluated. The array adjusts to the individual anatomy by a mechanism that fits a configuration of flexible coil elements closely around the wrist. With such adjustability, it is challenging to ensure robust electrical behavior and signal-to-noise (SNR) performance. These requirements are met by preamplifier decoupling and a suitable matching strategy based on pi networks that render the coil responses robust against changes in tuning, loading and mutual coupling. The robustness of the resulting SNR yield was studied by varying the effective coil matching over a wide range in a phantom imaging experiment. While SNR variation of up to 25% was observed at the surface of the phantom the SNR was essentially constant in the critical center region. A second SNR study in wrist phantoms of different sizes confirmed the benefits of bringing the coil elements very close, up to 3 mm, to the individual target volume. These findings were supported by initial in vivo imaging, exploiting high-sensitivity detection for highly resolved structural imaging.
Copyright 2009 Wiley-Liss, Inc.