Miniature Low-Noise High-Quality MRI Preamplifiers Abstract As a start-up high-RF-technology company with an outstanding core of technical personnel, Future Instruments LLC has the mission to be the first industrial group to design, prototype, test, and manufacture new """"""""miniature"""""""" preamplifiers in RoHS compliance for the medical systems industry in MRI. One of the fastest growing clinical applications in this powerful medical imaging modality is the so-called parallel imaging method where multiple receive coils are used in simultaneous signal processing to speed up imaging. The ability to reduce imaging time by a factor of 4 or more without a serious compromise of image quality is very important for patient comfort and picture fidelity. Examples are the reduction of blurring for human anatomies in motion, such as the heart and lung, and the time required for certain scanning procedures where the patients must hold their breath. To take full advantage of highly parallel imaging and the concomitant enhancement of disease diagnostics such as detection of cancer, large numbers of RF coils are required. While as many as 128 receiver-channel coils have been combined in some systems presently under study, most commercial RF coils have no more than 8 channels. Perhaps the biggest challenge in building these complex RF circuits is the size of the preamplifiers to be integrated in each coil. There is no existing commercial preamplifier small enough for the large numbers of channels envisioned. Preamplifiers in MRI are different from other technical areas in the need for low-input impedance (5 Ohms or less), nonmagnetic materials (to reduce image distortion), extremely low-noise figures, and robustness in the 64-300 MHz frequency range. In Future Instruments' mission to develop precisely what is needed for the many-channel RF system, their core competency and that of their collaborators at Case Western Reserve University is perfectly positioned 1) to design and optimize the circuit, printed circuit board, and selection of sourcing components and external prototyping firms, 2) to test a complete list of quality and safety factors including noise figure, stability, low-input impedance and linearity tests using network analyzers, spectrum analyzers and specialized test setups. The extensive criteria for this evaluation have been delineated in preliminary work, and the project target is to determine the performance level of a set of 200 preproduction preamplifiers and reach a decision of whether to go forward with the commercialization process or to revisit the device design stage to address any remaining performance problems. The long-term goal is to become a main supplier of new high-quality low-noise miniature preamplifiers for the MRI hardware industry. ? ? ?
