Purpose To introduce a quantitative tool that enables rapid forecasting of T1 and T2 parameter map errors due to normal and aliasing noise as a function of the MR fingerprinting (MRF) sequence, which can be used in sequence optimization. Theory and Methods The variances of normal noise and aliasing artifacts in the collected signal are related to the variances in T1 and T2 maps through derived quality factors. This analytical result is tested against the results of a Monte‐Carlo approach for analyzing MRF sequence encoding capability in the presence of aliasing noise, and verified with phantom experiments at 3 T. To further show the utility of our approach, our quality factors are used to find efficient MRF sequences for fewer repetitions. Results Experimental results verify the ability of our quality factors to rapidly assess the efficiency of an MRF sequence in the presence of both normal and aliasing noise. Quality factor assessment of MRF sequences is in agreement with the results of a Monte‐Carlo approach. Analysis of MRF parameter map errors from phantom experiments is consistent with the derived quality factors, with T1 (T2) data yielding goodness of fit R2 ≥ 0.92 (0.80). In phantom and in vivo experiments, the efficient pulse sequence, determined through quality factor maximization, led to comparable or improved accuracy and precision relative to a longer sequence, demonstrating quality factor utility in MRF sequence design. Conclusion The here introduced quality factor framework allows for rapid analysis and optimization of MRF sequence design through T1 and T2 error forecasting.
Coaxial cables commonly used to connect radio-frequency (RF) coil arrays with the control console of an MRI scanner are susceptible to electromagnetic coupling. As the number of RF channels increases, such coupling could result in severe heating and pose a safety concern. Non-conductive transmission solutions based on fiber-optic cables are considered to be one of the alternatives but are limited by the high dynamic range (>80 dB) of typical MRI signals. A new digital fiber-optic transmission system based on delta–sigma modulation (DSM) is developed to address this problem. A DSM-based optical link is prototyped using off-the-shelf components and bench-tested at different signal oversampling rates (OSRs). An end-to-end dynamic range (DR) of 81 dB, which is sufficient for typical MRI signals, is obtained over a bandwidth of 200 kHz, which corresponds to OSR = 50. A fully integrated custom fourth-order continuous-time DSM is designed in 180 nm CMOS technology to enable transmission of full-bandwidth MRI signals (up to 1 MHz) with an adequate DR. Initial electrical test results from this custom chip are also presented.
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