Purpose: To quantify changes in signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), specific absorption rate (SAR), RF power deposition, and imaging time in cardiac magnetic resonance imaging with and without the application of parallel imaging at 1.5 T and 3.0 T. Materials and Methods:Phantom and volunteer data were acquired at 1.5 T and 3.0 T with and without parallel imaging.Results: Doubling field strength increased phantom SNR by a factor of 1.83. In volunteer data, SNR and CNR values increased by factors of 1.86 and 1.35, respectively. Parallel imaging (reduction factor ϭ 2) decreased phantom SNR by a factor of 1.84 and 2.07 when compared to the full acquisition at 1.5 T and 3.0 T, respectively. In volunteers, SNR and CNR decreased by factors of 2.65 and 2.05 at 1.5 T and 1.99 and 1.75 at 3.0 T, respectively. Doubling the field strength produces a nine-fold increase in SAR (0.0751 to 0.674 W/kg). Parallel imaging reduced the total RF power deposition by a factor of two at both field strengths. Conclusions:Parallel imaging decreases total scan time at the expense of SNR and CNR. These losses are compensated at higher field strengths. Parallel imaging is effective at reducing total power deposition by reducing total scan time.

Purpose: To improve preamplifier decoupling in a quadrature phased-array coil using a new quadrature combiner configuration. Materials and Methods:A commercial six-element quadrature cervical-thoracic-lumbar (CTL) coil was used on a 1.5 T GE Signa Lx Scanner. The new combiner configuration is designed based on the fact that when one compares the amount of flux linkage of two loops with butterfly elements separated by the same distance, the loop elements have much higher coupling than the butterfly elements. Results:The results are demonstrated using an imagingbased element coupling measurement method. The new quadrature combiner configuration has introduced an approximately -8dB improvement in preamplifier decoupling. Conclusion:One-dimensional quadrature phased arrays can be built even if the preamplifier is not integrated in the coil. If the combiner is placed between the coil and the preamplifiers, the butterflies should be on the high impedance side of the quadrature combiner. The loops should see the low input impedance of the preamplifiers.