Indirect H-[C] MRS of the human brain at 7 T using a C-birdcage coil and eight transmit-receive H-dipole antennas with a 32-channel H-receive array.

The neuronal tricarboxylic acid and glutamate/glutamine (Glu/Gln) cycles play important roles in brain function. These processes can be measured in vivo using dynamic H-[C] MRS during administration of C-labeled glucose. Proton-observed carbon-edited (POCE) MRS enhances the signal-to-noise ratio (SNR) compared with direct C-MRS.

An RF coil design to enable quintuple nuclear whole-brain MRI.

Purpose: To bring metabolic imaging based on multi-NMR toward practical use from the RF hardware perspective.

Methods: A highly integrated RF coil is designed for whole-brain MRI and MRS targeted to five nuclear species: H, F, P, Na, and C. Dipole antennas and closely loaded local receiver loops are combined in this setup.

Tier-based formalism for safety assessment of custom-built radio-frequency transmit coils.

The purpose of this work is to propose a tier-based formalism for safety assessment of custom-built radio-frequency (RF) coils that balances validation effort with the effort put in determinating the safety factor. The formalism has three tier levels. Higher tiers require increased effort when validating electromagnetic simulation results but allow for less conservative safety factors.

Real-time assessment of potential peak local specific absorption rate value without phase monitoring: Trigonometric maximization method for worst-case local specific absorption rate determination.

Purpose: Multi-transmit MRI systems are typically equipped with dedicated hardware to sample the reflected/lost power in the transmit channels. After extensive calibration, the amplitude and phase of the signal at the feed of each array element can be accurately determined. However, determining the phase is more difficult and monitoring errors can lead to a hazardous peak local specific absorption rate (pSAR ) underestimation.

Conditional safety margins for less conservative peak local SAR assessment: A probabilistic approach.

Purpose: The introduction of a linear safety factor to address peak local specific absorption rate (pSAR ) uncertainties (eg, intersubject variation, modeling inaccuracies) bears one considerable drawback: It often results in over-conservative scanning constraints. We present a more efficient approach to define a variable safety margin based on the conditional probability density function of the effectively obtained pSAR value, given the estimated pSAR value.

Methods: The conditional probability density function can be estimated from previously simulated data.