On quantification errors of and proton density fat fraction mapping in trabecularized bone marrow in the static dephasing regime.

Purpose: To study the effect of field inhomogeneity distributions in trabecularized bone regions on the gradient echo (GRE) signal with short TEs and to characterize quantification errors on and proton density fat fraction (PDFF) maps when using a water-fat model with an exponential decay model at short TEs.

Methods: Field distortions were simulated based on a trabecular bone micro CT dataset. Simulations were performed for different bone volume fractions (BV/TV) and for different bone-fat composition values.

Reduction of vibration-induced signal loss by matching mechanical vibrational states: Application in high b-value diffusion-weighted MRS.

Purpose: Diffusion encoding gradients are known to yield vibrations of the typical clinical MR scanner hardware with a frequency of 20 to 30 Hz, which may lead to signal loss in diffusion-weighted MR measurements. This work proposes to mitigate vibration-induced signal loss by introducing a vibration-matching gradient (VMG) to match vibrational states during the 2 diffusion gradient pulses.

Theory And Methods: A theoretical description of displacements induced by gradient switching was introduced and modeled by a 2-mass-spring-damper system.