Abstract
A quantitative diagnosis using magnetic resonance imaging (MRI) can be disturbed by radiofrequency (RF) field inhomogeneity induced by the conductive implants. This inhomogeneity causes a local decrease of the signal intensity around the conductor, resulting in a deterioration of the accurate quantification. In a previous study, we developed an MRI imaging method using a two-dimensional selective excitation pulse (2D pulse) to mitigate signal inhomogeneity induced by metallic implants. In this paper, the effect of 2D pulse was evaluated quantitatively by numerical simulation and MRI experiments. We introduced two factors for evaluation, spatial resolution and maximum compensation factor. Numerical simulations were performed with two groups. One group was composed of four models with different signal loss width, to evaluate the spatial resolution of the 2D pulse. The other group is also composed of four models with different amounts of signal loss for evaluating maximum compensation factor. In MRI experiments, we prepared phantoms containing conductors, which have different electrical conductivities related with the amounts of signal intensity decrease. The recovery of signal intensity was observed by 2D pulses, in both numerical simulations and experiments.
Highlights
Radiofrequency (RF) field is applied to an object in magnetic resonance imaging (MRI) acquisition
We reported a new MRI imaging method using a two-dimensional selective excitation pulse (2D pulse) for mitigating the signal inhomogeneity induced by metallic implants.[9]
We evaluated the performance of a 2D pulse compensating the decreased MRI signal intensity due to conductors
Summary
Radiofrequency (RF) field is applied to an object in magnetic resonance imaging (MRI) acquisition. Some of them were focused on reducing eddy current effects on MRI images by applying a low frequency field.[5,6] Other approaches using an adaptive pulse sequence, such as view-angle tilting,[7] and multi-acquisition with variable resonance image combination[8] have been reported They still have challenges, such as low spatial resolution[5,6] and acquisition of multiple images.[7,8] We reported a new MRI imaging method using a two-dimensional selective excitation pulse (2D pulse) for mitigating the signal inhomogeneity induced by metallic implants.[9] the performance of this method was not evaluated quantitatively in the previous work.
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