RESUMO
PURPOSE: To demonstrate improved frequency selective fat suppression in MRI using a magnetic susceptibility matching foam by reducing B0 inhomogeneities induced within the body by air-tissue interfaces. MATERIALS AND METHODS: Flexible pyrolytic graphite (PG) composite foam was tailored to match the magnetic susceptibility of human tissue and was shaped to surround the cervical spine region. Field maps and frequency selective fat suppressed T1 -weighted FLASH images were acquired at 3 Tesla in both phantoms and six healthy necks. RESULTS: B0 field uniformity was shimmed to a target critical threshold of 1 ppm for fat suppression. The percentage of voxels in the phantom that did not achieve the critical threshold was reduced from 64% without the PG foam to only 1% with the foam. A similar decrease from 16% to 2% was observed in the in vivo region of interest. CONCLUSION: PG foam improved B0 field uniformity by moving air-tissue field gradients outside of the neck where they cannot cause MRI artifacts. The PG foams consistently mitigated signal dropout, improved overall SNR, and enabled more robust frequency selective fat suppression.
Assuntos
Tecido Adiposo , Artefatos , Carbono , Aumento da Imagem/métodos , Imageamento por Ressonância Magnética/métodos , Pescoço/anatomia & histologia , Adulto , Análise de Variância , Feminino , Humanos , Masculino , Imagens de Fantasmas , Valores de Referência , Adulto JovemRESUMO
PURPOSE: To evaluate a novel soft, lightweight cushion that can match the magnetic susceptibility of human tissue. The magnetic susceptibility difference between air and tissue produces field inhomogeneities in the B(0) field, which leads to susceptibility artifacts in magnetic resonance imaging (MRI) studies. MATERIALS AND METHODS: Pyrolytic graphite (PG) microparticles were uniformly embedded into a foam cushion to reduce or eliminate field inhomogeneities at accessible air and tissue interfaces. 3T MR images and field maps of an air/water/PG foam phantom were acquired. Q measurements on a 4T tuned head coil and pulse sequence heating tests at 3T were also performed. RESULTS: The PG foam improved susceptibility matching, reduced the field perturbations in phantoms, does not heat, and is nonconductive. CONCLUSION: The susceptibility matched PG foam is lightweight, safe for patient use, adds no noise or MRI artifacts, is compatible with radiofrequency coil arrays, and improves B(0) homogeneity, which enables more robust MR studies.