RESUMO
OBJECTIVE: To evaluate the agreement of three MR elastography (MRE) sequences in patients undergoing liver MRI for clinical care. Methods: A cross-sectional retrospective study was performed with 223 patients referred for liver MRI, including 12 patients with liver iron overload. Data obtained with spin-echo (SE) and gradient-echo (GRE) MRE sequences were compared. Multiple linear regression adjusted for the presence of liver fat was also performed to assess the correlation between fat infiltration and stiffness measurements results. Agreement between two SE sequences was assessed in patients with liver iron overload. Results: We found strong correlation between the GRE sequence and two SE sequences. Spearman's correlation coefficients between the GRE, SE, and SE-EPI MRE sequences in patients with liver R2* <75Hz were 0.74, 0.81, and 0.80. GRE-MRE failed in patients with liver R2* > 75 Hz. In this subgroup, the correlation coefficient between both SE-MRE sequences was 0.97. Liver fat did not interfere with the results. CONCLUSION: In clinical setting, there is a high correlation between the GRE and SE MRE stiffness measurements, independently of the degree of liver fat infiltration measured by PDFF. A strong correlation between SE-MRE sequences is found even in patients with iron overload. Advances in knowledge: Our study addresses liver iron and fat content simultaneously to describing the technical feasibility and correlation between different MRE sequences in consecutive unselected patients refereed for liver MRI. EPI SE-MRE should be considered an optimal alternative to assess liver fibrosis in patients in whom GRE-MRE failures, such as iron-overloaded, in pediatric, elderly, or severely ill populations.
Assuntos
Técnicas de Imagem por Elasticidade/métodos , Hepatopatias/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Meios de Contraste , Estudos Transversais , Estudos de Viabilidade , Feminino , Humanos , Interpretação de Imagem Assistida por Computador , Masculino , Pessoa de Meia-Idade , Estudos RetrospectivosRESUMO
MR image contrast is based on intrinsic tissue properties and specific pulse sequences and parameter adjustments. A growing number of MRI imaging applications are based on diffusion properties of water. To better understand MRI diffusion-weighted imaging, a brief overview of MR physics is presented in this article followed by physics of the evolving techniques of diffusion MR imaging and diffusion tensor imaging.