Evaluation of Superparamagnetic Iron Oxide for MR Imaging of Liver Injury : Proton Relaxation Mechanisms and Optimal MR Imaging Parameters





Purpose: To investigate the proton relaxation mechanisms and the optimal MR imaging parameters in superparamagnetic iron oxide (SPIO)-enhanced MR imaging of liver injury.<br> Methods: A liver injury model was created in the rat using carbon tetrachloride. The T<sub>1</sub> and T<sub>2</sub> relaxation effects of SPIO in normal and injured liver were estimated by <i>ex vivo</i> relaxometry. <i>In vivo</i> laser confocal microscopy of the liver was performed to simulate the distribution and clustering of SPIO particles in the hepatic macrophages. SPIO-enhanced MR imaging (1.5T) of normal and diseased rats was performed with variable parameters. The liver specimens were prepared for histopathological examination.<br> Results: Histopathological and laser confocal microscopic findings showed diffuse macrophage distribution but decreased intracellular clustering of SPIO in injured liver. <i>Ex vivo</i> relaxometry showed sustained T<sub>1</sub> and T<sub>2</sub> relaxation effects of SPIO in liver injury. On MR images obtained with moderate echo time (spin echo [SE] 2000/40 and gradient echo [GRE] 130/9.0/60°), injured liver showed significantly lower decrease in signal-to-noise ratio (SNR) than the normal liver, whereas little difference in SNR was found between the normal and injured liver on heavily T<sub>2</sub>-(SE 2000/80) and T<sub>1</sub>-weighted (SE 300/11 and GRE 130/2.0/90°) MR images.<br> Conclusion: Pulse sequences with a moderately long echo time (TE) may be more appropriate than heavily T<sub>1</sub>- or T<sub>2</sub>-weighted images for distinguishing normal and injured liver in SPIO-enhanced MR imaging because of the maintained T<sub>1</sub> and T<sub>2</sub> relaxation effect but decreased T<sub>2</sub>* relaxation effect of SPIO in injured liver.<br>


  • Magnetic resonance in medical sciences : MRMS

    Magnetic resonance in medical sciences : MRMS 5(2), 89-98, 2006-07-10

    Japanese Society for Magnetic Resonance in Medicine

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