Tatsuhiko Matsushita MS, Presenter: Nothing to Disclose

Tosiaki Miyati PhD, Abstract Co-Author: Nothing to Disclose

Norio Hayashi PhD, Abstract Co-Author: Nothing to Disclose

Naoki Ohno MS, Abstract Co-Author: Nothing to Disclose

Akihiro Kitanaka, Abstract Co-Author: Nothing to Disclose

Shigeki Ohtake MD, Abstract Co-Author: Nothing to Disclose

Takashi Hamaguchi MS, Abstract Co-Author: Nothing to Disclose

Two kinds of useful methods, i.e. R2* (iron content) analysis and fat fraction analysis, have been reported for evaluating the liver status using magnetic resonance imaging (MRI). Those methods are only used on a high-field MRI, but more than 15 % of MRI systems in the world are a low-field. We developed a method for analyzing R2*, and fat fraction of the liver tissue simultaneously with a low-field MRI system using modulus and real multiple gradient-echo (MRM-GRE) sequence to evaluate the liver metabolism.

On a 0.4-T open MRI system, modulus images of four gradient-echoes (TE of 4.4-35.6 msec) were obtained by MRM-GRE sequence at a time. A real part of the first opposed-phase echo image was also reconstructed to differentiate below and above the 50 percent fat fraction. The fat fraction and R2* were obtained from the parameters of a formula theoretically fitted with each echo signal. R2* and fat fraction were measured with MRM-GRE in the phantom (changing fat and iron content, respectively) and the liver in normal volunteers and patients with fatty liver. Fat fractions with MRM-GRE were compared with those using conventional double-GRE Dixon and MR Spectroscopy.

Fat fraction using MRM-GRE of the phantom was in good agreement with the actual value, however, fat fraction using double-GRE Dixon was either underestimated (< 50 %) or overestimated (> 50 %), R2* value of the phantom showed a strongly positive correlation with the actual iron content. MRI-derived fat fraction in fatty liver agreed with fat fraction using MR spectroscopy for human study. These results show that the MRM-GRE enables to differentiate the causes of signal reduction whether increasing R2*, i.e., increasing iron content (hemochromatosis) or increasing fat fraction (fatty liver).

The MRM-GRE method makes it possible to simply and accurately assess the fat content and the iron content with the low-field MRI system. The ability to obtain both of them at the same time allows one to optimize the advantages of each and thereby obtain more information about the liver metabolism.

With the low-field MRI system, the MRM-GRE method makes it possible to simply analyze regional physical functions in greater detail, i.e., diseases such as fatty liver and hemochromatosis.

Matsushita, T, Miyati, T, Hayashi, N, Ohno, N, Kitanaka, A, Ohtake, S, Hamaguchi, T, Simultaneous R2* and Fat Fraction Measurement of the Liver with Modulus and Real Multiple Gradient-Echo with Low-field MRI System.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11008728.html