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Iron and fat quantification

Hepatic iron concentration (HIC or LIC) can be estimated by both methods: T2* calculation or the signal intensity ratio (SIR) between the liver and the paravertebral muscles. Both methods have advantages:

  • T2* is certainly the best methods as soon phase oscillation due to steatosis is managed and as soon the shortest TE used allows a correct T2* estimation in case of high overload.
  • SIR method is easier to perform with no need of a multiecho gradient echo sequence since the measurement is "calibrated" by the muscle used as a reference. The precision is probably not as good as that obtained by the T2* assessment. The MR acquisition protocol must use the body coil. SIR method can better estimate high overload by reducing the TE below the value initially proposed. This reduction du TE introduce a phase contrast and can only be used when the signal is falled-down on the in-phase TEs.
  • The evaluation of the fat fraction (FF) can be done via phase imaging by comparing the signal of the liver on the images in phase and in phase opposition. A joint estimate is necessary because each overload can influence the quantification of the other overload.