Hepatic Iron Calculator

on MRI Scan

ACCESS TO THE HEPATIC IRON CALCULATOR ON MRI SCAN

 LiverMuscle 
 12312Ratio
DP-Hemocrom
T2-Hemocrom

 

Evaluation of results– Fe Quantification

The Liver Iron Concentration (LIC) measured by MRI Scan is equivalent to the one by liver biopsy. Its interpretation on micromoles Fe/g depends on the patient’s age; a hereditary hemochromatosis usually has a LIC value higher or equal to twice the patient’s years (hepatic iron >1,9). Normal LIC values are <36μmol Fe/g.

Within this specific model of CIL calculator, there are four cut points with 100% predictive values that can help to interprete the results:

RESULT(μmol Fe/g)VALUATIONINTERPRETATIONIC
< 20 μmolNo OverloadDismiss overload (VPN=100%)93,5-100
20 - 39 μmolSlight overload or No OverloadDismiss high overload (VPN=100%) (99% less than 50 μmol Fe/g on biopsy)95-100
40 - 79 μmolModerate overloadDoes not dismiss high overload (87% menos de 70 μmol Fe/g on biopsy)60-98
>79 μmolHigh overload If the result is higher than 85, high overload is confirmed  (VPP=100%)77-100

Internists are very used to work with micromoles (μmol), while hematologists work with milligrams (mg). We recommend giving the results in both measuring units.

Hepatic Iron Calculation on MRI Scan

Not only for Hereditary Hemochromatosis, but also for Secondary Hemochromatosis or Hemosiderosis, the iron concentration in the liver is the key parameter to conclusively diagnose iron overload, as well as to evaluate the need of a treatment.
The Osatek-SEDIA calculation model was validated in 2004 (1) and, since then, it has proved to be accurate for different iron overload levels. Like all signal intensity ratio methods, this one saturates with overload levels higher than 250micromoles Fe/g. It always recognizes the high overload, even though it loses precision within this range
(Figure 1).

This method is very simple and can be realized in all 1.5 teslas RM machines, with high reproducibility among different centers (2). A very important detail is that the acquisition of two gradient-echo sequences MUST NEVER BE DONE USING A SURFACE COIL. The acquisition of the two calculation model sequences MUST ALWAYS BE DONE WITH THE “Q-BODY” COIL INCORPORATED IN THE GANTRY The surface coil can be placed over the patient, but NEVER ACTIVATED.

This method provides a phantom to calibrate different machines and be able to certify its reproducibility on each machine (2). In Spain, 67 1.5 teslas machines from 59 centers have been calibrated until 2017 (see the list of calibrated centers). The phantom is free of charge and available for any MRI Center upon request (please contact jmalustiza@osatek.eus).

This method cannot be used in MRI machines with other magnetic field intensities than 1.5 teslas.

Several work pieces have proven that Osatek-SEDIA is the most precise Signal Intensity Ratio method (3-5).

References:

  1. Alustiza JM. MR quantification of hepatic iron concentration. Radiology 2004;230(2):479-84.
  2. Alustiza JM, Emparanza JI, Castiella A, Casado A, Garrido A, Aldazabal P, et al. Measurement of liver iron concentration by MRI is reproducible. Biomed Res Int. 2015;2015:294024.
  3. Juchems MS. ECR 2012 C-2248 Comparison of different MRI Methods for Determination of Liver Iron Content http://dx.doi.org/10.1594/ecr2012/C-2248
  4. Castiella A, Liver iron concentration quantification by MRI: are recommended protocols accurate enough for clinical practice? European Radiology. 2011;21:137-141.
  5. Wunderlich AP, Cario H, Bommer M, Beer M, Schmidt SA, Juchems MS. MRI-Based Liver Iron Content Determination at 3T in Regularly Transfused Patients by Signal Intensity Ratio Using an Alternative Analysis Approach Based on R2* Theory. 2016;188:846-52.