From the Guidelines
The recommended outpatient imaging modality for a patient with suspected hemochromatosis and elevated AST and ALT levels is MRI with T2 or R2 (R2=1/T2) sequences, specifically MRI-based hepatic iron concentration measurement**. This non-invasive technique accurately quantifies liver iron content without radiation exposure or invasive procedures, as stated in the EASL clinical practice guidelines on haemochromatosis 1. The MRI should be performed without contrast and focuses on measuring the paramagnetic effect of iron deposits in the liver tissue, which causes signal intensity changes proportional to iron concentration. Patients should fast for 4-6 hours before the procedure, which typically takes 30-45 minutes to complete. This imaging approach is preferred over liver biopsy for initial assessment and monitoring of iron overload in hemochromatosis patients, as it provides a comprehensive assessment of disease burden and can evaluate other organs potentially affected by iron overload, such as the heart and pancreas.
Some key points to consider when using MRI for hemochromatosis diagnosis and management include:
- MRI can be associated with high cost and limited accessibility, however validated software for use in hepatic iron quantification is freely available 1.
- R2* sequences are the best validated for quantifying iron in the liver 1.
- In patients with suspected aceruloplasminemia, MRI of the brain can also provide important additional information 1.
- The technique works because iron deposits create local magnetic field inhomogeneities that accelerate T2 relaxation times, allowing for quantitative assessment of hepatic iron concentration.
It's worth noting that other studies, such as the 2011 practice guideline by the American Association for the Study of Liver Diseases, also recommend therapeutic phlebotomy as the primary treatment for hemochromatosis, but do not specifically address the use of MRI for diagnosis and management 1. However, the EASL guidelines provide more recent and comprehensive recommendations for the use of MRI in hemochromatosis diagnosis and management, making them the preferred reference for this purpose 1.
From the Research
Outpatient Imaging Modality for Iron Panel
The recommended outpatient imaging modality for a patient with suspected hemochromatosis and elevated Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT) levels is Magnetic Resonance (MR) imaging.
Key Findings
- MR imaging is the most sensitive and specific imaging modality in the diagnosis of hemochromatosis 2.
- The susceptibility effect caused by the accumulation of iron leads to signal loss in the affected tissues, particularly with the T2*-weighted sequences, which makes the diagnosis of iron overload possible 2.
- MR imaging can estimate the hepatic iron concentration in a noninvasive way, thereby avoiding repeated biopsies 2.
- T2* relaxation is very accurate in diagnosing hepatic iron overload, even at low iron concentrations 3.
Advantages of MR Imaging
- Non-invasive and accurate technique for validating the evidence of even low hepatic iron concentrations 3.
- Can detect iron because of the field heterogeneity generated by haemosiderin 3.
- Additional information may be obtained by the combination of T1 and T2* mapping 3.
Comparison with Other Imaging Modalities
- Dynamic bolus-enhanced CT is the modality of choice in most situations, but MR imaging is competitive with CT 4.
- MRI has not become a primary modality because of cost, availability, patient selection, and variability of scanner capabilities among the many manufacturers and models 4.
- Ultrasound (US) is helpful in confirming cysts, but not as sensitive as MR imaging for diagnosing hemochromatosis 4.