MRI Liver — fat and iron quantification
Whole liver for the quantitative maps; a single mid-hepatic slice is used for some R2* schemes but volumetric coverage is preferred so that regional variation is visible.
Typical, not policy
Timings, volumes and delays here are representative values drawn from published guidance. Scanner generation, injector, cardiac output and local preference all move them. Confirm against your department's own protocol before you rely on a number.
When to use it
- Quantification and monitoring of hepatic steatosis, including in metabolic dysfunction-associated steatotic liver disease and in drug trials.
- Suspected or known iron overload from haemochromatosis or transfusion dependence, including cardiac iron on the same visit.
- Non-invasive alternative to biopsy for fat and iron burden.
- Assessment before living-donor hepatectomy.
Technique
- Multi-echo chemical-shift-encoded gradient-echo acquisition producing a proton density fat fraction map that is corrected for T2* decay and for the multiple spectral peaks of fat.
- R2* or T2* mapping for iron; separate cardiac T2* is acquired if cardiac iron is also being assessed.
- Simple dual-echo in- and opposed-phase imaging detects fat but does not quantify it reliably when iron is also present, because the two effects act in opposite directions.
- Vendor implementations and confounder corrections differ, so absolute values are not freely interchangeable between scanners.
Where it goes wrong
- Using dual-echo in- and opposed-phase signal drop as a quantitative fat measure when iron is present, which systematically under-reads fat.
- Sampling regions of interest over vessels, bile ducts or focal lesions rather than representative parenchyma.
- Comparing values across different scanners or software versions in a follow-up series.
- Severe iron overload causing such rapid signal decay that the fat fraction becomes unreliable.
Contrast
None
- No contrast at any point. Adding gadolinium to a quantification study wastes an agent and gains nothing.
Acquisition
- Breathing
- Breath-hold acquisitions of roughly 15-20 seconds, or free-breathing variants where available.
- Reconstruction
- Proton density fat fraction and R2* or T2* maps, with region-of-interest values sampled from each hepatic segment.
- Preparation
- Fasting for approximately 4 hours reduces bowel motion and gallbladder contraction; confirm the local interval. State whether the patient is in a hepatocellular carcinoma surveillance programme and whether prior CT or MRI exists — it drives agent choice. Breath-hold capacity determines whether dynamic imaging is feasible; flag patients who cannot hold for roughly 15-20 seconds.
Safety checks this protocol carries
Derived from the contrast agent and phases above, not authored here — which is why they cannot drift apart from what the protocol actually does.
- Prior contrast reaction and elective premedication· nurse pre scan
- Kidney function and gadolinium-based contrast· radiographer at scan
- Intravenous access adequate for the planned injection· radiographer at scan
- MR safety screening for implants and foreign bodies· radiographer at scan