MRI-PDFF (Proton Density Fat Fraction)
MRI-PDFF is a magnetic resonance scan that measures the percentage of fat inside the liver without a biopsy, giving a precise number that can be tracked over time.
Plain English
Patient-Friendly Explanation
MRI-PDFF is a magnetic resonance scan that measures how much fat is inside the liver without any biopsy or needle. It reports a percentage - for example 12 per cent - describing how much of the liver tissue is fat, and it is sensitive enough to detect small amounts of fat and to show change over time. The scan takes about 15 to 20 minutes, uses no radiation and needs no contrast injection. In weight management it is used to confirm fatty liver, to record a baseline before treatment starts, and to show objectively that liver fat is falling as weight comes down, which is often the reassurance patients need to stay with a programme.
Medical
Clinical Definition
MRI proton density fat fraction is a quantitative magnetic resonance biomarker that estimates the volume fraction of triglyceride within hepatic tissue while correcting for T1, T2 star relaxation, noise and confounders such as iron. It shows high agreement with magnetic resonance spectroscopy and with histological steatosis grade on liver biopsy, with areas under the receiver operating characteristic curve above 0.93 for detecting steatosis of at least 5 per cent. Hepatic fat fraction is graded approximately as mild below 10 per cent, moderate 10 to 20 per cent and severe above 20 per cent, and a commonly used diagnostic threshold for hepatic steatosis is about 5.2 per cent, although platforms vary slightly. Advantages over ultrasound include operator independence, a quantitative rather than qualitative report, and no ionising radiation, which makes it well suited to repeat assessment and longitudinal follow-up. Limitations include cost and scanner availability, contraindications to magnetic resonance imaging such as non-compatible implants, the need for breath-holding, and the important fact that it quantifies fat but not fibrosis. Liver fat falls in proportion to weight loss, with a reduction of 5 to 10 per cent of body weight lowering hepatic fat substantially and greater loss often normalising it, so MRI-PDFF is best interpreted alongside fibrosis assessment, typically transient elastography with a controlled attenuation parameter or a validated serum fibrosis score, because fibrosis rather than steatosis determines long-term prognosis.
Key Insight
Why It Matters
A number patients can see is a powerful motivator. Showing someone their liver fat fraction falling from 18 to 9 per cent after a few months is far more persuasive than telling them their liver enzymes look a little better.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: September 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
