Measurement of

Hepatic Fat and Iron by MRI

Thomas Jefferson University

Philadelphia, PA

Donald G. Mitchell, M.D.

• If you’re already measuring fat and/or iron, what can I

tell you in 10 minutes?

• If you’re not measuring fat or iron, this 10-minute talk

won’t get you there.

• Goals for the next 9 minutes:

• Use routine MRI as best noninvasive method for

evaluating hepatic fat and iron.

•Understand issues involved in measurement.

No Financial Conflicts to Disclose

Dual Echo GRE (2D or 3D) In-phase & Opposed-Phase with exact same anatomy

TE = 2.3 msec

TE = 4.6 msec

Fatty Liver Disease: Methods

• Dual GRE (2-point Dixon) » Included in routine protocols » Confounded by iron » Ambiguity near 50% lipid signal

• 3-point or multi-point Dixon » Longer acquisition » Resolves iron and other T2 differences » Algorithm should account for multiple lipid peaks » Must minimize T1 effects (e.g. low flip)

• Spectroscopy » Resolves 50% lipid ambiguity

Lifestyle Change 6 mos F/U

Sources of bias

Reeder SB, Cruite I, Hamilton G, Sirlin CB. Quantitative assessment of liver fat with magnetic resonance imaging and spectroscopy. JMRI 2011; 34:729-749.

•T1

•T2,T2*

•Lipid spectral complexity

•Noise

•Eddy currents

•J-coupling

•Field strength

Fatty Liver Disease: 3T

• Dixon Techniques » Shorter TE intervals

• Spectroscopy » Greater lipid-water

separation

TE = 1.15

TE = 2.3

Iron Overload: Methods

• Dual GRE (2-point Dixon) » Included in routine protocols » Confounded by lipid » Moderately sensitive

• Multi-echo GRE » Longer acquisition » Resolves lipid and spectral complexity » Too sensitive (can’t measure severe overload)

• Multi-echo SE » Even longer acquisition » Less sensitive to iron distribution

• ?Calibration between SI to iron concentration

Method of Gandon et al.

Thalasemia

TE = 4.2 msec

TE ~2 msec

1-19-01 1-12-99

Multi-Echo

TE = 4.6

TE = 2.3

TE = 3.5

TE = 1.2

TE = 0.9 TE = 1.7

TE = 2.6 TE = 3.5

TE = 4.3 TE = 5.2

Iron Overload

1. The double gradient echo technique, a current component of routine clinical MRI, is the most effective noninvasive method for evaluating hepatic iron.

2. Precise and accurate measurement by MRI of lipid and iron is possible, but not ready for prime time.