MRI Contrast Agents
Mark D. Herbst, M.D., Ph.D.
Contrast Agents
• Types
– Paramagnetic
– Superparamagnetic
– Diamagnetic
Comparison with X-ray Contrast
• In radiography (barium enema, UGI series,
angiography, arthrography, etc.) we image
the contrast agent itself.
• In MR we usually do not image the
contrast agent itself, but we image the
water near the contrast agent that is
affected by the contrast agent.
• Contrast agents change the T1 of the
water around them.
Barium Enema
Arthrogram
Brain CT with contrast
Brain MR with contrast
Chelates
• Chelate means “claw”
• Chelates surround an ion an make a cage
around it
• A chelate of gadolinium occupies all available
space around the ion except one
• Water molecules exchange in and out of that
one spot. When in that spot, the spins have an
extremely short T1. This accelerates the overall
relaxation rate, shortening T1.
Gd chelate
Gd-DTPA
Free Gd
NSF
• Nephrogenic Systemic Fibrosis
– Most likely caused by free Gd
– Prevent by screening patients for renal
disease
– Calculate estimated creatinine clearance
Estimate Creatinine Clearance
• http://www.chestx-ray.com/Practice/RenalInsuff.html
Liver Contrast Agents
Iron Magnetite,
superparamagnetic
agent
Makes liver black on
T2WI, mets show up
as bright white.
Other contrast agents
• MR colonography
• Water/saline contrast
• Negative oral contrast
– Geritol
– Blueberry juice, pineapple juice
MR Colonography
Figure 3. MR colonography
Geenen, R. W. F. et al. Radiographics 2004;24:e18
Copyright ©Radiological Society of North America, 2004
Negative contrast agents
• Used to make stomach contents black in
MRCP
• Geritol, blueberry juice, pineapple juice
– Iron in Geritol
– Mn in these juices
MRCP
Juices
"Contrast agents" – orange juice (OJ), grapefruit juice (GJ), apple juice (AJ), pineapple
juice (PJ), milk (M), prune juice (P), cranberry juice (CJ), blueberry and apple juice (BAJ), barium EZ Cat 2%
w/v (B), dilute barium (50:50 with water) (DB), concentrated gastrografin (GG), ferumoxsil (F)
and water (W).