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MRI Contrast Agents PowerPoint PPT Presentation


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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.

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MRI Contrast Agents

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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).


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