MRI MRI Contrast Agents 3

Question 1

Iron oxide nanoparticles (e.g., USPIO) used as MRI contrast agents primarily shorten which relaxation time?

Accepted Answer

T2 and T2* (susceptibility effect)

Answer

Iron oxide particles create local magnetic field inhomogeneities that predominantly shorten T2 and T2*, causing signal loss (darkening) on T2-weighted and gradient echo images.

Question 2

A patient with a GFR of 45 mL/min/1.73m² requires a contrast-enhanced MRI. According to ACR guidelines, which GBCA group is preferred?

Accepted Answer

Group III macrocyclic agents

Answer

The ACR recommends macrocyclic GBCAs (Group III) for patients with reduced renal function (GFR 30–60) due to their superior thermodynamic and kinetic stability.

Question 3

The 'late gadolinium enhancement' (LGE) pattern of subendocardial distribution in cardiac MRI is most consistent with which diagnosis?

Accepted Answer

Ischemic scar (prior myocardial infarction)

Answer

Subendocardial LGE following a coronary territory distribution is the classic pattern of ischemic scar from prior myocardial infarction.

Question 4

What is the primary reason gadolinium-based contrast agents should not be used in patients undergoing hemodialysis without a specific clinical indication?

Accepted Answer

Risk of NSF remains even after hemodialysis removes gadolinium

Answer

While hemodialysis can remove most gadolinium, some residual free gadolinium remains after each session, and repeated exposure can still cause NSF in high-risk patients.

Question 5

In dynamic contrast-enhanced (DCE) MRI of the breast, which kinetic enhancement curve pattern is most concerning for malignancy?

Accepted Answer

Washout (type III)

Answer

A washout (type III) kinetic curve — rapid initial enhancement followed by signal decrease — is most suspicious for malignancy due to arteriovenous shunting in tumor neovasculature.

MRI - Magnetic Resonance Imaging Practice Test

MRI - Magnetic Resonance Imaging Practice Test

MRI MRI Contrast Agents 3