Chapter 22: Magnetic Resonance Imaging and Computed Tomography of the Vascular System
A rare, albeit serious, risk of contrast-enhanced magnetic resonance angiography (CE-MRA) is the association between gadolinium-based contrast agents and nephrogenic systemic fibrosis. In which of the following scenarios may the linear chelates of gadolinium be considered safe?
A. Chronic renal impairment with eGFR < 30 mL/m2
B. Acute renal impairment
C. Perioperative liver transplantation
The answer is E. (Hurst’s The Heart, 14th Edition, Chap. 22) Different gadolinium contrast agents have been divided into low, medium, and high risk for causing nephrogenic systemic fibrosis1 by the European Medicines Agency. High-risk agents include the linear chelates of gadolinium, and these are contraindicated in patients with an eGFR < 30 mL/m2, acute renal impairment, and perioperative liver transplantation, as well as in neonates. Low-risk agents include newer cyclic preparations of gadolinium. These are considered safe in patients with an eGFR of more than 30 mL/m2, and they can be used in patients with an eGFR below this threshold if the benefit of undergoing contrast MRI outweighs the risk. The volume of contrast agent used in this case should be minimized and repetition within 7 days avoided.2 Gadolinium contrast agents are routinely used, and known to be safe, in the evaluation of patients with (often severe) forms of heart failure.
Before the advent of CE-MRA, nonenhanced magnetic resonance time of flight (TOF) imaging acquisitions were used to image the carotid arteries, demonstrating good agreement with digital subtraction angiography (DSA). Which of the following statements about the limitations of TOF imaging is false?
A. It is sensitive to turbulent flow
B. It tends to understimate the severity of stenoses
C. It has long acquisition times
D. It increases the potential for motion artifacts
The answer is B. (Hurst’s The Heart, 14th Edition, Chap. 22) TOF acquisitions are sensitive to turbulent flow, can overestimate stenoses, and have long acquisition times, increasing potential motion artifacts.2 Although TOF MRA remains useful for patients with contraindications to MRI contrast, such as renal insufficiency, CE-MRA has become the technique of choice for imaging the carotid arteries.
A 67-year-old man with a prior history of uncontrolled hypertension presented to the emergency department complaining of an acute-onset excruciating and sharp retrosternal chest pain ...