New Contrast Agent Allows for Rapid Vascular MRI in Claustrophobic Patients
Researchers at UCLA test the contrast agent ferumoxytol for magnetic resonance angiography scans that take less than 10 minutes.
A typical magnetic resonance angiography scan for imaging the major blood vessels of the body can take anywhere from 30 minutes to one hour. Patients with claustrophobia have difficulty remaining in the tunnel-like MRI coil for that length of time without moving.
As a potential alternative for these individuals, a team of physicians at the University of California, Los Angeles tested a new magnetic resonance angiography technique that can take a complete scan in less than 10 minutes. The technique uses a contrast agent called ferumoxytol, an ultrasmall superparamagnetic iron oxide particle, to maintain excellent image quality despite the brief test. They presented their results Feb. 3 at the CMR 2018 meeting in Barcelona.
“The method is intrinsically clinical and very practical. Even in patients who are not claustrophobic, it is equally possible to do extended field-of-view magnetic resonance angiography with ferumoxytol in a few minutes,” said study author J. Paul Finn, a radiologist at UCLA's David Geffen School of Medicine. “Fast, focused imaging protocols could be used to simplify and speed up vascular MRI studies of the chest, abdomen and pelvis.”
Typically, magnetic resonance angiography is performed with the rare earth metal gadolinium as a contrast agent. However, gadolinium cannot be used in patients with renal failure and has a relatively fast decline of vascular signal after intravenously entering the body. Patients must lie in the scanner for the gadolinium injection, which would further increase the anxiety of a claustrophobic individual.
Ferumoxytol, on the other hand, maintains a stable, strong vascular signal even after several hours and is appropriate for patients with renal failure. There is no rush to scan right after the injection, so the amount of time spent in the MRI coil can be minimized.
The study included seven claustrophobic patients with renal failure who agreed to participate in an MRI scan of less than 10 minutes. They ranged in age from 11 to 63 years old.
“Several patients referred for vascular imaging studies express anxiety about going into the MRI scanner due to claustrophobia,” said study author Puja Shahrouki, a radiologist at UCLA's David Geffen School of Medicine. “We negotiated with the patients, promising them that they would not have to spend more than 10 minutes in the machine. They all agreed, and we got excellent studies in all of them within the 10 minutes.”
The researchers scanned the each subject’s thorax, abdomen and pelvis with high-resolution 3-D ferumoxytol-enhanced MR angiography. All patients successfully completed the testing without adverse events, with an average scan time of 6.27 minutes, resulting in images of high diagnostic quality.
While the use of ferumoxytol for diagnosis has not yet been approved by the Food and Drug Administration, the results suggest that the new technique has the potential to reduce anxiety for claustrophobic patients while increasing scanner efficiency. Larger vascular MRI studies will determine whether ferumoxytol has sufficient advantages to be used regularly as an alternative to gadolinium.
Ghaneh Fananapazir, a radiologist at the University of California, Davis who was not involved in the study, believes that the results seem valid and has come to similar conclusions about the utility of ferumoxytol in vascular evaluations.
“Ferumoxytol provides an excellent imaging tool as an off-label contrast agent in evaluating vessels in patients with contraindications to other CT or MR contrast agents,” said Fananapazir. “It is especially useful in patients on dialysis with residual renal function, or in patients with kidney grafts with renal dysfunction.”
CMR 2018 is a joint EuroCMR/SCMR meeting organized by the European Association of Cardiovascular Imaging, a registered branch of the European Society of Cardiology, and the Society for Cardiovascular Magnetic Resonance.