High-resolution cardiac MRI? Don't hold your breath--literally

Radio-oncologists in Europe have achieved high-resolution cardiac magnetic resonance (CMR) imaging by using a ventilator that stops a patient’s respiratory motion for several minutes, according to research presented May 13, 2016 at EuroCMR 2016, held in Florence, Italy.

“In many imaging techniques, but particularly in CMR, you need a relatively long acquisition time and must correct for respiratory motion,” said research presenter Juerg Schwitter, MD, Director of the Cardiac MR Centre at the University Hospital Lausanne, in Lausanne, Switzerland.

“For decades we have had to correct for respiration when estimating the position and motion of the heart by CMR, and this is not always accurate,” he added.

Current CMR imaging can also be time consuming, as well as trying for the patient. Patients must hold their breath for each image, then recover before holding their breath for the next image.

To overcome these problems, Dr. Schwitter and colleagues tested the use of percussive ventilation (PV), which administers small volumes of air—“percussions”—with adjustable pressures and frequencies of 300 to 500 per minute. Air volumes are small so the patient’s chest doesn’t move, allowing apnea for several minutes. The procedure is noninvasive and patients aren’t sedated.

“Patients lie face up in the CMR machine and do not need to breathe. They say their chest feels a bit inflated during the ventilation but otherwise it feels okay,” Dr. Schwitter explained. “This enables the physicians to more accurately plan the field of radiation to apply in each patient.”

The researchers tested the PV system in a healthy subject and in a patient, and obtained high-resolution 3D images with a detailed view of the pulmonary vessels and with the lungs “frozen” in full inspiration.

“The possibilities with high-frequency percussive ventilation are huge,” Dr. Schwitter said. “You could run all the CMR sequences in one batch, which would be much faster. Data could be acquired constantly with fewer artifacts. We might be able to use this technique for diagnosis of sicker patients, who find breath holding difficult and need the imaging to be done quickly.”

The technique could collect high-resolution images with millimetric precision when needed—to localize scar in the myocardium or to see the anatomy of coronary arteries, valves, and malformations, for example.

“In the future, we could even imagine that if the patient is not breathing for 20 minutes or even longer, this technique could give a precise 3D representation of cardiac structures and help guide electrophysiology procedures such as ablation,” Dr. Schwitter predicted.

But first, larger studies with more patients are needed to validate PV MRI as well as evaluate its potential, he noted.