Daily Bulletin 2016

MRI Techniques May Reduce Need for Anesthesia in Children

Wednesday, Nov. 30, 2016

As evidence grows that anesthesia can adversely affect a child's cognitive development, presenters at Tuesday's Controversy Session suggested that radiologists could significantly reduce the time and discomfort associated with pediatric MRI through a variety of measures before and during scanning.

Although MRI is an effective alternative to CT in pediatric imaging that eliminates the risks associated with ionizing radiation, it often requires sedation or general anesthesia to help keep young patients calm and motionless for the exam. Though risks of immediate complications from anesthesia or sedation are generally well appreciated, there is a growing concern about potential risks related to neurotoxicity stemming from anesthetic agents. This toxicity is thought to carry the greatest risk when anesthesia is performed at a particularly young age, for prolonged times and for repeated procedures, said presenter Randall Flick, MD, MPH, an anesthesiologist with the Mayo Clinic in Rochester, Minn.

Randall Flick, MD, MPH

Randall Flick, MD, MPH

Donald P. Frush, MD

Donald P. Frush, MD

"In the past 10 to 15 years, a growing body of evidence, primarily from animal studies, shows that the anesthetic agents used in the operating room or sedation suites puts a developing brain at risk for injury," Dr. Flick said.

The Controversy Session, "A New Perspective on Radiation and Sedation Risk in Children: Should ALARA be as 'Low' or as 'Light' as Reasonably Achievable?" was moderated by Donald P. Frush, MD.

Studies on animals suggest that anesthetic agents can affect apoptosis — the process in which cells undergo programmed death as a normal part of brain growth.

"When you expose an animal to anesthetic agents, the number of brain cells that die off becomes much greater, causing deficiencies in the cognitive behavioral ability of those animals," Dr. Flick said.

While the effects of anesthesia on developing brains in animals are well characterized, according to Dr. Flick, the data on children are less clear. Studies have produced mixed results, although the Dr. Flick-led Mayo Anesthesia Safety in Kids (MASK) Study, currently in the data analysis stage, appears to support the association between anesthesia exposure and brain damage.

"These new findings confirm some results that we've seen in past showing an increased incidence of learning disabilities and ADHD in children who were exposed to anesthetic drugs more than once prior to age two," Dr. Flick said.

Taking a Holistic Approach to Imaging

Shreyas S. Vasanawala, MD, PhD

Shreyas S. Vasanawala, MD, PhD

The idea that pediatric patients must be exposed to either radiation from CT or MRI-related anesthesia represents a false dichotomy, according to study co-presenter Shreyas S. Vasanawala, MD, PhD, of Stanford University in Stanford, Calif. Certain MRI techniques can provide a viable alternative to CT while reducing or even eliminating the need for sedation and anesthesia in pediatric patients, Dr. Vasanawala said.

Efforts should begin in the pre-scanning stage, where the suite can be made to be more child-friendly and a child-life service may be available to help prepare children for the procedure. Dr. Vasanawala suggested that intravenous contrast administration be avoided, if possible, as the process of accessing a vein is often the most difficult part of the experience for the child. During scanning, silent MRI techniques and distraction devices like DVD goggles may reduce or eliminate the need for sedation.

New and improved MRI approaches produce diagnostic quality images while significantly reducing the time children need to spend in the MRI scanner, Dr. Vasanawala said. For instance, free breathing protocols can provide vital information about the state of the pediatric heart in just 10 minutes. In the abdomen, single MRI shots do an excellent job in suspected appendicitis cases, showing pus and edema and revealing alternative diagnoses like pancreatitis.

Volumetric acquisitions have numerous applications in musculoskeletal imaging, Dr. Vasanawala said, as he showed that a single, six-minute volumetric scan of the pediatric knee revealed findings like meniscal tears almost as well as images from a 30-minute acquisition.

"The quality of the imaging is quite good for the diagnostic purposes at hand," Dr. Vasanawala said. "If you try some of these techniques, you can reduce the depth, duration and frequency of anesthesia."

Question of the Day:

The NRC dose limit for radiation workers is 50 mSv/yr. How much radiation do flight crews and astronauts get?

Tip of the day:

Typically, mammography units have an HVL of 1cm. This means that a woman with a 6cm thick compressed breast needs at least four times as much radiation as a woman with a 4cm thick compressed breast.

The RSNA 2016 Daily Bulletin is owned and published by the Radiological Society of North America, Inc., 820 Jorie Blvd., Oak Brook, IL 60523.