VALHALLA, N.Y. — Outside of the X-ray, perhaps no other medical examination is as well known or as safe as the magnetic resonance imaging test, which is conducted 8 million times a year in the United States on patients ranging from people with brain tumors to famous athletes with knee injuries.
But Monday, officials at the Westchester Medical Center announced that something went horribly wrong on Friday with an MRI test on a boy, 6, who had just undergone surgery. Even though no metal objects are supposed to be in the testing area, because they will be pulled toward the 10-ton machine by its powerful electromagnet, a metal oxygen tank somehow made it into the examination room.
The tank, about the size of a fire extinguisher, became magnetized, then flew through the air at 20 to 30 feet per second and fractured the boy's skull.
The boy died on Sunday. And Monday, an autopsy conducted by the Westchester County Medical Examiner's Office confirmed that he had died of blunt force trauma, severe hemorrhaging and a contusion to the brain.
The hospital and the State Department of Health are investigating, and the Westchester District Attorney's Office is reviewing the case.
"This was a tragic and very disturbing accident," said David Hebert, a spokesman for District Attorney Jeanine Pirro.
In a statement, Edward A. Stolzenberg, president and chief executive of Westchester Medical Center, said that "the trauma was due to what can only be described as a horrific accident, and the entire medical center is grieving over the incident."
He also said that the hospital "assumes full responsibility for the accident" and "will do anything it can to ease the family's grief."
But very little additional information had emerged about the boy's case — including why he was in the hospital and who brought the oxygen canister into the room.
And there were far more questions about how a procedure considered so routine could have ended so horribly.
An MRI generates images of the body using strong magnetic fields and a computer. And since its introduction on a widespread scale within the last two decades, it has generally been considered very safe, according to Dr. Emanuel Kanal, a professor of radiology and neuroradiology at the University of Pittsburgh Medical Center.
There have been several MRI accidents, some fatal, involving metal objects as small as paper clips. One woman who underwent an MRI died because of an implanted aneurysm clip in her brain.
Another who forgot to pull a hairpin out of her hair required a procedure to extract the hairpin after it traveled up her nose and lodged in her pharynx.
And in Rochester last year, an MRI magnet pulled a .45-caliber gun out of the hand of a police officer and the gun shot a round that lodged in a wall.
The accident in Westchester also comes on the heels of a recent article in The American Journal of Roentgenology about the potential dangers of oxygen tanks being brought into MRI testing areas. In that study, researchers found that there had been five such accidents in 15 years, including four in the last three years, mostly involving patients on life support who have been wheeled into an examination room with an oxygen tank nearby.
"MRI is safe, but if something goes wrong, it can go very wrong," said Dr. Gregory Chaljub, a radiologist at the University of Texas Medical Branch in Galveston and the study's primary researcher.
The accident comes four months after Westchester Medical Center, a 1,000-bed institution that has tried in recent years to become the region's premier hospital north of New York City, was downgraded in the accreditation rankings after evaluators discovered alterations on a patient's chart.
But until Friday's accident, the hospital had never had any problems stemming from its three MRI machines, which complete 3,800 MRI tests a year, said Carin Grossman, a hospital spokeswoman.
It was not known why the boy was in the hospital, and Grossman said that any information about the child's surgery or personal details would not be released "because of patient confidentiality."
What is known is that on Friday morning, the boy, sedated, was placed inside the MRI — a General Electric Signa machine — with his head in the center of the machine. At some point, the tank was "introduced into the exam room" and, magnetized, was drawn to the center of the room, striking the boy, according to a hospital news release.