U.S. President Donald Trump said on Monday he had undergone an MRI examination, without saying why.

“It was perfect,” he told reporters on board Air Force One en route to Tokyo.

A magnetic resonance imaging scan uses magnets and radio waves to create detailed images of the inside of the body. It can be used to monitor a range of conditions.

Trump, 79, was the oldest person to be inaugurated as U.S. president when he retook the White House in January, and he is the second-oldest person to serve as U.S. president.

Earlier this month, the U.S. president’s doctor said Trump was found to be in “exceptional health” in a medical evaluation.