Mua A Cho, 28, of the Quynh Nhai District General Hospital confessed to the police that after taking heart and lung X-rays of the girl on May 21, he sent her into another room, locked the door and raped her.
The girl told her family right afterward, explaining that she was too scared to do anything inside the room.
Her family members rushed into the X-ray room to confront Cho and were prevented from assaulting him by security guards.
The hospital has suspended Cho pending the police investigation.
A person found guilty of raping anyone between 13 and 16 years old faces imprisonment of seven to 15 years.
Official data on sexual harassment is not regularly published in Vietnam. But out of 1,600 reported cases of child abuse last year, 80 percent involved sexual assault and in most cases involved someone close to the children or having authority over them, such as neighbors, relatives or teachers.