A loose screw causes havoc at a leading U.S. institution

November 1, 2007

The saga began in autumn 2006, when an MR technologist at Wayne State University in Detroit, Michigan, heard some noise due to arcing from the back of the machine during an examination. The image quality was completely destroyed. After responding to the service call, an engineer came and took apart the machine and found that some threads on a screw that held a cable to the gradient coil were burned.

The saga began in autumn 2006, when an MR technologist at Wayne State University in Detroit, Michigan, heard some noise due to arcing from the back of the machine during an examination. The image quality was completely destroyed. After responding to the service call, an engineer came and took apart the machine and found that some threads on a screw that held a cable to the gradient coil were burned. The arcing was due to the loose gradient cable. The screw had not been firmly fixed to the gradient coil during original installation, and it could not be turned all the way into its socket. Someone had forced the screw into its socket, thereby damaging the threads inside the socket.

"The challenge was how to quickly repair such an unusual problem," said Zahid Latif, from the university's department of radiology in a poster at the 2007 ISMRM/ESMRMB congress.

The manufacturer's engineers brought a self-tapping brass screw, and slowly installed it with epoxy. The new screw held the gradient cable for three months, but was loose again in February, and the same procedure was repeated. In mid-April, the engineers ramped down the 4T magnet, and used a torque meter to further tighten the screw. They expect this repair to last at least three years.