The government yesterday approved the sale of a tiny MRI probe that doctors can thread into a patient's throat to take extra-clear images from inside the body, replacing standard MRI's outside-the-body pictures.

Surgi-Vision Inc.'s miniaturized "endo-esophageal MRI coil," invented by researchers at Johns Hopkins University, was approved by the Food and Drug Administration. The Columbia, Md.-based company said it will begin selling the coil to doctors in January.

While nestling in the esophagus, the tiny probe gives an image of the aorta--the body's largest artery--that is nine times sharper than what standard MRI provides, said Ergin Atalar, a Hopkins radiologist. Cardiologists are studying whether the probe's clearer images will help doctors in determining who is at risk for heart disease before they get sick, he said.

MRIs, or magnetic resonance imagers, have coils that act as antennas for picking up electromagnetic signals from the body.

If doctors could get such an antenna inside the body, closer to the organs they're trying to see, the MRI would produce clearer images, Atalar explained.

Other companies have created internal MRI probes for use in the prostate. But Hopkins researchers designed a much tinier version that can be threaded down a patient's esophagus, allowing doctors to view the esophagus and the nearby aorta. Surgi-Vision's goal is to eventually create even tinier versions that can be squeezed into other parts of the body.