A solution of iron oxide injected into a patient's veins can significantly improve the ability of magnetic scanning machines to pinpoint extremely small cancers of the liver, doctors say.

The development should make it possible to detect this kind of cancer early, when it can still be removed surgically, and to better determine how far it has progressed, Dr. David D. Stark and colleagues at Massachusetts General Hospital report in the August issue of the journal Radiology.Doctors using the technique administer the iron oxide then take a cross-sectional picture with a standard magnetic resonance imaging, or MRI, scanner. The iron oxide is absorbed by healthy cells but not by cancerous ones, making the cancers clearly stand out on magnetic pictures.

Tests on 60 people showed that the technique could spot tumors as tiny as 3 millimeters, three times smaller can be found with other scanning methods.

Whether liver cancer is treated with surgery, chemotherapy or radiation depends on the stage of the disease.