An alternative screening test for breast cancer may catch the disease when mammograms fail to diagnose it.
While mammograms remain the gold standard for detection, they miss roughly 20 percent of cancer cases, according to experts, leaving some women to consider additional tests.
Among the alternatives is a new screening technique in which radioactive liquid is injected into a patient to detect cancer. The liquid passes out of the patient's body within a few hours, giving doctors time to look for cancer.
"Cancer cells are more active than normal cells, so they will take up more of this radioactive tracer than the rest of the surrounding cells," said Dr. Lillian Stern, at Methodist Hospital in Philadelphia.
Stern said if the cancer exists, a visible black spot will form.
"It's very useful in some cases to help us problem solve," said Dr. Betsy Angelakis, at the Lahey Clinic in Massachusetts. She said it's especially helpful in women with dense breast tissue, which can obscure cancer in a mammogram.
"At least 25 percent of mammograms will have some degree of cloudiness or breast density that can hide a cancer," Angelakis said.
The wait for a diagnosis can be a lonely, frightening time for any woman.
Barbara Hardy, 62, told ABC News she decided to follow up her mammogram with radioactive imaging because doctors found suspicious spots on her mammogram.
"Right now, I'm just very concerned," Hardy said. "I want to find out."
Another woman who spoke with ABC News, Ines Fusco, had a mammogram and an ultrasound and neither showed any sign of cancer. But because she felt a small lump in her breast, she was screened again with radioactive imaging.
Halfway through the test, the doctor noticed a black dot on the screen, which was cancer. Fuscio said she "knew there was something odd."
She had surgery to remove the cancer and because it was caught early, she said the test "saved my life. ... I give it all the credit in the world."
And Hardy's radioactive imaging revealed she does not have breast cancer, so, finally, she can relax.
Radioactive imaging is now offered at 33 hospitals in the United States but has not been tested on enough women to be considered a replacement for mammograms.