I get mammograms every six months. I get ultrasounds every six months. I get a breast MRI every year. That's my typical screening routine, intended to keep breast cancer from invading my life for a second time.

This combination of testing -- primarily the MRI part -- has not been typical for all at-risk women. It's just the plan my doctors have determined is the best insurance policy for me. But as of yesterday, the American Cancer Society began recommending regular use of MRI scans, rather than conventional mammograms, for women facing a breast cancer risk of 15 percent or more.

Family history places one to two percent of women at a 20 percent higher risk of developing the disease than women without such a history. Women carrying a BRCA1 or BRCA 2 gene mutation face a lifetime risk of up to 65 percent. And women with a personal history of the disease are at risk of a repeat diagnosis. These are the women MRI screening can help.

Recent studies show MRI to be much more sensitive than mammograms. And in an investigation of 969 women diagnosed with breast cancer in one breast, MRI found 30 additional tumors in the opposite breast previously missed by mammograms and physical exams.

Not typically used for routine screenings due to cost and a few false alarms -- sometimes the scans detect suspicious areas that once surgically tested turn out to be benign -- MRI is still the best tool for detecting more cancerous tumors earlier.

There is no proof yet that the cancers detected by MRI will translate into longer lives for patients. Life-extending benefits will become clear only after women are followed for a longer period of time.