Adding a newer test to digital mammograms can increase the detection rate for breast cancer and decrease nerve-racking false alarms, in which suspicious findings lead women to get extra scans that turn out normal, a study found.

Millions of women will get the newer test, tomosynthesis, this year. The procedure is nearly identical to a routine mammogram, except that in mammography the machine is stationary, while in tomosynthesis it moves around the breast. Sometimes called 3-D mammography, the test takes many X-rays at different angles to create a three-dimensional image of the breast. It was approved in the United States in 2011.

The verdict is still out on the long-term worth of this new technology. The new results are promising but not definitive, according to experts not associated with the study, published Tuesday in The Journal of the American Medical Association. Tomosynthesis has not been around long enough to determine whether it saves lives or misses tumors.

Even so, more and more mammography centers are buying the equipment, which is far more costly than a standard mammography unit, and marketing the test to patients as a more sensitive and accurate type of screening. It has come on the scene at a time when the value of breast cancer screening and the rising costs of health care are increasingly debated.