Noncalcified densities seen on mammography with only one view can usually be distinguished between a superimposition of normal tissue and a true mass obscured by surrounding dense fibroglandular tissue by obtaining an additional view. When the additional view suggests a mass, a lateral view is obtained to confirm the presence of a true mass or to localize it for further evaluation. Occasionally, the noncalcified density is not visualized on the lateral view, making further evaluation difficult. Pearson and associates evaluated the step-oblique mammography technique to determine its efficacy in these patients.

Women who had a noncalcified density on one mammographic projection were evaluated by step-oblique mammography. The step-oblique technique involves obtaining additional images taken obliquely, usually every 15 degrees beginning with the view in which the density is present. If the density is not seen with this technique, it is considered an artifact, and no further evaluation is needed. If the density is visualized and can be triangulated on step-oblique images, it is considered a real lesion. If appropriate, image-guided biopsies were performed. All patients enrolled in the study were followed for at least two years.

Step-oblique mammography showed 50 real lesions and 19 summation artifacts in the study population. All 50 real lesions were successfully localized in three dimensions using this technique. Of the 50 real lesions, seven patients were diagnosed with breast cancer. None of the patients who were followed by observation rather than biopsy developed a breast malignancy.

The authors conclude that the step-oblique mammography technique is an effective evaluation tool in patients who have noncalcified densities visible only on one view of multiple projections. This technique can assist in distinguishing between a summation artifact and a real lesion.