Efficacy of step-oblique mammography for confirmation and localization of densities seen on only one standard mammographic view.
OBJECTIVE
Step-oblique mammography is a technique used to determine with confidence whether a mammographic finding visible on multiple images on only one projection (but not elucidated using standard additional mammographic projections such as the roll view) represents a summation artifact or a true mass, and to precisely localize the true mass for further evaluation (if applicable). This paper describes the step-oblique technique and evaluates its efficacy.


METHODS
Between January 1, 1993 and December 31, 1998, 69 consecutive women underwent step-oblique mammography for the evaluation of densities seen on multiple images in only one standard projection. Additional images were obtained at 15 degrees stepped increments in obliquity. If a one-projection-only finding was not seen on step-oblique images, the density was judged to represent a summation artifact, completing the examination. If a density was visualized and could be triangulated concordantly on step-oblique images ranging from the craniocaudal to the 90 degrees lateral projection, then it was judged to represent a real lesion. Such a lesion was further characterized (mass, neodensity, architectural distortion, focal asymmetric density) and was localized precisely in three dimensions, permitting imaging-guided tissue diagnosis, if appropriate. For all study patients, we also recorded BI-RADS (American College of Radiology Breast Imaging and Data Reporting System) assessment categories; pathology results for biopsied lesions; and mammographic follow-up, clinical follow-up, and linkage to regional tumor registry for nonbiopsied lesions for which at least 2 years had elapsed since step-oblique mammography.


RESULTS
Step-oblique mammography differentiated 50 real lesions from 19 summation artifacts. All 50 real lesions, although initially visible on only one standard projection, were successfully localized in three dimensions. Subsequent management resulted in the prompt detection and diagnosis of seven breast cancers and 21 benign lesions. None of the remaining findings managed by follow-up rather than biopsy have subsequently been found to be malignant.


CONCLUSIONS
Step-oblique mammography is an effective means of evaluating the mammographic finding visible on multiple images on only one standard projection.
Pearson
K L
KL
Department of Radiology, University of California at San Francisco, 94143, USA.
Sickles
E A
EA
Frankel
S D
SD
Leung
J W
JW
D016477:Artifacts; D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008327:Mammography / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods*; D012680:Sensitivity and Specificity