Single-Projection Needle Localization
Linda M. Sanders · Journal of Breast Imaging · 2019
Mammographically guided needle localization for nonpalpable lesions is traditionally performed using the two-view method: needle insertion in one projection, followed by imaging in the orthogonal projection to assess needle depth before wire deployment. Performing localizations on a prone stereotactic biopsy table frees a mammography unit and eliminates fainting, a common problem during upright localizations. New stereotactic biopsy tables have improved resolution, and they provide a larger field of view, as well as tomosynthesis capability, making localization of lesions seen only on tomosynthesis feasible. Using an Affirm Prone Biopsy System (Hologic, Bedford, MA), single-projection needle localization can be performed as the needle carriage is rotated 90° relative to the direction of compression. Using this technique, two needle guides serve as gun sights to maintain a perfect trajectory. From the drop-down procedure menu, needle localization (rather than stereotactic biopsy) is selected, and the length of the wire is chosen according to the depth of the lesion. The target is chosen by employing either tomosynthesis or standard stereotactic images for lesion identification. Clicking on the lesion and accepting the computer-calculated x, y, and z values sends the coordinates to the needle carriage. The needle is moved electronically to the proper coordinates, and manually inserted by dialing the holder to the proper z depth; depth is ascertained on the first image. When proper depth is achieved, the wire is deployed. Any needle-delivered localization device may be inserted using this method.