Biopsy guided by molecular breast imaging (MBI)

Objectives Molecular Breast Imaging (MBI) uses planar imaging with single gamma photon emission to visualize breast cancers that are often occult on mammography in the 40-50% of women with radiographically dense breasts. Mayo Clinic has reported successful dense-breast MBI screening trials using only 4-8 mCi of Tc99m-sestamibi (off-label), a low whole-body dose approaching that of screening mammography. Our purpose was to provide MBI-guided biopsy capability for the ~15% of cases when an MBI-detected lesion is occult on ultrasound and mammography.

Methods MBI consists of a pair of opposed semiconductor (CZT) gamma photon cameras that mildly compress each breast in standard planar mammographic views. For 3D Cartesian (xyz) lesion targeting we use a third small orthogonal CZT camera. A stereotactic needle guide provides lateral access between the two main cameras for hub-to-hub insertion of the biopsy sampling device parallel to the chest wall. The needle track is verified by imaging a rod source prior to tissue sampling. MBI imaging of the biopsy tissue samples provides verification and guidance for pathology.

Results Laboratory testing with a point source and with sponge phantoms containing Tc99m-labeled frozen gelatin lesions demonstrate that MBI is capable of guiding the biopsy sampling needle to within less than 4 mm of the target lesion. The biopsy guidance accessory is capable of targeting and sampling lesions throughout the breast. The setup and MBI-guidance procedure are simple and quick. In ongoing multi-site clinical tests, the trade-off of dose and procedure time is being optimized.

Conclusions A simple and effective MBI-guided biopsy accessory has been built and tested and is pending FDA 510(k) clearance. Along with the prior demonstration of low-dose dense-breast MBI screening in pilot studies, the next step toward FDA clearance for adjunctive MBI screening will be multi-center trials.

Research Support NIH National Cancer Institute grants R42-CA128407 and R44-CA143716.