| Currently, High Field (1.5T) Superconducting MR imaging does not allow live guidance during needle breast procedures. The current procedure allows the physician only to calculate approximately the location and extent of a cancerous tumor in the compressed patient breast before inserting the needle. It can then become relatively uncertain that the tissue specimen removed during the biopsy actually belongs to the lesion of interest. A new method for guiding clinical breast biopsy is presented, based on a deformable finite element model of the breast. The geometry of the model is constructed from MR data, and its mechanical properties are modeled using a non-linear material model. This method allows imaging the breast without or with mild compression before the procedure, then compressing the breast and using the finite element model to predict the tumor's position during the procedure. A patient's breast was imaged in a 1.5T magnet, first uncompressed, then under plate compression. A deformable model of that breast was constructed. The model was deformed using virtual compression plates, and the displacements of a cyst, and of two vitamin E pills attached to the surface of the breast were recorded both in the real breast and in the deformable model. The simulation was done using custom-written software in such a way that the entire procedure took less than a half-hour to complete. The results were used to assess the parameters for optimal performance after several sensitivity and variational studies. Using the derived parameters, deformable breast models were constructed for three different cancer patients from their MR breast data. The displacements of the cancer lesions' center of gravity were tracked in the MR data sets, and in the deformed finite element breast models. The final results show that it is possible to create a deformable model of the breast based on the use of finite elements with non-linear material properties capable of modeling and predicting the deformation of the breast, in a clinically useful amount of time (less than a half-hour). |
