Biopsy Needle Localization Using Magnetic Induction Imaging Principles: A Feasibility Study

The accurate navigation and location of a biopsy needle is of main clinical interest in cases of image-guided biopsies for patients with suspected cancerous lesions. Magnetic induction (MI) imaging is a relatively new simple and low-cost noninvasive imaging modality that can be used for measuring the changes of electrical conductivity distribution inside a biological tissue. The feasibility of using MI principles for measuring and imaging the location of a biopsy needle in a tissue with suspected lesion was studied in simulations and with an experimental system. A contactless excitation/sensing unit was designed, and raster scan was performed on a thin tissue slab with an inserted standard 22 gauge stainless steel biopsy needle. A 30-mA, 50-kHz excitation field was employed, and the secondary-induced electromotive force (emf_s) was measured and plotted on a 2-D plane in order to yield an image of the needle location. The simulations demonstrated the significance of utilizing a ferrimagnetic core for the excitation coil in order to increase induced currents magnitude and scanning resolution. The experimental reconstructed images of the emf_s spatial distribution revealed the needle position and orientation, with an accuracy of 0.1 mm and a signal-to-background ratio of ~30 dB. High correlation (R² = 0.89) between the experimental and simulation results was observed. We conclude that MI principles exhibit a potential alternative to existing imaging modalities for needle biopsy procedures.