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 (R(2) = 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.