A novel MR-guided interventional device for 3D circumferential access to breast tissue.

MRI is rapidly growing as a tool for image-guided procedures in the breast such as needle localizations, biopsy, and cryotherapy. The ability of MRI to resolve small (<1 cm) lesions allows earlier detection and diagnosis than with ultrasound. Most MR-guidance methods perform a two-dimensional compression of the breast that distorts tissue anatomy and limits medial access. This work presents a system for localizing breast lesions with 360 degrees access to breast tissue. A novel system has been developed to perform breast lesion localization using MR guidance that uses a 3D radial coordinate system with four degrees of freedom. The device is combined with a novel breast RF coil for improved signal to noise and rotates 360 degrees around the breast to allow medial, lateral, superior, and inferior access minimizing insertion depth to the target. Coil performance was evaluated using a human volunteer by comparing signal to noise from both the developed breast RF coil and a commercial seven-channel breast coil. The system was tested with a breast-shaped gel phantom containing randomly distributed MR-visible targets. MR-compatible localization needles were used to demonstrate the accuracy and feasibility of the concept for breast biopsy. Localization results were classified based on the relationship between the final needle tip position and the lesion. A 3D bladder concept was also tested using animal tissue to evaluate the device's ability to immobilize deformable breast tissue during a needle insertion. The RF breast coil provided signal to noise values comparable to a seven-channel breast coil. The needle tip was in contact with the targeted lesion in 89% (25/28) of all the trials and 100% (6/6) of the trials with targeted lesions >6 mm. Target lesions were 3-4 mm in diameter for 47% (13/28), 5-6 mm in diameter for 32% (9/28), and over 6 mm in diameter for 21% (6/28) of the trials, respectively. The 3D bladder concept was shown to immobilize a deformable animal tissue phantom during needle insertion. It is concluded that the MR-guidance system accurately localizes small targets on the order of 3-4 mm in a breast phantom with 360 degrees rotational access.