Tissue Stabilization in MRI-Guided Breast Biopsy

Abstract

<p>Breast cancer is the most common form of cancer in women in the United States. Histopathological examination through breast biopsy is considered as the "Gold Standard" for a definitive diagnosis. Contrast-enhanced Magnetic Resonance Imaging (MRI) is often used for guiding the biopsy in those cases in which the tumor may not be detectable under Ultrasound or X-ray mammography. Stabilization of the breast tissue during the biopsy is critical for its success to ensure that the target would not be displaced due to the patient movement or tissue deformation. Conventionally, the breast tissue is immobilized by firmly compressing it between two parallel plates. However, high compression forces causes significant patient discomfort and can reduce the intake of the contrast agent, which negatively impact the image quality.</p> <p>This thesis introduces devices and control methodologies for active tissue stabilization in magnetic resonance imaging (MRI)-guided breast biopsy. Pneumatic and piezoelectric actuators have been considered for developing concept designs for MRI-compatible tissue stabilization devices. Only the pneumatic device has been prototyped and tested. The device is comprised of two pneumatically-actuated support plates that would stabilize the biopsy target movements during needle insertion. An optimized geometry for the support plates allows for a good degree of tissue stabilization without relying on large compression forces. The plate configuration can also be adjusted inside the magnet bore using pneumatic actuators driven by pressure-controlled valves that are placed in the MR control room. This capability allows for the compensation of the target displacement based on MR image feedback. When combined with a separate needle drive mechanism, this stabilization device would enable in-bore MR-guided breast biopsy in combination with an in-bore needle driver system. The proposed approach offers improved target stabilization at reduced compression force and patient discomfort, that may also enhance MR image quality as result of greater intake of contrast agent. The open-front design of the stabilization plates provides greater flexibility in selecting the needle insertion entry point, and active adjustment of the support plates based on MR feedback improves the targeting accuracy.</p> <p>A concept design for a MR-compatible needle driver mechanism using piezoelectric actuators is also proposed. Experiments performed on chicken breast tissue with a prototype of the device demonstrate the effectiveness of this mechanism in increasing needle targeting accuracy using two simple error correction strategies. Furthermore, MRI compatibility tests are carried out to asses the performance of the device inside MRI.</p>