Design of an MRI-Compatible Robotic Stereotactic Device for Minimally Invasive Interventions in the Breast†

Abstract

The objective of this work was to develop a robotic device to perform biopsy and therapeutic interventions in the breast with real-time magnetic resonance imaging (MRI) guidance. The device was designed to allow for (i) stabilization of the breast by compression, (ii) definition of the interventional probe trajectory by setting the height and pitch of a probe insertion apparatus, and (iii) positioning of an interventional probe by setting the depth of insertion. The apparatus is fitted with five computer-controlled degrees of freedom for delivering an interventional procedure. The entire device is constructed of MR compatible materials, i.e. nonmagnetic and non-conductive, to eliminate artifacts and distortion of the MR images. The apparatus is remotely controlled by means of ultrasonic motors and a graphical user interface, providing real-time MR-guided planning and monitoring of the operation. Joint motion measurements found probe placement in less than 50 s and sub-millimeter repeatability of the probe tip for same-direction point-to-point movements. However, backlash in the rotation joint may incur probe tip positional errors of up to 5 mm at a distance of 40 mm from the rotation axis, which may occur for women with large breasts. The imprecision caused by this backlash becomes negligible as the probe tip nears the rotation axis. Real-time MR-guidance will allow the physician to correct this error Compatibility of the device within the MR environment was successfully tested on a 4 Tesla MR human scanner

Improved tracking and switching performance of an electro-pneumatic positioning system

“…If electric motors are to be used as actuators in MRI-compatible robots, the motors need to be placed far away from the magnetic field and the surgical site [4], creating further design complications. Alternatively, it is possible to use pneumatic actuators to drive the surgical robots; see [5] as an example.…”

A General-Purpose MR-Compatible Robotic System

“…For these reasons, the motors were placed outside the scanner at the proximal end of the arm and coupled to the actuated joints with through-joint transmission lines [15]. This approach proved efficient for both the robot presented here and a robotic system we developed previously for MRI-guided interventions in the breast [7], [8] However, one should consider the performance limitations of such transmission systems that typically suffer from friction, backlash, and elasticity [15], [18]. In this system, the linear DoF showed negligible backlash and joint flexibility due to dynamic loading [18].…”

“…The concept of MR compatibility is discussed in the guest editorial of this special issue [29]. Several examples of MR-compatible manipulators have been developed, including a system for brain biopsies [5], two systems for breast interventions [6]- [8], one system for general use with the special "double-donut" scanners [9], [10], an endoscope positioner [11], two systems for prostate procedures [10], [12], and two general-purpose devices for use with standard cylindrical MR scanners [13], [14]. We review the development of a general-purpose robotic system at the Washington University for performing minimally invasive interventions with real-time MR guidance [14]- [17].…”

MRI Compatible Robot Systems for Medical Intervention

“…The use of robots inside the MRI scanner is a very attractive solution: a robot manipulates the intervention instruments while MR images continuously give feedback of the position of the instruments which are controlled by the robot. MR compatible robotic systems have been researched and developed for prostate biopsy and brachytherapy (Chinzei et al, 2000, Krieger et al, 2005, Fischer et al, 2006, Stoianovici et al, 2007a, breast intervention (Kaiser et al, 2000, Larson et al, 2004, interventional spinal procedure (Hempel et al, 2003), neurosurgery (Masamune et al, 1995, Koseki et al, 2002, interventional liver therapy (Hata et al, 2005, Kim et al, 2002, and cardiac intervention (Li et al, 2008). Design of a system operating inside or close to the bore of a high field MRI scanner is of significant complexity.…”