Collaborator: Dr. Aaron Fenster (Robarts Imaging Laboratories)
Background: Biomedical research using small animals often requires interventional procedures such as biopsies and injections. The success of a procedure is determined by the accuracy of the needle tip reaching the location of its target. If these procedures are performed inaccurately, the study can be jeopardized, either due to inability to repeat a procedure consistently in multiple animals or due to mortality or morbidity of the animals. We are developing a robotic manipulator for three-dimensional ultrasound-guided needle interventions that will address these issues. Possible applications of this technology include injection of contrast agents, cells, and therapeutic agents into mice and other small animal research models and aspiration biopsies of tumours in small animal cancer models.
Objectives: The robotic needle positioning system will be capable of accurately and repeatably reaching needle targets as small as 0.1 mm diameter. The needle positioning system will interface with a three-dimensional high-frequency ultrasound imaging system and image processing software will be developed to provide near-real-time needle and target position feedback to the robotic manipulator. Needle positioning accuracy will depend by the mechanical design of the manipulator and the temporal and spatial resolution of the image guidance.
Approach: The robotic manipulator (shown in the photograph of the device in the Image Gallery) possesses three degrees of freedom for positioning the needle in three dimensions. Two rotational joints are used to control needle orientation (roll and pitch). A third joint linearly translates the needle to perform insertion. The three intersecting axes create a remote centre of motion (RCM) that acts as a fulcrum for the three-dimensional orientation of the needle. The manipulator is calibrated using a macro lens CCD camera to find the centres of rotation about the pitch and roll axes separately. The needle position is adjusted to align the rotational axes and move its tip to the RCM. The calibration procedure compensates for manufacturing errors in the manipulator. The calibrated RCM defines the insertion point of the needle into the animal, and the needle tip is able to reach any point within a pyramidal volume extending below the RCM and delineated by the +/- 30 degree range of motion of the pitch axis, the +/- 45 degree range of motion of the roll axis, and the 20 mm range of motion of the translational axis. We are presently testing the needle positioning accuracy of the manipulator and exploring the feasibility of using a speckle tracking algorithm to measure sub-millimeter needle deflection, target displacement, and target deformation in 30 and 40 MHz ultrasound images acquired during needle insertion.
Recent Conference Presentations:
A.C. Waspe, H.J. Cakiroglu, J.C. Lacefield, and A. Fenster, "Design and calibration of a robotic needle positioning system for small animal imaging applications," American Association of Physicists in Medicine 47th Annual Meeting, Med. Phys., vol. 32, p. 2133, 2005.
A.C. Waspe, H.J. Cakiroglu, J.C. Lacefield, and A. Fenster, “A three-dimensional micro-ultrasound image-guided and robotically assisted needle positioning system,” 51st Annual Scientific Meeting of the Canadian Organization of Medical Physicists, Hamilton, ON, July 6-9, 2005.
