1. Declaration of Conflict of Interest or Relationship Speaker Name: Yong-Lae Park I have no conflicts of interest to disclose with regard to the subject matter of this presentation.

2. 2/14 Stanford University MRI-Compatible Haptics: Feasibility of Using Optical Fiber Bragg Grating Sensors to Detect Deflection of Needles in an MRI environment Yong-Lae Park, Santhi Elayaperumal, Elena Kaye, Kim B. Pauly, Richard J. Black, and Mark R. Cutkosky Stanford University

3. 3/14 Outline Background Fiber Bragg Grating (FBG) Sensors Prototype Development Experimental Results Conclusions and Future Work

4. 4/14 MRI-Guided Needle Procedures MR guided biopsy Lesion Localization Tumor Ablation Therapeutic Injection Problem: Needle Deflection

5. 5/14 Goal: Detection of Needle Deflection Existing Technologies –MR Tracking –Rapid MRI –Gradient-based Tracking Objective: MR-Haptics –Detection of needle deflection –Strain sensing approach

6. 6/14 Fiber Bragg Grating (FBG) Sensors Immune to electromagnetic Interference High resolution (0.1 με) Multiple sensors in one fiber Small (80 μm thick) and flexible Input Transmission Reflection FBG Optical Fiber Input Transmission Reflection Optical Fibers 5 mm FBG Needle

7. 7/14 Deflection Estimation using Beam Theory Curvature (1/ρ) Slope Deflection y x x x dy dx d2yd2y dx 2 εxεx d Curvature = 1 ρ = x2x2 x1x1 f(x) = ax 2 +bx+c Sensor 1 Sensor 2 ε x : strain measured by FBG sensor ρ: radius of curvature d: distance from neutral axis Slope = ∫ f(x) dx Deflection = ∫∫ f(x) dx

8. 8/14 Model Construction F1F1 F2F2 Sensor 1 Sensor 2 x1x1 x2x2 2 / L L = 15cm Tip Deflection EZEM MRI-compatible biopsy needle –22 ga x 15 cm –Material: Inconel 625 alloy

9. 9/14 Determination of Sensor Locations x2x2 x1x1 x2x2 x1x1 x2x2 x1x1 x 1 =25 mm x 2 =82 mm Deflection Error Plot Sensitivity of Deflection Error For x 1 For x 2 Minimum Error Region x2x2 x1x1 Sensor 1 Sensor 2

10. 10/14 Prototype Development Two FBGs on a biopsy needle Measure strains when deflected No artifact from the optical fiber (MR-image of the bent needle) No sensor noise Remote sensor interrogation original needle shape bent needle deflection Sensor 1 Sensor 2 25 mm 82 mm

11. 11/14 One Point Bending X 2 = 82 X 1 = 25 Sensor 1 Sensor 2 EZEM MRI-compatible biopsy needle –22 ga x 15 cm –Material: Inconel 625 alloy Deflection = - 5 mm, Error = 0.13 mm (2.6 %)

12. 12/14 Two Point Bending (S-curve) X 2 = 82 X 1 = 25 Sensor 1 Sensor 2 Deflection = - 10 mm, Error = 0.27 mm (2.7 %) EZEM MRI-compatible biopsy needle –22 ga x 15 cm –Material: Inconel 625 alloy

13. 13/14 Conclusions Less than 3% estimation error –in 5 mm deflection for one point bending –In 10 mm deflection for two point bending No artifacts on MR images No degradation of sensor accuracy in MRI environments

14. 14/14 Future Work Embedded FBGs Polymer Base Socket Biopsy Needle Optical Fibers Fabrication method Three dimensional sensing Force and position sensing in MR- compatible robotics Instrumented base socket