Declaration of Conflict of Interest or Relationship

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.

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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
Stanford University
3
Outline

• Background
• Fiber Bragg Grating (FBG) Sensors
• Prototype Development
• Experimental Results
• Conclusions and Future Work

4
MRI-Guided Needle Procedures

• MR guided biopsy
• Lesion Localization
• Tumor Ablation
• Therapeutic Injection
• Problem Needle Deflection

5
Goal Detection of Needle Deflection

• Existing Technologies
• MR Tracking
• Rapid MRI
• Gradient-based Tracking
• Objective MR-Haptics
• Detection of needle deflection
• Strain sensing approach

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Fiber Bragg Grating (FBG) Sensors

• Immune to electromagnetic Interference
• High resolution (0.1 µe)
• Multiple sensors in one fiber
• Small (80 µm thick) and flexible

Optical Fibers
Input
Transmission
FBG
Reflection
Optical Fiber
5 mm
FBG
Input
Transmission
Reflection
Needle
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Deflection Estimation using Beam Theory
ex strain measured by FBG sensor ? radius of
curvature d distance from neutral axis
Sensor 1
Sensor 2
x1
x2
Curvature (1/?)
x
1
Curvature

?
f(x) ax2bxc
Slope
Slope ? f(x) dx
x
Deflection ?? f(x) dx
Deflection
x
y
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Model Construction

• EZEM MRI-compatible biopsy needle
• 22 ga x 15 cm
• Material Inconel 625 alloy

L 15cm
2 / L
F2
F1
Sensor 2
Sensor 1
Tip Deflection
x1
x2
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Determination of Sensor Locations
Sensitivity of Deflection Error
Deflection Error Plot
For x1
Minimum Error Region
x2
x2
x125 mm x282 mm
x1
For x2
x1
x2
Sensor 1
Sensor 2
x1
x2
x1
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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

Sensor 2
Sensor 1
25 mm
82 mm
deflection
original needle shape
bent needle
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One Point Bending

• EZEM MRI-compatible biopsy needle
• 22 ga x 15 cm
• Material Inconel 625 alloy

Sensor 2
Sensor 1
X1 25
X2 82
Deflection - 5 mm, Error 0.13 mm (2.6 )
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Two Point Bending (S-curve)

• EZEM MRI-compatible biopsy needle
• 22 ga x 15 cm
• Material Inconel 625 alloy

Sensor 2
Sensor 1
X1 25
X2 82
Deflection - 10 mm, Error 0.27 mm (2.7 )
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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

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Future Work

• Fabrication method
• Three dimensional sensing
• Force and position sensing in MR-compatible
  robotics
• Instrumented base socket

Biopsy Needle
Polymer Base Socket
Optical Fibers
Embedded FBGs