Declaration of Conflict of Interest or Relationship Speaker Name: Yong-Lae Park I have no conflicts...

Declaration of Conflict of Interest or Relationship

Speaker Name: Yong-Lae ParkSpeaker Name: Yong-Lae Park

I have no conflicts of interest to disclose with regard to the subject matter ofI have no conflicts of interest to disclose with regard to the subject matter ofthis presentation.this presentation.

2/14Stanford 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

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Outline

• Background

• Fiber Bragg Grating (FBG) Sensors

• Prototype Development

• Experimental Results

• Conclusions and Future Work

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MRI-Guided Needle Procedures

• MR guided biopsy

• Lesion Localization

• Tumor Ablation

• Therapeutic Injection

• Problem: Needle Deflection

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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 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

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Deflection Estimation using Beam Theory

Curvature (1/ρ)

Slope

Deflectiony

x

x

x

dy

dx

d2y

dx2

εx

dCurvature =

1

ρ=

x2 x1

f(x) = ax2+bx+c

Sensor 1 Sensor 2εx: strain measured by FBG sensor

ρ: radius of curvature

d: distance from neutral axis

Slope = ∫ f(x) dx

Deflection = ∫∫ f(x) dx

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Model Construction

F1F2

Sensor 1 Sensor 2

x1

x2

2 / L

L = 15cm

Tip Deflection

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

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Determination of Sensor Locations

x1

x2

10 20 30 40 50 60 70

80

90

100

110

120

130

140

150

-16

-14

-12

-10

-8

-6

-4

-2

0

2

x 104

x2

x1

x1

x2

10 20 30 40 50 60 70

80

90

100

110

120

130

140

150

-2.5

-2

-1.5

-1

-0.5

x 105

x1

x2

10 20 30 40 50 60 70

80

90

100

110

120

130

140

150

-6

-5

-4

-3

-2

-1

x 104

x2

x1

x2

x1

x1=25 mm

x2=82 mm

Deflection Error Plot Sensitivity of Deflection Error

For x1

For x2

Minimum Error Region

x2 x1 Sensor 1 Sensor 2

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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

original needle shape

bent needle

deflection

Sensor 1 Sensor 2

25 mm

82 mm

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One Point Bending

X2 = 82

X1 = 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 %)

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Two Point Bending (S-curve)

X2 = 82

X1 = 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

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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

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