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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
3/14
Outline
• Background
• Fiber Bragg Grating (FBG) Sensors
• Prototype Development
• Experimental Results
• Conclusions and Future Work
4/14
MRI-Guided Needle Procedures
• MR guided biopsy
• Lesion Localization
• Tumor Ablation
• Therapeutic Injection
• Problem: Needle Deflection
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
6/14
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
7/14
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
8/14
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
9/14
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
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
11/14
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 %)
12/14
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
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
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