3D Elastography

1
3D Elastography
Enabling Technology to Better Segment Isoechoic
Lesions

• Harish Krishnaswamy, Parker Wilson
• Mentor Emad Boctor, Dr. Russell Taylor

2
Background

• Liver cancer represents a significant source of
  morbidity and mortality in the United States and
  worldwide 1.
• Often times, cancer lesions appear to be
  isoechoic making it harder to differentiate from
  normal tissue.
• Frequent cause of failure in assessing the region
  of tissue destruction often results in local
  failure or excessively loss of healthy liver
  tissue 2.

3
Motivation

• Radio-frequency Ablation (RFA) is emerging as an
  effective approach for treating liver tumors. Key
  problems problems include tumor localization and
  monitoring the progress of ablation.
• B-Mode ultrasound (US) is the most popular method
  of targeting hepatic ablations, yet it lacks the
  ability to monitor the progress of tissue
  ablation.

4
Goals

• Real-time monitoring of tissue ablation and
  assessment of region of tissue destruction.
• The use of 3D ultrasound imaging to track changes
  in tissue elasticity due to thermal ablation. 3
• Generating 3D Strain and 3D US at the same rate.
• Design optimal robotic end-effector to provide
  ideal palpating scenario

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2D Strain Based Modeling

• Elasticity is a good parameter to differentiate
  various types of tissues. 7
• Depending on the rigidity of the tissue, the
  palpation will generate different strain fields.

Figure. 1 2D representation of strain based
imaging model. The overlay represents an A-line
with 1D cascaded spring system of unequal spring
constants. 3
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System Overview

• The overall robotic strain based imaging system
  (L) and schematic drawing of the robots
  end-effector holding the US probe (R). The large
  probe serves as a compression plate. 3

7
Strain images with corresponding pathology and
B-mode images at 100oC, with the RFA device
perpendicular to the plane of imaging. The white
contour is created on the pathological picture
and matches with the determined strain images. 3
8
Series of strain images with mutual information
TDE, over several ablation temperatures, in both
axial and perpendicular probe positions. 3
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Experimental Design

• The Phantom will be constructed in such a way
  that the scatter density will the be the same
  through out.
• The concentration of the gel will vary between
  the soft gel background and the inclusion.
• Data Collection Protocol
• Palpate and Move
• Move with Incline Compression
• Zig-Zag Compression Motion

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Approach

• Implementing the Ophirs and Lorenzs Strain
  Algorithms.
• Use correlation map as a weighing kernel for the
  successive 3D strain reconstruction.

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Division Of Labor

• Project Manager Harish Krishnaswamy
• Designing Phantom and Implementation of Algorithm
  along with Parker W.
• Parker Wilson
• Collection of Phantom Data Set in addition to
  implementing correlation as a method of
  determining 3D strain reconstruction along with
  Harish K.

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Deliverables

• Minimum Collecting the data and implementing the
  basic strain algorithms in MATLAB.
• Expected Make further analysis and write up a
  MICCAI paper.
• Maximum To move MATLAB implementation to C and
  test the free hand approach.

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Timeline

• Mar 1 Completion of data collection.
• Mar 21 Completion of MATLAB strain algorithm.
• April 7 Finish paper and analysis for
  submission to MICCAI.
• April 21 Implementation of Strain Algorithm in
  C.
• May 1 Integration of the 3D Strain Ultra Sound.

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Dependencies

• Materials for Phantom gel construction to be
  provided by Emad Boctor in CISST lab.
• Time on ultrasound machine for data collection
  and testing.
• Synchronization between tracker and Antares
  (Siemens).
• Using LARS in comply mode.

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Budget

• Materials and lab time covered under Dr.
  Taylors grant money.

16
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