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Parathyroid Perfusion Oral Presentation 1-16-2014

IS

Itamar Shapira

Transcript

Parathyroid Perfusion Project

Gabriela Caires de Jesus, Tianhang Lu, Itamar Shapira, James Tatum, Yu Zhou

Laser Speckle

Performance

Current Setup

Informal Observations

Principals

  • Laser and Camera System
  • Microfluidics Pump

Lab Validation Progress

Primary Objective

  • Diffuse Reflection
  • Speckle Contrast
  • Basic Mathematical Background
  • 4 cm field of view
  • Lens component of design is largest, however weight and size reduced
  • Phantom quality is critical
  • Temporal processing gives the best resolution
  • Working distance is critical
  • Perfused parathyroid condition

System and Environment

Developing the optimal imaging technique to determine the perfusion state of PT tissue in situ.

  • Current Setup:
  • ambient light on
  • small camera and laser
  • single lens and notch filter
  • Quantifiable variable that relates to perfusion

Photo Credit: Jae Gwan Kim

Surgical workflow

Problem Statement

Sample Image

  • Non-perfused parathyroid condition
  • If a parathyroid gland’s perfusion source is damaged during surgical operation, it may lose perfusion and thus, parathyroid function, specifically bodily calcium homeostasis.
  • Surgeons lack an objective measure to determine the state of perfusion for the parathyroid gland.

Laser Speckle Image of Phantom

Design

Laser

  • Quartet Laser Pointer, 651 nm
  • Class 3a
  • 50 mm long
  • 49.9 g
  • Reduced length by 89.7% (from 485.4 mm to 50 mm)
  • Reduced weight by 92.67% (from 680.4 g to 49.9 g)
  • This led to the camera + lens as the new design constraint

Fixed Distance

CCD Camera

  • 768 x 494 resolution
  • 45.5 mm L x 43.5 mm W x 44 mm H
  • Weighs 140g
  • Reduced length by 51.1% (from 93mm to 45.5 mm)
  • Reduced weight by 27% (from 192g to 140g)

Background

Macro Lens

Experiment

  • Focal Length 18-108 mm
  • F-stop 2.5
  • 162 mm L x 62 mm Dia
  • Manual aperture adjustment

Current Results

Needs

Filter

  • Bandpass filter that allows only 652.98nm with 20nm bandwidth

Solution Description

Performance Metrics

Processing

  • LabView to capture images at 29.7 fps
  • 150 frames used for processing on average
  • About 5 seconds of image acquisition time
  • Matlab to process images using both spatial and temporal methods
  • Quantitatively assess flow, to validate system for use with small vessels
  • Phantom
  • Microfluidics capillary system
  • Fluid with a dye will be pumped in the microcapillary network
  • Flow can be measured

Recommendations

Conclusions

1. Measure of perfusion

2. Time of data acquisition

3. SNR due to light pollution

4. Field of view, currently 4 cm

Laser Speckle

  • Device must establish perfusion state of PT.
  • Not exact value but a relative value.
  • Device must be safe.
  • Device must be appropriate for clinical use.
  • Acquisition and processing time must not interfere with surgical flow.
  • Device should be maximally modular and low cost.

The parathyroid is located in the neck and produces parathyroid hormone (PTH)

Speckle ratio = mean intensity vessel/mean intensity background

  • Primary success depends on obtaining POC for a device capable of determining postoperative parathyroid perfusion.
  • Clinical utility and developer interest.
  • Use of animal model.
  • Gain approval to test on animals
  • Obtain speckle image of perfused vasculature
  • Determine the threshold for necessary perfusion in the parathyroid

1ul temporal: ratio =1.257

1.5ul temporal: ratio =1.083

2ul temporal: ratio =1.128

James Tatum