Laboratory Evaluation of a Next Generation Transversal Ultrasound System

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Laboratory Evaluation of a Next Generation
Transversal Ultrasound System

• Mark E. Schafer, Ph.D.
• President and Principal Scientist, Sonic Tech,
  Inc.
• Chief Technology Officer and VP, RD,
• Sound Surgical Technologies, LLC

I am a consultant to several phaco companies, and
have received research funding for this work
Contact email marks_at_sonictech.com
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Purpose Outline

• Purpose
• To provide baseline comparative data for
  different phaco devices, specifically for a newly
  introduced transversal system AMO Whitestar
  Signature with Ellips FX
• Testing focused on Clinically Relevant settings
• Outline
• Measurement results using several previously
  studied approaches
• Needle Shaft Temperature Rise (non-frictional)
• Cutting Effectiveness into artificial lens
  material
• Acoustic Output
• Compare results with another non-longitudinal
  phaco device Infiniti Torsional Ozil
• Discussion and Conclusion

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What are the technologies/modes?

• Standard Longitudinal phaco is an in/out motion
• Torsional or T-phaco uses a twisting motion
  of the tip rather than a longitudinal motion
  (only one of the two modes can operate at a time,
  therefore the need to switch back and forth)
• Transverse or Ellips uses a combination of
  side to side and in/out simultaneously may be
  used with either straight or bent tips

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Thermal Measurements Materials Methods

• High resolution thermal imaging (FLIR) camera
  records thermal image of hub, needle, and tip
• An open fluid chamber allows the entire length of
  the needle to be examined
• Cup designed so that fluid would only touch tip,
  to allow aspiration, but not interfere with
  thermal imaging
• Inner cutaway cup maintained fluid at desired
  level outer cup held overflow
• Hub, shaft, and tip tracked and separately
  recorded

• Full computer control and acquisition of thermal
  images for analysis
• Irrigation and aspiration flows balanced to mimic
  closed system in eye Fluid rate precisely
  measured at 30ml/min, at temperature of 220.5C
• Systems run for 5 second foot pedal time results
  scaled to 0.5 or 1 sec

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Thermal Testing Results

• Thermal imaging showed distributed heat sources
  for transversal mode included both the hub region
  and the shaft
• In longitudinal mode, the heat source was
  predominantly in the hub transition region
• Hyperpulse (WhiteStar) modes reduced the thermal
  rise
• Analysis was scaled to the one second on-time
  point, as shown in the graph by the vertical line
• Multiple experiments were conducted under the
  same conditions and the results averaged

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Thermal Testing Results

• The one-second temperature rise for Elllips at
  typical clinical settings of 25-50 amplitude, in
  a WhiteStar 6-12 mode, ranged from 2.1 to 3.5C
• In Longitudinal mode, for the same WS mode, the
  temperature rise was lower, on the order of 0.5
  to 1.0C
• The difference is due to the location of the heat
  source
• Note that this does not account for friction
  between the shaft and the sleeve, which would be
  significantly higher in longitudinal mode than in
  transversal or torsional

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Measuring Cutting Materials Methods

• Custom cutting force system
• Full computer control of motor and high
  resolution acquisition of position and force data
  for analysis
• Simulated lens target material
• Constant force (60g weight), measure displacement
  as a function of time

• Fluid rates maintained at 30cc/min
• 10 second experiment initial 2 seconds to
  establish position baseline systems then run for
  8 second foot pedal time
• Systems operated over a range of clinically
  relevant/recommended settings

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Cutting Effectiveness Results

• Multiple test runs conducted for each measured
  condition
• Penetration measured and analyzed to find a
  cutting rate in terms of millimeters per second

• Ellips cutting rates varied from 0.35mm/sec at
  25 setting to 1.7mm/sec at the 50 setting

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Acoustic Output Materials Methods

• Acoustic measurement system captures both the low
  frequency (handpiece drive) energy as well as the
  cavitational energy
• Rotational fixture allows mapping the
  distribution of energy, which relates to the
  motional direction of the tip
• Data can correlate to cutting efficiency
  depending upon cavitation readings

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Acoustic Output Results

• Drive energy levels match theory for
  longitudinal for transversal, less acoustic
  energy is generated because of the acoustic
  dipole pattern, as confirmed by angular data
• Difference between theory and measurement
  represents low frequency ultrasonic energy
  converted into Cavitation
• In Transveral mode, Cavitation is generated in
  region around the tip including the sides, rather
  than just at the front, as is the case for
  Longitudinal
• The front panel setting which denotes the start
  of Cavitation action matches the setting which
  demonstrates increased cutting effectiveness

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Comparison to Torsional
Test Metric Ellips FX (50 amp, WS 6-12) Torsional (100)
Thermal Rise at 1 second 3.5C 9.9C
Cutting Rate into lens material 1.7mm/sec 0.6mm/sec
Acoustic Output Comparable, and significantly less than longitudinal mode Comparable, and significantly less than longitudinal mode

• Transversal mode produces less internal heating,
  with improved cutting performance, in comparison
  with Torsional, at clinically relevant/recommended
  amplitude settings
• This is due in part because Transversal motion
  preserves some longitudinal component
• Transversal mode can also be used with straight
  tips, which permits more choices for the surgeon
  bent tips would be expected to have slightly
  better cutting performance, and higher acoustic
  output, without significantly higher thermal rise

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Discussion / Conclusion

• This study provided an initial investigation into
  this new phaco modality, which was only
  introduced into the market this year
• Additional work will be required to examine all
  the interdependent configuration possibilities,
  such as drive setting/mode and tip size and
  configuration
• Preliminary data suggest that Transversal mode
  demonstrates superior characteristics in terms of
  the balance of safety and efficacy, relative to
  other non-longitudinal modalities
• Ultimate goal is to provide users with a
  consistent set of metrics by which to compare
  different systems, permitting a better
  understanding of energy input and clinical
  outcome