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, R&D, Sound Surgical Technologies, LLC.

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Laboratory Evaluation of a Next Generation Transversal Ultrasound System

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Laboratory evaluation of a next generation transversal ultrasound system

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, R&D,

Sound Surgical Technologies, LLC

I am a consultant to several phaco companies, and have received research funding for this work

Contact email: [email protected]


Purpose outline

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


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

What are the technologies/modes?


Thermal measurements materials methods

Thermal Measurements: Materials & Methods

  • 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 22±0.5°C

  • Systems run for 5 second foot pedal time; results scaled to 0.5 or 1 sec

  • 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


  • Thermal testing results

    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


    Thermal testing results1

    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 3.5°C

    • In Longitudinal mode, for the same WS mode, the temperature rise was lower, on the order of 0.5 to 1.0°C

    • 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


    Measuring cutting materials methods

    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


    Cutting effectiveness results

    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


    Acoustic output materials methods

    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


    Acoustic output results

    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


    Comparison to torsional

    Comparison to Torsional

    • 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


    Discussion conclusion

    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


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