Technology 2017-12-13T01:20:14+00:00

Technology

Why HIFU therapy?

Doctors and researchers across the biomedical and biological fields use High Intensity Focused Ultrasound (HIFU) therapy to provide treatment or bioacoustics enhancement using ultrasound technology. While there are plenty of surgical options available, only HIFU allows for non-invasive surgical options to treat deep targets within the body (for conditions like kidney stones or to kill malignant cells) without causing collateral damage of surrounding tissue.

TED Talk on HIFU Surgery

How does medical HIFU therapy work?

An electrical impulse excites the HIFU transducer where electrical power converts into acoustic power at the radiating surface. The acoustic intensity increases as the acoustic power travels along the beam axis until it reaches the geometric focus (much like light from an optical lens). It is not until the acoustic power concentrates into a small enough cross-sectional area near the geometric focus before the energy becomes therapeutic. This therapeutic volume is in the shape of an ellipsoid and is defined from the acoustic maximum down to full width half power, or -6 dB pressure-squared.

Glossary/Definitions:

  • HIFU: High Intensity Focused Ultrasound (either uses a concave spherical aperture or plano-concave spherical lens)
  • HITU: High Intensity Therapeutic Ultrasound (high intensity, not necessarily focused)
  • FUS: Focused Ultrasound (same as HIFU)
  • MRgFUS: Magnetic Resonance Guided Focused Ultrasound
  • MR Compatible: Transducer contains no paramagnetic or diamagnetic susceptible materials
  • MR Safe: Contains no ferrous materials and is safe to be used in an MR environment, not necessarily artifact free
  • PCD: Passive Cavitation Detector
  • PAM: Passive Acoustic Mapping
  • TPO: Transducer Power Output
  • USgFUS: Ultrasound Guided Focused Ultrasound

HIFU Parameters

HIFU Single Element Transducers

Prioritizing technical tradeoffs when designing your therapy transducer will be useful when speaking with our technical staff. Below are some questions that will help us understand if a transducer from our Transducer Selection Guide will support your application, or if a custom transducer is required.

  1. Define your frequency.
    1. What is the treatment medium of interest? (I.e. in vivo swine prostate, in vitro bovine liver, deionized water, etc.)
    2. What is the acoustic effect of interest? (I.e. inertial cavitation, boiling histotripsy, thermal ablation, etc.)
    3. What is the focal length (from radiating surface to intended focus)? (i.e. 5 cm’s from the subjects entry plane to the intended focus)
    4. What materials will be present in the near field (i.e. ribs, skin, vasculature, etc.) up until the intended focus?
  2. Define the transducer geometry.
    1. What is the focal lateral width and axial length full-width-half-power of interest?
    2. What are your anatomical and/or structure limitations? Do you require a central opening for USgFUS imaging?
  3. Define your power.
    1. Peak and average power OR pressure (answer either):
      1. What are the required peak and average pressures at the focus to achieve the acoustic effect of interest? (i.e. 20.0 MPa_PNP of peak pressure) OR
      2. What is the required peak and average acoustic power at the radiating surface?
    2. What burst duration (in cycles), pulse repetition (rate or frequency) OR duty cycle do you intend to use?
  4. Do you require MR compatibility?


HIFU Array Element Transducers

HIFU array transducer and systems are useful for those are required to mechanically fix their transducer is with respect to the intended treatment area, and electrically steer the single focus in a 3-dimensional volume. In addition to the questions above, prioritizing technical tradeoffs when designing your array will be useful when speaking with our technical staff. Below are some questions that will help us select a standard array or design a custom array.

  1. Define number of channels.
    1. Do you require axial steering, lateral steering or volumetric steering?
    2. How many channels to you have access to?
    3. How much power per channel will your system output?
    4. If you do not currently have a multi-channel system:
      1. What steering range do you require down -3 dB amplitude?
  2. Grating lobes v. power density. Which is more important?