Absolute measurements of ultrasonic pressure by using high magnetic fields.

IEEE transactions on ultrasonics, ferroelectrics, and frequency control · 1999 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 3995

Study snapshot

PublicationIEEE transactions on ultrasonics, ferroelectrics, and frequency control · 1999

Study typeengineering

Reported directionUnclear

Evidence ratingInsufficient

Abstract

A hydrophone is introduced that exploits the emf signal generated in a conductor when sonicated in the presence of a uniform static magnetic field. The method uses a small metal coil or metal membrane as a hydrophone receiver. Acoustic signals at 748 kHz are introduced in 1.5 T and 4.7 T fields and recorded both through direct electrical contact with the hydrophone and via RF pick-up coils, allowing wireless placement of the hydrophone. Linear response Is confirmed over four orders of magnitude in the pressure amplitude. Waveforms determined from the detected voltage are shown to be in excellent agreement with those obtained using a calibrated polyvinylidene difluoride film, and absolute values correlate within 20%. The methods are conceptually suitable for use in the presence of the high and uniform field of commercial MR scanners. The hydrophone may appear particularly useful as a quality assurance device in therapeutic and diagnostic acoustic techniques that use MRI.

Machine Enhanced Logic

AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeengineering

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

Exposure0.748 MHz

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

A hydrophone concept is described that detects an EMF signal generated in a conductor when exposed to ultrasound in a uniform static magnetic field. Acoustic signals at 748 kHz were recorded in 1.5 T and 4.7 T fields, showing linear response over four orders of magnitude in pressure amplitude, with waveforms in excellent agreement with a calibrated PVDF film and absolute values correlating within 20%.

Outcomes measured

Hydrophone voltage response to acoustic pressure in static magnetic fields
Linearity of pressure measurement
Agreement with calibrated PVDF film hydrophone
Feasibility of wireless placement via RF pick-up coils

Limitations

No biological/health outcomes reported (engineering/measurement study).
Sample size and experimental details beyond field strengths and frequency are not provided in the abstract.

View raw extracted JSON

{
  "study_type": "engineering",
  "exposure": {
    "band": null,
    "source": "static magnetic field (MR-like) with ultrasound; RF pick-up coils used for signal detection",
    "frequency_mhz": 0.748,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "Hydrophone voltage response to acoustic pressure in static magnetic fields",
    "Linearity of pressure measurement",
    "Agreement with calibrated PVDF film hydrophone",
    "Feasibility of wireless placement via RF pick-up coils"
  ],
  "main_findings": "A hydrophone concept is described that detects an EMF signal generated in a conductor when exposed to ultrasound in a uniform static magnetic field. Acoustic signals at 748 kHz were recorded in 1.5 T and 4.7 T fields, showing linear response over four orders of magnitude in pressure amplitude, with waveforms in excellent agreement with a calibrated PVDF film and absolute values correlating within 20%.",
  "effect_direction": "unclear",
  "limitations": [
    "No biological/health outcomes reported (engineering/measurement study).",
    "Sample size and experimental details beyond field strengths and frequency are not provided in the abstract."
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "hydrophone",
    "ultrasonic pressure measurement",
    "static magnetic field",
    "1.5 T",
    "4.7 T",
    "MRI",
    "electromotive force signal",
    "RF pick-up coils",
    "wireless measurement",
    "quality assurance"
  ],
  "suggested_hubs": [
    {
      "slug": "who-icnirp",
      "weight": 0.2,
      "reason": "Involves exposure to strong static magnetic fields comparable to MRI, which can relate to guideline discussions, though this is an engineering measurement paper."
    }
  ]
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1109/58.808874
PubMed: 18244347

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