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Medical Physics - INIR: Ultrasound Y3 > International Ultrasound Standards > Flashcards

International Ultrasound Standards Flashcards

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1
Q

What conditions must ultrasound scanners meet in order to produce the higher derated intensity?

A

Must display real-time MI 7& TI values, must provide an ALARA education programme.

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2
Q

What is the limit for derated I(spta)?

A

720mW/cm^2

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3
Q

What in the limit for the derated I(sppa)?

A

190W/cm^2

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4
Q

What MI does 190W/cm^2 equate to?

A

MI=1.9

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5
Q

What is the MI limit for opthalmology?

A

MI=0.23

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6
Q

What information should be issued with transducers supplied by a manufacturer?

A
  • Maximum MI & TI values
  • Derated Peak negative pressure
  • Acoustic Power
  • Centre Frequency
  • Aperture Dimensions
  • Pulse duration
  • Focal lengths
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7
Q

What should be covered by the Track 3 Education Programme?

A
  • Benefits and Risk of Use
  • Risk of NOT use
  • Risk associated with increasing Acoustic power
  • Benefits of increasing Acoustic power
  • Responsibility of user at higher acoustic powers
  • ALARA principle
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8
Q

What is the I(spta) limit for ophthalmology?

A

50mW/cm^2

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9
Q

What are the MI and TI limits for ophthalmology?

A

MI - 0.23, TI - 1.0

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10
Q

What are the MI and TI limits for all other scanning? (FDA)

A

MI - 1.9, TI - 6.0

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11
Q

To what class, under EU MDD, do ultrasound scanners belong?

A

Class IIa - medium risk

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12
Q

Under IEC 60601-2-37, for what is the operator responsible?

A
  • Understanding the risks of the output of the equipment

- Obtaining the diagnostic information whilst minimising the risk to the patient.

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13
Q

Under IEC 60601-2-37, What are general requirements for using Ultrasound?

A
  • Prudent use and regular testing statements must be provided.
  • Real time MI and TI valuer must be displayed (if the scanner is capable of exceeding an MI or TI of 1.0).
  • Maximum Mi and TI values should be provided for each mode.
    Transducer surface temperatures must not exceed 43 (in”use”) or 50 (in air) degC.
  • For trans-oesophageal probes, real-time surface temperatures must be displayed if T exceeds 41 degC.
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14
Q

What guidance is given under IEC 60601-2-37?

A
  • There are no stated TI or MI intensity limits
  • Output should be limited due to the manufacturers risk management
  • TI values over 1.0 might best be avoided in obstetrics.
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15
Q

When is the MI of greater importance?

A
  • When using contrast material
  • Cardiac scanning (proximity to lung)
    Abdominal bowel scanning (presence of bowel gas)
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16
Q

When is the TI of greater importance?

A
  • 1st Trimester scanning
  • Foetal skull and spine scanning
  • Neonatal head scanning
  • Patients with fever
  • Poorly perfused tissue
  • Ophthalmic scans
  • If rib bone is exposed
17
Q

What are the temperature limits for transducer use when coupled to a patient?

A

Max temperature - 43 degC

Max temperature rise - 10 deg (external), 6 degC internal

18
Q

What equipment would you use to measure W0?

A

Radiation force balance

19
Q

What equipment would you use to measure I(ta)?

A

Hydrophone

20
Q

What is the formula for the mechanical index?

A

MI = p_/(fc^1/2)
p id the peak rarefactional pressure and derated by 0.3dB/MHz,
fc is the centre frequency of the probe

21
Q

What are the three TI measurements?

A
  • TIS - soft tissue
  • TIB - bone at focus
  • TIC - cranial bone
22
Q

What are the three different measurement set ups for TI?

A
  • Scanned
  • Unscanned with small aperture
  • Unscanned with large aperture
23
Q

What are the requirements for acoustic output reporting from IEC 61157?

A
  • Maximum non-derated p_, and I(spta), and W0 and fc must be provided for each mode
  • If p_< 1Mpa and I(spta) < 100mW/cm^2 then fewer parameters are required.
24
Q

What is the rationale behind the acoustic reporting parameters from IEC 61157?

A
  • The information can be used for exposure planning in bio-effects studies and exposure data in prospective epidemiological studies.
  • Nonlinear distortion causes major problems in the characterization of ultrasonic fields. Care should be taken when using the data.

Medical Physics - INIR: Ultrasound Y3 (6 decks)

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