International Ultrasound Standards Flashcards
What conditions must ultrasound scanners meet in order to produce the higher derated intensity?
Must display real-time MI 7& TI values, must provide an ALARA education programme.
What is the limit for derated I(spta)?
720mW/cm^2
What in the limit for the derated I(sppa)?
190W/cm^2
What MI does 190W/cm^2 equate to?
MI=1.9
What is the MI limit for opthalmology?
MI=0.23
What information should be issued with transducers supplied by a manufacturer?
- Maximum MI & TI values
- Derated Peak negative pressure
- Acoustic Power
- Centre Frequency
- Aperture Dimensions
- Pulse duration
- Focal lengths
What should be covered by the Track 3 Education Programme?
- 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
What is the I(spta) limit for ophthalmology?
50mW/cm^2
What are the MI and TI limits for ophthalmology?
MI - 0.23, TI - 1.0
What are the MI and TI limits for all other scanning? (FDA)
MI - 1.9, TI - 6.0
To what class, under EU MDD, do ultrasound scanners belong?
Class IIa - medium risk
Under IEC 60601-2-37, for what is the operator responsible?
- Understanding the risks of the output of the equipment
- Obtaining the diagnostic information whilst minimising the risk to the patient.
Under IEC 60601-2-37, What are general requirements for using Ultrasound?
- 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.
What guidance is given under IEC 60601-2-37?
- 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.
When is the MI of greater importance?
- When using contrast material
- Cardiac scanning (proximity to lung)
Abdominal bowel scanning (presence of bowel gas)
When is the TI of greater importance?
- 1st Trimester scanning
- Foetal skull and spine scanning
- Neonatal head scanning
- Patients with fever
- Poorly perfused tissue
- Ophthalmic scans
- If rib bone is exposed
What are the temperature limits for transducer use when coupled to a patient?
Max temperature - 43 degC
Max temperature rise - 10 deg (external), 6 degC internal
What equipment would you use to measure W0?
Radiation force balance
What equipment would you use to measure I(ta)?
Hydrophone
What is the formula for the mechanical index?
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
What are the three TI measurements?
- TIS - soft tissue
- TIB - bone at focus
- TIC - cranial bone
What are the three different measurement set ups for TI?
- Scanned
- Unscanned with small aperture
- Unscanned with large aperture
What are the requirements for acoustic output reporting from IEC 61157?
- 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.
What is the rationale behind the acoustic reporting parameters from IEC 61157?
- 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.
