Spring 2024 SPI Ch 7-10

• what's go-return time?

  the time it takes for an ultrasound pulse to travel from the source, bounce off an object, and come back to the detector
• go-return time aka

  time of flight
• in soft tissue, for every 13μs of go-return time the reflector is 1cm deeper in the body
• depth calculation formula

  Depth (mm)= 1.54 mm/μs ×go-return time μs / 2
• objects close to the surface have a short go-return time
• objects deeper inside have a longer go-return time
• what's PRP?

  the start of one pulse to the start of the next pulse

  
• **since a pulse travels to the reflector and back to the transducer, the total distance that a pulse travels is twice the reflector depth**
• PRP = go-return time
• what's this showing?

  PRP = pulse repetition period

  
• low PRP = shallow depths

  high PRP = deeper depths
• PRP is directly related to the maximum imaging depth
• PRP formula

  PRP (µs) = imaging depth (cm) x 13 µs/cm
• example for PRP problem

  when depth of view is set to 5 cm, PRP is 65 µs (5 x 13 µs)
• what's the speed of sound for soft tissue?

  1540 m/s or 154,000 cm/s
•  when depth is 20 cm, what is the PRP?

  PRP = 260 µs
• PRF is inversely related to the maximum imaging depth
• formula for PRF

  PRF (Hz) = 77,000 cm/s / depth (cm)
• example for PRF

  when the depth of view is set to 7.7 cm, then the PRF is 10,000 Hz

  (77,000/7.7)
• label the following

  :-{D

  A) wire

  B) case

  C) matching layer

  D) pzt

  E) backing material

  F) electric shield

  G) acoustic insulator