Range and Axis flashcards

Q: What is time of flight in ultrasound?- The time between pulse creation and echo reception.

Q: What is the speed of sound in soft tissue used in ultrasound systems? - 1.54 mm/μs (or 1540 m/s).

Q: What is the formula for calculating reflector depth?- Depth = (1.54 mm/μs × go-return time) / 2

Q: What is the "13 microsecond rule"?- For every 13 μs of go-return time, the reflector is 1 cm deep.

Q: What is Pulse Repetition Period (PRP)?- The time from the start of one pulse to the start of the next.

Q: How is PRP related to imaging depth?- PRP (μs) = Imaging depth (cm) × 13

Q: What is the formula for Pulse Repetition Frequency (PRF)- PRF = 77,000 / imaging depth (cm)

Q: What is axial resolution?- The ability to distinguish two reflectors that are close together along the beam’s path.

Q: How is axial resolution measured?- In units of distance (mm).

Q: What formula relates axial resolution to SPL?- Axial Resolution = SPL / 2

Q: What factors improve axial resolution?- Shorter SPL, shorter pulse duration, higher frequency, less ringing.

Q: What is the LAARD acronym used for?- It represents names for axial resolution: Longitudinal, Axial, Range, Radial, Depth.

Q: Axial resolution using wavelength and pulse cycles?- Axial Resolution = (Wavelength × # of cycles) / 2

Q: Axial resolution using frequency and cycles?- Axial Resolution = (0.77 × # of cycles) / frequency (MHz)

Q: What does a transducer do in ultrasound?- Converts electrical energy to sound and vice versa.

Q: What is piezoelectricity?- The ability of a material to generate voltage when deformed.

Q: What is PZT and why is it important?- Lead zirconate titanate, a man-made piezoelectric crystal used in ultrasound probes.

Q: What happens if PZT is heated above the Curie point?- It becomes depolarized and loses piezoelectric properties.

Q: What is the role of the matching layer in a transducer?- It matches impedance between PZT and skin to improve sound transmission.

Q: What is the thickness of the matching layer?- 0.25 × wavelength.

Q: What is the thickness of the PZT crystal?- 0.5 × wavelength.

Q: What does the backing (damping) material do?- Reduces ringing and shortens pulse duration.

Q: What are the drawbacks of backing material?- Decreased sensitivity, wide bandwidth, low Q-factor.

Q: What is Q-factor?- A unitless number representing the ratio of main frequency to bandwidth.

Q: Do imaging probes have a high or low Q-factor?- Low Q-factor (wide bandwidth).

Q: What defines a continuous wave (CW) probe?- A continuous electrical signal drives the PZT.

Q: How is frequency determined in a CW probe?- Frequency = electrical signal frequency.

Q: What determines frequency in a pulsed wave probe?- Speed of sound in PZT and its thickness.

Q: What happens to frequency if PZT is thinner?- Frequency increases.