In soft tissue, if the frequency of a wave is increased the Propagation Speed (PS) will... - Answer Remain the Same because stiffness and density affect
... [Show More] Propagation Speed.
What is the audible range? - Answer 20-20,000Hz
>20,000Hz=Ultrasound
Frequency is measured in - Answer Hertz (Hz)
is
Cycles per Second
Not affected by sonographer
Increase Frequency; Decrease Depth
A period is the length of time it takes for - Answer one complete wavelength to pass a fixed point
PRP is determined by - Answer Transmit time and receive time.
Period is measured in - Answer Time (μs)
When the sonographer changes the imaging depth what parameters are changed? - Answer PRP, PRF, Duty Factor
What is duty factor? - Answer The percentage or fraction of time that the system is transmitting a pulse (Time Sound is ON or ON-Time).
Propagation Speed in SOFT TISSUE - Answer 1.54 mm/μs
(1540 m/sec)
Unit of measurement for Pulse Duration, Duty Factor, PRP, and Period - Answer Time, (μs)
Pulse duration is determined by - Answer Sound Source Only
Pulse Duration is controlled by - Answer the ultrasound system and transducer
Pulse Duration Formula - Answer pulse duration (μs) = # cycles in pulse/frequency(MHz)
PD= Number of cycles in Pulse/ Frequency(Hz)
Spatial Pulse Length (SPL) (measurement) - Answer The distance that a pulse occupies in space from the start to the end of a pulse.
(mm)
Typical values for spatial pulse length in soft tissue. - Answer 0.1 to 1.0 mm
Spatial pulse length is determined by - Answer sound source and medium
Spatial Pulse Length is directly proportional to - Answer the Number of Cycles in the Pulse
and
the Wavelength
(Directly Proportional means that increased SPL will increase both the number of cycles in the pulse and the wavelength if increased).
Spatial pulse length is inversely proportional to - Answer Frequency (MHz)
(Inversely Proportional means that increased SPL will lower frequency. This is because axial resolution is better with lower frequency)
Pulse Duration (PD) - Answer The actual time from the start of a pulse to the end of that pulse; a single transmit, talking, or "on" time.
Time the pulse is on typically measured in (ms).
Pulse Length - Answer The distance of the pulse start to end or the
duration or length of a single pulse
Pulse Length is typically measured in (mm).
the ability of an object to resist compression and relates to the hardness of a medium? - Answer Stiffness.
Think:
↑ Stiffness ↑ Speed
↓ Density ↑ Speed
An increase in pulse repetition frequency would lead to: - Answer Increasing pulse repetition frequency, increases duty factor.
↑ PRF ↑ Duty Factor
Which of the following would have the highest propagation speed? - Answer Bone has the highest propagation speed, at 2000-4000 m/s.
What has the lowest propagation speed? - Answer air technically has the lowest propagation speed at 300 m/s
Which has the Slowest Propagation Speed?
Water
Soft Tissue
Bone
Lung tissue - Answer Lung Tissue
As imaging depth increases, the pulse repetition frequency (PRF) must: - Answer Decrease
As imaging depth increase, pulse repeition freqency (PRF) decreases.
↑ Imaging Depth ↓ PRF
What describes the amount of refraction that occurs at an interface? - Answer Snell's law
Refraction: the redirection of the transmitted sound beam
Snell's law describes the angle of transmission at an interface based on the angle of incidence and the propagation speeds of the two media.
Pressure is typically expressed in: - Answer Pascals (Pa)
The typical range of frequency for diagnostic ultrasound imaging is - Answer 1-20 Mhz is the typical range of frequency for diagnostic ultrasound imaging.
The attentuation coefficient in soft tissue is equal to: - Answer Attentuation Coeffcient = 1/2 (one half of the frequency in soft tissue)
The attentuation coeffcient (in dB/cm) is the rate at which sound is attentuated per unit depth.
Micro is denoted as: - Answer Micro is denoted as millionth (µ) [Show Less]