ARDMS SPI STUDY GUIDE 2023

ARDMS SPI STUDY GUIDE 2023 In soft tissue, if the frequency of a wave is increased the Propagation Speed (PS) will... Ans- Remain the Same because stiffness and density affect Propagation Speed. What is the audible range? Ans- 20-20,000Hz 20,000Hz=Ultrasound Frequency is measured in Ans- Hertz (Hz) is Cycles per Second Not affected by sonographer Increase Frequency; Decrease Depth A period is the length of time it takes for Ans- one complete wavelength to pass a fixed point PRP is determined by Ans- Transmit time and receive time. Period is measured in Ans- Time (μs) When the sonographer changes the imaging depth what parameters are changed? Ans- PRP, PRF, Duty Factor What is duty factor? Ans- 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 Ans- 1.54 mm/μs (1540 m/sec) Unit of measurement for Pulse Duration, Duty Factor, PRP, and Period Ans- Time, (μs) Pulse duration is determined by Ans- Sound Source Only Pulse Duration is controlled by Ans- the ultrasound system and transducer Pulse Duration Formula Ans- pulse duration (μs) = # cycles in pulse/frequency(MHz) PD= Number of cycles in Pulse/ Frequency(Hz) Spatial Pulse Length (SPL) (measurement) Ans- 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. Ans- 0.1 to 1.0 mm Spatial pulse length is determined by Ans- sound source and medium Spatial Pulse Length is directly proportional to Ans- 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 Ans- Frequency (MHz) (Inversely Proportional means that increased SPL will lower frequency. This is because axial resolution is better with lower frequency) Pulse Duration (PD) Ans- 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 Ans- 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? Ans- Stiffness. Think: ↑ Stiffness ↑ Speed ↓ Density ↑ Speed An increase in pulse repetition frequency would lead to: Ans- Increasing pulse repetition frequency, increases duty factor. ↑ PRF ↑ Duty Factor Which of the following would have the highest propagation speed? Ans- Bone has the highest propagation speed, at m/s. What has the lowest propagation speed? Ans- air technically has the lowest propagation speed at 300 m/s Which has the Slowest Propagation Speed? Water Soft Tissue Bone Lung tissue Ans- Lung Tissue As imaging depth increases, the pulse repetition frequency (PRF) must: Ans- Decrease As imaging depth increase, pulse repeition freqency (PRF) decreases. ↑ Imaging Depth ↓ PRF What describes the amount of refraction that occurs at an interface? Ans- 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: Ans- Pascals (Pa) The typical range of frequency for diagnostic ultrasound imaging is Ans- 1-20 Mhz is the typical range of frequency for diagnostic ultrasound imaging. The attentuation coefficient in soft tissue is equal to: Ans- 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: Ans- Micro is denoted as millionth (µ) What is described as the distance over which one cycle occurs? Ans- Wavelength is distance over which one cycle occurs, or the distance from the beginning of one cycle to the end of the same cycle. Remember, it asks for distance over which one cycle occurs. Stiffness and propagation speed are Ans- Directly Related Also remember: ↑ Stiffness ↑ Speed ↓ Density ↑ Speed Areas of high pressure and density are referred to as: Ans- Compressions What type of wave is sound? Ans- Mechanical and Longitudinal Wave The frequency ranges for ultrasound are: Ans- Ultrasound frequency is 20 to 20,000 Hz The speed of sound in soft tissue is Ans- Speed of sound in soft tissue is 1540 m/s Which transducer fires the elements in groups? Ans- Linear sequenced array fires the elements in groups The units for wavelength is Ans- Wavelength units are (Millimeters) Enhancement is caused by Ans- Weakly attenuating structures The wavelength in a material having a propagation speed of 1.5 mm/µs employing a transudcer frequency of 5.0 MHz is: Ans- 0.3 m