ARDMS SPI STUDY GUIDE.docx

In soft tissue, if the frequency of a wave is increased the Propagation Speed (PS) will... - correct answer Remain the Same because stiffness and density affect Propagation Speed. What is the audible range? - correct answer 20-20,000Hz 20,000Hz=Ultrasound Frequency is measured in - correct 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 - correct answer one complete wavelength to pass a fixed point PRP is determined by - correct answer Transmit time and receive time. Period is measured in - correct answer Time (μs) When the sonographer changes the imaging depth what parameters are changed? - correct answer PRP, PRF, Duty Factor What is duty factor? - correct 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 - correct answer 1.54 mm/μs (1540 m/sec) Unit of measurement for Pulse Duration, Duty Factor, PRP, and Period - correct answer Time, (μs) Pulse duration is determined by - correct answer Sound Source Only Pulse Duration is controlled by - correct answer the ultrasound system and transducer Pulse Duration Formula - correct answer pulse duration (μs) = # cycles in pulse/frequency(MHz) PD= Number of cycles in Pulse/ Frequency(Hz) Spatial Pulse Length (SPL) (measurement) - correct 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. - correct answer 0.1 to 1.0 mm Spatial pulse length is determined by - correct answer sound source and medium Spatial Pulse Length is directly proportional to - correct 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 - correct 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) - correct 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 - correct 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? - correct answer Stiffness. Think: ↑ Stiffness ↑ Speed ↓ Density ↑ Speed An increase in pulse repetition frequency would lead to: - correct answer Increasing pulse repetition frequency, increases duty factor. ↑ PRF ↑ Duty Factor Which of the following would have the highest propagation speed? - correct answer Bone has the highest propagation speed, at m/s. What has the lowest propagation speed? - correct answer air technically has the lowest propagation speed at 300 m/s Which has the Slowest Propagation Speed? Water Soft Tissue Bone Lung tissue - correct answer Lung Tissue As imaging depth increases, the pulse repetition frequency (PRF) must: - correct 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? - correct 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: - correct answer Pascals (Pa) The typical range of frequency for diagnostic ultrasound imaging is - correct answer 1-20 Mhz is the typical range of frequency for diagnostic ultrasound imaging. The attentuation coefficient in soft tissue is equal to: - correct 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: - correct answer Micro is denoted as millionth (µ) What is described as the distance over which one cycle occurs? - correct answer 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 - correct answer Directly Related Also remember: ↑ Stiffness ↑ Speed ↓ Density ↑ Speed Areas of high pressure and density are referred to as: - correct answer Compressions What type of wave is sound? - correct answer Mechanical and Longitudinal Wave The frequency ranges for ultrasound are: - correct answer Ultrasound frequency is 20 to 20,000 Hz The speed of sound in soft tissue is - correct answer Speed of sound in soft tissue is 1540 m/s