SPI PRACTICE EXAM

The typical frame rate of an Ultrasound system is? - Answer- Between 30 Hz and 100 Hz Temporal resolution is synonymous with frame rate. Typical frame rates in imaging systems are 30-100 Hz. - Answer- The temporal resolution or frame rate = 1/(time to scan 1 frame). Frame rate can drop down to 5 Hz. Pulse duration is related to bandwidth how? - Answer- Pulse Duration = 1 / Bandwidth Specular reflectors have physical dimensions that are what size in relation to the wavelength? - Answer- Greater Two identical systems produce a pulse. One pulse is 0.8 usec in duration while the other is 1.4 usec. The best radial resolution will be created by which system? - Answer- 0.8 Pulse duration (length of pulse) With a short pulse duration we have a small pulse length. The shorter the SPL the better the longitudinal resolution. To achieve better depth (axial) resolution. You must have what? - Answer- FEWER CYCLES PER PULSE -Axial resolution = SPL / 2 or # cycles in the pulse x wavelength / 2 - Answer- Ultrasound wave attenuation is denoted by which units? - Answer- dB (DECIBELS) If it takes 1/20 of a second to construct a single frame, what is the current frame rate? - Answer- 20 hz--Hz = cycles per second. The rate is 1/20th of a second. So 20 cycles per second = 20 Hz With a focused ultrasound beam, bioeffects...? - Answer- Are less likely to occur The smaller the beam the less likelihood of cavitation. Exam duration has the greatest effect on patient exposure. - Answer- Bioeffects intensity limit: SPTA >100 mW/cm2 Unfocused >1 W/cm2 or 1000 mW/cm2 Focused HIGHEST output intensities used with pulsed doppler. - Answer- Lowest output intensities are with gray-scale imaging. With which type of array are grating lobes most common? - Answer- Linear array Which equation is used to find the doppler shift? - Answer- Fd = 2 Fi v / c In standard d