Quick Reference:

  • Period x Frequency = 1
  • Intensity (W/cm2) = Power (w) / Area (cm2)
  • Wavelength (mm) = Propagation Speed / Frequency (MHz)
  • Propagation Speed (m/s) = Frequency (Hz) x wavelength (m)
  • Pulse Duration (us) = # cycles X period (us)
  • Pulse Duration (us) = # cycles / Frequency (MHz)
  • Spatial Pulse Length SPL (mm) = # cycles X Wavelength (mm)
  • PRP = 1 / PRF
  • PRF = 1 / PRP
  • PRF x PRP = 1
  • Duty Factor (%) = Pulse Duration / Pulse Repetition period X 100
  • Total Attenuation (dB) = Attenuation Coefficient (dB/cm) X Distance
  • Attenuation Coefficient (dB/cm) = Frequency (MHz)/2
  • Attenuation Coefficient (dB/cm)  = 0.5dB / cm / MHz
  • PRP = imaging depth (cm) X 13 microseconds / cm
  • PRF (Hz) = 77,000 cm / s / imaging depth (cm)
  • Axial resolution (mm) = SPL (mm) / 2
  • Axial resolution (mm) = (wavelength (mm) X # cycles in pulse) / 2
  • Axial resolution (mm) = 0.77 x #cycles in pulse / Frequency (MHz)
  • Near Zone Length (mm) = Diameter (squared) (mm) / 4 x wavelength (mm)

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I am the founder and lead Instructor here at ExamRefresh.com. I strive to help those that are entering the field of Ultrasound to be the best that they can be. Ultrasound is my passion.

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  1. alvarezdiana1 says:

    Hello there, thank you for your videos, they have been helping my classmates and I very much. We will be taking the SPI on August 7. We are all very nervous about this test. Keep up the great work :)

  2. Lisa DeVall says:

    I need help with the interactive console questions. On the registry, when you make the changes that you think they are asking, the image does not change. As a sonographer, I like to see my image as I “tweek” it. I didn’t know if my changes were correct or not. Can you post any of these images on your website to help? I have an account with exam Refresh and I love your website. I am preparing to retake the physics. I am an old sonographer that came up in the days when you did not have to be registered but our department has recently got accredited by the ACR and now we are required to be registered. I am old and trying to teach myself physics! It is so hard but your website is helping me so much! Thanks again!

    • I’m trying to get permission from the ARDMS to post images to help with the Interactive console questions. So far they don’t want anything other than what they provide. It’s very frustrating answering those questions because they are trying to simulate what it’s like in real life but if the image doesn’t change it falls short. They are pretty strict on the copyright for those questions. They best way is to try and visualize what would happen with the change you do make. If you adjust the wall filter what happens to the image. What effect does Power have or PRF. When you have a chance, get an image on a machine and see what happens. When you answer the question go with your first choice and move on. There’s no way to come to a better answer than what you think initially. Good luck.

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