Aliasing Artifact | Ultrasound Physics Course | Radiology Physics Course #23

*High yield radiology physics past paper questions with video answers*
Perfect for testing yourself prior to your radiology physics exam 👇

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*I have also created two RADIOPAEDIA LEARNING PATHWAYS*

WHAT’S INCLUDED?
✅This YouTube series Ad free
✅Constantly updated Radiopaedia articles
✅Summary slides
✅Key take home bullet points throughout
✅Multiple review quizzes
✅Short answer review questions
✅Official Radiopaedia course completion certificate

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Aliasing occurs when the pulse repetition frequency is less than twice the doppler shift frequency of the returning echo. This limit is known as the Nyquist limit. In this talk we review how aliasing occurs and what we can do to reduce aliasing in an image. We will review the determinants of pulse repetition frequency and the doppler equation and how these parameters influence the degree of aliasing in a spectral doppler ultrasound waveform.

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*Not sure if the question banks are for you?*
If you're here, you're likely studying for a radiology physics exam. I've spent the last few months collating past papers from multiple different countries selecting the most commonly asked questions. You'll be surprised how often questions repeat themselves!

The types of questions asked in FRCR, RANZCR AIT, ARRT, FC Rad Diag (SA), ABR qualifying Core Physics and MICR part 1 are surprisingly similar and the key concepts remain the same throughout. I've taken the most high-yield questions and answered them in video format so that I can take you through why certain answers are correct and others are not.

Happy studying,
Michael

#radiology #radres #FOAMrad #FOAMed

[karamhelal]

Dr Michael has been waiting his entire life to find an excuse to explain the wheel thing 😂, Awesome lecture 👍

[LuisAlejandroPérezLópez-xg]

It is incredible how easy you make it look with your videos. Thank you for all this, you have been of incredible help for my veterinary radiology pre-board theory exam. Best regards.

[ethloft]

I have a question. I've learned about aliasing, the Nyquist limit, and pulse wave doppler countless times. It almost makes sense; maybe you can connect the missing pieces?

In pulse wave doppler, the probe emits/receives ultrasounds at the pulse repetition frequency. The received sound wave frequencies are shifted either up or down depending on the velocity of substance (and the angle it's moving). If the frequency is shifted up too high (past the Nyquist limit for that given PRF), aliasing occurs.

But if the velocity in question is away from the probe, it causes a downshift, lowering the frequency. As far as I understand, Nyquist did not have a lower limit on frequencies to be detected, and yet, aliasing exists.

I read the original Baker et al paper and the Jensen et al paper, and it's still not clicking. Maybe someone can help?

[FetingGeting]

Can aliasing occur in other ways than with doppler? If so, then what does that look like?

[petercoombs]

Excellent lecture. TY Am curious as to why the ultrasound companpanies don't have a post processing option that stitches the frequencies below the line to those above and recalibrates the scale to allow this to be all represented above the line

[MohamedFayed-cgjq]

There is still a solution for aliasing. We can use 2 sample volumes and use a High PRF doppler.

[SamtaniPradeep]

Sir will aliasing artifact will also be seen in color doppler imaging?? Or it will only be seen in spectral doppler imaging??

[priyankaupadhyay]

how do we change the depth of the transducer to compensate for decrease in maximum Doppler shift . The actual depth of the vessel in the body will remain the same .

[paediatricspotcases]

Not cleared exactly for baseline and frequency reduction

[meghanakareddy]

Sir does transducer frequency changing mean switching between high frequency and low frequency transducers ?

[sambatsubhankararay]

Sir are these series enough for frcr part 1?

[deptofradiodiagnosismpsmc]

super sessions, great learning
sir please make videos on
CT anatomy of liver segments,
CT anatomy of lung segments with bronchial anatomy,
CT anatomy of deep neck spaces with their content,
CT mediastinal anatomy with standard mediastinal classification,