So you may have heard about the Doppler Effect.
The Doppler Effect is the change in sound frequency
that's based on whether the object creating the sound
is approaching or retreating from the object that's capturing the sound.
Doppler ultrasound is based on the Doppler Effect.
So it uses this concept to determine whether blood is flowing away from
or towards the transducer and the direction of flow is depicted by color.
Red indicates flow towards the transducer
and blue indicates flow away from the transducer
and this is usually done by convention.
This is an example of Doppler ultrasound showing again the flow within the right testicle.
You can see areas of blue and you can see areas of red
demonstrating flow in both directions.
Spectral Doppler demonstrates both the direction of flow and the waveform
and it provides a quantitative assessment of flow.
So you can see here again of the testicle,
you cans see color flow above and then you can see Doppler flow
which tells you the waveform of the flow
and this looks like it's an arterial waveform with a peak and then a down slope.
So ultrasound is a very safe diagnostic evaluation
and it really doesn't have any know side effects.
It's not associated with ionizing radiation the way CT and radiography are,
it's very small and can be portable, and it's actually very inexpensive.
It's often used in places where larger equipment is unable to be used.
It also allows for real-time evaluation using the cine images or the video.
There are many different uses of ultrasound.
It's often used to evaluate the gallbladder and the biliary system, the kidneys.
The scrotum is very well evaluated with ultrasound.
The female pelvis is a very common area of ultrasound use.
In pregnancy, ultrasound is actually one of the only things that are used
because it doesn't have any radiation and it doesn't really have any side effects.
It's often used on carotid or extremity vascular ultrasound
and is able to take a very good look at the superficial vessels.
So let's review.
We've now discussed radiography, CT, and ultrasound.
Radiography and CT both use ionizing radiation
while ultrasound uses acoustic energy and doesn't have the risks
associated with ionizing radiation.
Radiography is inexpensive and ultrasound is actually very inexpensive,
even less so than radiography. CT, of the 3, is the more expensive examination.
Both radiography and ultrasound can be performed portably.
CT, however, cannot and it comes with a very large machine.
Radiography can take just a few seconds, CT takes less than minute
but it is longer than a radiograph and ultrasound really can take just a few seconds as well
but it's very operator dependent so whoever's performing the ultrasound
can take as long as they need to evaluate the area of interest.
Radiography and ultrasound do not use any kind of contrast.
CT may or may not use contrast, depending on what area is being evaluated.