So let?s talk a little bit about ultrasound.
I think it?s important to have a good knowledge
of the background of the modality before we talk about
the essentials of anatomy and pathology.
So in this lecture we?re gonna talk about how ultrasound images are created
and we?ll learn about the different techniques used for ultrasound imaging
and also some of the common uses of ultrasound.
So ultrasound images are created
by the production of a high frequency sound wave
using a transducer or a probe which reflects off of the structure
that?s being evaluated. So the reflection that comes back to the probe
is then created into an image. This allows for both real-time or a static evaluation.
Static images can be captured like a photograph.
Cine images are video images that can be captured during real-time scanning.
This is an example of an ultrasound transducer
which is also called an ultrasound probe.
This is placed on the skin surface using a coupling gel
that?s applied to the skin first and this allows for the best contact
between the skin and the probe.
Probes however can also be transvaginal, transrectal, or transesophageal.
Transducers produce sounds of many different frequencies
and all of them are a lot higher than what humans can hear.
Higher frequency probes are used for more superficial structures
and lower frequency probes are used to penetrate deeper structures.
So when there?s an interface between two different types of tissue,
some of the sound is reflected back and some of the sound is transmitted through
and this is really the basic concept of ultrasound imaging.
The amount of sound that?s transmitted or reflected
really depends on the type of tissue that?s encountered.
Almost all of the sound is transmitted through fluid,
however, from bone and gas almost all of the sound is reflected back.
The reflected sound is encountered by the probe
which then sends an electrical signal to the computer
which then uses an algorithm and converts that signal into an image
and this is what we see on our screens when we evaluate an ultrasound image.
So there 2 different planes of ultrasound imaging which are standard.
The sagittal or the longitudinal plane is along the long axis of the body
or it?s along the long axis of the structure that?s being evaluated.
Transverse is the perpendicular plane and that?s perpendicular to the sagittal plane
whichever direction that sagittal plane will be in.
So this is an example of a sagittal orientation of the right kidney.
So we can see here, this is an outline of the kidney
and you can see this kidney in its long dimensions
so the hilum will be approximately here.
On this image, just to orient you a little bit more,
this is near the patient?s head and this is near the patient?s feet.
And this is typical of a sagittal image.
On the left side of the image, we have the head
and on the right side of the image, we have the feet.
Up here is anterior so this is the anterior abdominal wall
and back here will be the spine.
Transverse orientation is essentially transverse or perpendicular
to the longitudinal plane. So this is kind of a horizontal image
of the right kidney so typical for this, this will be the right side of the patient,
this will be the left side of the patient, and similar to a sagittal image
this is anterior or the abdominal wall
and this is posterior where the spine will be.
This right here is the outline of the kidney and adjacent to it is the liver.
So let?s review ultrasound terminology.
Every modality in radiology uses different terminology
and the terms that are used for ultrasound are echoic
because it relates to the sound wave echoes that go back and forth.
So when something is hyperechoic or echogenic,
it reflects many echoes and it appears white on ultrasound.
This is an example of a structure that is hyperechoic.
This is located within the left lobe of the thyroid
and you can see these multiple, tiny punctate areas
that are hyperechoic and they likely represent calcifications.
Hypoechoic means that it reflects some echoes
but not all of them and it appears gray on ultrasound.
So let?s take a look, this is an example of a lesion within the right breast
and you can see that the lesion is gray in appearance
which means that it is hypoechoic.
It?s not brighter than the surrounding tissue and it?s not completely black either.
It has an in between level of echoes.
Anechoic mean that reflects no echoes.
Everything is transmitted through and these structures will appear black
on ultrasound. This is an example again of a right breast lesion
which represents a cyst and you can see that the inside of this lesion
is completely black or anechoic.