Hi Learners, it's Em from SonoNerds and this video is on Unit 11, Modes. Unit 11, Modes. Way back in Unit 1, we talked about how a graph looks.
We have the y-axis as the vertical line, the x-axis as the horizontal line, and the z-axis representing more of a depth line which creates the 3D world. Now the concept of the graft is important as we think about the different ultrasound display modes. An ultrasound display mode is the way that the machine interprets and displays ultrasound information on the screen. Each mode has its own purpose.
There are three display modes that we are going to cover. Amplitude mode, which is known as A mode, brightness mode, or B mode, and motion mode, or M mode. While you are studying these different types of modes, Make sure you understand what they look like and what variable is displayed on each axis.
Section 11.1, A Mode. The A in A Mode stands for amplitude. In A Mode, the machine displays a graph that has a spiked appearance.
Each moment on that graph represents the amplitude or the strength of the returning echo. Really tall spikes are going to be really strong reflectors where shorter spikes are weak reflectors and no spike is no reflector. To create the graph, a dot basically travels along the screen mapping the reflections that are received from one scan line.
As the scan line receives a strong echo, the dot is going to jump upward. Weaker echoes are going to have less of a jump, and if there's no echoes, it just kind of flatlines. So if we could superimpose an image over what an A-mode display looks like, we would see that the strong reflectors are bright white, those weaker reflectors are going to be different shades of gray, and then the non-reflectors are black or anechoic.
And in this image we've done just that. Notice how we have really strong reflectors here and they match up with this really bright white strong reflector in the image. Notice how it's relatively flat through here? That's matching up with this dark anechoic area.
These weaker reflectors in between match up with the weaker grays or less strong reflectors in between. As that dot comes across the graph, it's going to get to a strong reflector, jump up. The next reflector is a little weaker, so it comes down a little bit stronger.
Really, really weak, weak, weak, weak, very anechoic. Another really strong one again. And so we're going to see this dot jump around, kind of mapping out these strong reflectors with these different spikes. Now what we're seeing in this image, is a picture of an eye.
And that's because ophthalmology practices, or eye doctors, are typically the ones that are going to be using A-mode. It actually works out really well for them to be able to see the parts of the eye and any abnormalities within the eye. And not that you need to know any of this, but the transducer is placed against the eyelid here. And then I believe we have the lens of the eye.
This is the kind of viscous fluid within the eyeball itself. And then this is the retina and back. And then I believe we get into the nerve. behind the eye. So the really big thing that you're looking for with amplitude mode is that those strong reflectors are going to be tall spikes, weak reflectors are short spikes, nor reflectors are flat or the anechoic areas on our images.
Another way to look at A-mode is to think about how it resembles a city skyline. The x-axis of the A-mode display shows us the time of flight of the pulse or the depth. So this is very superficial over here and this is getting deeper as the dot travels down the scan line into the depth of the image. So superficial structures on this side and we have deep structures on this side.
So the x-axis, the horizontal axis on this image represents depth. The y-axis is going to show us the amplitude or the strength of the reflectors. So remember the taller the reflector, the stronger the echo is returning. So very strong echoes. midline echoes, and weaker echoes.
Section 11.2, B mode. Now the B in B mode stands for brightness. So B mode is our grayscale mode and that is the one that we typically use to make our diagnostic images. The sector, which is the image window that creates our picture, is made up of many lines.
We've referred to these before as the scan lines. They are created by one pulse going down to the maximum depth, returning to the transducer, and each scan line is made of a pulse. On the display then, those scan lines are translated into tiny little dots which are called pixels.
In original B-mode, the pixel could either be on, which would represent a white pixel, or it could be off, which was a black pixel. I actually have an image of that here. This was one of the original B-scan images.
Again, pixels could either be on or they could be off. But current systems look much more like this, where we get a variety of blacks, whites, and grays in between. Describing B-mode in the terms of a graph is a little bit trickier though.
So far we've learned that the y-axis is the vertical line and the x-axis is the horizontal line. So it might be really easy to take a look at an ultrasound image and think, well this is y-axis, this is x-axis. The problem is though is that the vertical and horizontal line are referring to a point of origin.
And in our case, we consider the transducer our point of origin. So if the transducer is up on this top part of the image, our horizontal is actually going to be this direction. So the x-axis is the line coming from the transducer.
It is the line following these scan lines. So if that is our x-axis, what we are representing on the x-axis then is the depth of the reflector. So reflections that are near the transducer appear at the top of our images.
Reflections that are far away from the transducer appear at the bottom of our image. So this is the x. axis in our image. Now what gets even trickier is that we have a z-axis in our B-mode imaging.
I mentioned earlier that we have something called an oscilloscope, and an oscilloscope is a tool that we use to graph a wave. So we can get the amplitude and the sinusoidal waveform on a electronic device called an oscilloscope. So when that oscilloscope maps or graphs amplitude, it does so on the z-axis.
So what we end up getting in return then is brightness being displayed on that z-axis. So if you could almost pretend that each of these pixels is that spike coming out, kind of like in amplitude mode, if we have like really bright spikes coming out toward us in these pixels and no spikes coming out towards us in these pixels, we would kind of start to understand how amplitude... could be graphed on the z-axis.
So I know this one isn't super intuitive, so this is probably one of those memorized ones. X is depth, z is brightness in B mode. Section 11.3, M mode.
Now the M in M mode stands for motion. M mode is going to be used to graph the motion of anatomy over time, and this is going to be extremely helpful for many cardiac applications like watching the wall motion and measuring ventricle size, just to name a couple. OBGYN sonographers are going to use it to evaluate the fetal heart, and it can be used in emergency medicine to observe lung motion.
M-Mode uses one scan line as well, and along that one scan line it is going to map the motion that is occurring in that line. So as a sound beam enters and returns from the body, the machine displays different grays that correspond with the B-Mode image. And then it's going to do this very rapidly.
So motion can be detected within the one scan line. The sample rate, or how quickly the machine can sample down that one scan line, is equal to the PRF of the system. Remember, depending on what your depth is, is your PRP.
Your PRP then determines your PRF. So each pixel in the scan line of the beam mode is recorded over time in the M-mode graph. So if we see a horizontal line that is very squiggly, That anatomy is moving. If we see a line that's horizontal, that's going to show no motion. If an echo is near the top of the graph, that means it's more shallow, and if it's towards the bottom of the graph, it's a deeper structure.
Oftentimes we're going to see a B-mode image above the M-mode image, so we can correlate the structures that we're seeing in our M-mode graph and correctly place the M-mode scan line. So I know that was a lot. Let's go over this image and kind of recap some of that.
So here's our B-mode image up on top here. And you'll see that there is one scan line represented through the image. Now this one scan line actually has these little dashes through it. This is not always the case, but these are actually representing different depths. So at 5 centimeters here, that is going to correlate to the 5 centimeters on the M mode.
This dash represents 10. That is where we are here, down to 15 at the bottom of the image. represents down to 15 at the bottom of our M-mode graph. Now these numbers aren't always here, these dashes aren't always here, but it's the same idea regardless if you have a solid line or dashed line.
Structures at the top of your graph are superficial, structures in the bottom of your graph are deep in your image. Now as we are looking at what the M mode is displaying, if we have horizontal lines going across, that means this structure that is represented by these pixels within this line aren't moving. So any straight horizontal lines mean a structure is not moving. Compare that then to this line, which is very squiggly. This is all kind of connected.
We get these spikes and squiggles in here. Well, this line is going right through a valve. So we are seeing the changes of the anatomy along this one scan line over time during the scanning acquisition process. We can also see that this line is very echogenic. It matches up with this line that is very echogenic.
So the gray scale that we get within our M-mode graph matches up exactly with the B-mode pixel brightness that we are seeing. inner picture up on top. So here's an example of M mode being used to evaluate lung motion. Again, this isn't necessarily stuff that you need to know, but I just want to explain some pictures to you when I can.
I've got a rib here, a rib here. This is the chest wall and skin. And then underneath we can see actually not a whole lot of lung motion, but this is the lung underneath. So this is the scan line. Notice that this one is solid.
We've got five centimeters of depth. This one also has five centimeters of depth. We don't expect the skin of the chest wall really to move, so we see that we're not seeing a whole lot of motion in here. These are mostly horizontal, maybe a little bit of breathing motion, chest rising and falling.
And what they're looking for is to see this pleural space kind of sliding back and forth along the chest wall, and it actually happens not to be doing it very well. And we can see that reflected in our motion graph. We are not seeing a whole lot of movement.
in these lines. Let's compare that then to a heart which is clearly moving. Again we have our one M mode scan line coming down.
This represents one scan line in the image. This is that one scan line over time very quickly being mapped along with itself. Bright line on the bottom here represents this bright line in our B mode image. and we are going right through the ventricle wall so we can see the ventricle contracting and relaxing through the cardiac cycle. And so from here we can measure how much wall movement there has been, the size of the ventricle, multiple things that apply to cardiac measurements.
Same idea with OBGYN, we can place our cursor right over the fetal heart and from that fetal heart then we can find a pattern. within the M mode and we can find what the fetal heart rate is by measuring the distance between movements. Again we've got one line from the very tippy top of the picture all the way down to the bottom of the picture.
So these gray lines are not moving. They represent the skin and fat layer on mom. This black area represents the fluid that is around baby.
This gets into the skin line of baby and then the heart motion and then the spine of baby here and then back into like uterus and more mom parts behind it so we are seeing one scan line being mapped over time any motion that occurs through that scan line so in our m mode graph then we are seeing depth along the y-axis of the m mode so superficial at top moving down into the depth towards the bottom we then see time being displayed along the x-axis. This is old time getting to new time on this side. And what we saw with those last clips that we had, the time would come across, fill up the whole graph, get to the end, and then it would start over again.
refilling the time representation through this graph. And that is it. That is all we really need to know about the three different types of modes.
So again, be able to recognize what they look like by their images, recognize what they are displaying along the axis. So A mode was amplitude mode. It shows us amplitude in the y-axis, depth along the x-axis.
B mode is brightness mode. It shows us... depth along the x-axis, and brightness or amplitude on the z-axis. And then M mode is motion mode, and that is going to show us depth along the y-axis and time along the x-axis. Make sure that you go through your very brief activity in your workbook.
And then as usual, the workbook ends with some open-ended questions that you can use to quiz yourself.