Chapters Transcript Artifacts and Instrumentation: Bare Bones for the Boards Take Evaluation Hi hope everyone's awake this morning. But if you're not, I'm sure you'll be awake after this topic ultrasound imaging artifacts. When I was first asked to give this speech. The first thing that came to my mind was wavelength equals speed of sound over frequency. Now I don't want you to think that I'm some kind of physics guru because I'm not, but it's really simple as to explain how that came about. I had a clinical instructor and one day in the lab, she said when you're studying for your boards, try to relate the material to things that you can easily remember. She said, I always remember the speed, the wavelength equation because I have a brother named fred. Her name was Cindy. So she says so I always think Cindy over fred. So It's been 20 years and now every time I think of physics, the first thing that comes to my mind is wavelength equals Cindy over fred and I never even met fred. So the goal here is maybe through this and you can give you something to relate to some of these artifacts that you can just not spend as much time studying those and worry about things that you will need to spend more time on artifacts. Are these little pieces of information on an image that provide that report inaccurate data. Sometimes these artifacts are helpful as in the case of a hyper psychotic mass in the gallbladder. If there's posterior shadowing, you might think it's a gallstone which you can prove with one or two more images. If there is no shadowing, its might assume it's just a gallbladder polyp. This is why any Abnormality you find, you should visualize in two positions so that you can ensure that it's not an artifact. The ultrasound machine is like a really fancy computer with some few special parts adding information and translating it into a language of the computer understands it is programmed with the ultrasound assumptions. It assumes that the speed of sound is 1540 m/s. This is the case for soft tissue. But as you saw in the last presentation, it is not the case for bone, fluid or air. It assumes that the sound wave is traveling in a straight line, that the scan plane is very thin like a piece of paper and that the brightness of the echo image records corresponds with the reflective strength. Anything not following these assumptions results in an artifact. Here we have an image. What do you see? Does this patient have a duplicated aorta Before you get excited and start thinking of that paper, you're going to publish about this very rare and never published finding which I did prove with a quick pub med search. Let's think about what it could be. Was it imaged in two planes? The answer is going to be No. This is an example of refraction reflection is a violation of the assumption that the sound wave is traveling in a straight line. If any part of the sound wave is deflected laterally, the returning echoes will show a structure in the true an atomic position and a duplication that would be placed laterally here is that image again refraction. This is an image of the rights of clarion artery, the bright line under the artery is the clavicle. We see what appears to be a second vessel under the clavicle. Have we found another vessel? Is this refraction no fraction is lateral, this is posterior. This is a mere image artifact. When the sound wave encounters a bright reflector, the sound wave bounces before continuing posterior. Early think of a trampoline for me on a high adventure ropes course, which this actually did happen this summer and thankfully there is no photographic evidence of this situation, but I very enthusiastically jumped off that platform and swung on that Tarzan line towards that massive rope wall. At which point I hit the wall and went hurling back through space towards that platform again. And this is when I realized why that helmet they made me wear is so important and then I swung back and hit the rope wall and had to climb all the way up to the next platform. Mm The movement of the bouncing is what occurs when the sound wave hits a bright reflector like the bone or the diaphragm. The machine assumes that the sound wave is traveling in a single straight line, no bouncing, so the secondary echoes obtained after the initial bounce are displayed posterior like the reflections in a mirror. The mere image artifact can also produce a spectral analysis and it is my understanding that this might be a question on your boards as well. Again, mere image artifact. Reverberation is produced in a similar fashion to the mirror. Majority fact only instead of a large bounce, it is more like a vibration, like a tuning fork. The vibration, ping, pong back and forth, creates echoes equidistant apart. The first two reflectors are real and the remaining echoes are placed once again posterior as a result of the assumed linear sound wave. These are additional examples of refract reverberation. The common tale artifact is a form of reverberation. It usually occurs between two reflectors with high propagation speeds. This place is the extra reflectors so close together that they look like the tail of a comet. Unlike Halley's comment, this artifact has been visualized many times since 1986 and will be visualized many more times before the real comet returns. In 2061, extra sound wave vibrations can cause another type of artifact as well. The tissue brulee artifact, a brewing is disturbed turbulent flow. It can be heard as a swishing or murmur on consultation and on pal patient, it feels like a fine vibration or thrill. It can be seen on Doppler and color images on this spectral image. You can see what appears to be a secondary, lower velocity waveform. This is a tissue brewing artifact. If you see the very small blip during peak. Sisterly this is also another example of a spectral tissue tissue brewing artifact. Here we have two images of the renal artery. The one on the right, The one on the right appears to be um over gained or like it has a very small piece of bowel gas right over the artery. But you can see the turbulence, so you might be more likely to think something is going on next to it is the normal flow. The one on the right is a tissue brewing. And here's a color Doppler of the right renal artery with a tissue brewery artifact. You can see how the color bleeds in his turbulent in the area as the, as the blood flows through. And this is a clip of a normal right renal artery. Just for comparison, are we visualizing an occluded artery? Well, that just doesn't make any sense. How would the flo bee in the vessel Cogley, If that artie was included, notice the loss, the loss of shadows beneath it echoes beneath it. This is shadowing. This is caused by absence. This is an absence or diminished echoes in an area that should clearly have an image. It is caused by the continuation of a bright, reflective. It is useful in characterizing plaque distinguishing between a gallstone or a polyp a kidney stone or an angio poma. Shadowing can also be caused by refraction around a circular structure like the common carotid artery, the internal jugular vein, the aorta, the iBc, the bladder or the femoral vein. As shown in this clip, now that we have reviewed some of the most common artifacts in imaging, I hope that you can recognize them when performing ultrasound exams, reading ultrasound imaging or reviewing previous studies. In addition, I hope that you found at least one or five Cindy's owes over friends for yourself. Thank you. Mm. Created by
