hi learners it's em from sono nerds and this video is on unit 21 acoustic artifacts unit 21 acoustic artifacts in ultrasound an artifact is anything in the image that doesn't represent the true anatomy now some artifacts cause fake anatomy to appear or real anatomy to disappear sometimes the real anatomy is the wrong shape size location or brightness there are multiple mechanisms by which artifacts can arise most artifacts appear because the machine has made an assumption and then the way that the sound is interacting with the tissue causes that assumption to be invalid an assumption that the machine makes is that sound travels at 1540 meters per second we know the speed to be the propagation speed for soft tissue in reality though the beam travels through many different types of tissue and if the average speed for the area we're imaging varies from that 1540 meters per second then an artifact might appear other assumptions that the machine makes that can result in artifacts include sound traveling directly to a reflector and back that reflections only come from the anatomy and the main beam path that sound does not change direction and that the beam is narrow in all dimensions the machine cannot tell when the returning echoes are invalid so it displays the data that returns and in doing so artifacts are created other ways in which artifacts are created are mechanical errors and operator errors a broken crystal causes dropout which doesn't represent true anatomy in the image so this is an artifact same is true if the operator decreases the gain too much causing anatomy to disappear this results in an artifact as well even outside sources of energy like medical equipment can cause distortion of anatomy in the image artifacts can be categorized even further based on those invalid assumptions and what they do to the image or anatomy so we have resolution artifacts position artifacts and attenuation artifacts when studying artifacts focus on what the artifact looks like first you should be able to name an artifact based on its appearance in the image next try to understand what assumption or assumptions are invalid and why the artifact occurred as a sonographer it is also going to be very important for clinical imaging to know how to correct for an artifact when to leave it because it adds to the diagnosis or know that it is what it is because well physics section 21.1 resolution artifacts resolution artifacts occur when the detail in the image does not represent the true anatomy these artifacts typically occur because the beam is not as narrow as it needs to be in all planes resolution artifacts are associated with poor axial resolution poor lateral resolution and poor elevational resolution which is commonly known as slice thickness now the physics behind these artifacts was previously covered in detail in our resolution units but let's go ahead and review them briefly recall that axial resolution is related to the spatial pulse length when two objects that are parallel to the sound beam sit less than half the spatial pulse length from one another the machine will display them as one object the resulting image does not accurately represent the anatomy as two reflectors therefore it is an artifact poor axial resolution is typically seen with low frequency transducers to reduce the chances of this artifact the sonographer should use the highest frequency possible that allows the sound to reach the depth of the anatomy in reality our anatomy is showing separate reflectors these ones are the closest ones together if they are less than half of the spatial pulse length the image is going to show them as one reflector this is an artifact because it does not truly represent the anatomy in reality lateral resolution is equal to the sound beam width when two objects that are perpendicular to the sound beam sit less than the beam width from one another the machine will display them as one object the resulting image does not accurately represent the anatomy as two reflectors and therefore this is again an artifact this is also known as point spread artifact to improve the lateral resolution the area of interest should sit within the focal zone of the beam the sonographer typically places the focal point at the area of interest for the best lateral resolution so again we have reflectors in the body that are now perpendicular to the beam and if two beams sit too close together so that they are less than a beam width apart in the image they will be displayed as one reflector again because this does not represent what is in reality the anatomy of the body this is an artifact elevational resolution is related to how thick the beam is if the beam is too thick echo information from above or below the slice can be detected in the image when the elevation resolution is poor the artifact is known as slice thickness artifact partial volume artifact or suction thickness artifact in this image we can see part of the duodenum being recorded in the gallbladder lumen elevational resolution partially overlaps with position artifacts because reflections are in the wrong location slice thickness artifact will mostly be apparent in structures that should not have any echoes within but do to correct this the sonographer should try a one and a half d array transducer an annular transducer or use harmonics so in reality the gallbladder sits very close to the duodenum the gallbladder typically is anechoic which means no echoes within because of slice thickness artifact if we are imaging towards the edge of the gallbladder we might partially catch some of the duodenum anatomy and the machine is going to think that is from the main beam and it's going to display it in our picture so when we look at anechoic structures slice thickness artifact ends up probably being the most prevalent because now we can see echoes within it that we wouldn't expect so these small little echoes along the edge here are truly outside of the plane or due to the thickness of the slice and most likely represent echoes from the nearby duodenum slice thickness artifact is commonly in all of our pictures it's just more apparent on places where we should not see any echoes but end up seeing them because of the artifact section 21.2 position artifacts positioned artifacts are artifacts in which anatomy appears in the wrong location anatomy can be displayed in the wrong location because sound changed directions and we'll see that with refraction mirror artifact and multi-path artifact all the sound didn't return directly to the transducer like we see with reverberation ring down or comet tail artifact mirror artifact and multi-path artifact sound energy from outside of the main beam interacted with reflectors as we see with grading and side lobes and slice thickness or propagation speed issues such as we see with speed error and range ambiguity remember that the machine is like a big stopwatch the machine times how long it takes for echoes to be sent and reflections to occur so it knows what depth to place those echoes at it also expects that echoes returning come from the direction that the beam was steered and will place echoes that are returning along the beam path now a lot of the artifacts that we see are positional for some a change in transducer position will resolve the artifact for many of them though the artifact is a result of acoustic physics refraction occurs when sound enters the body and bends or changes directions from the original path of the beam the beam expects that any reflections that are coming back are coming back from the original path so when other reflections come back they are mapped to that path so refraction artifact causes an exact replica of anatomy to be placed to the side of true anatomy now the side by side or lateral placement of the false anatomy is also going to degrade lateral resolution as it is going to obscure the anatomy that should be there in reality we commonly see refraction artifact occur under areas that are going to change the path of the beam so here this gray block is probably representing like abdominis muscle and let's just say this is representing the aorta so in reality we have some muscles and one aorta now the beam is going to come into the body go through that muscle layer and through that muscle layer there is going to be some refraction recall that refraction occurs when there is a difference in propagation speed so as that beam passes through the muscle it refracts and interacts with the aorta because the machine thinks that whatever echoes are returning because of this refraction should be in this path the machine is going to map that to this path so what we end up getting in our picture are the true aorta or the true anatomy because other beams have imaged that and placed that there and then we have the fake anatomy because other beams have refracted and placed that fake anatomy lateral to it so again refraction remember it's an exact replica and it's placed to the side of true anatomy it's going to be difficult to know for sure which one is the true anatomy versus the false anatomy so here's an example of refraction and this is occurring with the aorta again we have the beam coming in through the abdominal muscle it refracts at that point and some of that sound energy is going to interact with the real aorta these echoes are going to return to the transducer but because the transducer thinks that it's coming from this path it places those echoes coming back into that path causing the duplication here's another example of an aortic valve again we've got an exact replica we're side to side so we have our true aortic valve and the refraction has caused a fake aortic valve to be placed off to the side mirror artifact is going to occur when sound interacts with a strong specular reflector at an oblique incidence the beam is reflected towards another structure causing sound to travel in another direction before heading back to the transducer mirror artifacts are more likely to occur near air field structures like the lungs and the diaphragm is a common specular reflector that is involved in the mirror artifact vessel walls and chamber walls also being strong enough reflectors to create this artifact so in reality we have maybe some sort of structure within the anatomy near a strong specular reflector like the diaphragm now the sound is going to come in to the body at an oblique angle so that's the important part we're coming into that specular reflector at an oblique angle that reflector is actually going to send some information back towards the transducer but it's going to send a lot of sound information off to the side and if that sound information interacts with structures those structures are also going to send their echo information back to the transducer what ends up happening is that the machine believes that this interaction that occurred with that beam is somewhere in the path and so we will see it get mapped into the direction that the beam was occurring now more beams are going to come out because we're using multiple beams to create our full picture and so when that second beam comes out it'll actually interact with the real anatomy which will also be displayed in the picture so mere artifacts are going to create exact replicas of anatomy and the important part here is that it is deep to the true anatomy so this is the mirror artifact they're typically on the opposite side of the mirror or specular reflector and they are going to be equal distance from the specular reflector as well so here's an example using the diaphragm and the liver of a mirror artifact sound came in at an oblique angle bounced off the diaphragm which is this bright white line here bounces off interacted with this structure and then got sent back to the transducer transducer was like all right that was mapped into this beam that was headed this direction let's put that information here more beams came through to create the rest of the image and those accurately identified the structure being in this location again notice that they are on opposite sides of the specular reflector they are the same distance from the reflector they are exact replicas of one another and the big part is that the artifact is deep to the true anatomy note too that because this is the diaphragm anything on this side is the abdominal cavity anything up on this side is the thoracic cavity and this happens to actually all be lung so this is not more liver up here this is not another mass up here this actually should be lung tissue but because of the mirror reflector the specular reflector near that lung tissue we're getting the mirror artifact here's another example this is of the heart again we have our specular reflector area through here this is all going to be lung around the heart and we can see an exact replica occurring the artifact is a part that is deep into the image here's another example using blood vessels we'll see this occur with this as well the back posterior wall of the blood vessel is acting as our mirroring reflector so the sound comes in interacts with this the way that the sound bounces through there it flips it and creates a mirror image deep to the real vessel this is of the subclavian artery so this happens to actually also be lung right underneath it here so around the lungs sometimes around some of the bowel gas is where we typically see these mirror artifacts typically just changing your angle of insulation is going to help with mirror artifacts sometimes also reducing your gain helps with it as well just because it's going to decrease the inflections that are returning multi-path artifact is another example of sound changing direction before returning to the transducer now this one's pretty similar to mirror artifact but this time it's the specular reflector that is duplicated and placed a little bit deeper artifactually so the beam path interacts with the specular reflector at an oblique angle again and then the sound is redirected to another off-axis strong reflector it will bounce off this reflector and then return to the transducer remember that the machine again is timing how long these echoes are taking to get back and because it's taking some different directions it's going to lengthen the path and therefore the time that the reflection echoes are going to return and when that occurs the machine is going to place them deeper into the image so again the beam comes in interacts with the strong reflector and oblique angle which is going to send some of the sound in a different direction now as the beam interacts with this other strong reflector that beam is going to take a little bit longer to be sent back to the transducer and what we end up seeing then is that the specular reflector is replaced a little bit deeper into the body now we could also get mirror artifact from this as well it all just kind of depends on what that other reflector is and how the sound is interacting through this area so sometimes you'll get mirror artifact sometimes you'll get multi-path artifact now what's different about the multi-path is that you don't get that true exact replica so multi-artifact is going to create a similar appearing anatomy that is also deep to the true anatomy so here we have an example of a multipath artifact occurring with the bladder now the sound comes in bounces off the strong reflection of the posterior wall maybe got over sent over to this wall maybe bounced up to this wall to this wall and then eventually made it back to the transducer so the sound just kind of bounced all around the bladder before returning to the transducer the transducer thinking well i sent a beam this way thinks whatever echoes returned along that path should be mapped to this area and so what we see is kind of a similar appearing bladder not quite an exact replica but it's still deep to the true anatomy with a similar appearance this is very common to see in regards to the bladder again we've got a lot of bowel gas in this area which helps to create that multi-path artifact as is the case with most of our positional artifacts just changing your angle of insulation is going to help a lot with the multipath artifact reverberation artifact occurs when sound bounces between two reflectors with each bounce a lot of sound energy is redirected to the other reflector and some is going to return to the transducer now the transducer reads each bounce as returning echoes that each take a little longer to return so the machine places them each a little deeper now reverberation occurs at many interfaces in the body and the stronger the reflectors are the more apparent the reverberation artifact appears the transducer and specular reflectors can cause reverberation so can two specular reflectors within the body and it's also really commonly seen with devices such as needles or mechanical valves so reverberation artifact causes equally spaced reflectors to be displayed deep into the image so for example let's say we have two strong reflectors within the body sound is going to come in bounce off this first one and it's going to go back to the transducer and the image will show that first strong reflector now sound will continue through bounce off the next strong reflector and some of that energy is going to go back to the transducer and the machine displays it so the first two reflectors in the image are true reflections but what happens at this point then sound is just going to bounce back and forth between the two reflectors it'll bounce some will go back to the transducer so we get another picture and it'll send come back bounce off of this one some of that will return and it kind of just keeps bouncing through here until the sound attenuates and we kind of lose the rest of the sound energy but what we end up seeing in the image are equally spaced kind of looks like a stepladder reflectors going into the image you might notice that they will get a little bit darker as they attenuate but the real key part of reverberation is that equal space between each of the reflectors moving parallel with the sound beam deeper into the image so remember it's really just that sound ping-ponging between either two really strong reflectors in the body sometimes it's the transducer and a strong reflector or sometimes it's because of some sort of medical device like a needle mechanical valve an iud something artificial to the body so here's an example of reverberation using a needle this patient is having some sort of biopsy done the needle is the first strong reflector and this is the real one now the needle technically has two sides to it we these are hollow needles so we're going to have sound bouncing in between the hollow part of the needle and that is what we're seeing then are these equal distance reflectors because sound continues to bounce in between the hollow part of the needle so looks like a little step ladder equal distance apart we're noticing that we're getting some attenuation as we get deeper into the body because the sound is starting to weaken as it continues to bounce and then it's parallel with the sound beam here's another example of reverberations we have a mechanical valve sound is bouncing in between the parts of the mechanical valve so we've got our first real reflectors and then we have reverberations equally spaced deeper into the image and attenuating as they go reverberation can happen at any point we actually get reverberation right at the top of our screen we don't actually have two reflections right at the top of our skin line we actually have some reverberations happening in this area so the first one is a true reflection the second one is then reverberation between the transducer and the skin line and if we could look really closely with super eyes or something we'd probably see more reflections in that same pattern going down but they are going to attenuate relatively quickly now ring known artifact occurs under the same conditions as reverberation but they're going to arise from structures that are much closer together so the spaces appear almost squeezed out in a more dense line appears now ring down artifact can aid in the diagnosis of some diseases for example comet tail artifact is often seen behind small air bubbles so air in the biliary tree would exhibit ringed down artifact it's also seen in something called adenomyometosis of the gallbladder or you might see it with small surgical clips it's important to know that ring down artifact is also known as comet tail artifact and so again ring down artifact causes a bright line parallel with the sound beam path due to sound bouncing between very small structures so here's an example of tiny little bubbles all sitting next to each other and these bubbles don't perfectly fit with one another what we end up having are spaces in between the bubbles and they kind of look like little funnels and when the sound beam interacts with that little funnel it's actually going to bounce around in here and then send a wave back and all these little bounces are going to send waves back so we see comet tail artifact as a result of air either in the lungs or within the organs and it helps to diagnose the presence of air so here's an example again we're at the diaphragm here this is the liver and this is all lung tissue and so we are seeing comet tail artifact at this location because of the small air bubbles within the lungs so you can see how it looks very similar to reverberation but they're very very tiny the lines are a little bit more dense there's less space in between each of the lines and they're parallel with the direction of the sound beam here's another example of comet tail occurring off of a mechanical valve it's these lines very very very dense lines occurring from the sound bouncing in between very small structures here's another example of air within the biliary tree of the liver we have a little bright reflector here this is where the air or the gas bubble is located and then we have comet tail artifact just behind it again that is because sound is interacting with that small space of the gas bubbles here's a picture of a gallbladder this is the gallbladder wall in adenomyomatosis we're going to see actually little crystals within the gallbladder wall and the way that the sound interacts with the crystals of the gallbladder wall creates that comet tail artifact so reverberation is sound bouncing between two strong reflectors that have a good amount of distance in between them it's going to create large equally spaced gaps in between those strong reflectors where comet tail kind of gets rid of all those large spaces makes a very very dense line because the structures that the sound is interacting with has become much smaller lobe artifact occurs when sound energy escapes the main beam and then interacts with some strong reflectors off to the sides and the system believes that these echoes that are returning from the sides are actually in the main beam and so it's going to display those echoes in the image so lobe artifact incorrectly displays echoes from anatomy that is lateral to the main beam now these are usually going to be low level echoes again these are more apparent over areas that should be free of echoes like the gallbladder like blood vessels like the chambers of the heart if the side lobes interact with strong enough reflectors they can produce a replica of the off-axis strong reflector now remember that side lobes are the result of single element transducers where grading lobes are the result of array transducers so array transducers can use apodization to reduce grading lobes and sub dicing can be used on single or array elements to reduce the lobe artifact the lobe artifact is very similar to slice thickness but recall that slice thickness is kind of an above and below the anatomy where loeb artifact is going to be a side to side now because it is a side to side artifact loeb artifact degrades lateral resolution so when the artifact appears over anechoic areas they can mimic pathology we always want to make sure that we try different angles and different planes to determine if the echoes are real pathology or anatomy from an artifact this diagram here just shows us again we have that main beam coming from the transducer if this was an array transducer these would be gradient lobes if the gradient lobes interact with a strong reflector off to either side machine is going to say hey that came from the main beam let's make sure to put that in the picture so lateral anatomy is falsely displayed in the image because the machine thinks it came from the main beam speed error artifact occurs when the medium that the sound is traveling through is different than 1540 meters per second when the medium has a faster propagation speed it's going to result in a shallower placement of echoes where slower propagation speeds are going to result in a deeper placement of echoes fat for example has a propagation speed of about 1450 meters per second so structures under enough fat tend to be placed a little bit deeper so in our example here we have a reflector that sits within three different speeds or three different mediums as the sound wave travels through here in reality this reflector is at the same level no matter what is around it but the sound beam is going to travel in 400 meters per second is very very quick so it's going to travel very quickly through here bounce off and travel very quickly back to the transducer now because the transducer is timing how long this takes and is assuming that it's 1540 meters per second it's going to say hey that went really quick place that shallow as the sound interacts through the 1540 meters per second this is what the machine is expecting and it places it at its accurate location in the third medium as the sound travels through a slower medium it's going to take a lot longer for this to interact with the reflector and return to the transducer again the stopwatch is going the machine thinks that took a long time so let's place that deeper faster mediums are going to result in a shallow placement where slow mediums are going to result in a deep placement so when we see speed error on the image it's going to make anatomy appear almost broken or like a step off from itself or displaced due to propagation speeds other than 1540 meters per second so here's an example of the diaphragm again this is another really common place that we see it and that's because the liver has a little bit faster propagation speed than soft tissue so here we have the diaphragm and it looks almost broken in this area and it's not really broken what occurred is that this spot here most likely was traveling a little bit faster than 1540 meters per second so the strong reflectors of the diaphragm were placed a little higher or a little more shallow another way we could look at it without knowing for sure is that possibly the sound was traveling a little slower through this part of the medium so this section of diaphragm maybe got placed a little bit deeper into the body but again that speed air artifact is going to look like structures that should be continuous or kind of broken or just a step off from one another because of different speeds here's an example again in the liver now we've got a mass within the liver that has a different speed so sound is coming through the liver all of the diaphragm over here and over here was assumed to be 1540 meters per second and gets placed correctly in those areas but as this beam travels through this mass it got slowed down and because it has a slower propagation speed any echoes that return after that are going to take a little bit longer so the machine thinks they're a little bit deeper so the diaphragm is not broken it doesn't actually have this little chunk that should be hanging down it's because the speed through the medium was a little bit slower and the machine timed that to be a little bit deeper now range ambiguity is very similar to aliasing in doppler but in the 2d image remember that the machine isn't supposed to send another pulse until all echoes return however some echoes come back after the next pulse is sent and these echoes are going to appear within the next pulse's image so range ambiguity artifact is more prevalent when the machine is imaging very shallow the sound is still going to propagate and interact with more reflectors and once these reflections come back the machine is going to think they came from the current image and it's going to display them within the shallow frame the best way to combat range ambiguity is to increase the depth which will solve the issue by reducing the prf and then include anatomy that was causing the artifact so for example the sound is coming in to the anatomy and let's say we have a couple reflectors in the shallow part and then we have a deep reflector and our image might be set to just a very shallow portion or shallow depth so the sound is going to interact with these reflectors just fine and it's going to display them the issue is that the sound is still going to propagate through typically it propagates through until it attenuates and it's going to continue sending reflections back now most of the time we have enough depth so that our prp and our prf all match up and we're doing a very good job at imaging and having attenuation occur so we're getting the real pictures but when we decrease our imaging depth we are increasing the prf and decreasing the pulse repetition period which means it can send a ton of pulses to keep getting information very quickly but just because the sound is being refreshed already after we traveling for the shallow distance it doesn't mean that it's attenuated enough to not continue to interact with reflectors so a pulse is sent out and this image is created the sound keeps going and might interact with a deep set reflector those echoes will eventually make it back to the transducer the transducer is going to think it came from the shallow area and place it in the image so the easiest way to correct for this then is to just increase your depth so you are giving the machine a little bit more time to process all of those echoes returning section 21.3 attenuation artifacts attenuation artifacts occur when sound interacts with a reflector and the attenuation of sound is either greatly affected or minimally affected in ultrasound we rely on the echogenicity of tissue to help tell us more about it if the attenuation over a section of anatomy causes it to appear overly dark or overly bright then the resulting image has artifact in it now attenuation artifacts also help to tell us more about the reflector causing the change in attenuation sometimes we leave attenuation artifacts because they aid in a diagnosis so attenuation artifacts are going to include shadowing edge shadow enhancement and focal enhancement so shadowing is going to occur when the sound energy is attenuated greatly by a structure the result is that there is not enough sound energy behind the structure to continue producing echoes so the machine sees this area as having no echoes and it is coded as an anechoic or hypoechoic area now shadowing can be very helpful for diagnosing calcified anatomy and pathology like plaque gallstones kidney stones etc now the stenographer needs to decide if the shadows should be worked around or if they should stay in the image so again shadowing is the result of sound interacting with highly attenuating structures the result is either an anechoic area which means no echoes in the image or a hypoechoic area which means darker than expected area on the image here's an example of a gallbladder with gallstones in it gallstones are highly attenuating structures so as the sound comes in to the body it's going to interact and send back all these echoes doing a great job except for when it interacts with these highly attenuating structures sound interacts with the gallstones and is either absorbed or completely reflected or scattered any one of our attenuation factors and that leaves no more sound energy to produce what is occurring behind the gallstones there should be lots more stuff down here we should see more gallbladder we should see more of the portal vein we should see some more of the duodenum there is not enough sound energy to produce any more meaningful echoes behind those highly attenuating structures so this is shadowing here's another example of shadowing this is the aortic arch through here and there's a bit of plaque within the aortic arch that plaque is a highly attenuating structure and because of that we get shadowing behind it we can see where there isn't plaque there's plenty of soft tissue behind the aortic arch but because of that highly attenuating structure there's no more sound energy to produce echoes from this area and therefore we see our shadowing now sometimes you want to work around the shadowing again we are up at the heart typically our footprint from our phased array transducers is small enough that it can fit within a rib space ribs are highly attenuating structures and so if we're kind of overlapping a rib we might get a shadow down one side of our image so we want to work around that so we can get rid of that extra shadow and be able to see the anatomy clearly here's another example as babies get older their bones get a little bit more calcified and they start to shadow we don't want to miss the anatomy that's back here so we'll want to work around it coming from different angles to avoid coming directly over highly attenuating structures so again shadowing behind highly attenuating structures can appear anechoic or just a little bit more hypoechoic we can actually see some of that hypoechoic part here we've got the leg this is the knee femur along here we can still see some echoes in here but this area is a lot darker than what we would expect so this is kind of a hypo echoic area where this is producing more of an anechoic area and shadowing can take on either appearance oftentimes it takes on more of that anechoic appearance now if you see shadowing in your picture and you need to work around it trying a different angle trying a different window is probably your best bet sometimes you can use your tgc's to brighten this up and maybe get a little bit more information from that area but typically if you have a very very strong attenuating structure you're probably not going to get enough sound energy to make anything meaningful behind it now edge shadow is going to appear very similar on the image to regular shadowing but instead of attenuation due to a structure the sound beam is actually going to refract and diverge due to a rounded interface now the refraction sends the sound energy in another direction and the divergence weakens the sound beam leaving no sound energy for what is directly behind the curve so ed shadow is seen with curved structures creating an anechoic or hypoechoic line behind the curve due to refraction and divergence so in this one the sound is coming down it's interacting with this gallbladder here the curve right here is causing either sound to go off in another direction that's the refraction and it's also causing the sound beam to kind of spread out as well which weakens it and what we end up seeing are kind of hypochoic to anechoic bands coming directly from the curve parallel with the sound beam where it should have been here's another example at a fetal head we have the curve of the cavalrium here sound is coming down striking this curve and refracting and diverging creating an edge shadow that does not have enough sound energy to produce any meaningful echoes at this point now enhancement is kind of the opposite of shadowing enhancement occurs when the sound energy is minimally attenuated by a structure the result is that there is a lot more sound energy behind these structures making anything behind it reflect more sound energy which the machine codes as brighter echoes just like shadowing can be helpful enhancement is also helpful in distinguishing things like cis or other water-like fluid-filled structures we know that solid pathology typically does not enhance where benign fluid-filled pathology does so again enhancement is the result of sound interacting with low attenuation structures the result is going to be hyperechoic which means brighter echoes so the result is hyperechoic anatomy behind the area on the image so here's our example of enhancement we have sound energy coming in when that sound interacts with this fluid filled area it does not attenuate remember water basically had zero attenuation effect on sound so no attenuation occurs in this area which means we have a lot more sound energy once the sound starts interacting with soft tissue again and because the strength of the sound beam the strength of the echoes that are returning are going to be coded to brighter whites we see that hyperechoic area now compare that to the anatomy that's next to it sound came through it attenuated normally as it would through here so we start to see a little bit darker down here it attenuates as we would expect because this area caused very little to no attenuation we still have a lot of sound energy and that stronger sound energy is going to cause stronger reflectors stronger reflectors are typically brighter in our image here's another example sound is coming in through the liver all of the sound that came in over here this isn't attenuating normally it went through the liver attenuates a little bit keeps sending echoes back until it attenuates completely and we've almost completely lost all of our sound information down here until we get to the diaphragm but when the sound interacted with this fluid-filled structure or cyst there was no attenuation during this time so the sound that finally strikes the liver in the posterior part or behind the cyst has a lot of energy and because of that those echoes then are sent back appearing a little bit stronger to the machine so the machine codes them a little bit brighter now focal enhancement operates kind of under the same principles of regular enhancement that there is more sound energy in an area however with focal enhancement the sound energy is increased at the focal point and a band of increased echogenicity arises from this area so focal enhancement causes a horizontal band of hyperechoic tissue due to the increased intensity of sound energy at the focus so the focal point is not displayed in this image but it's most likely right here and what we see is a banding from side to side causing focal enhancement and that again comes back to the fact that at the focus is our most intense part of the beam it has the most energy and the stronger the beam is the stronger the reflectors are going to be from that area and stronger reflectors are coded as brighter pixels here's another example we can see the focus here we can see this banding that comes across that is the focal enhancement the energy is stronger therefore the reflections are stronger from this area this is a very easy fix usually you just bump your tgc's over to make it match up with the surrounding tissue section 21.4 other artifacts at the top of the unit i mentioned that artifact is anything that doesn't really represent true anatomy now one of the key features of ultrasound that allows us to see anatomy is the idea that echoes are going to interfere with one another creating tissue texture this is called speckle and speckle technically is an artifact speckle is going to add kind of a grainy appearance to the entire image and this is especially prevalent near the near field now modern ultrasound machines do have techniques in which speckle can be reduced but one of the biggest ones is for the sonographer to use a higher frequency transducer so remember that that speckle allows us to see tissue texture but we can actually kind of smooth out the speckle or reduce the speckle to help us kind of minimize the variation or the grainy appearance that speckle causes so here's an example of speckle reduction being off you can see that everything has a very grainy appearance to it lots of fluctuation in the tissue that we're seeing here turn speckle reduction on we start to see everything very smooth much more blended and this is going to be more realistic to what our organs are they don't have a bunch of little grainy pieces in them they're actually very smooth remember all of these borders all of these textures that we're seeing are all due to interference which causes the speckle so technically speckle is an artifact because it is not truly representing the smoothness or the texture of the organs but it does represent the texture of the tissue as we know it by ultrasound other things that we know to cause interference in the image from outside of the body and ultra system include electronic interference this can include other machines or surgery cautery we know that biological interference can occur if a person is very hungry and their stomach is gurgling you might see some interference occur on your images or if the patient's talking or any other external noise can sometimes show up in your images so this example here is an image being taken during surgery and the surgeon is cauterizing something using a tool and what we're seeing is artifact from that tool being used while the ultrasound machine is operating sometimes it can just be from something being plugged into the same outlet sometimes it's just other machinery that's in the area that's kind of operating on the same frequency so it's always a really good idea to take other frequency transducers with you especially when you're going portable because it's easier than to change them out and see if you're still getting that electronic interference with a different frequency transducer we've talked a lot about different ways to reduce artifacts based on the angle that you're coming at from your transducer and things that you can do as a stenographer to help your artifacts but there are also a lot of new machine techniques that can help us to reduce the appearance of noise and speckle enhancement shadow and other things and we talked a lot about those in unit 15a so just as kind of a quick recall to that we talked about spatial compounding which combined images from three differently steered beams facial compounding is really good at getting rid of enhancement shadow edge shadow that kind of stuff because it is changing how the sound beam moves around those structures frequency compounding is going to combine images from different frequencies so it's going to combine low frequency pictures with the high frequency pictures and that's just going to make for a nicer picture all around and lastly coated excitation is another tool remember it uses complex pulses that are uncoated upon reception but it is also helpful for reducing artifacts especially ones like range ambiguity so remember to never set your image and forget it make sure that you're making adjustments when necessary take a look at your gain your depth and your focus make sure you're always getting the best images possible and that brings us to the end of our artifacts lecture now remember take a look at those pictures see if you can recognize what the artifact being displayed or being represented by the picture is you should be able to recognize them just by looking at them reverberation has the big spaces in between looks like a step ladder enhancement has the brightness behind a structure where shadow has darkness behind a structure comet tail is going to be a really bright dense line coming off of a structure mirror artifact is going to be a deep exact replica where refraction creates a lateral exact replica so really look at the picture see what you can identify first once you have a good command of how the artifacts look then really start looking at what are the physics behind it is it something to do with propagation speed is it something to do with how the sound beam is traveling that made it deeper or shallower into the body what is the physics behind the artifact appearing and then lastly have a rough idea of some things you can do to change that artifact being there again sometimes we want to leave the artifacts but we don't always and so for example mirror artifact you can change what angle you're coming out so you're not coming out that specular reflector with such a strong oblique incidence angle or you can use your tgc's or your gain to kind of hide the mirror artifact on the other side of the diaphragm or whatever your reflector is but again first and foremost focus on recognizing what the reflectors are what their names are and then secondly why they are appearing in your workbook you do have some activities in which you can practice identifying artifacts and then you also have your nerd check questions the open-ended questions that you can double check your knowledge of the material presented