hi learners it's em from sono nerds and this video is on unit 15b resolution number four spatial and contrast resolution unit 15b resolution number four spatial in contrast so now that we've learned a little bit more about the different types of imaging processing we can formally discuss spatial and contrast resolution while this probably won't be the last reference resolution i do think it will be the last dedicated discussion surrounding resolution there are still a few more concepts that we need to learn about and how they affect different resolutions but after this unit the basics are covered and we can just keep adding to our resolution knowledge now we have talked about or will talk about all of these resolutions on this image and remember that resolution really is just another term for the accuracy so we're talking about accuracy in space accuracy over time accuracy in contrast and then our axial lateral and elevational accuracies have to do with how the wave comes out of the transducer are the pulses short is the beam thin is the height thin so we can see that there's a lot of things that we have covered that are going to affect the accuracy of our image or the resolution of our images we've already discussed temporal resolution in detail as well as axial lateral and elevational resolution and you heard a lot of comments about spatial resolution and contrast resolution when we were talking about the imaging processing techniques so we're going to spend a little bit more time focusing on these two types of resolution just to finish up our conversation we'll start with section 15b 0.1 spatial resolution so spatial resolution is the machine's ability to display the detail of the anatomy correctly so sometimes it's also referred to as detail resolution spatial resolution includes the three scanning planes that a transducer creates so axial lateral and elevational as well as some of the tools on the machine so really anything tools or transducers that change the accuracy of the image is going to affect the spatial resolution when we think back about the things that we've learned up into this point there are a lot of circumstances that we have control over as sonographers that are going to affect the spatial resolution we can change the line density pixel density is kind of built into the machine but we can definitely change gain increase it or decrease it we can turn spatial compounding on or off uh frequency compounding again kind of built into the machine display again up to the manufacturer so it is coded excitation for right magnification another perfect example of something that we can change as sonographers it's do we want to use right magnification versus read magnification yeah we want to use right because that is going to improve our spatial resolution which improves the accuracy that we're seeing the anatomy which is the ultimate goal of our job get accurate pictures of the anatomy so when you're scanning you really need to pay attention to those choices that you're making and how they affect your image and because axial lateral and elevational resolution are all under the spatial resolution umbrella it's going to come back quite often to your transducer choice and your frequency choice and that is why we keep coming back to the clinical discussion of why high frequencies are good why you want to set your gain appropriately why we're moving the focus to where it should be making the beam thinness at a region of interest those are all very very important physical concepts that are going to change the accuracy of the images that you are creating section 15b point 2 contrast resolution now contrast resolution is the system's ability to display different grays and when we have enough contrast resolution we can see borders between structures very clearly without losing the detail of the image so sometimes contrast resolution is included under the umbrella of spatial resolution because it does add to the detail of the picture however detailed resolution is going to be a little bit more transducer dependent where contrast resolution is really more system dependent and contrast resolution was determined by the scan converter because the amount of bits per pixel determined how many grades the system could process but now that most of our systems use eight bits and can display 256 shades of gray we are actually more limited by what we can see with our human eyes remember we can't see 256 shades of grey we're much more limited around the 30 to like 64 i've seen in some different types of literature so to improve contrast resolution for us we need to bring those amount of choices down and we do that through reducing dynamic range and by doing so this is going to allow our eye to be able to see those more subtle differences in the soft tissue so remember that our scan converter has bits of memory assigned to the pixels if we have one bit of memory that means the pixels can be on or off they're only able to display black and white just like this picture here two bits we can see four shades of gray four bits sixteen shades of gray and what most of our modern systems are are eight bits so we can display 256 shades of gray so we are no longer limited by the amount of memory assigned to the bits in our contrast resolution this is a non-issue we're getting really good displays of gray choices the issue comes in that this is almost too much this is way too much for our eyes to make any difference out of so what the machine needs to do is take these 256 grays compress them down into a set of grays that we are more capable of processing with our own eyes we get into that more reasonable range for our eyes by using dynamic range typically reducing dynamic range and so what reducing the dynamic range means is that we are going to take those 256 grays and re-categorize them into something usable by our eyes when we reduce those choices down to those fewer grays we actually end up being able to see subtle differences now instead of having everything just kind of look grey to our eyes so reducing your dynamic range is going to improve our contrast resolution especially as sonographers trying to pick out those differences in the tissue so in this image here what we are seeing is a soft tissue phantom and the soft tissue phantom we'll learn about in a few units towards the end of the program but what we are seeing is a substance that mimics soft tissue so it has the same propagation speed of 1540 meters per second and what you'll see at these arrows are little circles that have different echogenicities and these different echogenicities are telling us where the contrast resolution sits for the system in the way that it's set up right now so we can see that we have very good contrast resolution here we can see the borders of this very bright white circle we can see them very well a little bit harder on the next one but we can still see those pretty well getting pretty tricky on this third one and the fourth and the fifth one they're there but they're pretty difficult to see and that is because we don't have very good contrast resolution in this level of grays so if we were to reduce the dynamic range that is being used to image this picture we would tell the machine reassign different levels of grays that are a little bit more spread out so we can tell these grays apart from the rest of that background noise in the rest of the background gray so really when you reduce your dynamic range you are making the picture a little bit more contrasty which helps our eyes to pick out the borders of structures and here's another example using actual ultrasound images the top picture is using a dynamic range of 70 and the bottom one is using a dynamic range of 30. now if you're questioning what dynamic ranges don't worry we are going to get into it in our next unit but what i really just want to point out kind of as a precursor to it is that this is really showing us that contrast resolution our top image is very gray there's just a lot of gray in it we still have whites we still have blacks there's just a lot of grays in between so this is a wide or high dynamic range because there are just a lot of choices of grays that are getting placed into the picture compare that to the bottom picture then again we have blacks and we have whites but more things are black more things are white we're just getting a lot more contrast in this image you're really able to see some of these structures really clearly these little portal veins that are in the liver the walls the ligamentum vinosum here they all just stick out a little bit more their borders are more defined therefore we get to see a little bit more detail we get to see better contrast resolution and really that's it for contrast and spatial resolution i did not do any activities or a nerd check for this section as it is really just kind of a final summary of those two resolutions and remember we will keep adding to it especially when getting to our doppler section we'll talk a little bit more about some of the resolutions we've talked about already but as for now we've covered a good chunk of the types of resolutions and really have laid a good basic background for them