all right let's go over some great basics and calculations um you guys had a great calculation homework that i wanted you to go through but we'll do a couple examples here okay so just a basic understanding of what a grid does we'll get more into that into image production course but essentially um the grid wants to help us get rid of the scatter radiation it blocks that scatter radiation that's kind of coming off at an angle and it allows the primary radiation to go through the grid will be before the detector okay just so i don't want that to be confusing what is the purpose of it grids were primarily used to improve image contrast and they're most often used on parts that are 10 cm or greater the grid is made up of lead strips that absorb the secondary which is your scatter radiation that would otherwise sort of make your image not as great okay um depending on the ratio of the grid which is the height of the lead strips to the distance between them the frequency of the grid number of lead strips or lines per inch the grid can absorb up to 90 percent of the secondary radiation that would otherwise reach your image right we're no longer using films i probably should update that word um basically it's essential for the technologists to adjust those factors when they are using a grid because your numbers grid versus non-grid will change you can change the kbp but most often technologists choose to change the mass only for the grid and my little person here it'll go up here in the corner all right so grid ratio because the grid is formed by a series of thin lead strips and then there is an interspace material which we want because that is where your your primary is going to be absorbed through or go through and not be absorbed the lead's going to block it right lead blocks so if you ever get like a test question that asks you possible materials for interspace material it can't be lead if the middle here was lead and the lines are led nothing's getting through right it's not going to work um but so there's a grid ratio formula which is the height of the lead strips over the distance between them so the height of these strips versus the distance between them okay will be a grid ratio formula and the higher the grid ratio the better it improves your image the um more efficient it cleans up that scatter so it works harder there's a series of grid ratios and these will change as we're moving along right or what your facility has for a grid ratio um might be different i've never actually seen a 16-1 but maybe it's out there most often um now we're seeing like six to ones on a lot of our digital portables um we'll see eight to ones are very common a lot of times the table grids are a ten to one or a twelve to one um but you wouldn't know that unless you pull the grid out of there and just for fun who's gonna do that maybe just me um but you might see a lot of those different ones all right so i have a practice grid question here if the height of the lead strips is 1.6 millimeters and the distance between the lead strips is 0.1 millimeters the ratio of the grid as well so you're simply just going to put this into your grid ratio formula which is h over d right so the height of the lead strips is 1.6 divided by the distance between 0.1 equals 16. grid ratio is written like this so it's a 16 to 1 okay this is a super grid ratio super easy math all right the trick is to find the key terms so height of the lead strip distance between them ratio of the grid right so i just kind of broke this down for you again um how to separate that out okay here's some more practice questions these are super easy these aren't giving you any distractors or any any extra info to kind of trick you at all so the height of the strip and the distance um the distance between is the same on everyone and so i'm not trying to make life hard on you just some practice and these are on your homework assignment too so it's really easy the point one and the one point two see how it's twelve to one are you seeing a theme here point eight it's eight to one point five is five to one all right this is not super hard math okay don't make it crazy all right the one that i want you to watch out for is the one that has the extra info so this question here is an example that is using a distractor to try and trip you up so a grid has lead strips five millimeters high 0.5 millimeters apart and 1.6 millimeters wide what is the grid ratio we know your grid ratio formula is h over d so i've highlighted the correct stuff that i want you to have okay five millimeters high is your h 0.5 millimeters apart is your distance so height over distance right 5 divided by 0.5 gives you a 5 to 1 grid the distractor is this 1.6 millimeters wide that's the trick one sometimes you'll see this as thickness it's talking about the thickness of the lead strip or the width of the lead strip that is not what i want you to use you have to use the distance between the lead strips so this apart or it'll say distance between that's what you have to use and if you do the math and it doesn't come out to sort of a five to one six to one eight to one ten to one if it comes out as a random number you're doing your formula wrong so you're plugging in the wrong um factor so just watch for those i call them distractors i don't know what you wanna call them but they're there just to bother you all right so grid bucky factor these are fairly easy for each grid ratio they have a factor to use on multiplications most of them the cheater is to just cut it in half so five to one is two six to one is three each one's four ten to one's five until you get to the twelve and for some reason twelve and ten are the same at five and sixteen ones is six so these um you just have to memorize and i think um cheryl has a song she calls it two three four five five six if that helps you remember it all right um practice question here calculating non-grid to grid all right four mass non-grid was used repeat the exposure um with a ten to one grid what's the new mess how do you figure that out this one's super easy you simply multiply the original mass by the grid bucky factor all right you've got to go back so we are going to find our 10 to 1 grid that we used and the grid factor or the bucky factor of that is five so i'm going to take my original mass that i use with non-grid i'm putting a grid on i now have to increase my technique to get through that grid so i'm going to multiply the 5 by 4 and that gives me 20. so my new mass for that exam using a grid is now going to be 20. and just remember anytime it's asking you to add a grid your number is going to go up it's going to be higher than non-grid always um okay non-grid to grin another example here the only difference um with this one is if you notice in the beginning of this question that's giving me 300 ma and 1 15 of a second used to expose a radiograph made without a grid but now it wants me to figure out the new mass with a six to one grid i want you to do a hard stop here because you have to figure out your mas first so if it's giving you m a and second separately you've got to calculate those first before moving on so m a times time i know you guys know this one equals mass so these together give me 20 mass you're going to multiply that original mass now by the bucky factor so we are going to multiply the 20 mass by 3 because the 6 to 1 is a 3 for a factor and that gives me 60. so 60 is the new mass that i will use with a 6 to 1 grid instead of the 20 with non-grid and 20 is really high for non-grid don't worry about these numbers and not making a ton of sense but it will okay grid to non-grid is the reverse so we're using a 12 to 1 grid or 12 mass with the 8 to 1 and now we're going to repeat without a grid what's the new mass all you do is divide this time so an e to 1 has a bucky factor of 4 you are simply going to divide 12 mass by the factor of 4 that gives me a 3. so when i'm if i'm going from 12 mass with a grid to non-grid my number is going to drop right because it's going to be less without a grid so i'm going to use three