hi this is rishy agal and this video is intended for first year Radiology residents who are just about to start their first rotation in chest Radiology I want to show you the lines and Stripes that I look at on a chest x-ray so here I have a normal chest x-ray and I have a normal chest CT and this is of the same patient and we're going to use the CT to correlate the stripes that we see on the chest x-ray Okay so so the first thing that I look at is the trachea and the trachea is a midline loosen structure here and you can see that it's normally deviated slightly to the right here and that's because of the left-sided aortic Arch it causes that slight shift of the trachea to the right the trachea ends right here in this triangular shaped Corina um let me see if I can make that a little bit more pronounced for you and that's the Corina um while I'm looking at the trachea I'm also looking at the parat tracheal Stripes so the this is the right Parral stripe and this is the left parat tral stripe and this these parat tral stripes are made up of um vasculature so the thing that forms the border of the right parat tral stripe is the SVC here and the border of the left parat tral stripe is the left subclavian artery here and normally the parat tral stripes are pretty Lucent structures because in addition to vasculature we're looking at the lungs okay these things overlap the lungs um but they can be more dense or more um convex if there's lymph node enlargement so for example if you have parat tral lymph nodes this border rather than being more concave and fairly Lucent it'll bulge outward and it will become denser and the same is true of the right parat tral stripe okay so the next structure that I look at on the chest x-ray is the aortic Arch and the descending aorta so we mentioned that the aortic Arch is just to the left of the trachea and it causes slight deviation of the trachea to the right if you follow that line of the aortic Arch downward then that is the descending aorta so in a young patient the descending aorta should be very straight and it can in this case overlap on the left paraspinal line which we'll talk about in a second but you should be able to see it all the way down and you could see it on CT so this is this is the left ventricle this is the ascending aorta here we have the right braus calic artery the left common kateed artery and the left subclavian artery so if we continue that here's the end of the aortic Arch we're going posteriorly now you could see that straight line of the descending aorta and the important thing to note about the descending aorta on chest tray and on CTS for that matter is that it's a posterior structure so if you have something for example in the lung right here then that mass or pneumonia could obscure the descending aorta if you lose the line of the descending aorta that tells you that whatever you're looking at whether it's a mass or a pneumonia is in the left lower lobe because you can see this is the major fys here this is the upper lobe and this is the lower lobe because the descending aorta is a posterior structure okay the next structure I look at after looking at the aorta is the AP window AP stands for aoro pulmonary and what it refers to is this little divot right here this little concavity and it's right between the aortic Arch and the pulmonary artery that's why it's called called AP and if we look at it on CT this is the aortic Arch and then I'm scrolling backwards this is the pulmonary artery and you can see this is a normal patient and so the only thing in the AP window in this patient is fat fat in the mediastinum and that's why it's concave if you were to see this as a convexity or a bulge then that could mean that the patient has enlarged lymph nodes now the second part of the AP is the p and the pulmonary artery is along the inferior border of the AP window and it's this straight line here and if we go to the CT you can see that the pulmonary artery forms that Contour of the media stum there okay so aortic Arch AP window pulmonary artery okay the next structure that I look at after the pulmonary artery is the left atrial appendage so the left atrial appendage I'm going to scroll backwards now is right here and you can see the left atal appendage forms the border with the lung this is the lung this is the left atrial appendage and then if I scroll forward here the next structure is the left ventricle so just going straight down from the left atrium this is the left ventricle okay so if we sum up the left-sided border of the media stylum we have the aorta the AP window the pulmonary artery the left atrial appendage and the left ventrical all right once I'm done looking at the left-sided structures I then look at the right sided structures and there's not that many of them basically you have the right atrium here and if you continue superiorly you have the SVC now at some point the SVC breaks into the um the right brachio falic vein and the left brachio falic vein um but after it breaks into that you you basically lose it and you don't see that border anymore but um mainly the thing that makes the Border in the right side of the media stum is the SVC and this inflection point the point where um you lose the straight line and you start to get this curving line that is the Cave oal Junction or the superior Catal Junction it's where the SVC joins and dumps into the right atrium and that's an important Landmark because that's the location where you want Central lines to terminate ideally the next thing that I look at is the AO esophageal line and the ASO esophageal line is exactly what it sounds like it's the two structures the azus and the esophagus and the interface that those structures form with the adjacent lung and that line starts here at the diaphragm and you could see it go up and here when it we we get to about the level of the Corina we lose that line and it just gets obscured by other structures but that is the normal AO esophageal line but if we go to the CT this is the esophagus it's this Lucent tube structure and this is the aigus vean and note that they're basically right next to each other and what we're looking at when we look at the chest x-ray is that interace face the interface between the Aus and esophagus and the adjacent lung all right once you've cleared the mediastinal structures the next thing to look at are the hila and theila are paired structures on either side of the medium and they can be difficult to evaluate and to know what's Normal and abnormal on um when you're first starting out looking at chest x-rays but a few tips are that the hila should be about the same density and they should be at about the same size so if you see one hilum that's larger than the other or more dense than the other that can be a sign that there's something abnormal another sign to look for is that the highla should be at about the same horizontal level okay if you see one hilum being pulled up or another highum being pulled up then that is an indicator that there's volume loss on that side okay the hila if you if you BCT the lungs where the hila you should have about the same amount of space above and below that line okay most of the opacity that you see in the pulmonary hila comes from the pulmonary arteries okay those are the most dense largest structures in theila in a normal person you also have pulmonary veins coming in and then you also have broni the broni are Lucent structures so they they don't contribute opacity to the hila the hila can be enlarged in patients who have enlarged pulmonary arteries as in pulmonary hypertension or they can be enlarged in patients who have enlarged lymph nodes all right once you finish looking at the hila the next thing to do is to evaluate the lungs themselves so it's going to be hard to explain what to do and how to do this you really just have to practice ice it but in general what I do is I look at each lung individually so I'll use the magnifying tool and look at this lung and go from top to bottom usually in sort of some sort of a zigzag motion and then I'll look at the other one in the same way magnifying it um and looking at that lung individually then I zoom back out and look at both lungs comparing the density um you know comparing the size and making sure that basically they look about the same when you get to the rotation we can talk more about the different patterns of abnormalities that you might see but that's generally how I approach looking and scan scanning for disease okay once I've evaluated the lungs the next thing I look at are um the plura so the way to do that is basically to run your eye along the borders of the lung just to make sure that you don't see any abnormalities so what abnormality might you see well in the plura the most common thing is a plural fusion and in an upright patient plural fluid will collect here in the costophrenic Angles and you'll see instead of a nice sharp angle here you'll see a meniscus here if it's if it's small or you might just see you know complete obscuration of that angle if it's a larger plural fusion um another thing you might see is a pneumothorax so in an upright patient go to the lung apases and make sure that the lung a the lungs go all the way to the plural surface now you don't want to see for example a viseral plural line here and then loosen see beyond that line that's a sign of a pneumothorax once I've finished looking at the plura the next thing I do is look at the bones um the soft tissues and the upper abdomen that's especially important in patients who are coming in with trauma you want to make sure there's no rib fracture or clavical fracture no free air under the DI frag now when you're counting the ribs the easiest thing to do is start with the first rib so the first rib anteriorly has this large sort of irregular costochondral Junction here it joins up with the manubrium medially and if you follow that back that is the posterior part of the first rib so all you have to do from there is just count down so this is the first rib two 3 here we have clav 4 5 6 7 8 9 10 11 12 okay so if you just start with the first rib basically you can't go wrong then I look at the clavicles I look at the scapula the soft tissues and the upper abdomen and one thing to look for in the upper abdomen is free air this is normal air in the stomach okay um you could see that there's rugal folds there you could see that this air is displaced a centimeter or two from the the top of the left Hemi diaphragm free air will show up as a Lucent line or a crescent and it can be on one side it can be on both sides it can be under the right Hemi diaphragm as well as the left and basically you have to look at the history so if it's an inpatient and you see free air you know usually it's a surgery patient or they just put in a gastrostomy tube um but you have to make sure that you have something that explains it in an ed setting if a patient comes in with free in par tal air the thing to be worried about is perforation of the bowel or perforation of any Hollow viscus once you're done looking at the frontal radioradio graph there's a few clear spaces that you should be able to identify in all normal patients on the lateral radiograph this is the sternum and right behind that is the Retro sternal clear space this is the trachea right behind that is the retr tracheal clear space and this is the retrocardiac clear space these are all areas of the lung that you should be able to identify on normal patients also on the lateral radiorc angles here and these costophrenic angles um are a lot more sensitive in detecting fluid than the frontal radio graph in other words it takes a lot more fluid to show up as an abnormality on the frontal here than it is back here okay it only takes about 50 milliliters of fluid here whereas it might take maybe double that or 150 milliliters of fluid to show an abnormality here on the frontal okay the other structures on the lateral radio graph are the Hyer structures so I'm going to blow this up and point out this rounded lucency here this is the left upper low bronchus and if I go to lung windows on here the left upper low bronchus is right there so it's also called the left main stem bronchus left upper low bronchus Continuum so you can see this is the left upper low bronchus and this is the left main stem bronchus okay and that's an important Landmark on the lateral radio graph because there's a lot of structures that sort of go around it so just anterior to it you can see that there's this rounded sort of structure here and that is the right pulmonary artery which is right here and then there's another structure that sort of Loops over it right there and if we go to the left side that is the left pulmonary artery right there okay and this interval going from about here to here should be relatively clear um I don't know if you guys can appreciate that but there's a lot more opacity from here to here than there is from here to here and if you have a completion of this circle by opacity that's something called The Donut sign and that's a sign of lymph node enlargement in the hila and in the media stum another important sign on the lateral if I'm going to zoom out here is the spine sign so the spine sign is um a sign that is used to detect airspace disease in the lower lobes so in a normal patient the spine going from top to bottom should become more Lucent as you go in that direction and that's just because when you go up higher there's a lot more soft tissue that the beam has to penetrate and that's why it's more opaque here and down here there's a lot more lung and so it's a lot easier for the beam to penetrate and that's why the spine is more loosen here inferiorly now if you are looking at the spine and you're going down the spine and all of a sudden see an opacity where the spine is becoming more opaque as you go down that's a sign that there is an abnormality perhaps a mass maybe a plural Fusion maybe uh pneumonia that is obscuring the spine all right so that's basically a quick overview on how to look at a chest x-ray um for firste residents okay um this is not really meant to be a comprehensive learning tool but sort of an introduction um if you want a good text I recommend that you pick up a copy of this book felson's principles of chest rank canology a program text so it's in its fourth edition now but this is a really good book and it'll show you how to look at chest x-rays and including both inpatient and outpatient and if you can finish this book by the time you get to your first chest rotation you'll be well ahead of the Curve