this video is an introductory video designed to give you a solid systematic approach to chest x-rays in part 2 we're gonna practice applying this approach by looking at a few illustrative cases of common things that you're gonna see and things that you shouldn't miss the two most important things to take away from this first video are 1 learning normal anatomy while really getting used to what normal looks like and then to a solid approach to both frontal and lateral chest x-rays there are a few things that we're gonna cover first but the anatomy and the approach are the main things that I want you to take away from this video so let's get started this is a chest x-ray when most resources try to teach you an approach the first thing that they tell you to do is to look at a bunch of quality things like patient name date a few technical things about film quality I'm gonna skip over most of this a lot of basic chest x-ray resources give you a laundry list of things to think about when you're looking at chest x-rays and to be honest it can be a little bit overwhelming at first so let's keep it simple and focus on the basics with that being said I'm gonna mention a few technical things that I actually do think are important once you know the basic anatomy things like how you can tell if the patient is rotated but again for this video don't get tied down with little details here and there focus on the basic principles and the big picture as you know chest x-rays use x-rays a form of ionizing radiation and it's probably important that you know about how much radiation that is and how to explain the radiation dose to patients this bar graph shows typical effective radiation doses for different imaging studies in millisieverts it's important to know that the background radiation dose that we are exposed to by just living on earth from just background radiation which is very low is about 3 millisieverts per year this helps us put these doses into perspective a chest x-ray uses about 0.1 millisieverts of radiation a very small amount this is on the order or about 10 days of background radiation a body CT for comparison is on the order of a few years of low-level background radiation still a relatively low dose for a single exam don't get too bogged down with any of the numbers here the key is that you know that yes chest x-rays do use radiation but the dose is very low and it's on the order of days of background radiation there are a number of different chest x-ray views that you're commonly going to see including PA when the x-rays come from posterior to anterior through the body ApS which are usually performed portably is the opposite so the x-rays are coming from anterior to posterior these can either be done in a supine position with the patient lying flat or upright if the patient is sitting or standing we also have lateral chest x-rays that we'll show you and then other special views like a lateral decubitus views where the patient's on their side and we'll talk about applications in the next video the most common view that you're probably going to order and probably gonna see for outpatients and relatively mobile patients in the emergency department is a PA view and again that means that the x-ray beams are going from the posterior side of the patient to the anterior side of the patient the film is on the anterior aspect of the patient and is exposed by beams that make it through things that are closer to the film are going to look smaller and anything further away from the film is going to look relatively magnified so with that in mind we can see why the orientation of the x-ray beams matter here we have two films one is a P and the other is PA the one on the left is the AP view and the on the right is the PA view the film is usually labeled but you can usually tell by just looking at the pictures things closer to the film are going to look smaller and sharper and things further away from the film are going to look relatively magnified on the PA view you can see that the heart is smaller you can see the anterior ribs which I've outlined here are relatively sharper and the overall quality of the film is better on the PA film here as a result of all of these things we're gonna see more of the lungs on the PA film and we're also gonna be able to pick up more abnormalities the PA and lateral films are the two standard chest x-rays that you're gonna see most commonly in practice for eMobile patients like patients from the ICU who often get films daily they are often taken portably by the patient's bed in AP so back to our chest x-ray we mentioned that x-ray beams that make it through the patient can be detected on the other side and those that don't make it through obviously cannot on an x-ray areas that don't attenuate the x-rays as much I II the x-rays that make it through easily show up as darker this means that in general less dense things look darker like the lungs and more dense things look brighter we covered the basic radiographic density's in the introduction to CT video and abdominal x-ray video so we won't belabor the point but it's important to remember the main radiographic density's remember on CT we can quantify densities on a scale called the Hounsfield unit scale this is also covered in other videos like the introduction to CT video in more detail but for x-ray things are a little bit more simple so don't worry about the stuff for now in general we can simplify this to four principal radiographic densities we have air that is very low density we have bone and metal that are higher in density are going to show up as brighter and then in between we fat water and soft tissue remember fat is less dense than water if we mix oil and water oil floats because it's less dense and it's gonna show up as slightly darker than soft tissue and water and if we look at a normal chest x-ray we can immediately apply this basic knowledge although these structures are overlapping and any point on the image or on the x-ray is a reflection of all of the materials between the x-ray source and the film at that particular location you can still identify the radiographic density's the lungs are filled with air and show up as very dark the bones are denser and show up relatively brighter soft tissues are slightly less dense and there are even a few places on the x-ray where you just see fat and are relatively low density so for example you have subcutaneous fatty tissue that you see part of here that's darker than the soft tissues adjacent you also see between the musculature planes of fatty tissue here that are relatively darker and again this is a normal chest x-ray another location where you commonly will see fat normally is up here in the neck this is important to know because when you have pneumomediastinum or air in the mediastinum it can track up into the neck and gas in the neck soft tissues is often a sign for pneumomediastinum for inexperienced readers they might look at the fat here and wonder if it's gas so remember what this normally looks like okay now that you understand the basic densities let's go through the normal anatomy and we're gonna go into order here so number one here shows where the trachea is on a normal plane film number two the right mainstem bronchus number three the left mainstem bronchus number four is the left pulmonary artery number five is the right upper lobe pulmonary vein number six is the right inter low bar artery number seven is the right pulmonary vein for number four to seven it's not as important when you're starting out to be able to distinguish them individually instead just get used to what the normal high-low look like and we'll talk about that and show examples of it in a bit number eight is the normal a or tech arch number nine is the SVC number ten is where the as igus arches or as a kiss vein is number eleven is the right heart border which is made of the right atrium remember the right ventricle is an anterior structure and number twelve is the left heart border which is mainly the left ventricle and a little bit of left atrium I'll also draw your attention to the space between the aorta here or the air-duct notch and the pulmonary artery here this here is called the AP window for a for aorta P for pulmonary artery this should be concave this is convex or filled in that's AB if this is convex or filled in that's abnormal this is a labeled lateral film and we're gonna go through the anatomy here and shortly go through an approach number one here is the trachea number two is bronchus intermedius number three is the left upper lobe bronchus number four is the right upper lobe bronchus number five is the left pulmonary artery and number six is the right pulmonary artery from one to six the only important things I think you need to know are you have a trachea here you have Lucent circles which are the upper lobe bronchi on both sides and then anteriorly you have a density that is the right pulmonary artery and posterior superior lis you have the left pulmonary artery density as well okay so you're gonna see a lucency down the middle a density anteriorly and a density posterior superior Lee you're gonna have a relative paucity of densities in this inferior region here and this is normal if you have densities that are surrounding the entire bronchus here that is often a sign of lymph adenopathy called the doughnut sign so get used to this normal pattern at the Hilah lucency down the middle density anterior to it is the right pulmonary artery and density posterior superior li7 is the pulmonary vein confluence h is the aortic arch 9 is the SVC 10 or the anterior heart border is the border of the right ventricle 11 and 12 are the posterior border of the heart here made up of the eleven left atrium and twelve part of the left ventricle I also want to point out a few other things about a normal lateral chest x-ray this lucency posterior to the sternum here is called the retrosternal airspace this should usually be relatively dark this region here behind the heart is called the retro cardiac space you'll notice that as you go down the spine and the spinal elements are outlined here the lung gets more and more Lucent this is called the spine sign the lungs should get more loosened as you go more inferiorly down the spine on the lateral you have the costophrenic angles here and this is where fluids gonna collect when you have small pleural effusions blunting of this is the sign of pleural effusion the lateral chest x-rays are much more sensitive to smaller pleural effusions than the frontal chest x-rays the right and left hemidiaphragm ZAR marked off here as well in telling which ones which there are a few different ways you can do that the one that I caught most commonly uses that the right hemidiaphragm you're gonna see extend very clearly from posterior to anterior where the left hemidiaphragm you often lose it when it touches the heart also the right hemidiaphragm is usually higher than the left and this can be confirmed in the frontal okay now that we've gone through the anatomy we're gonna go through a basic approach to chest x-ray this is something that's gonna be systemic and something that you're gonna practice over and over and over again and it's gonna become second nature so let's start with a frontal x-ray so this is a PA film I generally start by looking for lines and tubes and making sure that they're appropriately positioned things that you're commonly gonna see include chest tubes mediastinal drains endotracheal tubes in the trachea and central lines we're gonna talk about specific positioning of these tubes in another video I then look at the heart when I'm looking at the heart I start by looking at the borders of the heart and the size of the heart when I'm looking at the size I'm looking for enlargement radiologists commonly use a cardiothoracic ratio on PD on PA films namely the ratio of the size of the heart in horizontal distance to the size of the entire chest here from pleura to pleura the cardiothoracic ratio is normally less than 0.5 on a PA film I then look at the position of the heart this is a normal position seeing if it's shifted one way or the other I then look for anything that's very bright namely calcifications or metal in the valves or in the pericardium and then look for anything that's very dark namely gas so looking for gas around the heart in the setting of pneumopericardium so to review when I'm looking at the heart I'm looking at borders size position thing that's things that are very bright and things that are very dark when I look at the mediastinum I'm doing the exact same thing I'm looking at the borders we see a normal AP window here we see normal contours the size the position looking for a shift of the mediastinum anything that's very bright like calcifications metal foreign bodies etc anything that's very dark namely pneumomediastinum when we have pneumomediastinum ER pneumopericardium what's the difference well pneumo just means gas or air and if it's pneumopericardium it's gas in the pericardial sac that stays in the pericardial sac and the reflection of the pericardium ends at the base of the great vessel so you're only gonna see gas below that level and your mo pericardium pneumomediastinum you have gas throughout the mediastinum which often two sex more superiorly in the mediastinum and then up into the neck commonly as well as a general point whenever you see air anywhere where it's not supposed to be you need to figure out why it's there I like to break this down simply by breaking it down into three categories one air from outside the body two air from inside the body and three air from gas forming infection in this setting of numa numa mediastinum for example air can come from outside the body for example if they had a recent surgery or open procedure in line placement or trauma it can come from inside the patient for example from esophageal perforation or it can come from a gas forming infection which is relatively rare so remember when you're trying to figure out why there is gas in an abnormal location think is it coming from outside the patient somewhere inside the patient or gas forming infection I then look at the lungs and I'm comparing both sides to look for asymmetry normally it's symmetric and then I look at each lung more closely by zigzagging up the lungs for more subtle abnormalities again remember that there's lung behind the diaphragm as well as behind the heart here as well what I'm looking for abnormalities in the lung the main things you're looking for include consolidation which are going to look like fluffy brighter opacities cloud like opacities or other words that are used to describe consolidation you're gonna look for masses which are more rounded abnormalities and you're also gonna look for abnormal reticulation in other words too many lines in order to pick up a reticular abnormality it's good to know what the normal vasculature looks like I generally split the lungs into thirds we have the medial third the middle third and the peripheral third as you move out peripherally you're gonna have less and less markings as you can see from normal vessels in the peripheral third you should have next to no or no markings in a normal situation if you see too many lines here peripherally that's abnormal once I've looked at the lungs I look at the pleura so I follow the pleura around in both lungs mainly looking for pneumothoraces aka gas in the pleural space and pleural effusions the most sensitive locations in an upright film are gonna be the costophrenic angles for a pleural effusion you're gonna see blunting of the costophrenic angle here it's very sharp remember lateral films are more sensitive than frontal films for pleural effusions and I'm also gonna look in an upright patient for small pneumo authorities at the apex of the lung you can also look for pleural calcifications I then look at the abdomen and you can watch the abdominal x-ray video for more details the main thing you don't want to miss is free gas or free air under the diaphragm and a patient who hasn't recently had surgery this is often seen with bowel perforation which is something you don't want to miss I then look at the bones and soft tissues starting with the spine looking at each of the particular bodies I look at the ribs both the anterior ribs and the posterior ribs I generally screen he's quickly looking screening the clavicles the scapula here in any parts of the shoulders we can see as well as the soft tissue is taking a quick look for any obvious gas or high-density material once I've looked at all of these things I have four checkpoints at places where people commonly miss things the first is the apices small pneumothoraces and small masses are often missed here two is the hila get used to what these normal hila look like I look at the retro cardiac region again again a common place for Mis pathology and then the retro diaphragmatic regions of the lungs as a brief aside I did mention that I would briefly touch on a couple of quality things first to tell if the patient is rotated I look at the medial aspects of the clavicles in comparison to the spinous processes here the spinous processes should be more or less halfway between the medial aspect the clavicles in order to determine if the patient had a good enough inspiration we generally want to see six anterior ribs or ten posterior ribs projecting over the lungs so here we have one two three four five six at least anterior ribs and several posterior ribs as well so this is a good inspiration lastly when someone says a film is overexposed it means that too many x-rays got through and were detected on the film so if a film is overexposed it generally means that it looks too dark and an underexposed film usually looks brighter so it's the opposite of what we usually think with photography to review this approach again we have lines and tubes we have the heart remember borders size position things that are too bright things that are too dark mediastinum same thing borders size position things that are too bright namely classifications and metal things that are too dark looking for gas looking at the lungs making sure to compare and not remember the blot and not forget the blind spots looking at the pleura looking at the upper abdomen the bones and soft tissues screening them and then looking for our check points again the apices the hila the retro cardiac region and the retro diaphragmatic region this is a normal lateral film there are a lot of different things that you can look at and we talked about the anatomy and I'll briefly orient you again so this is the spine here there's the trachea here that you can see very well you see lucency and you see the right pulmonary artery here that's lighter anteriorly and the left pulmonary artery posterior superior lis remember there's a relative paucity of density in this inferior region here get used to what that normal high-low looks like because the lateral can be very helpful to determine if there is true adenopathy because beginners are usually a little bit worse at looking at the lateral films compared with the PA films I'm gonna give you a very simplified approach to the lateral chest x-ray we're gonna look at five main things that I'll mention a few others but if you remember those five things you're well ahead of the curve okay I look at the retrosternal airspace which should be loosened here it's brighter that's up at the top because the patient's arms are here but in general this should be loosened and if it's not I can indicate pathologies such as most commonly an anterior mediastinum mass I look at the retro cardiac area which should be loosened here I then look at the spine signs so I'm looking at the spine itself but also looking at the lungs over line so the lungs should get more and more loosen as you move more inferior lis oftentimes if you have consolidation in either of the lower lobes you're gonna see that that does not happen and there is something here that makes it look brighter I then look at the hila and we talked about that Anatomy again just now looking for evidence of lymph adenopathy mainly and then looking at the cost over neck angles remember that the lateral film is more sensitive for plural fusions than the frontal film so again a simplified lateral chest x-ray includes looking at the retrosternal air space the retro cardiac air space looking at the spine sign and the spine itself looking at the hilar anatomy and making sure there's not lymph adenopathy and looking at the costophrenic angles now that we've gone through the normal anatomy and you have a basic approach you're getting to know what normal looks like when you go through your approach you're gonna need to pick up things that are abnormal this is gonna come with practice we're gonna go through an example now in the next video is exclusively dedicated to picking up those abnormalities in my experience when people first start reading x-rays they're more often oversensitive but calling things that are normal abnormal but the more you practice and the more you see the better and more confident you're gonna get you're also gonna get to know what the most common pathologies look like so in the next video we're gonna apply our approach to several bread-and-butter cases and things that you shouldn't miss let's finish off this video by reading this chest x-ray this is a 60 year old smoker so I'm gonna start looking for lines and tubes there's no lines or tubes looking at the heart this is a portable film but it's not unlocked it's in normal position the borders are okay I don't see anything bright I don't see any gas the mediastinum size position contours are okay ap window is normal there is calcification in the aorta suggestive or in keeping with calcified a fish aquatic disease and then look at the lungs comparing both sides and then zigzagging up each of the lungs looking for more subtle abnormalities I look at the pleura there's no pleural effusion or pneumothoraces there's some scarring at the apices here no pneumothorax no pleural effusion look at the abdomen nothing to comment on bones and soft tissues look okay I then look at my checkpoints so the apices the hila these are normal Hilah the retro cardiac region and the retro diaphragmatic region okay for those of you that were paying attention you'd pick up on this abnormality here this ended up being a lung cancer so it's obviously very important that it was picked up on this chest x-ray okay so that's the end of this video the main things I wanted you to take away are the basic anatomy a basic approach to frontal and lateral chest x-rays and really getting used to what normal looks like the best way to get better at chest x-rays is to keep practicing and keep looking at cases the next video as I mentioned a couple times is going to review several cases to help you practice your chest x-ray skills