hi, it's luke here, and in this video i'mgoing to teach you, in a nutshell, how to read a pa chest radiograph. reading a chest x-ray is a vital skill formedical students and doctors, and often comes up in exams. while there are also other chestfilm views, pa is the most useful, and by far the most common view you will encounter,so this is what i will be teaching in this short video. as this video is teaching the skill of readinga chest x-ray, i will not cover the more advanced skill of how to diagnose particular chestpathologies. by the end of this video, i hope that youwill:
1) have a working background knowledge ofthe theory behind chest films. 2) be able to use a systematic approach whenreading a pa chest film 3) be able to recognise and comment on anymajor abnormalities 4) be able to present your findings to a colleaguein a coherent manner. using my outstanding artistic talents anda bit of ms paint magic, i'm going to briefly demonstrate how a pa film is taken. this is the x-ray beam emitter, which firesa cone-shaped beam of radiation towards the patient, and this is the cassette, where thex rays are absorbed, some magic happens, and a picture is made.
the most important property of the beam ofradiation passing through the patient is that it passes more easily through light thingswith a low density, like air, and passes less easily through dense, heavy things like boneand fluid. because the image is negative, the bits of the film with less x-ray exposureshow up lighter. this is why bone appears white. the other important thing to consider is thata chest x ray is a 2 dimensional representation of a 3 dimensional object. pa, or postero-anterior,means back-to-front, but in latin to make us sound smarter. that's the direction thex-ray beam travels. because the x-ray beam is divergent and cone-shaped,objects at the back of the chest will appear
larger and more translucent than objects atthe front. because of the direction of beam travel, dense objects in the posterior chestmay hide objects in the anterior chest. next, we're going to work through the anatomythat can be seen on a normal chest film. as you can see, there's a letter l in thetop corner, telling you which side is left. first of all, let's look at the airways. youcan see the borders of the trachea as it runs down the centre next, we will look at bones. the bone i haveoutlined here is the left first rib, running from posterior at the top to anterior at thebottom. the first rib isn't always visible on a chest film, but if it is, you can useit to count all the way down. on a pa film,
the beam hits the posterior ribs first, sothese are the ones most visible. here you can clearly see down to the anterior 8th rib. the next bit outlined is the right clavicle. the borders of the diaphragm are outlinedhere. notice that the right hemi-diaphragm is higher than the left. this is normal, andis due to the liver lying underneath. on the left side, you might see a bubble underthe diaphragm. this is a gastric bubble in the stomach and is a normal finding. next, we will look at the borders of the heartand major blood vessels. let's do this clockwise, from top to bottom.
first you have the subclavian artery.then the aortic arch the pulmonary arterya small bit of the left atrium the left ventriclethe right atrium the superior vena cavaand the ascending aorta now onto the lung fields, and we'll startwith the lobes. i've outlined roughly where each lobe is located on the film.first the right upper lobe, then the right middle lobe, which touchesthe right heart border and the right lower lobe, which touches theright hemidiaphragm hopefully, you noticed that there is someoverlap between lobes, particularly between
the lower lobe and the other two. this isbecause of the three-dimensional structure of the lungs. the lower lobe occupies a spaceposterior to the other two lobes, and also to the dome of the diaphragm. it doesn't touchthe right heart border, like the middle lobe does, because the heart is anterior in thechest. the left is a bit easier, with only 2 lobes.the upper lobe now looks like it takes up almost the whole lung field, and touches theleft heart border. the left lower lobe is similar to the right, and shares a borderwith the left hemidiaphragm. finally, let's look at the lung hila, thismess of squiggly stuff above and behind the heart. the hila consist of pulmonary bloodvessels, the main bronchi, and lymph nodes,
although you should not be able to see lymphnodes in a normal patient. there is an indentation in the hilum on each side called the hilarpoint, and normally, it's higher on the left than right. ------------ now, before we jump into how to analyse achest x-ray, i'm going to talk you through how i would present a normal one to a colleague.this is an ideal scenario where we assume that we have the patient's information andwe know what kind of radiograph it is. "this is an upright pa chest film of mr duffy,taken on the 1st of january this year. exposure is adequate, the patient is not rotatedand there is no motion blurring.
airway is central and patent no fractures, lesions or defects are visiblein the bones cardiac silhouette is not enlarged both hemidiaphragms appear normal with noblunting of the costophrenic angles the edges of the heart and major vessels areclearly visible. left and right lung fields are clear throughout,a gastric bubble is visible, and there is normal hilar shadowing. in summary, this is a normal upright pa chestfilm." any systematic approach to reading a chestx-ray always starts the same way: making sure
you have the correct one! so the first stepto reading any cxr is: 1. check the patent's name and the date theimage was taken. it seems obvious, but make sure you have theright x-ray for the right person. some patients share the same name, so it's also good practiceto check the patient's dob or hospital number. many mistakes are made because people overlooktrivial details such as these. 2. check the type of film. often, you willbe told the type of film, but if not, there are clues you can look for. first, you wantto know from which direction the x-ray was taken? pa, ap or lateral. while a lateralfilm is easy to spot, differentiating between an ap and pa requires a bit of sherlock holmesclue hunting.
look at the clavicles and scapular edges onthis pa film. now let's look at the ap. do you see any differences? (pause). notice howon the ap projection, the borders of the scapulae are sharp, and appear to lie over everythingelse, while the clavicles appear to be obscured by the ribs and other structures. also noticethat the heart appears abnormally wide. secondly, you want to know the position ofthe patient. are they upright, or lying? again, hopefully this information is available. ifnot, in an upright patient, you might see a fluid level in the stomach. 3. check if the film is technically adequate.a useful mnemonic to remember the three aspects of technical quality is rip - rotation, inspiration,penetration. to check rotation, look at the
clavicular heads, and spinous processes. ifthe spinous processes are halfway between the clavicular heads, the patient is normallyrotated. next, check for adequate inspiration by lookingat the mid clavicular line and seeing which anterior rib intersects the diaphragm at thispoint. it should normally be the 5th, 6th or 7th. more ribs means the lungs are hyperinflated(often seen in copd). less means that the patient may not have taken in a full breathwhen the x-ray was taken. finally, check the penetration of the rays.simply put, an overpenetrated film is too dark, an underpenetrated one is too white.a trick to judge penetration is to look in the region of the heart. if you can see thespaces between the vertebrae and pulmonary
vessels through the heart, penetration isadequate. this diagram shows how the x-rays travel through these structures, with theheart on the left, a pulomary vessel in the middle, and the spine on the right. in an underpenetrated film, the weak x-raysfail to penetrate even the soft tissue of the heart, meaning the heart appears justas white as bone. in an overpenetrated film, the powerful x-raysgo straight through the small, soft pulmonary vessels as if they weren't even there, makingthem invisible, while the heart appears darker than it should. 4. look at the big picture. when you're examininga patient, you observe the whole patient from
the end of the bed before delving into thesmall details, and it's the same with examining a piece of imaging. look at the whole thing.can you immediately see any obvious abnormalities, like a large lung mass? 5. now we start to look at the details. thereare many different systems that people use to do this, and you may find your own thatworks for you, but the most commonly used system is the alphabetic approach, as it'seasy to remember and you're unlikely to miss anything.let's start with a, which stands for airway. a normal airway is central and open. an airwaythat deviates to one side may be due to a tension pneumothorax.
b stands for bones. with bones, start at thetop and work your way down, making sure you look at all bones visible on the film. theoutlines of each bone should have a smooth contour, and a break in the contour couldbe a subtle indication of a fracture. also look for any lesions where bone is more orless dense than it should be, such as the punched-out lesions often seen in multiplemyeloma. whilst looking at the bones, you should also look at the external soft tissuefor any abnormalities. c is the cardiac silhouette. on a pa film,the heart should be less than half of the chest width. an enlarged cardiac silhouetteis most commonly caused by cardiomegaly. pericardial effusion is another important cause.
d is the diaphragm. a normal diaphragm hasa sharply visible border, curves downwards at the edges, and the costophrenic angles- these bits - should be clearly visible, as should the cardiophrenic angles. a poorlydefined hemidiaphragm might be due to a lower lobe consolidation, whilst a blunted costophrenicangle is likely due to a pleural effusion. e is the edge of the heart. here, you're lookingfor something called the "silhouette sign" are the heart borders clearly defined? ifnot, this indicates that there is lung consolidation present. remember the normal anatomy? theright heart border touches the right middle lobe, while the left heart border touchesthe left upper lobe. these borders may be less well defined if there is consolidationin these lobes, such as in this example of
right middle lobe consolidation. f is the fields of the lung. normal lung fieldsare roughly symmetrical and have these faintly fuzzy lung markings throughout, representingnormal vascular and lung soft tissue. one thing to note is that, when describingthe lung fields, there is no 'correct' terminology, as long as what you say effectively communicateswhat you are trying to describe. for example, you could describe what you see here as 'patchyshadowing', 'widespread areas of increased density', 'multifocal opacification', or youmight even get a way with 'a load of white fuzz that probably shouldn't be there'. look carefully from the top, at the apices,to the bottom, where the lung extends just
below the diaphragm. compare left to right. firstly, see if there are any areas wherenormal lung markings are absent, as this may indicate collapse or pneumothorax. can you see where the lung markings are absentin this one? (pause) this patient has a left-sided pneumothorax.i've outlined the area where lung markings are absent. also notice that the left hemidiaphragmis flattened compared to the right. also look at the lung fields for any areasof abnormal shadowing, such as in this patient with tuberculosis... any opaque masses, suchas this patient with lung cancer... and for any fluid levels, such as in this patientwith pleural effusion. remember that you only
see fluid levels in upright patients. g is the gastric bubble. a normal gastricbubble is a small dark area under the diaphragm with a fluid level.if the patient has a hiatus hernia, you may see the gastric bubble above the diaphragm. h is the hila. normally, only the pulmonaryblood vessels are visible around the hila, so visible lymph nodes are an abnormal finding.look also for masses and calcified areas. this x-ray shows a patient with hilar lympahdenopathysecondary to tuberculosis. lastly, i stands for instruments. instrumentsrefers to all those things doctors like to put onto, or into patients, pads, wires, cables,tubes etc. etc. sometimes it's obvious what
you're looking at, sometimes it's not, soif you don't know what it is, don't worry about it. now that you've been through the whole x-raythoroughly and systematically, it's a good idea to go back through your findings andsummarise them in the same order. remember your steps. 1. patient's name, and date of the film 2. the type of film (position and direction) 3. technical quality (rotation, inspiration,penetration) 4. look at the big picture and take note ofobvious abnormalities
5. systematic analysis using abcdefghi check the airway is central and patentcheck the bones for fractures or lesions check the heart is not abnormally enlargedcheck the diaphragms are visible, dome shaped and the angles are intactcheck the edges of the heart are clear check the lung fields for normal lung markingsand abnormal shadowing check the hila for lymph nodes or masseslook for instruments now it's the fun part. using the method ihave taught you, it's your turn to try a couple of practice examples. pause the video at eachimage and write down your findings, and if you're feeling clever, you can make an attemptat diagnosis.
pause the video now. the first thing you probably noticed is thatthere's an abnormality on the right hand side, so let's move onto the details to figure outwhat's going on. the airway is deviated towards the side ofthe abnormality. the edge of the right hemidiaphragm is completely obscured. the right heart borderis further from the midline than you would expect. the lung fields are asymmetrical,with the right being smaller than the left, and there is an area of high opacity in theinferior right lung with absent lung markings. putting this information together - the silhouettesign at the right hemidiaphragm suggests a right lower lobe problem. the asymmetry ofthe lungs, and right deviation of the trachea
and mediastinal structures suggests a reductionin right lung volume. add to this the area of opacification with absent lung markings,and you have a classic picture of a right lower lobe collapse. now onto the next example. first thing to comment on here is the technicalquality. the patient may be rotated slightly, although it's difficult to tell, and it'shard to see the intervertebral spaces through the heart, suggesting underpenetration. themost striking thing to note is that the lungs are overinflated, with the 8th anterior ribintersecting the diaphragm at the mid clavicular line.
going through our system shows:there are flattened hemidiaphragms on both sides with blunted costophrenic angles. there are also small areas of increased opacityin the hila. the hyperinflated lungs and flattened diaphragmare characteristic of copd. the blunted costophrenic angles are a bit of a red herring, as theyare a result of a flattened diaphragm. the areas of opacity in the hila are likely dueto calcification of pulmonary blood vessels, so i would strongly suspect that this patientwas a heavy smoker. smoking is bad for you and this is what happens, so don't smoke! -----
this is the end of the video. to summarisewhat you've learnt: a little bit of background anatomy goes along way in interpreting chest x rays. start with the trivial stuff before divinginto trying to diagnose the patient. remember to comment on technical quality usingr.i.p use the abcdefghi approach smoking is bad. i'd like to acknowledge www.radopaedia.orgas the source for all of my x-ray images. it's an awesome website full of free educationalimages. for anyone who wants to learn more about chestx-rays, and wants to look more into how to
diagnose pathologies, i highly recommend thetutorials on www.radiologymasterclass.co.uk thank you for watching my video, i hope youlearned plenty from it. please leave a comment or suggestion in the comment section below.
No comments:
Post a Comment