How to Interpret a Chest X-Ray (Lesson 1 - An Introduction)

An introduction to the interpretation of chest X-rays, covering the basic principles of using X-rays in medical imaging, as well as the conventional X-ray views (i.e. PA, lateral, and AP).

[@birdog23]

aced my chest abdomen final with this series, wanted to come back to the first video to tell whomever sees this to watch all of these, because this is taught very well.

[@StrongMed]

Congrats! I'm glad the series was helpful!

[@wiliantolucas5433]

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[@giuseppetardini1424]

TRANSCRIPT
LEARNING OBJECTIVES:
• to be familiar with the basic physics and method of obtaining chest X-rays
• to be familiar with the basic chest X-ray views (e.g., PA, lateral, AP)
Along with the EKG, the chest x-ray is one of the most common diagnostic tests in medicine that does not involve drawing blood.
There are many INDICATIONS FOR GETTING A CHEST X-RAY:
• evaluation of symptoms (e.g. shortness of breath, chest pain, cough, hemoptysis, fever, unexplained weight loss)
• evaluation of physical signs picked up on a physical exam (e.g. hypoxemia, abnormal pulmonary exam)
• evaluation of the placement of central lines, nasogastric tubes and endotracheal tubes
• screening for pneumothorax after lung biopsy, central line placement, and pacemaker placement
• evaluation of suspected pacemaker lead fracture
There are a FEW SITUATIONS that are NOT PRESENT IN THIS LIST:
• routine chest X-rays prior to surgery in the overwhelming majority of patients are of no benefit and should be avoided
• routine screening chest X-rays for lung cancer and smokers are also inappropriate, although there may be benefit in screening chest CT-scans
HOW DOES THE CHEST X-RAY WORK?
• we need a source of X-rays, which themselves are a form of electromagnetic radiation
• X-rays are carried by photons, just like visible light, but have higher frequencies and thus higher energies, so they penetrate tissues much better
• unfortunately, these high-energy photons can cause DNA damage, leading to cancer, which is why X-ray exposure should generally be limited
• to detect the presence of X-rays we need a detector:
○ for the first 100 years of X-rays in medicine, the detector was a photographic plate or film
○ now, however, most hospitals have replaced these with digital detectors which allow for real-time viewing as well as improve post-exposure digital manipulation
• finally, of course, we will need a patient to stand in between the source and the detector
• the typical position of the patient would be facing away from the source, hands on the hips, and chest against the detector (the reason to put the hands on the hips is essentially to keep the arms from obscuring the view of the thorax)
• once we have the source, the detector and the patient, we may turn on the X-ray for a very brief, predetermined length of time, and X-rays, that is high-energy photons, will shoot out of the source
• some of the photons will pass right through the patient, some will be absorbed by the interposed organs and tissues, and some will be scattered around the room
• for the purpose of examing the X-ray film, it is actually the pattern of photons that are blocked which are of interest, as these create a shadow of the internal organs
WHAT ARE THE FACTORS THAT DETERMINE HOW MANY PHOTONS PASS THROUGH A PARTICULAR SPOT ON A PATIENT TO REACH THE DETECTOR? IN OTHER WORDS, WHAT ARE THE FACTORS THAT DETERMINE SHADOW BRIGHTNESS ON AN X-RAY?
• DENSITY OF THE INTERPOSED TISSUE (technically, this depends not just on the literal density, as mass per unit volume, but also independently on the atomic mass of the particles in the interposed tissue):
○ let's imagine a table with an empty glass jar placed upon it, filled just with some air and covered by a metal lid; on the far side of the jar is our photographic film, which starts off white; we fire some X-rays at the jar, which of course are not in the visible spectrum; as the X-rays travel across the table, the ones that either pass around the jar or through the jar interact with the film; any part of the film where many X-rays struck has turned black, while parts of the film where no X-rays struck have remained white, and the parts of the film where a modest amount of X-rays struck show various shades of gray; since air has a very low density, X-rays easily passed thorugh the jar and thus the jar appears empty on the film; the metal lid has blocked nearly all the X-rays, which has left a sharply demarcated rectangular patch of white, unexposed film
○ now, let's imagine a jar of water and repeat the very same procedure, exposing it briefly to X-rays which also exposes the film behind it; in this case, water is denser than air, so it blocks more X-rays, and therefore the content of the jar now appears gray on the film; it is important to realize that even if the fluid in the jar is completely transparent, it will still block X-rays and therefore look gray; the fraction of X-rays a substance blocks has absolutely nothing to do with its color or degree of translucency within the visible light spectrum
○ now, let's imagine what would happen if X-rays struck a skull; the resulting image would be lighter than the jar of water, but not pure white like the image formed from the metal cap of the jar
○ in summary, there is a SPECTRUM OF RADIO-DENSITIES into which different materials fall: those that allow most X-rays through are called RADIOLUCENT (BLACK), while those that block most X-rays are called RADIOPAQUE (WHITE)
○ for medical X-rays, there are essentially FOUR CLASSES OF MATERIAL (from the most radiolucent to the most radiopaque):
§ AIR, which is the most radiolucent
§ FLUID and SOFT TISSUE
§ BONE
§ METAL
• THICKNESS OF THE STRUCTURE (the thicker the structure, the brighter it will appear on the X-ray film):
○ if we take a single, relatively thin glass of water, and expose it to X-rays, most will pass through, resulting in a very dark image on the film
○ if instead we line up to glasses in a row and shoot X-rays through both, twice as many will be blocked, and the resulting image will therefore be more gray, because the specific parts of the film, corresponding to the shadow of the glasses, have been relatively less exposed
• DURATION OF EXPOSURE (short exposures lead to images that are too bright, while long exposures lead to images that are too dark)
○ for the X-ray interpreter, this factor is only relevant when trying to understand a technical error in image acquisition
○ imagine we have two glasses of water again, with a very brief X-ray exposure; during that brief amount of time, few X-rays have an opportunity to pass through the water, so the film where the shadow of the glass was cast is relatively underexposed, and thus relatively bright; if I use a medium exposure, the film behind the glass will receive more X-rays and thus the glass appears a little darker; finally, if I use a very long exposure, even though the glasses of water are in the way, there is enough time for many X-rays to pass through, so the glasses appear fairly dark on the film
The result of the passage of X-rays through the patient is an image formed on the photographic film of the shadows cast by the various structures in the patient's chest. From the pattern of white, black and gray, we can INFER THINGS ABOUT THOSE CHEST STRUCTURES:
• dark areas correspond to air-filled structures, such as the lungs
• areas that are medium-gray in brightness must correspond to structures composed of either fluid and/or soft tissue, such as the heart
• since the layout of the human body is amazingly consistent from person to person, each major line and shape on the X-ray correspond with a known and identifiable anatomic part
There are TWO QUICK PRACTICAL THINGS to point out:
• when we remove the film from the detector stand, we flip it around horizontally: the consequence of this is that the left side of the film, as we are looking at it, actually corresponds to the right side of the patient, and viceversa; this puts the X-ray in the same orientation as if we were standing in front of the patient and looking directly at him or her
• in radiology, the term view refers to the orientation of the person relative to the beam of X-rays; at this point there are THREE VIEWS TO KNOW:
○ POSTERIOR TO ANTERIOR VIEW: the X-rays entered the body squarely in the back and exited squarely out of the front; in most cases, the PA view will automatically be accompanied by the lateral view
○ LATERAL VIEW: as the term implies, the lateral view is the two-dimensional projection of the patient's internal structures as seen from the side
○ ANTERIOR TO POSTERIOR VIEW: the PA view should be distinguished from another situation, common in the hospital where patients may be physically unable to stand due to weakness, confusion, surgical wound or invasive tubes; in that circumstance, when the patient is in a hospital bed, a portable X-ray source will be wheeled into the patient's room, an X-ray film will be placed into a metal tray and slid behind the patient's back, and the X-rays will be passed through the patient from front to back; they are inferior in quality to PA films for a number of reasons

[@TalsonHacks]

this was helpful, thank you, Giuseppe

[@amulyablessy0557]

Thanks 😊

[@MohamedAli-nr6jq]

This is really helpful honestly, thanks allot.

[@threebigideas3488]

Wow. Glad I found this channel. What a great act of altruism and commitment to teaching. You should be proud of the content you created for others.

[@ranjitm07]

thank you strong medicine for uploading such valuable videos.without this videos it was impossible for me learn basics of chest x ray by just reading text books.

[@BasimAyoub]

Thank you Eric
I enjoyed it beyond what you would think and hands down this is the best X-ray series I have watched in years.
Have a blessed day
Job MD

[@yusefsma4916]

Thank you very much!
It is clear, short, to the point.
The animation makes it much more comprehensive !
The quality of the video is excellent !

[@jackilynbyrd3365]

Thank you for this series, for sharing your knowledge. I am in an FNP program and I already feel more confident after lesson 1. Working my way through!! :)

[@jkahn5350]

That was brilliant. All these years and I didn't have a clue about the physics of what I was viewing. Thank you Eric.

[@Vikasbhagat79]

Just one word for you Dr Strong...BRILLIANT

[@sarahhall9668]

Thank you so much for these great lectures. As a medical student this is teaching me so much for my placement/exams.

[@shariqazmi5015]

You are doing a great work Dr strong

[@michellemunoz1193]

THANK YOU SO MUCH!
Due to COVID-19, I'm not having radiology classes right now, so these videos are being salvation for me and my knowledge.

[@prathima5323]

Thanks a lot. Excellent presentation. All your lecture series so far have been very clear in presenting difficult to understand concepts of common conditions. Looking forward for more and more topics. Can't thank enough.

[@pabos1993]

Very scientific and simple! You are a great professor Dr Strong

[@mimiplac49]

This is a great course. Thank you so much for all you are doing.

[@user-vw3zd2jp3d]

The course outline looks great,specific and concise.

[@raymongonzalez7726]

Thank you for the lectures, I realized had a decent understanding of CXRs when I was able answer the examples correctly at the end.

[@bahtois4741]

This video series is GOLD

[@eshakarkhanis3059]

Dear Dr Strong, M a Medical student...Studying Physiotherapy.... thankyou so much for these X-Ray Series...Much needed to learn from the basics to actual interpretation of them...Thankyou soooo much.....Your to the point focused explanation definitely broaden my perspective and gave a depth to it..I did forward this to my physio n mbbs mates...amazing...LOVE FROM INDIA>>>

[@learnwithveer]

Thank you so much for putting so much effort to educate the medicos..ur hard work is truly appreciated..🙏🏽🙏🏽🙏🏽

[@theafricanobserver8785]

owesome, your channel is my savior

[@Diyaaeddin]

Thanks from across the globe! The videos are quite helpful.

[@liasosa4100]

Clear and precise information, so helpful for beginners, thanks so much!

[@raghebshalabny5523]

your ppts are amazing . Thank you sir !

[@MsMotherFuzzy]

This is great! Just what I needed, thank you.

[@devrajlamichhane4499]

you are the best. Thank you for making this video Dr.

[@WildlifeTshirts]

I'm very excited I found your videos. Thanks u 4 uploading.

[@CritER2023]

Thank you very much for your passion in sharing knowledge! I love your videos!!

[@munirabdullatif2022]

comprehensive,simple to understand
good job, thanks a lot

[@yakirachapu2377]

Awesome series of videos!! Great job!!

[@MrPridizzle]

Thank you so much Dr. Strong!

[@jiyugu]

Thank you for your wonderful lectures.

[@iimaanbare8559]

This my first day I watched your video, hope I will enjoy and learn more 🙏🙏

[@jas9233]

Thank you so much! I wish I came by these lectures when I first started studying radiology. Your concise and easy to follow animations definitely made the steep learning curve a lot less steep. Chest radiology is very different from MSK radiology and your videos were a pleasure to watch. I forwarded this series to a bunch of my colleagues in Chiro school and they felt the same way I so. We are starting the abdominal module next and were wondering if you can whip something up? Again, thank you so much for sharing your tips!

[@StrongMed]

Thanks for the feedback, and for sharing the videos with others! I'm definitely planning on 1-2 videos about abdominal X-rays, and eventually (in the distant future), hopefully a series on abdominal CT too. Unfortunately, I'm very far behind on viewer requests and on videos that have more immediate benefit at my own school that I can't offer any estimate of when I might get to them. Thanks for watching!

[@learnteach2learn729]

Thank you Eric these videos are great

[@Benjuolo]

Really helpful. Thanks

[@petrogurti2170]

thank you, this was well presented and it's a really helpful medical info

[@zbjordan23]

Excellent series!

[@nightelf7701]

Thank you Dr. Eric!!

[@ATNye]

Thank you for this great resource.

[@finias246]

Thank you, Dr. Strong.

[@jenniferhernandez5964]

fitfn some chin l.C.F. and a whip up

[@mohamedahmedzakariazaki8844]

You're a true genius!

[@abdulazeez.98]

Your videos are really really helpful.

[@mustafamukaram7412]

Very informative and nice way of explanation, thank you .

[@rajanrakesh4755]

Thank you so much dr for this video , it is amazing

[@drgarimasingh8471]

Very informative video... Just binge watched all....

[@tinkageorgewilliam871]

This is amazing... thanks. Makes me a better clinician in future.

[@jiteshgonnade1702]

thank you, awesome videos.

[@gungunmasti5438]

Sir u r excellent. Love from radiology students and best wishes

[@eltiobry3859]

this is so much helpful, thank you very much

[@DavidLee-tn3mo]

Great resource. Thanks

[@mdadike]

so helpful,may God bless you

[@saadnacheikhelmahdycardio1791]

Excellent and amazing présentation
U made it so clear and easy
Thank u so much really this was so helpful

[@TheCriticalCarePractitioner]

Fab as ever! Thanks Eric.

[@madalinaada2868]

amazing! ty!
the patient at the end is so funny :)) (a roman statue) his face is like : draw me like one of your french girls

[@bivoist]

Thanks.This is really helpful for me.

[@DrHieu585]

Thanks so much!
You are my great teacher :-)

[@aaaa-in9sv]

AMAZING EXPLANATION

[@sarvejanasukhinobavunthu712]

thanks a lot DR Eric

[@Mahadevan760]

Thank you, the differences between, white's, black's , and grey;s, was always nebulous, and uncertain for me, your explanation has cleared up a lot of doubts.

[@muhammadqasim-qh4ox]

Great lecture. Thank you

[@ramkrishnapandey410]

Thanks ,nice collection

[@bivoist]

Thanks Dr.Eric, Please CT imaging lectures please.

[@StrongMed]

I hope to someday include CT interpretation, but that's not an area of expertise for me, so I'ill need to work on recruiting a radiologist. Unfortuantely, recruiting quality teaching faculty to volunteer their time to make free videos for TH-cam has proven to be a challenge...

[@Homycraz2]

I have a friend who might be able to help!

[@user-do5hg6vr7e]

@@StrongMed ,you are great sir.

[@yourtube7539]

ur the best doctor God bless u

[@alialshehry9037]

Thank you so much .. I love it

[@RicardoPerez-vt1sq]

Hi Dr. strong , I have always had confusion to understand how the x ray works. Im student of medicine in Cd. Juarez México,
Thank you for sharing your knowledge .

[@debashiskumar6954]

thanks my icon Dr. Eric Strong!

[@neuroq7396]

amazing explanation 😍😍😍

[@Koyanginuna]

Really helpful in my radiology round

[@canwetalklips_3570]

Thank you, I like to learn more.

[@gaerlaninciong6132]

thank you for sharing this video

[@khushbashdar6686]

Thanks you so much ...it is really wonderful...

[@SusanKnisely]

Thanks Eric!

[@rockernoobsthurein]

Great job!

[@imarcastro51]

Great video!

[@sunving]

Thanks Doctor ,

[@luispedrobarbosa9709]

Thanks a lot, this videos are very helpfull!!!!

[@nathanaelkebede5073]

Thank You so much!!!

[@darwintuscano8625]

god bless you.. this is a big help..

[@ajh195]

Dr. Strong this is so great so much better than my professor in medical school. Can you please upload the other three imaging modalities CT, MRI & UL?

[@xalhaid]

YOU ARE AWESOME

[@seham7198]

very helpful 💓

[@ravibansal3751]

Very helpful ..Thank u😊

[@daminibisen547]

Thank you Sir

[@avelinaruiz7103]

helpful lecture....Thanks

[@ASilver526]

great vid thank you,

[@immacdoshi8383]

very useful learning

[@zinminhtet1478]

Thanks You Sir!

[@nimrahali3796]

Amazing.

[@sheikhbilal103]

Wonder full, Sir.
Amazing... U are doing it in free.
Want to know besides chest xray series any other series is by your good self.

[@StrongMed]

I've got all kinds of medical education video series: ECGs, pulmonary function tests, antibiotics, shock, IV fluids, approach to symptoms, diagnostic reasoning, etc... th-cam.com/channels/Fq5vPnNRNNNysLrktz4aSw.html

[@manu27190]

thanks sir for this video

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very good.excellent

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THANK YOU SOO MUCH

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Thanks a lot.

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Thank you sir useful video

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thanks you very much sir very nice video. thanks alot

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Very helpful thx

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Thank you

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Youre amazing..

[@abdullahalansari2163]

thank you very much for these videos , I'm from Iraq and I really love this content , it's very useful , thank you again .

[@lexmoga1740]

wonderful presentation with animation.