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How do Doctors read X-rays?

by Dr.Sal MD on author

xray image

When I started as a medical student, we still read real x ray films by sticking them up against a bright panel. All the x rays I get today are either dictated reports from a radiologist, or digital images on my computer screen.

Reading an X ray is really a task of pattern recognition. We compare the image in front of us with mental recollections of normal x rays we've seen before and against the anatomical schema we learn from diagrams and dissecting cadavers. In the same way that you can recognize a familiar face from a crowd of strangers in a blink, doctors can see pathology on an X-ray in a split second too. In fact, one type of doctors are the rock stars of reading x rays - Radiologists. They spend the majority of their working day huddled over computer monitors dictating reports on the x rays burnt that day.

The x-ray picture at the top of this page shows an obvious error that immediately caught my eye. The heart is rotated the wrong way: the tip at the base should be pointing to your right. I think the uploader seeing the faint 'R' in the upper right corner of the image assumed that was the right side. It's not, the person facing you in the image has their right hand side on your left hand side. So their 'R' marker should be on your left.

Because our visual processing is so dominant in our cognitive powers (optics takes up a third of your brain while 8% is used for processing touch and 3% for hearing) learning to read x rays is much easier than learning to read programming or another language for example. Seeing patterns in nature and recalling them comes naturally to all of us.

If you'd like to learn how to read x rays quickly, my suggestion would be to first divide your body into imaginary segments: head, neck, chest, abdomen, spine, arms, and legs. Then for each area get three pictures: an anatomical drawing like Netter's of the expected structures in the area to give you a mental lay of the land, then a normal x ray of the area, and then an x ray of the abnormality you're trying to learn and contrast the images in your mind looking for the differences that jump out at you. My final recommendation is to keep in mind that blinding white areas on the images are bone, and pitch black areas are air, and all he gray stuff has a density between the two. That gives you an optical appreciation for the hardness or softness of the area you're looking at helping you to mentally find your way.

Doctors also have a few cheats to help us out reading x rays. One, is context. If the story driving the x ray is a productive cough you immediately start looking for pus pockets instead of broken ribs - while if they fell off a ladder you do the reverse. The medical history primes us what and where to look. Second, if something is subtle, we can compare present x-rays to previous ones to make the pathology boil to the surface by employing contrast. And finally, we have the open door technique: not sure what you're seeing, then peek out your door and see which of your colleagues has their door open, skip on over and ask for their opinion - two heads are better than one.

Why do X rays often have more than one view to read?

If you're sent for a chest x-ray for example, you might notice that they shoot one film straight through your chest (PA), and then one from the side (lateral). The reason for this is to mentally construct a three dimensional space for the viewer. For example, say you're 6 years old and you swallowed a shiny quarter your gramp gave you, that coin will light up brighter than bone on the front view x ray. But from this vantage point you have no idea whether it's in the trachea (windpipe) to the front or lodged at the esophagus (swallow pipe) behind it. Looking at both the front and side views gives depth perception. And their are other types of views too, especially when it comes to joints, for example scaphoid views for wrists, Y views for the shoulder/arm connection, skyline views for knees e.t.c. In each case, these specialized views bring the body part of interest to the forefront creating a more flattering and useful picture.


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