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Why You are Struggling with X-Ray Physics

Updated: Dec 21, 2023

In my experience, you’re struggling with radiation physics for one reason: You missed out on a key foundational concept- and it’s probably not even your fault. Different professors have different methods for teaching these complex topics, and sometimes your learning style just doesn’t match with their teaching style. You’ve sat in the lecture, you’ve gone to office hours, and that advanced concept still doesn’t make sense—why? Because you missed step one! Here are three basic concepts I regularly see students struggling with in x-ray physics.  

1.  How are x-rays generated?

Remember that drawing of how electrons flow through the x-ray tube? Remember how electrons are generated and how they interact with the anode to create photons?

If you’re like most of my students, you’re nodding your head yes- except you can’t draw out each step. Without a complete front to back, back to front understanding of how x-rays are made, you’re going to struggle with every other concept that comes after relating to x-ray generation.

The process can be simply explained like this: In the x-ray tube, electrons are generated through thermionic emission and are attracted to the anode where they interact with the heavy metals and generate x-ray photons. These photons are directed out of the x-ray tube through the window and towards the target.

Without being able to freely verbalize this process, you will confuse yourself when we begin to talk about target interactions and scatter. Which brings us to our next topic!

2. How can I tell the difference between tube

interactions and scatter reactions?

Remember that diagram of the x-ray tube? Remember how electrons are attracted to the anode where they interact and create photons? Remember how scatter interactions happen outside the x-ray tube?

You will notice that the emphasis in both questions is WHERE these processes happen. In an x-ray tube, we start with electrons—NOT PHOTONS. In a scatter interaction we start with photons—NOT ELECTRONS. By identifying what starts the interaction, you will be able to easily assign it to its correct category- and in a multiple-choice situation that means you’ve eliminated answer choices early in the process.

3. Where does the energy for the x-ray come from?

The law of conservation of energy is another concept that I believe is too easy on the surface and so it gets glossed over by a lot of professors and students because it’s easy to memorize and move on.

Yes. The law of conservation of energy is simple. Energy cannot be created or destroyed only transformed or transferred. But what happens when you suddenly need to apply this law to understand what is happening during thermionic emission? Or x-ray production? Or scatter reactions? Or why the x-ray tube might overheat? If you have memorized the law, that’s a great first step—but if you don’t understand what it really means, you’re going to be in trouble on a lot of concepts- and those concepts aren’t as easy.  

Basic concepts in medical imaging can appear simple on the surface and cause you to say “yeah, that’s easy I’ll remember that!” But by not focusing on the small details of these concepts and really committing them to memory by understanding them, you are doing yourself a huge disservice down the road!

If you're interested in learning more about how you can better understand these foundational principles, sign up for a FREE 15 minute session with our instructor today!

What is the hardest thing with radiation physics for YOU?

  • It's the Math!

  • I can't get the details right.

  • Scatter and X-Ray generation look the same.

  • I struggle with it all.



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