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When you have your X-Ray tube, and want to make X-Ray for your X-Ray scanner or whatever. Then you get electrons from the cathode, which hit the anode, and from that produce a spectrum of X-Rays due to Bremsstrahlung, and characteristic lines from electrons jumping from shell to shell. This gives the continuous spectrum, and the sharp peaks from the characteristic lines.

My question is then: When you do an X-Ray, of a leg, or something, is it all the X-Rays that you use, both from bremsstrahlung and the characteristic lines, or do you somehow remove the continuous spectrum, or something, and only use the characteristic line X-Reay ?

Denver Dang
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2 Answers2

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Both the continuous spectrum and the characteristic lines are used; however, in some cases a filter such as aluminum can be used to remove low energy xrays that are not needed, so as to reduce xray exposure, as explained here: http://www.cyberphysics.co.uk/topics/medical/Xray.html

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DavePhD
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  • But isn't that a problem ? To get a nice contrast, you sometimes need not to high energies, and sometimes not to low. But if you get the whole spectrum, doesn't that interfere with the contrast ? Or maybe that is just a thing you have to account for ? – Denver Dang Jun 05 '14 at 21:52
  • the reference explains that for softer tissue like breasts low energy is important, so filtering out lower energies can not be used. – DavePhD Jun 05 '14 at 21:54
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An x-ray technologist can adjust the intensity of the x-rays by adjusting the kilovoltage across the gap. A hand requires about 60 Kvp (kilovolts peak), a shoulder about 70kvp, (which is where you’d begin to use a grid to reduce scattered radiation, an adult abdomen about 80kvp, and an adult chest about 110 kvp.

Short version of answer: The entire spectrum up to a peak is produced, and lower energy x-rays below 50kv are filtered.

Robert Destefano
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