7.3.2 X-ray Production

Reference: Weidner and Sells

Created October 19, 1995


7.3.2.1 Review of X-ray Definition

Recall from our initial physics review that x-rays are not defined in terms of their energy but rather in terms of their origin. To review, there are two sources of x-rays:

  1. Characteristic x-rays from inner shell vacancies

  2. Slowing or braking - Bremsstrahlung of electrons near the nucleus
It turns out that for x-ray imaging both of these x-ray types comprise the typical x-ray spectrum illuminating a patient.

7.3.2.2 X-ray Tube Basics

Although more properly discussed in the instrumentation course, we will introduce the components of the typical x-ray tube here. The following is a schematic based on Hendee (p. 68):

In this drawing the following points should be emphasized in x-ray production:

It is of interest to note that this reaction has been of experimental interest for the treatment of tumors by loading the tumor with boron and putting the patient in a neutron flux. The short range alphas have been shown to kill tumor cells.

7.3.2.3 Typical Spectrum

The resulting x-ray spectrum is adapted from Hendee:

It shows the effects of the filter in removing the low energy photons preferentially, and the presence of the K-alpha and K-beta characteristic x-rays.

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Douglas J. Wagenaar, Ph.D., wagenaar@nucmed.bih.harvard.edu