link to lecture transcript - UT-H GSBS Medical Physics Class Site

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We can’t evaluate this integral in closed form, but if we look at Johns & Cunningham Table A4, we’ll see different values for Compton coefficients for each material. These values differ slightly from those for a free electron gas because of the fact there is binding energy. 38
So what is the effect of binding energy? Here is a plot of Compton coefficients versus photon energy for a free electron gas, oxygen, and lead. We see the curve for the free electron gas on top; below that is the curve for oxygen; the lowest values are for lead. First of all, notice the binding energy only has an effect on the Compton coefficient at low energies; once you get above 100 keV, the binding energy essentially has no effect. Binding energy is more important for higher Z materials. This also makes sense. So the impact of binding energy on Compton coefficient is most noticeable for high- Z materials. In general, if we look at energies where the Compton effect is the predominant interaction, the effect of binding energy is not significant. 39
Page 1 and 2: Today, we continue our talk about C
Page 3 and 4: We previously derived an equation f
Page 5 and 6: So σ 0 is the classical cross sect
Page 7 and 8: Let’s look at this graph. Notice
Page 9 and 10: What about the dependence of the Co
Page 11 and 12: The energy transferred to the elect
Page 13 and 14: If we plot the energy transfer coef
Page 15 and 16: The energy transfer coefficient has
Page 17 and 18: What about the scatter coefficient?
Page 19 and 20: Using this equation we can now plot
Page 21 and 22: This probability is represented by
Page 23 and 24: This figure is a plot taken from Jo
Page 25 and 26: We can always calculate what the ma
Page 27 and 28: Remember dσ/dE is relatively const
Page 29 and 30: Now we also look at the graph and s
Page 31 and 32: First, let’s recall that the atte
Page 33 and 34: What we now want to find out is how
Page 35 and 36: So far, our approximations have bee
Page 37: These values were tabulated by Hubb
Page 41 and 42: At higher energies there is no diff
Page 43 and 44: Note that this graph is for very lo
Page 45: The fraction of energy transferred

link to lecture transcript - UT-H GSBS Medical Physics Class Site

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