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

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At low energies, however, the energy transfer coefficient is strongly suppressed. Compton scatter is not a good energy transfer mechanism at low energies. To recap, energy transfer via Compton scatter is very efficient at high energies, but at low energies Compton scatter is not an efficient mechanism for energy transfer. 16
What about the scatter coefficient? Remember when we have attenuation, two things can happen. Some of the energy can be transferred to charged particles, while some of the energy can go to a scattered photon. So the scatter coefficient is going to be equal to the total coefficient minus the energy transfer coefficient. At low energies, the energy transfer is small, so the scatter coefficient is approximately equal to the total attenuation coefficient. Compton scatter is not a good process for transferring energy to charged particles at low energies, but this is also consistent with classical scatter, so we do wind-up getting the coherent scatter in the limit of low energies. At high energies, almost all of the energy gets transferred to charged particles. Consequently, q y the scatter coefficient approaches pp zero. So the scatter coefficient goes between the total attenuation coefficient at low energies and zero at high energies. Now, let’s use this information about coefficients to deduce some properties of energy transfer and energy absorption. 17
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: The energy transfer coefficient has
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 and 38: These values were tabulated by Hubb
Page 39 and 40: So what is the effect of binding en
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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