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

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Compton scatter involves the interaction between a photon and a single electron. The probability of Compton scatter is almost independent of Z; it decreases slightly with increasing energy. When Compton scatter occurs, some of the energy is scattered and some of the energy is transferred into the Compton electron. The amount, the distribution of energy, depends on the angle of emission of the scattered photon and the energy of the incident photon. 44
The fraction of energy transferred to kinetic energy of charged particles per collision increases with increasing photon energy. For low energy photons, energy transfer is low, σ tr is much smaller than σ; Compton scatter is not an efficient means of energy transfer. For high energy photons, σ tr is approximately equal to σ, and Compton scatter is an efficient method of energy transfer. And finally, in soft tissue Compton scatter is the most important process in the energy range of 30 KeV to 30 MeV. We’ve spent a lot of time on Compton scatter. The reason we’re spending a lot of time on it is because Compton scatter is a very important process. It’s the most important process in the therapy energy range and matches the photoelectric effect for importance in the diagnostic energy range. 45
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 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: Note that this graph is for very lo

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

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