In beam modelling with Pinnacle RTPS, What is the role of the
flattening filter? What is the advantage of flattening filter free
and what is the main restriction.
In beam modelling with Pinnacle RTPS, What is the definition of
a “harder spectrum”? How would a “harder” 6MV spectrum change
theshape of the corresponding percentage depth-dose curve?
In beam modelling with Pinnacle RTPS, The source size is defined
to give geometric penumbra width, explain what else contributes to
thepenumbra width? Explain why width of D80-20 is used
to characterise penumbra width? Would the D80-20be
wider or narrower at high energy and why?
In beam modelling with Pinnacle RTPS,
For a 6MV beam:a) What is the maximum photon energy?b) What is
the mean (roughly) photon energy?c) How does the spectrum affect
the depth dose penetration?
a. Explain why filtering of an X-ray beam causes a simultaneous
decrease in beam quantity and increase in quality [a diagram may be
useful]
b. The two main mechanisms by which X-rays interact with matter
are via Compton scattering and absorption by the photoelectric
effect. By referring to the dependence of these effects on X-ray
energy, explain what happens to X-ray image quality when using
excessively high tube voltages