Particle Therapy and Depth Scan Quiz

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What is the effect of low energy beam contamination on the entrance region?

It increases the peak/entrance ratio

It has no effect on the entrance region

It may affect the entrance region (correct)

It causes a decrease in dose at the entrance region

How does a short effective source distance affect the peak/entrance ratio?

It makes the peak wider

It has no effect on the peak/entrance ratio

It increases the peak/entrance ratio

It decreases the peak/entrance ratio (correct)

What is the impact of non-elastic nuclear reactions on dose distribution?

They increase dose at the entrance region

They make the peak narrower

They have no impact on dose distribution

They move dose from the peak upstream (correct)

What makes active range modulation more complicated than passive range modulation?

The change in shape of the Bragg peak Signup and view all the answers

What happens to the Bragg peak as depth increases?

It disappears Signup and view all the answers

What is the main reason for the difference in dosimeter response between Ionisation Chamber and Faraday Cup?

The shape of the ionization chambers Signup and view all the answers

In proton therapy accelerators, what is the classification of proton energies for the intermediate energy range?

50 MeV ≤ Ep ≤1,000 MeV (1 GeV) Signup and view all the answers

What is the dominant component of the prompt radiation field produced by protons in the therapeutic energy range of 67–330 MeV?

Neutrons Signup and view all the answers

Which factor mainly determines the effective mass stopping power from experimental data?

Range of the particles Signup and view all the answers

What is responsible for the production of secondary particles in proton therapy accelerators?

Beam line elements Signup and view all the answers

What is the significance of the fact that the coefficient is not very material-dependent in the context of stopping depths?

It simplifies the design of passive range modulators. Signup and view all the answers

How do materials other than water affecting the incident proton energy impact the Bragg curve?

It results in a similar Bragg curve in comparison to water alone. Signup and view all the answers

In the context of cyclotron-based therapy facilities, why are degraders used to change the beam energy?

Variable-energy cyclotrons are very expensive and slow to change energy. Signup and view all the answers

What is the main effect of multiple Coulomb scattering on protons passing through a slab of material?

It leads to a Gaussian distribution of projected displacement. Signup and view all the answers

What is the task of multiple scattering theory in predicting θ0 for protons passing through a slab of material?

To predict θ0 given the scattering material and thickness, and the incident proton energy. Signup and view all the answers

In the context of the text, what does the term 'transverse equilibrium' refer to?

The condition where the number of protons reaching the ionization chamber is exactly compensated by those scattering away from it Signup and view all the answers

How does using a large ion chamber differ from using a small ion chamber in a sufficiently broad beam?

The large ion chamber measures the 'true' Bragg peak, while the small ion chamber would not Signup and view all the answers

What happens to the dose on axis in a sufficiently broad beam as depth increases?

It decreases due to out-scattering of the protons Signup and view all the answers

What is the purpose of applying a large number of Pencil Beams (PBs) close together and doing a depth scan with a small Ionization Chamber?

To show the vanishing of the Bragg peak along the axis Signup and view all the answers

How does the effective mass stopping power compare when measured using a small Ionization Chamber and a large 'pancake' Ionization Chamber?

It is equivalent in a sufficiently broad beam but not in a narrow beam Signup and view all the answers