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13 Cards in this Set
- Front
- Back
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W quantity. How does it change with energy |
Basically constant at diff energies |
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What is LET? How is it diff from stopping power |
LET increases with increasing energy. LET is a measure of local material energy gain. Stopping power is total particle energy loss. LET is < or = stopping power due to brehmmstrahlung and delta ray losses |
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What are collisional and radiative stopping power |
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Range |
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Proton advantages |
Constant distribution with depth. Beam can be changed so bragg peak falls within appropriate tumor margins (range modulation). Sharp lateral distribution and penumbra because beams scatter through smaller angles than electrons |
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Proton disadvantage |
Beam contamination with neutrons. |
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Protons interact with matter bu |
Inelastic scatter with atomic electrons which is main source of energy loss. Elastic scatter with nucleus which is responsible for sharpness of lateral penumbra. Nonelastic nuclear interactions cause neutron dose and produce secondary protons heavy ions neutrons and gamma Rays. Bremmstrahlung interactions with nucleus |
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Heavy in interactions with matter |
Inelastic scatter with atomic electrons. Elastic scatter with atomic nucleus (grazing or head on collision). Nuclear fusion at 5MeV/mu |
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What is optimum in for RT and why? |
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What are mass of prions? What charge used in RT? How do they differ from other heavy particles? |
273x an electron. Negative. More pronounced peak because its attracted to nucleus which then disintegrates and produces star formations made of protons neutrons alpha and nuclear fragments |
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Why is boron-10 used in bnct |
No radioactive and readily available. High LET particles are emitted. Particles' combined path length are 1 cell diameter which spares normal cells. Boron chemistry is well understood and can be put in many chemicals. In BNCT b-10 is absorbed by tumor and when irradiated by neutrons short range alpha and lithium ion are ejected and deposit most of dose in tumor cell |
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Do high energy neutrons have good penetration? |
No |
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How are neutrons produced for RT |
Deuteron beam hits tritium to produce helium, neutron, and energy. Or deuteron ie accelerated to hit a usually beryllium target to produce neutron in stripping rxn |
