Lecture 2

Question 1

charged particle interactions- which cells do more

Answer 1

heavier particles behave differently in these, where alpha particles and protons are charged particles and heavy. The lighter ones like electrons and stuff do not behave as differently

Question 2

3 ways to deposit energy (giving up energy)

Answer 2

excitation, ionization, radioactive losses

Question 3

what is excitation

Answer 3

incoming particle excites the target atom by shifting an orbital electron and moves one to increased energy state (draws away from the nucelus) and boosts to outermost shell and so it gives off EM radiation since closer is in lower energy and outer is in higher energy

Question 4

what is ionization

Answer 4

remove orbital electron (greater than binding energy of orbital electron) and the ejected electron fives off a delta ray, which can go on to interact with additional atoms

Question 5

what is a delta ray

Answer 5

the secondary electron produced by ionization, which is a way to deposit energy

Question 6

how much energy do delta waves deposit from energetic electrons in soft tissue

Answer 6

70%

Question 7

At 40 eV electrons, what is the relationship between ionization and excitation

Answer 7

they should be equal

Question 8

how many secondary electrons are produced from a 10 kEV electron

Answer 8

450 secondary with energy between 10 and 70 KeV

Question 9

what is the energy that below which, electrons can no longer produce ionization

Answer 9

11.2 eV

Question 10

what is Brensstahlung radiation

Answer 10

charged particle comes close enough to nucleus so it is slowed down by nucleus and it is shifted.

Question 11

what is annihilation

Answer 11

positron combines with an electron, which produces two gamma rays equal to the mass energy of a positron and electron. at 511 keV each, and they go in opposite directions.

Question 12

what type of imaging modality uses annihilation

Answer 12

PET imaging

Question 13

what is specific ionization and how is it used

Answer 13

it is energy happening for a long time with photons, but with protons, they deposit at one depth which is called the Bragg peak. This is dose dependent, so it dumps its energy at one depth. It is used in proton beam therapy to target specific tissues without affecting others.

Question 14

neutron interactions

Answer 14

cannot excite or ionize. They interact with the nucleus sometimes and release a charged particle.

Question 15

what do neutrons interact best with

Answer 15

they interact best with light nuclei in H,CO,

Question 16

what happens when a neutron hits a nucelus

Answer 16

recoil of the nucleus so that it loses energy via excitation or ionization then the neutron is captured and turns an H1 usually into an H2

Question 17

What are the Xray (photon) interactions

Answer 17

Daylight scatter, Compton scatter, photoelectric effect

Question 18

what is daylight scatter and what is it also called

Answer 18

classical or coherent scatter; Xray is emitted with the same energy but in a different direction.

Question 19

does the energy and deflection change with Rayleigh scatter

Answer 19

shallow deflection energy and there is no net change in energy. It tends to come into play with low energy. There is no ionization and no absorbed dose

Question 20

why is rayleigh scatter important in imaging

Answer 20

it comes up in imaging degradation