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Flashcards in Exam 2 Deck (40):
1

Discovery of X-rays

Roentgen, November 11th

2

What is the difference between linear accelerators and a Co 60 treatment machine?

Co 60 has a live source which produces gamma rays and Linear accelerators are electric and produce x-rays

3

kVp

Quality of radiation, the grays, determines contrast

4

mAs

Refers to the quantity of the radiation. Density = the overall blackness of an image

5

filtration

Hardens the beam

6

HVL

The thickness of absorbing material necessary to reduce x-ray intensity to half of its org value. Org = 100%, 1 HVL = 50%, 2 HVL = 25%, etc.

7

D max

depth in tissue where 100% of the dose is deposited

8

Advantages of higher energy?

More forward scattering, deeper penetration, skin sparring

9

Cyclotron

Mainly used for research, can produce protons and neutrons

10

Co 60 Machine

Live source. longer the beam is on, the worse the side effects. Older the source, longer the tx

11

Co 60 half life

5.2 years, about 1% /month

12

2 gamma ray

(Co60) 1.17 MV 1.33 MV. Avg energy = 1.25 MV

13

What is the difference between gamma rays and x-rays

Gamma rays come from a live source and x-rays are electronically generated

14

Penumbra

fuzzy edges, P=S(SSD-SDD)/SDD

15

Cyberknife

Treat any part of the body

16

IORT

Intraoperative radiation therapy

17

Main component of the stand

Klystron, waveguide, circulator, cooling system

18

Klystron

Generates and amplifies high power microwaves to accelerate e-

19

Waveguide

Transports microwaves from the klystron to the accelerator guide

20

Circulator

Prevents back flow of microwaves

21

Major parts of the gantry

Electron gun, Accelerator structure, treatment head

22

Electron gun

Produces electrons and injects them into the accelerating structure

23

Accelerator structure

Long and cylindrical, electrons accelerated to near c nay microwaves

24

Bending magnet

in the tx head, bends the beam of e- in 270 degrees

25

Target

Anode, electron beam hits to produce x-rays

26

Primary collimator

Helps shape the beam and set the maximum field size limit

27

Carousel

Holds the flattening filter and the scattering foil

28

flattening filter

treating with photons

29

scattering foil

treating with e-

30

Dual ionization chamber

Measures the output of the machine, shuts the machine off after dose requested is reached

31

2nd collimater

Field size jaws, X1, X2, Y1, Y2

32

Dmax of 4 MV photons

1 cm

33

Dmax of 6 MV photons

1.5 cm

34

Dmax of 10 MV photons

2.5 cm

35

Dmax of Co60

.5 cm

36

Homogenous beams?

Electron beams

37

How can you determine the max energy of a photon beam?

energy / 1/3
EX: 6 MV/(.333) = 2 MV average energy

38

Therapeutic dose?

E/4 = cm
EX: 6/4 = therapeutic dose at 1.5 cm

39

Effective dose

E/3

40

Stopping dose

E/2, no more energy after this point