Electrons

Question 1

choose e- to give ? DD

Answer 1

90% DD to desired depth, which is 1/2 of the probable e- E

Question 2

e- used to treat lesions at what depth

Answer 2

superficial lesions < 7cm in depth

Question 3

e- advantages over superficial regarding bone dose

Answer 3

no increase dose to bone

Question 4

e- beam calc algorithm

Answer 4

pencil beams

Question 5

e- are scattered outward by

Answer 5

steep projection

Question 6

e- are scatter inward by

Answer 6

steep depression

Question 7

e- max range dependent on

Answer 7

E

Question 8

e- fall off is

Answer 8

rapid dose fall off

Question 9

e- skin dose is

Answer 9

high

Question 10

tx head component for e-

Answer 10

• scattering foil

- no target

Question 11

e- significant impact on tissue ?

Answer 11

inhomogeneities

Question 12

brems tail is what on a beam curve

Answer 12

slowly decreasing portion of an e- beam curve

Question 13

Rp stands for

Answer 13

practical range

Question 14

e- block thickness formula

Answer 14

MeV/2 + 1

Question 15

R90 is

Answer 15

MeV/4

Question 16

R80 is

Answer 16

MeV/3

Question 17

ballooning effect on e- requires you need to adequately

Answer 17

cover target volume

Question 18

in field blocking, block thickness must be adequate to reduce transmission to

Answer 18

< 5%

Question 19

e- cone size affects

Answer 19

beam output

Question 20

e- cone distance from pt

Answer 20

at least 5cm from skin surface

Question 21

uniformity of e- beams are better than

Answer 21

photon beams

Question 22

if air gap increases dose ?

Answer 22

dose decreases

Question 23

TBI uses

Answer 23

spoilers

Question 24

spoiler scatters

Answer 24

e-

Question 25

TBI total dose

Answer 25

12 Gy

Question 26

TBI dose rate

Answer 26

10-15 cGy/min

Question 27

TBI frequency

Answer 27

bid

Question 28

dose rate of e- varies with

Answer 28

field size & E

Question 29

%DD e- depends on

Answer 29

E

Question 30

to calc e- E you take ? of tumor

Answer 30

3x max depth of tumor

Question 31

field margin for e- must be selected so target lies within?

Answer 31

90% line

Question 32

e- range in lung is increased by a factor of

Answer 32

3

Question 33

CET stands for

Answer 33

coefficient of equivalent thickness

Question 34

in CET, the attenuation by a given thickness of inhomogeneity is equivalent to

Answer 34

attenuation by a certain thickness of water

Question 35

CET for compact bone

Answer 35

1.5 g/cm^3

Question 36

CET for spongy bone

Answer 36

1.1 g/cm^3

Question 37

e- density of lung tissue varies depending on

Answer 37

depth

Question 38

dose in tissue from of a less dense area (air/lung) is ?

Answer 38

decreased b/c scattering less

Question 39

e- range is larger in lung (less dense tissue) making lung dose ?

Answer 39

increase

Question 40

therapeutic range of e-

Answer 40

90% iso line (E/4)

Question 41

when CW tx w/e-, beam E is often chosen so what line is at interface?

Answer 41

80% line

Question 42

e- matching at surface causes ? at depth

Answer 42

hot spot

Question 43

e- advantages over superficial regarding skin sparing

Answer 43

small amount of skin sparing

Question 44

e- advantages over superficial regarding underlying tissue

Answer 44

greater sparing of underlying tissue

Question 45

e- advantages over superficial regarding output

Answer 45

greater output & faster treatment

Question 46

brems tail is generated where

Answer 46

scattering foil

Question 47

brems tail represents

Answer 47

photon contamination

Question 48

Rp is where e- have actually

Answer 48

stopped

Question 49

Rp formula

Answer 49

MeV/2

Question 50

e- block thickness below 10 MeV is

Answer 50

3mm block

Question 51

ballooning effect occurs with what radiation

Answer 51

e-

Question 52

what do higher isolines look like on ballooning effect

Answer 52

taper

Question 53

ballooning effect requires larger than expected

Answer 53

field size to cover entire volume

Question 54

ballooning effect aka

Answer 54

flowering pot effect

Question 55

isolines appear ? in ballooning effect

Answer 55

flat

Question 56

e- blocking affects

Answer 56

beam output

Question 57

e- SSD affects

Answer 57

beam output

Question 58

uniformity of e- beams have smaller ? than photon beams

Answer 58

horns at beam edge

Question 59

if air gap increases dose profile is

Answer 59

more rounded

Question 60

in TBI, surface dose increases with ? spoiler to surface distance

Answer 60

decreased

Question 61

in TBI, point of max dose build up moves closer to surface with ? spoiler to surface distance

Answer 61

decreased

Question 62

in TBI, ? becomes principle source of e- contamination of beam

Answer 62

spoiler

Question 63

what increases dose to tissue in buildup region for TBI

Answer 63

spoiler

Question 64

only 20-50% isoline into penumbra region causes difficulty in what

Answer 64

matching fields

Question 65

CET can be used to correct

Answer 65

e- change in dose

Question 66

e- density of lung tissue average is

Answer 66

0.5 g/cm^3

Question 67

Lateral scatter equilibrium exists when the field size is ? Of the e- energy

Answer 67

Of the order of the e- energy