Quiz 2 (PPT 3)

Question 1

Defined as desired modification in the spatial distribution of radiation by insertion of any material in the beam path

Answer 1

Beam modifier

Question 2

Types of beam modification:
eliminates radiation dose to certain parts of an area where the beam is directed

(Flattening, Compensation, Shielding or Wedge filtration?)

Answer 2

Shielding

Question 3

Types of beam modification:
Allows normal dose distribution to be applied to the treated area whereas to even out the dose distribution

(Flattening, Compensation, Shielding or Wedge filtration?)

Answer 3

Compensation

Question 4

Types of beam modification:
Allows for a tilt in the radiation isodose curves

(Flattening, Compensation, Shielding or Wedge filtration?)

Answer 4

Wedge filtration

Question 5

Types of beam modification:
Where the distribution of the beam is altered by reducing the central exposure area relative to the peripheral

(Flattening, Compensation, Shielding or Wedge filtration?)

Answer 5

Flattening

Question 6

Review slide 2

Question 7

Other types of wedges:
Single, centrally located wedge in the head of the linac that is placed within the beam for a fraction of treatment time. The longer the wedge stays in the field the larger the wedge angle

Answer 7

Motorized wedge

Question 8

Other types of wedges:
Uses motion of collimator jaw or leaves during treatment delivery to modify the dose distribution
Greater range of wedge angles
Less restricted field sizes than solid wedges
Time efficient (no need to enter treatment room)

Answer 8

Enhanced dynamic wedge

Question 9

Other types of wedges:

Uses three dimensional compensation to modulate the dose distribution in a non linear way

Answer 9

Field in field treatment planning technique

Question 10

MLCs:

Some linacs can have up to ___, ___ or ___ leaves

Answer 10

80, 120, 160

Question 11

MLCs:

Most leaf thicknesses are ___ or less

Answer 11

1cm

Question 12

MLCs:

Made of ___ alloy

Answer 12

Tungston

Question 13

MLCs:

Uses ___ and ___ design

Answer 13

tongue, groove

Question 14

Some disadvantages of MLC’s include: (4)

Answer 14

No island blocking
Jagged field boundary
Field matching difficult
Penumbra is larger

Question 15

Cerrobend blocks:

Composed of ? (4)

Answer 15

bismuth, cadmium, lead, tin

BLT w. Cheese

Question 16

Cerrobend blocks:

Melting point __ degrees F

Answer 16

158

Question 17

Cerrobend blocks:

Usually created ___ thickness which is equivalent to ___ of Pb and provides ___ of attenuation

Answer 17

7.5cm, 6cm, 5HVL

Question 18

Cerrobend blocks:

Some advantages over MLC’s include that they are ___ conformal and ___ ___ can be created

Answer 18

more, island blocks

Question 19

Cerrobend blocks:
Some disadvantages include having to physically lift and ___ blocks in linac for individual fields and having to construct and touch ___ ___

Answer 19

insert, hazardous material

Question 20

Compensators:
Used initially to address tissue irregularities for sloping surfaces but today can also be used for tissue inhomogeneities ___ the body

Answer 20

inside

Question 21

Materials can include Pb, aluminum, wax, brass, lucite

Answer 21

Compensators

Question 22

Can be designed via a CT scan and treatment planning computer

Answer 22

Compensators

Question 23

Can be used for photon and electron treatments

Answer 23

Compensators

Question 24

Tissue equivalent material
Commonly used materials
Paraffin wax
Cotton or gauze soaked in water
Superflab elastic gel
Used to bring dose to surface (build up)
Made in various thicknesses 3mm, 5mm, 1cm, 1.5cm

Answer 24

Bolus

Question 25

Skin dose:

As beam angle of incidence increases skin dose ___

Answer 25

increases

Question 26

Skin dose:

As field size increases, skin dose ___

Answer 26

increases

Question 27

Hinge Angle = 180 - (__ x __)

Answer 27

2 x Wedge Angle