Exam Review 9/4 PPT5

Question 1

Old setup technique where pts had to be moved between each field.

Answer 1

SSD technique

Question 2

Set-up technique where distance from radiation source to isocenter is always the same. SSD changes as gantry rotates around the pt.

Answer 2

SAD technique

Question 3

Where is beam flatness defined at?

Answer 3

10 cm depth in water

Question 4

What portion of the beam is measured in beam flatness?

Answer 4

80%

Question 5

The edges (20%) of the beam are not measured for beam flatness. Why?

Answer 5

Penumbra

Question 6

How does flatness change with depth?

Answer 6

Deeper than 10 cm - middle hump
Shallower than 10 cm - lateral horns

Question 7

Are lateral horns quality or quantity?

Answer 7

Quantity (# of photons)

Question 8

Flatness is the __ of photons

Answer 8

quantity

Question 9

How does filtration effect beam quality?

Answer 9

Hardens beam

Question 10

How does filtration effect output?

Answer 10

4x

Question 11

Can you use same flattening filter for more than one energy?

Answer 11

no