Mosby's Chapter 6: QA and Equipment

Energy range for Grenz

5-15 kV

Superficial Machines energy range

50-150 kV

Superficial therapy machines were also known as ______ _______ _______ ______

Low energy Crookes tubes

Orthovoltage energy range

150-500 kV

Orthovoltage SSD

On the skin surface

What are the 3 main components to the Linac

1. Gantry

2. Drive Stand

3. Couch

What are the 5 main components to the Gantry?

1. Klystron/Magnetron

2. Circulator

3. Accelerating Waveguide

4. Electron Gun

5. Cooling System

Where is the source of electrons in the linac

Electron gun

Final e- energy is _________ (directly/indirectly) proportional to the length of the waveguide

Directly

Klystron is used for ____ (low/high) energy linacs and generated _____ (low/high) frequency microwaves

High; high

Magnetron is used for ____ (low/high) energy linacs and generated _____ (low/high) frequency microwaves

Low; High

Which energy source can amplify microwaves?

Klystron

High energy machines have _________ (vertical/horizontal) accelerator tubes

Horizontal

What directs the e- down and out towards the target?

Bending magnet

What are the two types of bending magnets used

1. 90°

2. 270°

Which type of bending magnet minimizes spatial dispersion of the beam?

270°

Intensity of an e- beam is higher in the _______

Center

A raw e- beam is referred to as a ______ beam

Pencil

What is used to spread the electron beam and achieve uniform fluence across the collimated area?

Scattering foil

To make photons/x-rays in a Linac, what happens?

• e- beam is accelerated towards the target

• E- hit tungsten tsarget

• E- decelerate

• Energy created is converted to x-ray photons

T/F: flattening filter is used for photons

False

What's the purpose of a flattening filter

To evenly distribute the energy of the beam

The initial exit of the beam is collimated by the _______ (primary/secondary) collimator

Primary

After hitting the primary collimator, what does the beam hit

Ion chamber

Ion chamber purpose

Keeps track of dose rate and beam symmetry

What happens to the beam after the ion chamber?

It hits the secondary collimators (MLCs)

What is the max field size for MLCs

40 × 40

Where is the field size of a linac defined at?

The isocenter

Values regarding machine output and performance are taken during _________ testing

Acceptance

What values are compared during acceptance testing?

Output values to what manufacturer promises