Ford

Question 1

How is the electron current in a LINAC changed when switching from photon to electron mode?

Answer 1

It’s decreased by 100x.

Photon mode is incredibly inefficient, so a much higher current is needed.

Question 2

How is a monitor chamber changed when switching from photon to electron mode?

Answer 2

It’ll require a new calibration.

Signal-to-dose calibration for each electron energy.

Question 3

How do the A1 and B1 parts of the monitor chamber monitor an electron beam?

Answer 3

A1/B1 measures beam symmetry in the radial direction.

Question 4

How do the A2 and B2 parts of the monitor chamber monitor an electron beam?

Answer 4

A2/B1 is a measure of the beam symmetry in the transverse direction.

Question 5

How do these different parts (A1, B1, C1, D1) of the monitor chamber monitor an electron beam?

Answer 5

(C1+D1)/(A1+B1)

It is a measure of beam flatness in the radial direction.

Question 6

How do these different parts (A2, B2, C2, D2) of the monitor chamber monitor an electron beam?

Answer 6

(C2+D2)/(A2+B2)

It is a measure of beam flatness in the transverse direction

Question 7

Where does the superficial skin dose come from if the photons need some buildup region to generate electrons to deposit the dose?

Answer 7

They come from photon interactions within the head of the LINAC (collimators, flattening filters, etc).

Question 8

How does field size affect skin dose?

Answer 8

Increasing the field size increases the skin dose!

Question 9

How do you test the alignment of the collimator rotation axis w/the light field?

Answer 9

Field size

Question 10

Which QA device has a strong angular response?

Answer 10

Diode