Radiotherapy

 

[1]     Draw an ionisation chamber.

[2]     What is it measuring?

[3]     Where is the charge collected?

[4]     What effects do temperature and pressure have on the readings?

[5] Prior to an Sr-90 check, what else do you need to consider about the electrometer? (Leakage test).

[6] Asked about the Heel Effect on the orthovoltage machine? What is it, explain the curve and how do we overcome this is our measurements?

[7] Draw an electron depth dose curve.

[8] Explain each part of the curve.

[9] How does the curve vary with energy? Why?

[10] Draw a treatment head (linac).

[11] What are the purposes of the secondary collimators?

[12] How is the field size defined? Is it a 10 x 10 cm field at the isocentre or at 100cm FSD?

[13] How would you measure the field size? Film? (50%).

[14] Can you determine the beam flatness from this film?

[15] How would you do that?

[16] Asked about head scatter measurements. Why are they performed?

[17] Are they utilised in the treatment planning system?

[18] Why do we do dmax profile scans and measurements?

[19] If you had a particular area of a field blocked out, how would you calculates the required treatment time?