Monitor Unit Hand Calculations Quiz

1. 180cGy is prescribed to a depth of 12cm at a point 5cm off of the central axis. Compute the required monitor units for a 6MV beam delivered 105SSD with a field size of 12x12cm2. Here %DD = 75.3, Sc = 1.008, Sp = 1.009, TMR = 0.82, and OAF = 1.023.

Question 1 of 3

2. A TBI patient is to be treated at a distance of 4m (SAD) using bilateral beams to a dose of 3Gy prescribed to a depth of 15cm.  How many MU per field should be delivered?
DepthTMR
5cm0.97
10cm0.86
15cm0.75
20cm0.66

Question 2 of 3

3. A 10MV photon beam has a PDD of 0.839 at a depth of 7cm using an SSD setup. The same beam has a TMR of 0.913 at a depth of 7cm using an SAD setup. Assuming a prescription depth of 7cm, which setup would have a higher maximum dose and by how much?

Question 3 of 3


 

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