Module 1

Unit 4: Quiz

Instructions: Answer the multiple choice questions below, then click on the "Process Questions" button at the end of the quiz to see your score in the adjacent message box. The program will not reveal which questions you answered incorrectly, only how many points you have. Go back and change your answers until you get them all right. (At that point the page frame will change to pink.)

Points to note: (1) Questions with one or more possible answers give a point for each correct answer, but also subtract a point for each wrong answer! (2) The program will not attempt to score your efforts at all if you have not tried at least half of the questions. (3) This quiz is for your own use only. No record of your progress is kept or reported to anyone.

1. After changing the field size from 10 x 10 cm² to 20 x 20 cm²...
...the slope of the PDD after zmax becomes steeper. 
...zmax is significantly increased. 
...the surface dose is slightly increased. 
2. Tick the correct statement(s)!
A couch height of 0.0 cm corresponds to a SSD of 100 cm.
If you increase the couch height the SSD is increased.
A change of the couch height has no effect on the percentage dose distribution.
A change of the couch height has no significant effect on the depth of the dose maximum.
3. After changing the energy of the photon beam from 6 MV to 18 MV...
...zmax is increased. 
...the dose at the surface is decreased. 
...the PDD is the same as the one for a field size of 20x20 cm². 
4. In water, for a field size of 10 x 10 cm², 100 MU, 6 MV photon beam, what SSD results in an absolute         dose of 1 Gy in the depth of the dose maximum?
100 cm 
101.6 cm 
98.4 cm 
95 cm 
105 cm 
5. The fact that the isodose distribution in Unit 2, Task 3 isn't symmetrical at first can be explained by...
...the inverse square law, considering the fact that the sources of the two beams have                   different distances to the phantom.
...the fact that the two beams enter the phantom from different directions.
The fact can't be explained.
6. Tick the correct statements.
The wedge factor is the ratio of doses with and without the wedge, at a particular point in a           phantom along the central axis of the beam. 
To compensate the reduction in beam transmisson produced by the wedge, the wedge              factor is used in MU calculations.
The wedge factor is independent of the wedge angle. 
For standard settings and a 45 degree wedge the wedge factor is ~0.48. 
Generally, the larger the wedge angle the larger is the wedge factor. 

     Points out of 10:

This consummately cool, pedagogically compelling, self-correcting,
multiple-choice quiz was produced automatically from
a simple text file of questions using D.K. Jordan's
dubiously original, but publicly accessible
Think Again Quiz Maker
of October 6, 2008.

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