Lecture 4 and 5: Dose Distribution, Scatter Analysis, Dosimetric Parameters

Why does PDD increase with increasing SSD?

The effect of z decreases (inverse-square factor)

The meyneord factor works well for what sized fields and depths?

Small (small scatter contribution)

What does the meyneord factor overestimate?

increase in PDD with increased SSD

Backscatter factor

TAR at d_max

TAR vs. Mayneord factor

TAR considers scatter

When is the SSD setup used for dose calculations?

single field treatments

When is the SAD setup used for dose calculations?

multiple field treatments

If the field size is increased, does beam output increase or decrease?

increase

r_c

the side of the equivalent square for the collimator field size

r_d

the side of the equivalent square for the field size in the phantom

Does TMR increase or decrease with increasing depth?

decrease

Does TMR increase or decrease with increasing field size?

increase

Does TMR increase or decrease with increasing energy?

increase

How is PDD and TMR related?

inverse square correction

TPR

dose ratios for different depths but same point distance from the source

Which is an SSD setup?

A