Photon Field Match Vid

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10 Terms

1
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feathering

move junction between two fields after some # of fx which softens the dose along the field edges


2
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what is the purpose of feathering?

smears out and reduces both cold & hot spots between fields overtime of tx

3
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why use GAP

needed to formulate the hot and cold spots between two fields

4
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Rule of similar triangles

g1/d = L1/SSD1

5
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Solve for g: GAP

G1= (L1xd)/SSD1

6
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Total gap

(L1 x d)/SSD1 + (L2 x d)/SSD2

7
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Why do collimator and couch rotation

Match divergence of the beams so there aren't significant hot or cold spots

8
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To account for divergence of field 2

Kick couch toward side of the beam treating

9
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Field 2 equation

tan-1(L2/SAD)

10
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Field 1 equation

tan-1(L1/SSD)