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Dose per MU formalisms:

factor-based dose calculations

Modulation with non-physical wedges

Non-physical wedges are delivered with one of the Y-jaws moving in or out during beam at

variable dose rate and at variable speed.

Wedge factors:

• do not depend on depth (no beam hardening)

• vary with beam energy and off axis position

Varian EDW

• Y-jaw motion into field (0.5

.

cm from opposing) jaw; in

variable speed and dose rate

• Jaw positions per MU: stored lookup (GSTT) tables;

one per beam energy

• 7 wedge angles in total (as combination of

60

°

wedged and open fields)

• WF depends on energy, wedge angle, field size and

off-axis position (along Y direction; asymmetric fields)

• WF

0.4 - 1

Siemens VW

• Y-jaw motion out of field, starting from 1

.

cm of

opposing jaw

• Jaw positions per MU: calculated using a

mathematical algorithm with energy dependent

parameters.

• Multiple wedge angles between 10

°

and 60

°

• WF depends on energy, wedge angle, field size and

off-axis position (along Y direction; asymmetric

fields)

• WF

1 from calculation points on CAX

In MU formalisms WF for non-physical wedges are either derived from

measurements or are calculated (from GSTT data)