Brainlab RT/RS Hardware User's Manual page 44

Collimator Mount
Verify a secure and rigid fixation of the collimator within the collimator mount before use
When using conical collimators the LINAC jaws have to shield the radiation outside the
lead core.
Be aware that the positioning accuracy of the LINAC jaws can vary depending on the type
of LINAC used.
The LINAC jaw positions used during treatment must be identical to the LINAC jaw
positions used during beam measurements.
Ensure that the LINAC jaws do not overlap the circular collimator opening.
To avoid unintended leakage radiation using conical collimators the LINAC jaw size must
be smaller or equal 56x56 mm² for all Linacs except for Novalis classic.
Verify for every treatment field that the correct, intended conical collimator is actually
mounted to the LINAC, especially if a treatment plan contains treatment fields with different
conical collimator sizes.
Ensure that any treatment accessories, such as conical collimator mount and conical
collimator of the size which is required by the treatment plan, are installed properly in the
beam path before delivery. Your treatment delivery systems may not be able to assert a
beam interlock in case of missing or wrong accessories. Also refer to the documentation
provided for the Brainlab Treatment Planning System.
Do not to use a higher photon energy than 25 MV for treatments.
Operate the LINAC with photons only when using conical collimators.
Collimator Diameters and Jaw Sizes
Verify by inspection that the area outside the shielded lead core of the conical collimator is
completely covered by the jaws. The models and range of conical collimator apertures differ
significantly. For Brainlab conical collimators, to avoid radiation outside the conical collimator or
leakage at the edge of the field resulting from potential set-up inaccuracies (mechanical collimator
alignment, jaw positioning, and other tolerances), Brainlab recommends using the jaw settings
listed in the table below. If properly implemented, these settings will aid in keeping the jaw shaped
field size tight around the largest conical collimator.
Brainlab conical collimators used with all LINACs including Novalis Tx, but not including
Novalis
Diameter of largest conical collima-
tor in use at site [mm]
up to 7.5
8
10
12.5
14
15
16
44
Recommended size of jaw-shaped field for all conical col-
limators [mm²]
14 x 14
14 x 14
16 x 16
18 x 18
20 x 20
20 x 20
22 x 22
Hardware User Guide Rev. 4.9 RT / RS Stereotactic Hardware