How to do a few things we rarely do..

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How to do a few things we rarely do..

• Moustache field
• Custom collimation/bolus

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Moustache field
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Nose and upper lip are treated with an en face
field using mixed (41) electrons (20 MeV) and
photons (6 MV)Nasal cavities are filled with
bolus. Skin collimation is used and wax bolus is
applied.
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• The facial lymphatics are treated with en face
  field using 6 MeV electrons (usually with a
  15-20 gantry angle).
• This field is set up after the primary tumor
  field and neck fields are approved.

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• The neck can be treated with parallel-opposed
  lateral photon fields matched to the facial
  lymphatic fields or with IMRT

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Skin reaction
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How to make a custom lead mask and/or custom bolus
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The field is outlined on the skin. Lubrication is
put around the hairline and the hair is covered
with Saran wrap and eyes with gauze dressing.
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A cardboard with the patients contour is cut out
and placed around the head. Fill the nostrils
with lubricated cotton and place straws in the
mouth for breathing.
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Inform the patient that impression mixture will
be poured over the face.
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Get ready to mix!
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Pour the impression material over the face,
ensuring adequate thickness over the nose. Work
quickly!
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Plaster strips are placed over the impression to
hold it together.
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After hardening (about 5 minutes from the start
of mixing), the impression is carefully removed.
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Cover the straw holes with plaster so the stone
mixture doesnt leak out.
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Coat the impression with lubricating jelly and
pour in dental stone. Make sure to vibrate the
stone before pouring to release the air bubbles.
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The mold is removed the next day.
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A thin sheet of lead is cut to the predetermined
size. A hole is drilled through the center of
the sheets and enlarged to approximate the
radiation field. The sheets are then pounded onto
the mold with a rubber hammer. The shape of the
hole is further trimmed to fit the field. The
procedure is repeated until the proper thickness
is reached.
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A customized beeswax bolus is made directly on
the mold. Pottery clay is used to build a dam of
the desired depth 1 cm beyond the field outline.
The stone mold is lubricated and melted wax is
poured into the dam (layer by layer). A hot knife
can be used to trim the bolus.