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New Breast Configuration with Brassiere
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Skin Dose
Data on increased skin dose due
to the ipsilateral cup were submitted to the FDA. These data
provided a comparison of skin dose increased by the
Treatment Brassiere to the increase found for various
thermoplastic positioning devices on the market. The skin
dose due to the cup material (0.25 mm thick for small cups
to about 0.63 mm thick for very large cups) was found to be
substantially less than for other positioning devices. The
FDS has issued a 510-(k) marketing clearance for the
Treatment Brassiere.
Reduction of Unwanted Dose
The semi-rigid, transparent
brassiere cups reshape the ipsilateral breasts to
symmetrical forms which rise directly up from the chest
wall. The volume of irradiated tissue decreases
substantially by eliminating mammary folds, and the unwanted
radiation to the contralateral breast, heart, lungs, and
ribs is greatly reduced. The dose distribution in the breast
becomes more uniform.
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Cross
Section of Phantom
with Unconfined Breast Shape |
Cross
Section of Phantom
with Breasts Reshaped by
Treatment Brassiere |
Repeatability of Position
The ipsilateral cup is
positioned repeatably on the patient by markings made on the
patient's skin through small holes at the medial, lateral,
and superior aspects of the cup.
Increased Flexibility of Fitting
By Truncation of Cups
A Pattern and then a cup are
made of the reshaped breast, but the anterior portion of the
cup is cut off. These truncated cups permit the fitting of
breasts of moderately different volumes into the same cup,
while maintaining full skin-sparing in the most sensitive
area.
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Exploded View of
Typical Brassiere
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Breast Cup Showing
Mark-Off Holes
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Contralateral Breast Shielding
The fabric covering which
compresses the contralateral breast affords a base for a
lead shield to reduce scatter dose. A 0.015 in. (0.38 mm)
sheet of lead is easily formed by hand into a cup which can
be placed over the breast when the patient is supine and
which remains in place by gravity. The plies substantially
reduce scatter dose to the contralateral breast. However,
shielding must be used judiciously if primary beams pass
through it.
Cup Selection
Cups are divided into four
groups corresponding to small thoraxes (chest breadths from
27 to 32 cm), medium thoraxes (32 to 36 cm), large thoraxes
(36 to 42 cm), and extra large thoraxes (over 42 cm).
The proper cup is selected for a
new patient by measuring her chest breadth when supine and
while wearing her clothing brassiere. This indicates the
group from which the best fitting cup will be found. The
clothing brassiere size is a rough guide to the first cup to
be tried. Thereafter larger or smaller cups will be tested
to find the best cup. (Note that there is poor correlation
between the brassiere size and breast volume of a patient).
L or R marks on cups, indicate left or right sides. Left and
right cups are not interchangeable.
Preliminary Patient Data
Patient Measurement Charts are
used to facilitate selection of the proper cup for a
patient. Chest breadth is measured with a patient caliper,
so the correct group size can be selected.
The chart provides for recording
cup hole locations, applicable (of course) to both phantom
and patient.
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Lead Shield Over Contralateral Breast
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Sanitation
Although the possibility of
cross-contamination is remote, it can be eliminated almost
completely by lining cups with Saran wrap while the proper
cup size is being selected.
Users have recommended that cups
be dedicated to the same patient throughout the course of
treatment, after which it is to be discarded. This
eliminates further need for the Saran wrap, and there is no
risk of cross contamination from cups.
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Patient Data |
Dimension with Caliper
Patient Chest Breadth
(supine with brassiere)
_____________________________________ cm |
Reference
Phantom (without brassiere) |
| Chest Breadth (cm) |
SMALL
29.5 |
MEDIUM
31.5 |
LARGE
39 |
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IPSILATERAL-CUP HOLES
DIMENSIONS WITH 3DMD
TM
(cm) |
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Medial
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Lateral
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Superior |
| Along table length
(CC) |
______ |
______ |
______ |
| Across table
(Lateral) |
______ |
______ |
______ |
| Normal to the table
(AP) |
______ |
______ |
______ |
| Note:
Some dimensions are taken with either end of the
pointed transverse pin through the AP rod (near the
bottom of the rod) in contact with the skin or the
phantom. No correction is needed for the pin
length. |
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Patient
Measurement Chart
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A New Level of Quality Assurance
Planned breast treatments are
essentially predictive. Every link in the chain connecting
dose prescription to dose distribution must be accurate, or
have only small, off-setting errors. However, a patient's
dose distribution within the ipsilateral breast and thorax
cannot be measured.
The treatment planning system,
therapy machines, patient positioning, human performance,
and many other factors cannot be checked as a whole, because
there is no clinically-feasible method for comprehensive
dose measurements within the ipsilateral breast and thorax.
The Treatment Brassiere serves
another extremely important function, in addition to
improving treatments. By standardizing breast contours and
almost eliminating mobility during the course of treatment,
it becomes possible to accurately represent the treated
breast of a patient by a tissue-equivalent phantom breast.
Consequently, it is possible to deliver a treatment to a
phantom breast which will have the same dose distribution as
if delivered to a patient's corresponding breast. However,
only the phantom treatment can be measured in sufficient
detail for evaluation.
Reproducing and Measuring the
Breast Treatment of a Patient by a Phantom
The substitute patient consists
of (1) a breast, which fits precisely into a cup which, in
turn, has been molded about a reshaped ipsilateral patient
breast; (2) a thorax; and (3) an adaptor section molded
integrally with the breast. This section is required because
the breast must be fitted to a phantom that is smaller than
the patient. A line is scribed to distinguish the breast
proper from the adaptor (which represents chest-wall
tissue).
This assembly is a fully valid
substitute for a patient, except for a relatively minor
factor. The adaptor section cannot duplicate completely the
contours of a patient, but this section represents tissue
for which doses are to be minimized; the exact magnitude of
these doses is not a critical issue.
The basic cup library consists
of a gradation of breast volumes divided into four groups,
based upon chest breadth. Total Quality Assurance may be
implemented with any selected series of
breast volumes,
which are based upon the volumes of the breasts of
individual patients.
Brassiere Models
