operative breast irradiation, the presence of bone
共ribs兲 may
be a dose-limiting factor if a sufficiently high single-fraction
dose were delivered which could induce bone necrosis.
A previous investigation has examined basic dosimetric
parameters for the Intrabeam device, and a simple analytical
model for evaluating measured dose characteristics.
5
This in-
vestigation showed that good agreement could be obtained
between measurement and the model, at least within the
limitations of the measurements. The current investigation
extends this by considering a more complete model using a
Monte Carlo simulation, as well as considering the implica-
tions of dose distributions from the source for possible out-
comes of the Intrabeam trial, including the effect on nearby
bone and the possible effects on dosimetry introduced by
target positional uncertainty and variations in dose prescrip-
tion methods.
II. METHODS AND MATERIALS
A. Spectral measurement
Spectra for the 30 kVp, 40 kVp and 50 kVp beams were
measured using a cadmium zinc telluride detector
共CdZTe-
type XR-100T-CZT, Amptek Inc., Bedford, MA
兲 connected
to a MCA8000A multi-channel analyzer
共Amptek Inc., Bed-
ford, MA
兲. The source–detector distance was maintained at
one meter, and a 1 mm diameter pin-hole was used to reduce
beam intensity. Throughout this study, measurements were
made in a direction along the axis of the device away from
the tip housing the source in order to maintain consistency.
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