AbstractID: 6719 Title: Wire or Balloon? Searching for an Optimal Solution for
Intravascular Brachytherapy.
There are several possibilities to categorize intravascular brachytherapy
systems currently used in clinical practice and trials. One distinct difference is whether
the radioactive source material is confined to a wire structure, centered or not in the
vessel lumen, or whether it is spread out over a surface, which is brought close to the
lumen wall.
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This investigation identifies fundamental differences between these two
approaches and their clinical implications. The study focussed on the beta emitting P-32.
Using Monte Carlo simulations with EGS4, target coverage, influence of positioning
error and distortion of the dose distribution by coronary stents have been investigated.
Monte Carlo results were enhanced by GAFchromic film measurements.
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The radial dose fall-off in the target region was found to be steeper for a
balloon system. However, the comparably shallower fall-off of the wire-type systems is
very sensitive to positioning uncertainties. A half-millimeter shift, for example, will
cause the dose to change by a factor of two at the vessel wall and by a factor of 1.8 at the
prescription point (2.5 mm vessel diameter, prescription to 1 mm into the vessel wall).
It is shown that the influence of stents is more significant for a wire-type system. They
show double the dose variation behind a stent at radial prescription distance.
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While wire-type systems show a shallower radial dose fall-off over the
target region, balloon systems are advantageous in regard to positioning uncertainties and
stents.
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: First author is a consultant for RadioVascular Systems, Inc.
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