AbstractID: 6879 Title: Dosimetric Effects of Source Motion in Intravascular Brachytherapy
In catheter-based Intravascular Brachytherapy (IVBT) delivery without centering
devices, the radioactive source is constantly moving inside the coronary artery due to
patient heart beating. The dosimetric impacts for such motion have not been reported. In
this work, we have calculated the dose effects due to source offsets from the center of the
vessel using the Monte Carlo method. The three most commonly used IVBT sources, 32P
(Guidant), 90Sr/90Y (Novoste) and 192Ir (Cordis), are considered. A series of random
offsets is used to model a constantly moving source. Source motion effects, in both lateral
and longitudinal directions, are investigated. The overall dose from a source with random
or static offsets is compared with that from a centered source. The calculation with a
static offset is the method used so far to examine the noncentering effects. The presence
of a calcified plaque and a metallic stent is also considered. The overall dose from a
source with random lateral offset is not significantly different (< 10% at 2 mm radial
distance) from that based on a centered source, indicating the dose effect of source
noncentering may not be important in the clinic. The calculation with a fixed offset is too
simple to assess the actual situation and it may overestimate the noncentering effects. For
the longitudinal source offset, a wide penumbra can be observed, resulting in a reduction
of the effective treatment length of the source. The lateral source motion effects should
be considered in IVBT dose evaluation or planning.