AbstractID: 7003 Title: Intravascular coronary brachytherapy: dosimetric consideration
on the source pullback and vessel curvature
The dose variations at the source junction for a long curved lesion in a two-step
pullback intravascular radiation treatment were studied with the radiochromic film
dosimetry. Dose distributions of catheter-base 90Sr/Y beta source train were measured in
solid and liquid water. Minimal fluctuation of measured doses was achieved by utilizing
the scan axis alignment and proximal-distal data smoothing. Reconstructed dose
distributions were used to investigate the effects produced by mismatched source trains
and curved vessels. For 2.5 mm mismatch of gap or overlap at the source junction, more
than 50% reduced or enhanced point dose with respect to the prescription dose can occur
at the 2-mm radial depth. Due to the steep dose gradient, only 3- 4% of total treatment
volume of a 30 mm long cylindrical volume with radial distances between 2.0 and 4.0
mm received higher than the prescription dose at the 2-mm radial depth in the overlap
case. In addition, for both overlap and gap cases, at least 90% of the treatment volume
received within 20% of the dose delivered by the perfectly matched case. Additional
relative point dose perturbation caused by the curvature of 300-450 bent 40 mm source
trains shows 15-20% deviations between the inward and outward transaxial dose rates at
the 2-mm radial depth. Caution should be taken to assure proper matching source trains
during the pullback procedure for the intravascular coronary brachytherapy.