Source displacement during the cardiac cycle in coronary endovascular brachytherapy.
OBJECTIVE
Preliminary clinical trials employing catheter-based endovascular brachytherapy show promising results in reducing restenosis after coronary intervention. Failure analysis of these studies showed a significant number of failures at the treatment margin. It is hypothesized that one of the possible causes for marginal failure is the longitudinal seed movement during the brachytherapy procedure. In this study a quantitative analysis was performed to determine the magnitude of the source displacement during the cardiac cycle.


METHODS
Cine-angiograms of the Iridium-192 (Ir-192) active source seeds or dummy source seeds in place were reviewed frame by frame for 30 patients enrolled from various clinical trials using the Cordis catheter delivery system with a Ir-192 seed ribbon. The proximal and distal source points were measured in reference to branching vessels closest to the respective seed during the contrast phase of the cine-angiogram. The two frames showing the maximum source displacement were captured. After appropriate demagnification, longitudinal source displacement was measured. The data were tabulated for proximal vs. distal ends and for different coronary vessels.


RESULTS
The longitudinal source displacement is significant with overall mean and standard deviation of 1.1 and 0.8 mm, respectively. The range is from 0.0 to 5.4 mm.


CONCLUSIONS
The contribution of source movement should be included into the treatment length to avoid "geographic miss" and the subsequent marginal failure.
Giap
H B
HB
Division of Radiation Oncology, Scripps Clinic, La Jolla, CA 92037, USA. hbgiap@pol.net
Bendre
D D
DD
Huppe
G B
GB
Teirstein
P S
PS
Tripuraneni
P
P
D015906:Angioplasty, Balloon, Coronary; D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D002932:Cineangiography; D003327:Coronary Disease / Q000000981:diagnostic imaging / Q000517:prevention & control / Q000532:radiotherapy*; D005548:Foreign-Body Migration / Q000000981:diagnostic imaging; D006801:Humans; D007496:Iridium Radioisotopes / Q000627:therapeutic use*; D055502:Secondary Prevention; D017211:Treatment Failure
D007496:Iridium Radioisotopes