Dose distributions on bifurcated coronary vessels treated with catheter-based photon and beta emitters in intravascular brachytherapy
MEDICAL PHYSICS(2002)
摘要
The dose distributions in the bifurcated vessels treated with intravascular brachytherapy line sources are complicated and depend on the bifurcation geometry consisting of a main and a branch vessel at different angles. To investigate the dosimetric effects at the bifurcation, calculations were performed on branching vessels of various, bifurcation angles ranging from 20degrees to 90degrees. Two catheter based delivery systems were considered in the calculations using a 40 mm long radioactive sources of Ir-192 or Sr-90/Y. It was assumed that the bifurcated vessel was treated in two separate source insert ions, once for the main vessel and later for the branch vessel. Calculations were performed for different values of source gap from 0 to 9 mm, at the junction of main and branch vessels. Our results indicate that main vessel always receives a higher dose (up to 200%) when the branch vessel is also treated. Hot spots at portions of the main vessel near the junction cannot be totally avoided without severely underdosing the branch vessel. For bifurcation angle greater than 45degrees, a 4 min source gap can almost ensure that overdosing of the main vessel does not exceed 60% and underdosing of the branch vessel does not exceed 10% for Ir-192. However, for Sr-90/Y, the same is not possible unless the bifurcation angle is larger than 70degrees. Dose heterogeneity using Sr-90/Y is more sensitive to the value of source gap than Ir-192 because Sr-90/Y source provides a sharper dose-fall-off than Ir-192. For both photon and beta emitters, there is no acceptable solution for bifurcation angles less than 30degrees, where the activity of the line source has a uniform distributions. Appropriate choice of gap at the junction can only help to reduce either overdosing of the main vessel or underdosing of the branch vessel, but not both. (C) 2003 American Association of Physicists in Medicine.
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关键词
intravascular brachytherapy,bifurcation,Ir-192,Sr-90/Y,dosimetry
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