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Dosimetric effects of source-offset in intravascular brachytherapy
1Department of Radiation Oncology, University of Maryland, Baltimore 21201, USA. ochib001@umaryland.edu
Medical Physics
|May 7, 2002
Summary
Radioactive source displacement in intravascular brachytherapy (IVBT) significantly alters radiation dose, especially with calcified plaques or stents. Understanding these dosimetric impacts is crucial for effective treatment planning and accurate dose prescription.
Area of Science:
- Medical Physics
- Radiation Oncology
- Cardiovascular Interventions
Background:
- Intravascular brachytherapy (IVBT) involves placing radioactive sources within blood vessels.
- Cardiac motion and lack of centering devices can cause radioactive source displacement (offset).
- Source offset can lead to significant dosimetric inaccuracies in IVBT.
Purpose of the Study:
- To investigate the dosimetric impact of lateral and longitudinal radioactive source offsets in IVBT.
- To evaluate how calcified plaques or metallic stents influence these dosimetric effects.
- To analyze dose variations for commonly used IVBT sources (32P, 90Sr/90Y, 192Ir).
Main Methods:
- Utilized the MCNP Monte Carlo code for dose calculations.
- Simulated both static and random (2D) source offsets.
- Assessed effects with and without the presence of calcified plaques or metallic stents.
Main Results:
- Static lateral offsets can change dose by up to a factor of 4.
- Random lateral offsets increased dose by 5-15% at 2 mm.
- Calcified plaques/stents exacerbated dosimetric effects.
- Longitudinal offsets reduced effective treatment length by 15-18%.
- Beta sources showed greater offset effects than gamma sources.
Conclusions:
- Source offsets significantly impact IVBT dosimetry, necessitating consideration in treatment planning.
- Dose changes due to offsets require adjustments in dose prescription.
- Reduced effective treatment length from longitudinal offsets must inform source length selection for adequate target coverage.