Guidance of intracoronary radiation therapy based on dose-volume histograms derived from quantitative intravascular ultrasound

Application of ionizing radiation to prevent restenosis in atherosclerotic vessels treated by balloon angioplasty is a new treatment under investigation in interventional cardiology and radiology. There is variability in dose prescription, and both γ- and β-emitters are used, leading to a wide range of dose distribution over the arterial vessel wall. The authors present a new modality of dosimetry based on a method that three-dimensional (3-D) image reconstruction of electrocardiogram (ECG)-gated intravascular ultrasound (IVUS) images. Dose volume histograms (DVH) are used to describe the cumulative distribution of dose over two specific volumes: i) at the level of the luminal surface, defined with a thickness of 0.1 mm from the automatically detected contour of the highly echogenic blood-vessel interface, and ii) the adventitia volume is computed considering a 0.5-mm thickness from the echogenic media-adventitia interface. DVH provide a tool for reporting the actual delivered dose at the site believed to be the target: the adventitia, and to detect excessive radiation which could lead to vascular complications. Simulation of a γ-emitter or of a radioactive source train in the center of the lumen are possible. The data obtained from the first ten patients included in the β-irradiation trial (BERT 1.5) conducted in the authors´ institution are presented, supporting the use of DVH based on quantitative IVUS measurements for optimal dose prescription in vascular interventional radiation therapy.