Comparison of different methods to define a target volume for external beam radiation therapy of restenotic coronary arteries

Purpose: Different methods have been described to define a target volume for the treatment of restenotic (stented) coronary arteries by external beam radiation therapy (EBRT). The purpose of this study was to explore two methods to define a target for such therapy, and to compare these with previously investigated methods. Materials and methods: The 3-D position of a stent throughout the cardiac cycle in the three major epicardial coronary arteries was measured in three patients by single-breathhold multislice spiral CT and breathhold biplane conventional X-ray angiography, both indexed in time with the ECG. The volume through which the stent traversed (STV) during the cardiac cycle was determined by use of displacement measurements. Results: For multislice CT and biplane angiography, respectively, the mean STV was 1.23 cm³ (range 0.65-2.22 cm³) and 2.81 cm³ (range 1.60-4.99 cm³). The STV represented only a fraction of the whole heart volume in all patients, that is, equal to or less than 0.4%. Conclusions: Multislice CT and biplane angiography allowed the measurement of a relatively small potential target, that is the STV, for EBRT of restenotic stented coronary arteries. Both studied imaging modalities are instrumental for targeting the STV by highly conformal radiation therapy in case of restenotic stented coronary arteries.