Characterization of a soft X-ray source for intravascular radiation therapy

Purpose: A soft X-ray device for intravascular radiation therapy of resteno sis is characterized in terms of dose delivery for several artery configura tions, including arteries with implanted stents, calcified plaque, and nonc entered sources. Methods and Materials: The Monte Carlo code MCNP4B was used to determine th e X-ray fluence and energy spectra for 15, 20, and 30-kV X-ray source gener ating voltages. Dose as a function of distance was calculated under a varie ty of artery conditions. Results: Calculated depth-dose profiles for the X-ray sources are within pr esumed artery dose tolerance limits for the range of generating voltages co nsidered. Treatment times to deliver 8 Gy to the adventitia range from 2.7 minutes to 6.7 minutes for the 20-kV generating voltage and a 3-cm-long les ion, depending on the diameter of the artery. The does perturbation due to stent wires or calcified plaque is found to be more severe for the X-ray so urces than for the radioactive sources. The effects of noncentering are fou nd to be similar for radioactive sources and X-ray sources with generating voltages of 20 kV or higher, Conclusion: The results of this study indicate that soft X-ray sources are suitable candidates for intravascular radiation therapy over a wide range o f artery sizes, tissue compositions, and stent configurations. (C) 2001 Els evier Science Inc.