PubMed · 9677902
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H M Jones. 1998. Change is certain, progress is not.. https://doi.org/10.1177/175045899800800306
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PURPOSE: A soft X-ray device for intravascular radiation therapy of restenosis is characterized in terms of dose delivery for several artery configurations, including arteries with implanted stents, calcified plaque, and noncentered sources. METHODS AND MATERIALS: The Monte Carlo code MCNP4B was used to determine the X-ray fluence and energy spectra for 15, 20, and 30-kV X-ray source generating voltages. Dose as a function of distance was calculated under a variety of artery conditions. RESULTS: Calculated depth-dose profiles for the X-ray sources are within presumed artery dose tolerance limits for the range of generating voltages considered. 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 lesion, 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 sources than for the radioactive sources. The effects of noncentering are found 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 of artery sizes, tissue compositions, and stent configurations.
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Whether acute and direct percutaneous transluminal coronary angioplasty improves the incidence of nonsustained ventricular tachycardia in patients surviving acute myocardial infarction is not known. In 400 consecutively studied patients, Lown classification IVb on Holter monitoring was only associated with arrhythmia morbidity, whereas reduced ejection fraction was related to total and cardiac mortality and arrhythmia morbidity.