Low-energy 103Pd gamma (X-ray) source for vascular brachytherapy

Abstract

Purpose: This article describes the merits of 103Pd, a low energy x-ray emitter, as a new and potentially superior candidate for intraluminal brachytherapy. 103Pd can be ion implanted into different materials, designs, and devices for vascular brachytherapy.

Methods: The mass-analyzed ion implantation process has been used to embed the desired activity of 103Pd into the surface of 316L stainless steel stents. The low-energy, 21-keV x-ray from 103Pd delivers reasonably homogeneous radiation to the vessel wall and loses intensity rapidly beyond the immediate vicinity of the source. Shielding for 103Pd x-rays is trivial and the issues regarding safety, health hazards, storage, and handling are easily manageable.

Results: Experimental data on 103Pd ion-implanted stents show a clean gamma-ray spectrum devoid of any radioimpurity. Activity measurements within a batch demonstrate little stent-to-stent variation (approximately 2%), excellent axial and radial uniformity (<10%), and minimal dissolution in a saline environment (approximately 0.02%). The dosimetry shows the focused radiation field for 103Pd stents and rapid fall-off beyond a few millimeters of the stent. Furthermore, the 103Pd dosimetry indicates that a 350 muCi stent will deliver approximately 14 Gy at 1-mm distance, over its lifetime.

Conclusion: 103Pd is an appropriate source for vascular brachytherapy. It has an appropriate combination of half-life (16.93 days) and energy (21 keV). The half-life of 103Pd delivers the dose with an acceptable dose rate for stent applications while, at the same time, allowing for manageable shipping, storage, and/or disposal.