Graduate Thesis Or Dissertation
 

Determining the activity distribution on a radioactive stent using plastic scintillation techniques

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/wh246v28k

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  • Re-occlusion of arteries following percutaneous transluminal coronary angioplasty (PTCA) remains a post-operative issue in the treatment of artery blockage. This re-narrowing of the luminal cavity, a condition called restenosis, has been attributed to the injury induced by PTCA balloon insertion. While arterial recoil can be completely prevented by a coronary stent, this device is ineffective in halting neointimal hyperplasia or vascular remodeling. However, recent studies have demonstrated that stenting in conjunction with radiation therapy to the injured artery can reduce smooth muscle cell (SMC) proliferation and the subsequent effects of the added extracellular matrix. Human and animal trial studies have shown that ³²P ion-implanted stainless steel stents are effective in reducing restenosis. Concerns regarding a non-uniform dose distribution from the short-range beta particles emitted from a stent's open geometry have resulted in the development of techniques to adequately determine stent surface activity distributions. Current methods rely on autoradiographic techniques using radiochromic foil exposure analysis. The purpose of this research was to determine the efficacy of employing electronically based detection methods for determining activity uniformity rather than foil exposure. A highly collimated solid organic scintillating plastic was optically coupled to a photomultiplier tube in order to detect beta emission from selected surface regions of a neutron-activated 316L stainless steel Guidant Multilink[superscript TM] stent. Irradiation of the stent activated ⁵⁵Mn, producing high energy, beta-emitting ⁵⁶Mn as a substitute for ³²P. Both Monte Carlo computer modeling and experimental results demonstrated that inconsistencies in activity attributed to stent geometry could be detected. Because a stent is comprised of repeating structures, this technique may be used to detect deficiencies in activity not associated with the predicted irregularities of activity caused by geometry. Such a detection device may be more appropriate and efficient in the industrial setting for quality assurance than current techniques using radiochromic film exposure.
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