The increasing life expectancy of the European citizens together with improvements in surgical devices and implantation procedures is leading to more frequent and longer term use of medical implants. Many of the materials used in implants are not truly inert in the aggressive corrosive environment of the human body with allergic, toxic and even carcinogenic reactions being the result of the migration of metal ions into the body. It is therefore increasingly important that reliable and sensitive methods of measuring release be developed and applied in conditions simulating as closely as possible the real life situation.
One method which offers the possibility of non-intrusive on-line determination of low release rates in simulated body fluids is the Thin Layer Activation method (TLA) which uses a high energy charged particle beam (Cyclotron) to selectively activate areas of a sample creating radio-nuclides in a well defined depth. Following activation of the sample any transfer of material due to surface degradation processes such as corrosion leads to changes in the activity of the sample and its immediate environment which can be characterised using Ξ³spectroscopy. This technique offers high sensitivity, area selectivity and the ability to discriminate between release products originating from the device and those naturally present in biological fluids.
In this work the application of the TLA technique will be outlined so as to demonstrate how it may be used to examine the corrosion behaviour and chemical release rates of health damaging metals such as chromium and nickel from stainless steel.