Development of Biomedical Devices for the In Vivo Measurement of Toxic Elements

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In Canada, people are exposed to a number of toxic elements both medically and environmentally. We often monitor exposure through blood and urine, but these only report recent exposure, while health effects are often a result of long term exposure. In my laboratory, we design and build radiation-based biomedical devices that measure retention and storage of elements in the body. Our devices can be used to assess and monitor health effects linked to chronic exposure. I propose to develop technology for the safe, painless measurement of gadolinium (Gd), chromium (Cr), cobalt (Co), elements that people can be exposed to medically, and for fluorine (F), arsenic (As) and selenium (Se), elements which are in people's drinking water in some areas of Canada. ***My students and I will develop the devices using an established methodology. We will start by investigating an element's physical properties to determine a suitable radiation technique. This may depend on the organ at risk, e.g., if we wish to assess the kidney, the technique must penetrate through several cm of tissue, but if we wish to measure skin, it must only penetrate a few mm, because deeper measurement provides no information but increases the radiation dose. We will explore multiple techniques, although my research group commonly uses 2 to build our devices: x-ray fluorescence analysis (XRF) and neutron activation analysis (NAA). In XRF, a person is irradiated with low energy x- or -rays, and we measure emitted characteristic x-rays. In NAA, a person is irradiated with a low energy neutron beam, and the x- and -ray emission measured. Our devices quantify a person's elemental content by comparing their signal to one from appropriate calibration standards. Having chosen a promising technique, we proceed by assembling a simple device, and collecting experimental data using basic calibration standards. At the same time, we will develop the input to a Monte Carlo computer code to model this first pass' system. We will compare the Monte Carlo result against the experimental data and adjust until the code is validated. We will then run a series of changes in the code to predict a better' device, which we will then build and test. We iterate back and forth, multiple times, from experiment to model, and back to experiment, until we develop a system that has the detection capability that we require. A perfected biomedical device can take years to develop, but once detection limits approach the level required, we perform extensive radiation dosimetry measurements, which allow us to show that our devices are feasible for measurements of people. The NSERC development is then complete and successful and the device proceeds to in vivo testing.***The development of these new biomedical devices is important to Canada: they will allow physicians and public health policy makers to ensure that Canadians are protected from the serious, yet preventable, disease caused by toxic elements.**