|M.Sc Student||Wolfson Helen|
|Subject||Pulsed Electron Spin Resonance Miniature Sensors for|
Tooth Biodosimetry and Oxymetry
|Department||Department of Biomedical Engineering||Supervisor||Professor Aharon Blank|
|Full Thesis text|
Electron spin resonance (ESR) is a very useful and robust spectroscopic method for the measurement of paramagnetic materials with many applications in science and technology. This work focused on two potential clinical applications of ESR: biodosimetry and skin oximetry.
Major nuclear events are rare, but still probable scenarios, for which modern society must be prepared. As a result of such events, populations may be exposed to doses of ionizing radiation that could cause direct clinical effects within days or weeks. There is a critical need to determine the magnitude of the exposure of individuals by measuring the radiation absorbed dose. In this work, a miniature ESR sensor that includes a static field source and a microwave resonator for in-vivo measurement of paramagnetic defects in tooth enamel was developed (Fig. a). These defects are known to be a good marker for quantifying the ionizing radiation dose absorbed in teeth. The sensor is a significant improvement upon existing designs due to a more compact configuration, with a typical length of just 30 mm and total weight of 220 g (compared to 1kg up to 30kg in previous works). Using this sensor, signals of teeth irradiated with a dose of just 2 Gray were clearly detected- an improvement from previous designs.
Oxygen concentration in the skin is an important clinical indicator for monitoring cases such as chronic wounds, skin cancer, diabetes side effects, and limb amputation. Currently, this data is obtained by electrochemical technique which has many drawbacks and limitations, making it unattractive for standard medical practice and care. We developed an alternative, ESR based device, which can obtain the oxygen concentration through measurements of the spin-spin relaxation time (T2) of paramagnetic species interacting with the molecular oxygen. Our device makes use of a specially-designed permanent magnet, with a typical length of 36mm and weight of 150g, combined with a small microwave resonator, to enable the acquisition of ESR signal and T2 of paramagnetic spin probe placed on the skin (Fig. b). This approach may provide much faster and more accurate readings of the oxygen concentration in the skin, as compared to the electrochemical method, without sacrificing system simplicity and portability, thus making it potentially highly attractive for future clinical use.