Development Of The Magnet System And Data System Of EPR Spectrometer For In Vivo Tooth Dosimetry

Nuclear or radiological emergencies will cause a large number of people to beexposed to excessive radiation. To detect the absorbed dose of the people timely andinstantly in the nuclear or radiological emergency is a unresolved problem. As oneof the important means to solve this problem, using electron paramagnetic resonance(EPR) technology to measure the dose of human teeth in vivo receives wideattention. This thesis involves the optimal design of the magnet system and datasystem of the EPR spectrometer specialized in measuring human teeth in vivo.Research contents and general results are as follows:1. To address the problems existing in the magnetic pole geometry of currentmagnetic field device when performing in-vivo measurement, we use finite elementanalysis software Ansoft Maxwell to simulate the magnet, and calculate the intensityand uniformity of the magnetic field with a broader distance between magnetic polesthan required dimension in in-vivo measurement. An improved design modifying themagnet is proposed, in which the distance between magnetic poles of the mainmagnetic field is able to further extend, making it convenient to contain the mouthand to place the high frequency modulation coil. The optimized magnetic polegeometry also improves the uniformity of the magnetic field. To solve thenonlinearity of the scanning magnetic field output under linear drive current input,drive current is corrected by means of inverse calibration according to the field-timecurve, and the linearity of the scanning field is achieved. Through simulation,comparisons are made between the performances of various modulation coils, basedon which we determine the operating mode of the modulation field suited for in-vivotooth measurement and the coil geometry, as well as design and manufacture thecoil-matched modulation power amplifier drive circuit that can establish a100kHzmodulation magnetic field whose intensity is no less than0.5mT at the testing areaof the cavity.2. Through our development of the EPR spectrometer data system, we achieve the capabilities of scanning field control, microwave mode signal display,microwave power output control, and EPR signal acquisition. We use dataacquisition card as the control card to integrate the initially separated hardware. Byadopting the USB-based data acquisition card, our work eliminates theinconvenience of traditional PCI controller card’s reliance on PCI expansion slot ofthe desktop, thus improving the expandability and portability of the spectrometer.3. Developed in LabVIEW environment, our EPR spectrum analysis software iscapable of spectrum data query, baseline correction, spectrum noise reductionfiltering, and spectrum intensity calculation, therefore meeting the basicrequirements for dose calculation of the human teeth EPR spectrum. Written inLabVIEW, this software is user-friendly as well as accessible to furtherdevelopment.This thesis has completed the development work of the magnet system and thedata system, which are two significant components of the EPR spectrometer that isspecialized in measuring human teeth dose in vivo. It makes a progress in applyingthe method of using X-band EPR to measure tooth dose in vivo, and eventually laysa foundation for the development of the EPR spectrometer specialized in in-vivodose measurement in a nuclear or radiological emergency.