Study For Detection Method Of Liver Iron Overload Based On Magnetic Induction Method

Liver iron overload is a common disease, which is mainly caused by the inheritedreason (such as hereditary hemochromatosis) or the acquired reason (such as periodicblood transfusion) so as to make progressive iron accumulate in the liver. Being toxic,the excess of iron in the liver can damage hepatic cells, and finally lead to hepaticfibrosis, cirrhosis and ever hepatoma. Accurately measuring liver iron concentration(LIC) is quite essential for the early diagnosis and treatment of the patients. Magneticinduction method is a promising technique to detect liver iron overload, which offers theadvantages of safety, contactless, simple instrument and low cost over the others.However, it has faced many difficulties in clinical application. In this paper we analyzethe principle and feasibility of magnetic induction method for measurement of liver ironoverload, and our studies mostly focus on the coil system in the magnetic inductionmeasurement system. Aiming at increasing the real part of signal/carrier ratio (SCR) ofthe receiver coil and its sensitivity, we design the improved coil system models. Ourwork can be presented by the following four parts:The first part discusses the relation between the iron and human health, as well asthe reasons and risks of iron overload particular the liver iron overload. We sum up thedevelopment of non-invasive measurement methods of liver iron overload, andintroduce the research status of magnetic induction method for measurement of liveriron overload.The second part introduces the fundamental principle of detection method of liveriron overload based on magnetic induction method. Firstly we describe the physical andbiological basics of magnetic induction method for measuring liver iron overload, andmainly analyze the relation of the liver iron overload, the liver iron concentration, andthe hepatic magnetic susceptibility. Then the electromagnetic field theory which isapplied in magnetic induction method is introduced in detail.The third part briefly introduces the magnetic induction measurement system atfirst. Then we analyze the simplified coil system model theoretically and obtain theSCR equation of the receiver coil. The drawback of regarding the excitation coil as themagnetic dipoles in previous studies is proposed, and the true distribution of magneticfield of the excitation coil is derived. We simulate the relation curve between Re(SCR)and magnetic susceptibility of the object, and the affection which the geometricaldimensions of circular disc make on the Re(SCR). We also compare the differentobjects and the receiver coils by simulation. The principle analysis and simulationresults validate the feasibility to apply magnetic induction method for measurement ofliver iron overload and show that the previous analysis has some theoretical errors.In the fourth part, we design a new type of excitation coil which can counteract the primary magnetic field itself at the receiving position based on the property of SCRequation of the receiver coil, and the simulation results show that the sensitivity ofRe(SCR) can be increased effectively when using this new type of excitation coilcompared with the circular excitation coil. To solve the difficulty that eddy currenteffect interfering with the measurement of magnetic susceptibility, an improved coilsystem based on the static field magnetization principle is presented. We use a directcurrent excitation to eliminate the eddy current effect, and a rotary receiver coil toobtain the induced voltage. The simulation results validate the possibility of theoryanalysis. We also introduce the primary idea of designing the experiment measurementsystem at the end of the chapter.