The Design And Implementation Of Digital Receiver For Low/Medium-Field Magnetic Resonance Imaging Systems

Magnetic Resonance Imaging is a significant application of NMR. Nowadays, MRI spectrometer is one of the key tools in medical diagnostic and scientific researches. The method and technology of MRI have had a rapid progress profiting from development in super conducts, electronics, imaging process technology and computer science. It has raised more requirements on MRI spectrometer, which is an important part in MR scanner. Digitization is a trend which can be applied in MRI spectrometer with high performance and low cost. Digital receiver is a functional component of the spectrometer. The design and construction is developed in this thesis. Also a method to synchronize the transmitter and receiver is proposed.The main content of the thesis include:First, the basic principle of MRI is introduced in this part. It includes the conception of special encoding, K space etc. Besides, some basic pulse sequence are displayed and discussed briefly.Second, the structure of MRI system is described which is composed of several subsystems: the magnetic system, the gradient system, the RF system and the spectrometer. The components of the spectrometer such as transmitter, digital receiver and pulse field generator are discussed in details.Third, the hardware design of a digital receiver is described. Regarding low field (<5000Gs) application, the resonance frequency of hydrogen is less than 25MHz, digital technique, direct RF sampling and digital down converter are used to make the whole design easy.Finally, a method to synchronize the transmitter and the receiver is proposed. It is independent from the special construction. So it is universal for general digital spectrometer.