A digital receiver with fast frequency- and gain-switching capabilities for MRI systems.
OBJECTIVE
In this article, two issues pertaining to MRI digital receivers are addressed. One is the maintenance of phase coherence between the transmitter and the receiver-an effective solution is proposed, in which the receiver frequency is switched synchronously with the transmitter frequency. The other is the dynamic range of the receiver-gain-switching technique is utilized to improve the dynamic range. To meet the hardware requirements of these solutions, a digital receiver with fast frequency- and gain-switching capabilities was implemented.


METHODS
The primary components of the proposed digital receiver are a variable gain amplifier, a high-speed analog-to-digital converter and a single-chip digital receiver core. The radio-frequency magnetic resonance signal is directly sampled by the analog-to-digital converter and processed in the digital receiver core. By pre-storing the receiver waveform in the on-board SDRAM, the frequency and gain of the receiver may be switched very quickly.


RESULTS
The performance of the proposed digital receiver is verified by embedding it in an imaging spectrometer. It is then demonstrated by conducting experiments on a home-built 0.3-T magnetic resonance imaging system.


CONCLUSIONS
The results show that the phase coherence between the transmitter and the receiver and the dynamic range of the receiver are greatly improved. Consequently, the proposed digital receiver may be useful for obtaining multiple-slice two-dimensional magnetic resonance images with very high resolution.
Shanghai Key Laboratory of Functional Magnetic Resonance Imaging, Department of Physics, East China Normal University, 3663 North Zhong-Shan Road, 200062 Shanghai, People's Republic of China. rpning@phy.ecnu.edu.cn
Ning
N
Ruipeng
Dai
D
Yidong
Yang
Y
Guang
Li
L
Gengying
D004867:Equipment Design; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D011846:Radio Waves; D011856:Radiographic Image Enhancement / Q000295:instrumentation*; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D018511:Systems Integration