A device and method for maintaining phase coherence of transmit/receive channels

Abstract

The present invention relates to a device and method for maintaining the phase coherence of transmitting / receiving channels, wherein the device includes a transmitting module and a receiving module, the transmitting module includes a first programmable logic device and a DDS; the receiving module includes a second programmable logic device and NCO, the transmitting module also includes a transmitting free clock generated internally by the first programmable logic device, and the receiving module further includes a receiving free clock generated internally by the second programmable logic device; The receiving free clock has the same frequency as the transmitting free clock. The invention can maintain the accuracy of phase coherence of the transmission / reception channel, shorten the time delay and improve the real-time performance.

Description

technical field [0001] The invention relates to the technical field of magnetic resonance imaging, in particular to a device and method for maintaining phase coherence of transmission / reception channels. Background technique [0002] Magnetic resonance imaging technology, as a non-destructive diagnostic method that can reflect multi-dimensional information, has been widely used in medical pathological diagnosis and basic scientific research; at the same time, magnetic resonance spectroscopy has played an important role in chemical analysis and biomacromolecular research. effect. The nuclear magnetic resonance console is the core component of the nuclear magnetic resonance spectroscopy instrument and imaging system, and its main function is to control the transmission of pulse sequences and the reception of magnetic resonance signals in real time. Compared with the spectrometer, the magnetic resonance imaging system adds a gradient component for three-dimensional positioning...

AI Technical Summary

Problems solved by technology

But in this method, when it is necessary to switch the phase of the transmitting source and the receiving source, the external bus controller needs to read the phase of the reference source first and output it to the external bus, and then the transmitting source and the receiving source receive the current phase of the reference source through the external bus interface. Output the phase value and set it as the phase of the current RF signal, which will cause a long time to set the reference source phase, which will cause trouble for the strict timing relationship between the real-time pulse sequence and the control pulse signal, and if the external bus adopts a parallel bus The circuit structure is more complicated in the design of the method; if the serial bus method is used, the setting time is longer

At the same time, the method of using an external bus to maintain phase synchronization requires software to read the phase of the reference clock and write it into the phase accumulator inside the NCO of the transmitting source and receiving source, and the software operation is affected by the real-time nature and interruption of the operating system The impact of the software may cause the uncertainty of the delay of the software operation, and the participation of the microprocessor is required. At this time, the microprocessor cannot perform other tasks.

Usually, the transmitting source and the receiving source are designed with a modular structure, so when the transmitting source and the receiving source belong to different circuit modules, the surrounding environment may cause interference to the external bus signal, thereby reducing the reliability of the reference signal setting. Sex, or increase the difficulty of circuit design

In addition, when this method updates the phases of the transmitting source and the receiving source, it updates their phase accumulators. To achieve phase coherence, it is first necessary to clear the current NCO phase accumulator value, and then set the value due to the pulse sequence NMR experiment. The initial value of the phase of the NCO is accumulated with the current phase value of the reference clock read from the external bus, and then it can be written to the phase accumulator of the NCO, which makes the process of updating the phase accumulator cumbersome and increases the delay time

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