RF transmit system and method, MRI system and pre-scan method and storage medium thereof
The present invention relates to an RF transmit system and method, MRI system and a pre-scan method and medium thereof. The RF transmit system comprises: an RF output unit, for generating and outputting an RF pulse signal; an RF amplifier, for amplifying the RF pulse signal; and a signal processing unit, for communicating the amplified RF pulse signal to an RF transmit coil of the MRI system and outputting a feedback signal to the RF output unit, wherein the RF output unit generates a linearity compensation control signal based on the feedback signal and a predetermined feedback signal-linearity compensation value-relationship, so as to carry out linearity compensation for the RF pulse signal outputted by the RF output unit. The RF transmit method corresponds to the above noted system and the MRI system comprises the above noted RF transmit system. The pre-scan method comprises the RF transmit method. Instructions recorded by the medium may execute the above noted RF transmit method and pre-scan method.
1. An RF transmit system of an Mill system, comprising:
an RF output unit, for generating and outputting an RF pulse signal;
an RF amplifier, for amplifying the RF pulse signal;
a signal processing unit, for communicating an amplified RF pulse signal to an RF transmit coil of the MM system and outputting a feedback signal to the RF output unit, wherein
the RF output unit generates a linearity compensation control signal based on the feedback signal and a predetermined feedback signal-linearity compensation value-relationship, so as to carry out linearity compensation for the RF pulse signal outputted by the RF output unit;
wherein the feedback signal comprises a forward feedback signal and a reverse feedback signal; and
wherein the RF output unit is configured to:
decide current load characteristics of the RF transmit coil based on the reverse feedback signal and determine whether a feedback signal-linearity compensation value-relationship corresponding to the current load characteristics exists;
generate a new feedback signal-linearity compensation value-relationship under the current load characteristics if no feedback signal-linearity compensation value-relationship corresponding to the current load characteristics exists.
2. The RF transmit system according to claim 1 , wherein the forward feedback signal is communicated to the RF transmit coil by the signal processing unit, wherein
the RF output unit determines a linearity compensation value corresponding to the forward feedback signal based on the predetermined feedback signal-linearity compensation value-relationship and generates the linearity compensation control signal based on the determined linearity compensation value.
3. The RF transmit system according to claim 1 , wherein the reverse feedback signal is fed back from the RF transmit coil to the signal processing unit and outputted by such signal processing unit; and wherein the RF output unit is configured to:
determine a linearity compensation value corresponding to the forward feedback signal based on the feedback signal-linearity compensation value-relationship corresponding to the current load characteristics if a feedback signal-linearity compensation value-relationship corresponding to the current load characteristics exists; and generate the linearity compensation control signal based on the determined linearity compensation value.
4. The RF transmit system according to claim 3 , wherein the RF pulse signal outputted by the RF output unit comprises a group of pulse signals having a central frequency generated according to a preset sequence; the group of pulse signals have different amplitudes; and the central frequency is a central frequency of an RF excitation pulse adopted when the MM system carries out scanning with respect to a current load.
5. The RF transmit system according to claim 4 , wherein if no feedback signal-linearity compensation value-relationship corresponding to the current load characteristics exists, then the RF output unit is further configured to:
calculate open-loop characteristics of the RF output unit and the RF amplifier under the current load characteristics based on the forward feedback signal; and
generate a feedback signal-linearity compensation value-relationship corresponding to the current load characteristics according to the open-loop characteristics.
6. The RF transmit system according to claim 5 , wherein the amplitude variation of the applied group of pulse signals is greater than 40 dB and the phase thereof remains constant.
7. The RF transmit system according to claim 3 , wherein if a feedback signal-linearity compensation value-relationship corresponding to the current load characteristics exists, then the RF output unit is further configured to:
determine a priority feedback signal-linearity compensation value-relationship for recommendation, based on a predetermined deep learning network and according to the current load characteristics.
8. The RF transmit system according to claim 1 , further comprising a memory, for storing the predetermined feedback signal-linearity compensation value-relationship.
9. An MRI system, comprising:
an RF transmit coil; and
the RF transmit system according to claim 1 .
10. An RF transmit method for an MRI system, comprising the steps of:
generating and outputting an RF pulse signal by an RF output unit;
amplifying the RF pulse signal by an RF amplifier;
communicating the amplified RF pulse signal to an RF transmit coil of the MM system by a signal processing unit and outputting a feedback signal to the RF output unit;
generating a linearity compensation control signal based on the feedback signal and a predetermined feedback signal-linearity compensation value-relationship outputted by the RF output unit, so as to carry out linearity compensation for the RF pulse signal outputted by the RF output unit;
wherein the feedback signal comprises a forward feedback signal and a reverse feedback signal; and the step of generating a linearity compensation control signal further comprises the following the sub-steps:
deciding current load characteristics of the RF transmit coil based on the reverse feedback signal;
determining whether a feedback signal-linearity compensation value-relationship corresponding to the current load characteristics exists; and
generating a new feedback signal-linearity compensation value-relationship under the current load characteristics if no feedback signal-linearity compensation value-relationship corresponding to the current load characteristics exists.
11. The RF transmit method according to claim 10 , wherein the forward feedback signal is communicated to the RF transmit coil by the signal processing unit and the reverse feedback signal is fed back from the RF transmit coil to the signal processing unit and outputted by such signal processing unit; and the step of generating a linearity compensation control signal further comprises the following the sub-steps:
determine a linearity compensation value corresponding to the forward feedback signal based on the feedback signal-linearity compensation value-relationship corresponding to the current load characteristics if a feedback signal-linearity compensation value-relationship corresponding to the current load characteristics exists; and generate the linearity compensation control signal based on the determined linearity compensation value.
12. The RF transmit method according to claim 11 , wherein the RF pulse signal outputted by the RF output unit comprises a group of pulse signals having a central frequency generated according to a preset sequence; the group of pulse signals have different amplitudes; and the central frequency is a central frequency of an RF excitation pulse adopted when the MRI system carries out scanning with respect to the current load.
13. The RF transmit method according to claim 12 , wherein the sub-steps of generating a new feedback signal-linearity compensation value-relationship under the current load characteristics comprises:
calculating open-loop characteristics of the RF output unit and the RF amplifier under the current load characteristics based on the forward feedback signal; and
generate a feedback signal-linearity compensation value-relationship corresponding to the current load characteristics according to the open-loop characteristics.
14. The RF transmit method according to claim 13 , wherein the amplitude variation of the applied group of pulse signals is greater than 40 dB and the phase thereof remains constant.
15. The RF transmit method according to claim 11 , wherein when a feedback signal-linearity compensation value-relationship corresponding to the current load characteristics exists, the step of generating a linearity compensation control signal further comprises the following sub-step:
determining a priority feedback signal-linearity compensation value-relationship for recommendation, based on a predetermined deep learning network and according to the current load characteristics.
16. A pre-scan method for an MRI system, comprising:
receiving a central frequency for pre-scan predetermined by the MRI system;
executing the RF transmit method according to claim 10 , so as to generate a linearity compensated RF pulse signal, wherein the compensated RF pulse signal has the central frequency; and
outputting the linearity compensated RF pulse signal which is then communicated to the RF transmit coil after amplification, so as to cause the RF transmit coil to generate an RF field for exciting a load serving as a scanned object.
17. A non-transitory computer-readable storage medium, having coded instructions recorded thereon and when the instructions are executed, the RF transmit method according to claim 10 is executed.
18. A non-transitory computer-readable storage medium, having coded instructions recorded thereon and when the instructions are executed, the pre-scan method according to claim 16 is executed.