CN104644172A - Method and system for controlling black blood in time-reversal steady state free precession quick imaging sequence - Google Patents

Abstract

The invention relates to a method and system for controlling black blood in a time-reversal steady-state precession fast imaging sequence. The method includes: scanning and imaging through a time-reversal steady-state precession fast imaging sequence; and applying a dephasing gradient with a preset size in at least one direction of layer selection, phase encoding and frequency encoding during scanning. The method and system for controlling black blood in the above time-reversal steady-state precession fast imaging sequence, by applying a phase gradient in at least one direction of layer selection, phase encoding, and frequency encoding during scanning, makes the The area improves the suppression effect of the blood signal, thereby improving the quality of the imaging image.

Description

Black blood control method and system in time-reversed steady-state precession fast imaging sequence

technical field

The invention relates to the field of magnetic resonance imaging, in particular to a method and system for controlling black blood in a time-reversal steady-state precession fast imaging sequence.

Background technique

Time-reversed Fast Imaging with Steady-state Precession or Contrast Enhanced Fourier Acquired Steady-state (CE-FAST) is a T2-weighted (T2WI, T2-weighted imaging, transverse relaxation time weighted imaging) gradient echo sequence. When the time-reversal steady-state precession fast imaging sequence is used for scanning imaging, when the blood vessel flow rate is slow, the blood signal suppression effect is poor, that is, the black blood effect is poor, resulting in poor image quality.

Contents of the invention

Based on this, it is necessary to provide a black blood control method in a time-reversal steady-state precession fast imaging sequence that can improve the imaging image quality for the problem of poor imaging image quality when the blood vessel flow rate is slow.

In addition, it is also necessary to provide a control system for black blood in a time-reversal steady-state precession fast imaging sequence that can improve the image quality of the imaging.

A method for the control of black blood in a time-reversal steady-state precession fast imaging sequence comprising:

Scanning imaging by time-reversal steady-state precession fast imaging sequence;

During scanning, a dephasing gradient with preset intensity is applied in at least one direction of layer selection, phase encoding and frequency encoding.

In one embodiment, the method also includes:

Increases the strength of the dephasing gradient.

In one of the embodiments, the step of increasing the intensity of the dephasing gradient comprises:

Increasing the magnitude of the dephasing gradient or extending the duration of the dephasing gradient.

In one of the embodiments, when the dephasing gradient is applied in the stratification direction, the preset strength of the dephasing gradient is in a preset ratio to the gradient strength of the stratification.

In one embodiment, the preset ratio is 0.2 to 0.5.

A control system for black blood in a time-reversed steady-state precession fast imaging sequence comprising:

Scanning module for scanning imaging by time-reversal steady-state precession fast imaging sequence;

The addition module is used for applying a dephasing gradient with a preset intensity in at least one direction of layer selection, phase encoding and frequency encoding during scanning.

In one of the embodiments, the system also includes:

An adjustment module, configured to increase the intensity of the phase gradient.

In one of the embodiments, the regulating module is further configured to increase the magnitude of the dephasing gradient or prolong the duration of the dephasing gradient.

In one of the embodiments, when the dephasing gradient is applied in the stratification direction, the preset strength of the dephasing gradient is in a preset ratio to the gradient strength of the stratification.

In one embodiment, the preset ratio is 0.2 to 0.5.

The method and system for controlling black blood in the time-reversal steady-state precession fast imaging sequence above apply phase gradients in at least one direction of layer selection, phase encoding, and frequency encoding during scanning, so that the magnetic resonance signal is more sensitive to flow , while not affecting the signals of stationary organs or objects, the suppression effect of blood signals is improved, thereby improving the quality of imaging images.

In addition, increasing the intensity of the dephasing gradient can further improve the effect of controlling blood flow inhibition.

Description of drawings

Fig. 1 is a flowchart of a method for controlling black blood in a time-reversal steady-state precession fast imaging sequence in an embodiment;

Figure 2 is a timing diagram of time-reversal steady-state precession fast imaging sequence scan;

Figure 3a is the imaging image of abdomen without phase gradient scan;

Figure 3b is the image of abdomen with gradient scan with diffuse phase;

Fig. 4 is a structural block diagram of a black blood control system in a time-reversal steady-state precession fast imaging sequence in an embodiment;

Fig. 5 is a structural block diagram of a black blood control system in a time-reversal steady-state precession fast imaging sequence in another embodiment;

Fig. 6 is a device architecture diagram for time-reversal steady-state precession fast imaging.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

As shown in FIG. 1 , it is a flow chart of a method for controlling black blood in a time-reversal steady-state precession fast imaging sequence in an embodiment. The control method of black blood in the time-reversal steady-state precession fast imaging sequence, including:

Step 102, scanning and imaging through time-reversed steady-state precession fast imaging sequence.

Specifically, the echo time is the time point when the echo of the magnetic resonance signal is generated.

Step 104, applying a dephasing gradient with a preset intensity in at least one direction of layer selection, phase encoding and frequency encoding during scanning.

As shown in Fig. 2, it is a time sequence diagram of time-reversal steady-state precession fast imaging sequence scanning. A time-reversal steady-state precession fast imaging sequence is used to scan a certain area of the human body, such as the imaging area of the abdomen, and periodic radio frequency pulses are applied to the imaging area to make the magnetization vector of the imaging area reach a resonance steady state. The setting of repetition time between pulses depends on other factors such as imaging area intensity, layer thickness, signal acquisition bandwidth and selective absorption rate. In order to improve the signal-to-noise ratio of the image, the minimum value should be taken as much as possible. The gradient of layer selection is used to selectively excite a specific region in the imaging, so that the radio frequency pulse only excites the protons at the specified position; the phase encoding is used to encode the spatial phase of the magnetic resonance signal; the frequency encoding is used to encode the frequency of the magnetic resonance signal coding. Phase encoding and frequency encoding are used to spatially encode the magnetic resonance signals to identify magnetic resonance signals acquired at different positions in the imaging region to generate magnetic resonance images. Data acquisition is used to acquire magnetic resonance signals. The phase refocusing gradient is used to offset the phase encoding gradient; the frequency refocusing gradient is used to offset the frequency encoding gradient; the layer selection refocusing gradient is used to offset the layer selection gradient. The refocusing pulse in the layer selection direction is placed after the acquisition, so that the free attenuation signal is out of phase, and the signal cannot be acquired during readout, and the spin echo component is retained, so that the spin echo component can be acquired in the next excitation cycle get.

When the dephasing gradient is applied in the layering direction, the preset strength of the dephasing gradient is in a preset ratio to the gradient strength of the layering. The preset ratio is 0.2 to 0.5, but not limited thereto.

The method for controlling black blood in the time-reversal steady-state precession rapid imaging sequence above applies a phase gradient in at least one direction of layer selection, phase encoding, and frequency encoding during scanning, so that in areas with slower blood flow, The suppression effect of the blood signal is improved, thereby improving the quality of the imaging image.

Figure 3a is an abdominal imaging image without gradient gradient scan; Figure 3b is an abdominal imaging image with enhanced gradient gradient scan. The signals of blood vessels in the liver and abdominal artery indicated by the arrows in Figure 3a are significantly higher than those in Figure 3b.

In one embodiment, the method for controlling black blood in the time-reversed steady-state precession rapid imaging sequence further includes: increasing the intensity of the dephase gradient. Increasing the intensity of the phase gradient can further improve the effect of controlling blood flow inhibition.

The step of increasing the intensity of the dephasing gradient includes: increasing the magnitude of the dephasing gradient or prolonging the duration of the dephasing gradient.

As shown in FIG. 4 , a control system for black blood in a time-reversed steady-state precession rapid imaging sequence includes a scanning module 420 and an adding module 440 . in:

The scanning module 420 is used for scanning imaging through time-reversed steady-state precession fast imaging sequence.

The adding module 440 is used for applying a dephasing gradient with a preset intensity in at least one direction of layer selection, phase encoding and frequency encoding during scanning.

When the dephasing gradient is applied in the layering direction, the preset strength of the dephasing gradient is in a preset ratio to the gradient strength of the layering. The preset strength of the dephase gradient is in a preset ratio to the gradient strength of the slice. The preset ratio is 0.2 to 0.5, but not limited thereto, and can be specifically set as required.

The black blood control system in the time-reversal steady-state precession fast imaging sequence above applies a phase gradient in at least one direction of layer selection, phase encoding, and frequency encoding during scanning, so that in the area where the blood flow velocity is relatively slow, The suppression effect of the blood signal is improved, thereby improving the quality of the imaging image.

As shown in FIG. 5 , it is a structural block diagram of a black blood control system in a time-reversal steady-state precession fast imaging sequence in another embodiment. The black blood control system in the time-reversal steady-state precession rapid imaging sequence includes a control module 460 in addition to the scanning module 420 and the adding module 440 .

The adjustment module 460 is used to increase the intensity of the dephasing gradient. Specifically, the regulating module 460 is also used to increase the magnitude of the phase-out gradient or prolong the duration of the phase-out gradient.

Increasing the intensity of the phase gradient can further improve the effect of controlling blood flow inhibition.

As shown in FIG. 6 , it is a device architecture diagram for fast imaging of time-reversal steady-state precession. In Fig. 6, a magnet 601, a gradient coil 602 and a radio frequency coil 603 are arranged in the magnetic resonance shield 600, and the device also includes a gradient signal amplifier 605 and a gradient signal amplifier 605 connected to the gradient coil 604 outside the magnetic resonance shield 600 The detected gradient signal is amplified to obtain a gradient pulse sequence 606, which is sent to the processor 607 for processing. The device also includes a radio frequency signal detector 608 connected to the radio frequency coil 603, a digital converter 609 connected to the radio frequency signal detector 608, a radio frequency signal amplifier 610 connected to the radio frequency coil 603, and the digital converter 609 is connected to the processor 607 . The radio frequency signal amplifier 610 amplifies the radio frequency signal to obtain a radio frequency pulse sequence 611, and sends it to the processor 607 for processing. After the processor 607 processes the gradient pulse sequence 606 and the radio frequency pulse sequence 611, it is displayed on the display 612. Print by the printing device 613 . When the time-reversed steady-state precession fast imaging device scans and images, the patient 621 is laid flat on the hospital bed 620, and the patient 621 is placed in the magnetic field of the radio frequency coil and the magnetic field of the gradient coil, and then scans.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (10)

1. the control method of black blood in stable state precession time reversal fast imaging sequences, comprising:

By stable state precession time reversal fast imaging sequences scanning imagery;

At least one direction applies the loose phase gradient of preset strength in scanning in layer choosing, phase code and frequency coding.

2. the control method of black blood in stable state precession time reversal fast imaging sequences according to claim 1, it is characterized in that, described method also comprises:

Increase the intensity of described loose phase gradient.

3. the control method of black blood in stable state precession time reversal fast imaging sequences according to claim 2, it is characterized in that, the step of the intensity of the described loose phase gradient of described increase comprises:

Increase the amplitude of described loose phase gradient or extend the persistent period of described loose phase gradient.

4. the control method of black blood in stable state precession time reversal fast imaging sequences according to claim 1, it is characterized in that, when described loose phase gradient be applied to layer select on direction time, the gradient intensity that preset strength and the described layer of described loose phase gradient select becomes preset ratio.

5. the control method of black blood in stable state precession time reversal fast imaging sequences according to claim 4, it is characterized in that, described preset ratio is 0.2 to 0.5.

6. the control system of black blood in stable state precession time reversal fast imaging sequences, is characterized in that, comprising:

Scan module, for passing through stable state precession time reversal fast imaging sequences scanning imagery;

Add module, in scanning, at least one direction applies the loose phase gradient of preset strength in layer choosing, phase code and frequency coding.

7. the control system of black blood in stable state precession time reversal fast imaging sequences according to claim 6, it is characterized in that, described system also comprises:

Regulation and control module, for increasing the intensity of described loose phase gradient.

8. the control system of black blood in stable state precession time reversal fast imaging sequences according to claim 7, it is characterized in that, described regulation and control module is also for increasing the amplitude of described loose phase gradient or extending the persistent period of described loose phase gradient.

9. the control system of black blood in stable state precession time reversal fast imaging sequences according to claim 6, it is characterized in that, when described loose phase gradient be applied to layer select on direction time, the gradient intensity that preset strength and the described layer of described loose phase gradient select becomes preset ratio.

10. the control system of black blood in stable state precession time reversal fast imaging sequences according to claim 9, it is characterized in that, described preset ratio is 0.2 to 0.5.