A magnetic resonance non-enhanced lower extremity arteriovenous combined imaging method

Abstract

The application discloses a kind of magnetic resonance non-enhanced lower limb arteriovenous combined imaging method, belong to medical image technology field, including S1, judging acquisition times, and carrying out first acquisition, S2, set the delay time of data acquisition, S3, configure fast interrupt steady state, and carry out data acquisition, S4, repeat S1-S3 until all regions are completed first acquisition Data collection process, S5, switch to second acquisition, and judge acquisition times, and carry out second acquisition, S6, using the same process as S2 and S3 carries out data acquisition, S7, repeat S5 and S6 until all regions are completed second acquisition Data collection, S8, image reconstruction is carried out, and the arteriovenous separation image map is obtained, the application uses above-mentioned method, by fusing fast interrupt steady state sequence and golden angle radial sampling track, realize lower limb arteriovenous synchronous high contrast imaging under the condition of not needing electrocardiogram control.

Description

Technical Field

[0001] This invention relates to the field of medical imaging technology, and in particular to a method for non-contrast magnetic resonance imaging of the lower extremities' arteries and veins. Background Technology

[0002] Non-contrast enhanced magnetic resonance angiography (NCE-MRA) of the lower extremities is a non-toxic, non-invasive vascular imaging method that does not require contrast agents. Compared to traditional lower extremity vascular imaging examinations such as digital subtraction angiography (DSA) and computed tomography angiography (CT angiography, CTA), NCE-MRA has advantages such as no ionizing radiation and no reliance on contrast agents. It is helpful in the diagnosis and treatment of peripheral arterial and venous diseases and is now widely used in clinical practice.

[0003] In current contrast-free clinical practice, lower extremity venous system imaging mainly relies on Doppler ultrasound. However, ultrasound has inherent limitations such as limited signal-to-noise ratio and strong operational dependence. Arterial NCE-MRA imaging usually requires ECG gating to achieve accurate scanning, but electromagnetic interference from magnetic resonance imaging often significantly reduces signal stability and weakens the timing accuracy of ECG gating, a problem that is particularly pronounced under ultra-high field strength.

[0004] Meanwhile, in existing non-contrast imaging techniques, arterial and venous assessments need to be performed in steps, requiring patients to go to multiple departments to undergo arterial and venous scans separately. This not only significantly prolongs the examination time (usually more than two independent scans), but also causes repeated consumption of medical resources, including equipment occupation, manpower input, and energy consumption. Summary of the Invention

[0005] The purpose of this invention is to provide a magnetic resonance non-enhanced lower limb arteriovenous imaging method. Based on the imaging foundation of no contrast agent and no ionizing radiation, it achieves synchronous high-contrast imaging of lower limb arteries and veins by fusing a rapidly interrupted steady-state sequence with a golden angle radial sampling trajectory, without the need for ECG gating.

[0006] To achieve the above objectives, the present invention provides a method for non-contrast magnetic resonance imaging of the lower extremities' arteries and veins, comprising the following steps:

[0007] S1. Determine the number of data collection attempts and perform the first data collection.

[0008] S2, Set the data acquisition delay time;

[0009] S3. Configure fast interrupt steady state and perform data acquisition;

[0010] S4. Repeat S1-S3 until all areas have completed the first data collection process;

[0011] S5. Switch to the second acquisition method, determine the number of acquisitions, and perform the second acquisition.

[0012] S6. Data acquisition is performed using the same process as S2 and S3;

[0013] S7. Repeat steps S5 and S6 until all areas have completed the second data collection.

[0014] After the data collection for S8, the first and second acquisitions are completed, image reconstruction is performed to obtain an arteriovenous separation image.

[0015] Preferably, the process of the first acquisition in S1 is as follows:

[0016] S11. Set the number of data collections;

[0017] S12, Select the imaging area;

[0018] S13. Apply a double-inverted arterial labeling pulse to the proximal end of the imaging region.

[0019] Preferably, the calculation process for the delay time in S2 is as follows:

[0020] ;

[0021] in This indicates the distance from the proximal boundary of the marker band to the center of the imaging region. This represents the average blood flow velocity in the target blood vessel. express Time buffer amount.

[0022] Preferably, the process in S3 is as follows:

[0023] S31. Select several fast interrupt steady-state modules to form a fast interrupt steady-state sequence as the core acquisition module;

[0024] S32, Perform periodic processing on each fast interrupt steady-state module. Radio frequency pulse reset steady-state magnetization;

[0025] S33. Apply radio frequency and gradient phase scrambling between every two fast interrupt steady-state modules;

[0026] S34. Set the number of radial lines. And the included angle between radial lines Strictly meet the golden angle,

[0027] ;

[0028] in This indicates the repetition time of a single radial sampling within the fast interrupt steady-state module. This indicates the average cardiac cycle duration in the target vascular region;

[0029] S35. Each radial line samples the center of the k-space with the number of samplings set in S11, forming several subsets of k-space data.

[0030] Preferably, the process of S5 is as follows:

[0031] S51. After all areas have completed the first data collection process, the second data collection process is carried out by alternately switching the collection direction through a U-shaped path.

[0032] S52. Set the number of data collections;

[0033] S53, Select the imaging area;

[0034] S54. Apply a single inverted vein marking pulse to the distal end of the imaging area.

[0035] Preferably, the double-inverted artery labeling pulse in S13 and the single-inverted vein labeling pulse in S54 are both co-modulated with the gradient direction of the imaging slice selection pulse, as follows:

[0036] Step 1: Mark the gradient of the pulse selection layer With imaging layer selection gradient The gradient configuration mode can be either the same polarity mode or the opposite polarity mode;

[0037] Step 2: Solve for the spatial displacement of fat The process is as follows:

[0038] ;

[0039] in This indicates the difference in proton chemical shift between fat and water. Indicates the strength of the main magnetic field. This represents the gradient of the currently applied layer.

[0040] Preferably, the same polarity mode needs to satisfy... and They have the same polarity, and ,in This indicates the amount of fat spatial displacement in the marked area. Indicates the spatial displacement of fat in the imaging area and This indicates a gap of 10-20 mm between the marker band and the imaging area; the reverse polarity mode needs to meet the following requirements. and Opposite polarities, and .

[0041] Preferably, the process of S8 is as follows:

[0042] S81. Based on all k-space data subsets from the first acquisition process, the image is reconstructed to obtain the arterial marker image, at which point the venous blood phase is highlighted.

[0043] S82. Based on all k-space data subsets from the second acquisition process, the image is reconstructed to obtain the vein-marked image, at which point the arterial blood phase is highlighted.

[0044] S83. Subtract the arterial marker image from the vein marker image, that is, subtract the venous bright blood image from the arterial bright blood image, to obtain a pure arterial image.

[0045] S84. Subtract the vein marker image from the arterial marker image, that is, subtract the arterial bright blood image from the venous bright blood image, to obtain a pure vein image.

[0046] S85. Obtain arteriovenous separation image and complete the angiography process.

[0047] Therefore, this invention employs a non-contrast magnetic resonance imaging method for lower limb arteriovenous fusion with the aforementioned structure. Compared to traditional stepwise lower limb arteriovenous imaging techniques (such as ultrasound + DSA), this invention achieves simultaneous arteriovenous fusion imaging of the lower limbs for the first time in a single contrast-free scan by using a U-shaped path alternating acquisition of proximal double-reverse arterial markers and distal single-reverse vein markers. This reduces redundant equipment usage and medical resource consumption. Furthermore, compared to NCE-MRA techniques that require ECG gating (such as FBI / QISS), this invention uses a golden-angle radial sampling (111.25°) and a periodic magnetization reset mechanism that rapidly interrupts the steady-state sequence, completely avoiding ECG gating dependence and resolving the problems of magnetic resonance electromagnetic interference and gating failure in patients with arrhythmias.

[0048] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0049] Figure 1 This is an overall flowchart of a non-enhanced magnetic resonance imaging method for combined arteriovenous imaging of the lower extremities according to the present invention;

[0050] Figure 2 The image shows the 5T lower limb scan results in an embodiment of the magnetic resonance non-contrast lower limb arteriovenous combined imaging method of the present invention. From left to right, these are the coronal MIP projections of the arteries and veins in the embodiment. Detailed Implementation

[0051] Example

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0053] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0054] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0055] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0056] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0057] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0058] like Figure 1 and Figure 2 As shown, the present invention provides a method for combined arteriovenous imaging of the lower extremities using non-contrast magnetic resonance imaging, comprising the following steps:

[0059] S1. Determine the number of data collection attempts and perform the first data collection attempt (Acq.1).

[0060] S11. Set the number of data collections;

[0061] S12, Select the imaging area;

[0062] S13. Apply a double-inverted arterial labeling pulse to the proximal end of the imaging area. The total thickness of the double-inverted arterial labeling pulse is 200-400mm, causing the blood in the labeling area to spin and flip.

[0063] S2. Set the data acquisition delay time, dynamically adjusted according to the physiological flow rate of the target blood vessel, to ensure that the labeled blood is within the target vessel's physiological flow rate. The precise inflow into the center of the imaging region before completion, and the delay time calculation process are as follows:

[0064] ;

[0065] in This indicates the distance from the proximal boundary of the marker band to the center of the imaging region. This represents the average blood flow velocity in the target vessel; values ​​are taken as 15-40 cm / s for arteries and 5-15 cm / s for veins. express Time buffer amount.

[0066] S3. Configure fast interrupt steady state and perform data acquisition;

[0067] S31. Select several fast interrupt steady-state modules to form a fast interrupt steady-state sequence as the core acquisition module;

[0068] S32, Perform periodic processing on each fast interrupt steady-state module. Radio frequency pulse reset steady-state magnetization;

[0069] S33. Apply a 117° RF phase cycle and phase scrambling gradient between every two fast interrupt steady-state modules to suppress residual spin coherence.

[0070] S34. Set the number of radial lines. And the included angle between radial lines Strictly adhering to the golden angle, and combining radial sampling at the golden angle with a single-layer complete cardiac cycle coverage design, it effectively suppresses blood flow pulsation artifacts and reduces motion artifacts, making it particularly suitable for patients with peripheral vascular disease exhibiting strong lower extremity arterial pulsations.

[0071] ;

[0072] in This represents the average repetition time of a single radial sample within the fast interrupt steady-state module. This indicates the average cardiac cycle duration of the target vascular region. This condition ensures that the single-layer imaging time covers the entire cardiac cycle (including systole and diastole) and suppresses blood flow pulsation artifacts.

[0073] Radial line angle The full radial spoke sampling is 111.25°, which was obtained from "Golden-Angle Radial MRI: Basics, Advances, and Applications".

[0074] S35. Each radial line samples the center of the k-space with the number of samplings set in S11, forming several subsets of k-space data to avoid ECG gating dependency.

[0075] S4. Repeat S1-S3 until all areas have completed the first data collection process;

[0076] S5. Switch to the second acquisition method, determine the number of acquisitions, and perform the second acquisition.

[0077] S51. After all areas have completed the first data collection process, the collection direction is switched alternately through a U-shaped path: head-to-foot (H→F) for Acq.1; foot-to-head (F→H) for Acq.2, to carry out the second collection (Acq.2) process.

[0078] S52. Set the number of data collections;

[0079] S53, Select the imaging area;

[0080] S54. Apply a single-inverting vein labeling pulse to the distal end of the imaging area. The thickness of the single-inverting vein labeling pulse is 100-200mm.

[0081] S6. Data acquisition is performed using the same process as S2 and S3;

[0082] S7. Repeat steps S5 and S6 until all areas have completed the second data collection.

[0083] After the data collection for S8, the first and second acquisitions are completed, image reconstruction is performed to obtain an arteriovenous separation image.

[0084] S81. Based on all k-space data subsets from the first acquisition process, the image is reconstructed to obtain the arterial marker image, at which point the venous blood phase is highlighted.

[0085] S82. Based on all k-space data subsets from the second acquisition process, the image is reconstructed to obtain the vein-marked image, at which point the arterial blood phase is highlighted.

[0086] S83. Subtract the arterial marker image from the vein marker image, that is, subtract the venous bright blood image from the arterial bright blood image, to obtain a pure arterial image.

[0087] S84. Subtract the vein marker image from the arterial marker image, that is, subtract the arterial bright blood image from the venous bright blood image, to obtain a pure vein image.

[0088] S85. Obtain arteriovenous separation image and complete the angiography process.

[0089] Both the double-inverted artery labeling pulse in S13 and the single-inverted vein labeling pulse in S54 are co-modulated with the gradient direction of the imaging slice selection pulse. This achieves spatial separation fat suppression through the chemical shift effect. By co-modulating the polarity of the labeling gradient and the imaging gradient, spatially selective fat suppression of the imaging area is achieved without increasing additional scan time. The process is as follows:

[0090] Step 1: Mark the gradient of the selected layer by the pulse. With imaging layer selection gradient The gradient configuration mode can be either the same polarity mode or the opposite polarity mode;

[0091] Same polarity mode needs to satisfy and They have the same polarity, and ,in This indicates the amount of fat spatial displacement in the marked area. Indicates the spatial displacement of fat in the imaging area and This indicates a gap of 10-20 mm between the marker band and the imaging area; the reverse polarity mode needs to meet the following requirements. and Opposite polarities, and .

[0092] Step 2: Solve for the spatial displacement of fat The process is as follows:

[0093] ;

[0094] in This indicates the difference in proton chemical shift between fat and water. Indicates the strength of the main magnetic field. This represents the currently applied layer gradient, which can be adjusted... and The polarity and intensity of the fat markers cause the fat imaging area to overlap spatially with the fat imaging area, thereby suppressing the fat signal in the imaging area.

[0095] In this embodiment, the total thickness of the double-reverse arterial labeling pulse is 400 mm, the thickness of the single-reverse vein labeling pulse is 200 mm, and the gap between the labeling band and the imaging area is 10 mm. ), corresponding The imaging layer thickness is selected as 3mm, corresponding to ;

[0096] By adjusting and The polarity and intensity of these properties ensure that the gradient configuration satisfies the Reversed SLIP pattern:

[0097] ;

[0098] ;

[0099] This ensures that the fat marking area and the fat imaging area overlap spatially, thereby achieving a fat suppression effect.

[0100] that angle The configuration ensures uniform coverage of the k-space and maximum decorrelation of adjacent radial lines, while the collaborative undersampling design suppresses periodic motion artifacts.

[0101] Fast interruption steady-state sequence average Based on the subject's average heart rate of 72 bpm ( )

[0102] ;

[0103] This condition ensures that the single-layer imaging time covers the entire cardiac cycle (including systole and diastole) and suppresses blood flow pulsation artifacts;

[0104] Image reconstruction in this embodiment utilizes compressed sensing technology. The kt SPARSE algorithm is employed, reducing reconstruction time to one-third of traditional methods. Artery marker map (Acq.1) – vein marker map (Acq.2) generate a pure vein image; conversely, a pure artery image is generated, as shown below. Figure 2 As shown.

[0105] Compared to CTA / DSA technology, which involves ionizing radiation and requires contrast agents, this invention is free of ionizing radiation and nephrotoxic contrast agents, significantly reducing the health risks to patients and providing a safe imaging assessment solution for sensitive groups such as children and those with renal insufficiency.

[0106] The golden angle sampling architecture of this invention is naturally compatible with compressed sensing reconstruction, which improves scanning speed while maintaining image quality. Combined with deep learning reconstruction algorithms, it can be extended to low-field devices, promoting the popularization of primary healthcare.

[0107] Therefore, this invention employs a non-contrast magnetic resonance imaging method for lower limb arteriovenous fusion with the aforementioned structure. Compared to traditional stepwise lower limb arteriovenous imaging techniques (such as ultrasound + DSA), this invention achieves simultaneous arteriovenous fusion imaging of the lower limbs for the first time in a single contrast-free scan by using a U-shaped path alternating acquisition of proximal double-reverse arterial markers and distal single-reverse vein markers. This reduces redundant equipment usage and medical resource consumption. Furthermore, compared to NCE-MRA techniques that require ECG gating (such as FBI / QISS), this invention uses a golden-angle radial sampling (111.25°) and a periodic magnetization reset mechanism that rapidly interrupts the steady-state sequence, completely avoiding ECG gating dependence and resolving the problems of magnetic resonance electromagnetic interference and gating failure in patients with arrhythmias.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for combined arteriovenous imaging of the lower extremities without contrast enhancement using magnetic resonance imaging, characterized in that, Includes the following steps: S1. Determine the number of data collection attempts and perform the first data collection attempt. The process is as follows: S11. Set the number of data collections; S12, Select the imaging area; S13. Apply a double-inverted arterial labeling pulse to the proximal end of the imaging area; S2, Set the data acquisition delay time; S3. Configure fast interrupt steady state and perform data acquisition, as follows: S31. Select several fast interrupt steady-state modules to form a fast interrupt steady-state sequence as the core acquisition module; S32, Perform periodic processing on each fast interrupt steady-state module. Radio frequency pulse reset steady-state magnetization; S33. Apply radio frequency and gradient phase scrambling between every two fast interrupt steady-state modules; S34. Set the number of radial lines. And the included angle between radial lines Strictly meet the golden angle, ； in This indicates the repetition time of a single radial sampling within the fast interrupt steady-state module. This indicates the average cardiac cycle duration in the target vascular region; S35. Each radial line samples the center of the k-space with the number of samplings set in S11, forming several subsets of k-space data. S4. Repeat S1-S3 until all areas have completed the first data collection process; S5. Switch to the second acquisition method, determine the number of acquisitions, and perform the second acquisition. The process is as follows: S51. After all areas have completed the first data collection process, the second data collection process is carried out by alternately switching the collection direction through a U-shaped path. S52. Set the number of data collections; S53, Select the imaging area; S54. Apply a single inverted vein marking pulse to the distal end of the imaging area; S6. Data acquisition is performed using the same process as S2 and S3; S7. Repeat steps S5 and S6 until all areas have completed the second data collection. S8. After the data collection for both the first and second acquisitions is completed, image reconstruction is performed to obtain an arteriovenous separation image. The process is as follows: S81. Based on all k-space data subsets from the first acquisition process, the image is reconstructed to obtain the arterial marker image, at which point the venous blood phase is highlighted. S82. Based on all k-space data subsets from the second acquisition process, the image is reconstructed to obtain the vein-marked image, at which point the arterial blood phase is highlighted. S83. Subtract the arterial marker image from the vein marker image, that is, subtract the venous bright blood image from the arterial bright blood image, to obtain a pure arterial image. S84. Subtract the vein marker image from the arterial marker image, that is, subtract the arterial bright blood image from the venous bright blood image, to obtain a pure vein image. S85. Obtain arteriovenous separation image and complete the angiography process.

2. The method for combined arteriovenous imaging of the lower extremities without enhancement according to claim 1, characterized in that, The calculation process for the delay time in S2 is as follows: ； in This indicates the distance from the proximal boundary of the marker band to the center of the imaging region. This represents the average blood flow velocity in the target blood vessel. express Time buffer amount.

3. The method for combined arteriovenous imaging of the lower extremities without enhancement according to claim 2, characterized in that: Both the double-inverted artery labeling pulse in S13 and the single-inverted vein labeling pulse in S54 are co-modulated with the gradient direction of the imaging slice selection pulse, as follows: Step 1: Mark the gradient of the pulse selection layer With imaging layer selection gradient The gradient configuration mode can be either the same polarity mode or the opposite polarity mode; Step 2: Solve for the spatial displacement of fat The process is as follows: ； in This indicates the difference in proton chemical shift between fat and water. Indicates the strength of the main magnetic field. This represents the gradient of the currently applied layer.

4. The method for combined arteriovenous imaging of the lower extremities without enhancement according to claim 3, characterized in that: Same polarity mode needs to satisfy and They have the same polarity, and ,in This indicates the amount of fat spatial displacement in the marked area. Indicates the spatial displacement of fat in the imaging area and This indicates a gap of 10-20 mm between the marker band and the imaging area; the reverse polarity mode needs to meet the following requirements. and Opposite polarities, and .

Images