CN104771246B - Method for visually reconstructing cruciate ligaments of knee joint - Google Patents

Abstract

The invention discloses a method for visually reconstructing cruciate ligaments of knee joints, which comprises the steps of data acquisition, coordinate system unification, extraction of spatial coordinates of the cruciate ligaments, visual image reconstruction of the cruciate ligaments, image measurement and the like; the invention can realize the digital fusion of CT and MRI, is simple and effective, can guide the knee joint ligament operation, and can not increase the burden of patients.

Description

A method for visual reconstruction of the cruciate ligament of the knee joint

technical field

The invention relates to the medical field, in particular to a method for visually reconstructing the cruciate ligament of the knee joint.

Background technique

An ideal reconstruction of the cruciate ligament of the knee should fix the graft at its anatomical insertion point and simulate its normal shape, which requires a comprehensive understanding of the patient's individual anatomical data, especially the condition of the target ligament and its adjacent bone structure. Among various imaging techniques, computed tomography (CT) is better at visualizing bone structures, while magnetic resonance imaging (MRI) has higher resolution of soft tissues. Due to the different imaging principles of MRI and CT, it is difficult to achieve integration, so there is no CT and MRI all-in-one machine in the world. In clinical practice, when both CT and MRI are needed, the two can only be put together and interpreted by medical staff based on experience, which is relatively subjective and may cause certain errors, which is very helpful for individualized surgery. limited. In order to solve this problem, Zhang Qiang and others in China used dual-source CT to study the cruciate ligament, and drew the structure of the insertion point of the anterior cruciate ligament based on the CT image. hand drawn. However, the research by Hu Yanjun and others only used two imaging methods, CT and MRI, and simply spliced the two images without realizing real image fusion. Foreign Bowers et al. have also reported knee meniscus reconstruction based on MRI, but did not use image fusion technology.

At present, there is no effective method to digitally fuse MRI and CT images, and there is no MRI and CT all-in-one machine. Most of the existing cruciate ligament image research methods use either MRI or CT to reconstruct the image of the target site, and cannot simultaneously reconstruct soft tissue and bone structure in the same image. And the existing method of combining the two is only to carry out MRI and CT scans on the same part, and then simply overlap the images, or simply cut some target parts in one of the images, and then Paste it into the corresponding image. These methods have two major disadvantages: first, it is not a digital fusion image in the true sense, with strong subjectivity and poor accuracy, and is only equivalent to "paper-cutting" to a certain extent; second, the operation is complicated and inefficient, and batch processing cannot be realized deal with.

Contents of the invention

The invention aims to provide a method for reconstructing the cruciate ligament of the knee joint, which can realize the digital fusion of CT and MRI, is simple and effective, can guide the operation of the knee joint ligament, and does not increase the burden on patients.

In order to achieve the above object, the present invention is achieved by adopting the following technical solutions:

The method for visually reconstructing the cruciate ligament of the knee joint disclosed by the present invention comprises the following steps:

Step 1. Data collection: fix the target knee joint at 0° straight, conduct CT and MRI scans successively within 30 minutes, and export their respective Dicom data;

Step 2. Unify the coordinate system: select 3 indication points on the CT and MRI images, mark them separately and extract the coordinate positions of the 3 points, and then use the 3 points on the MRI or CT to determine the coordinates according to the principle of 3-point surface determination. The surface is used as a reference to obtain the transformation function between the two coordinate systems, and according to the transformation function, the spatial coordinate data of all points in the corresponding image are transformed and corrected;

Step 3. Cruciate ligament spatial coordinate extraction: frame-select the image structure of the cruciate ligament displayed on each level of the sagittal plane, coronal plane and transverse plane, and extract the position coordinates of all points within the selected range that meet the threshold range;

Step 4. Visual image reconstruction of the cruciate ligament: increase the gray value of the extracted data at each point by a predetermined value and then re-import it into the CT, and reconstruct the two-dimensional and three-dimensional images of the knee joint cruciate ligament with adjacent bone structures in the CT;

Step 5. Image measurement: measure the structure of the cruciate ligament and its insertion point in the reconstructed image to obtain individualized measurement data.

Further, before step 4, it also includes verifying the conversion data, synchronously reconstructing the two-dimensional images of CT and MRI, selecting the same layer, and overlapping the two images through pixel extraction. The image whose overlapping degree reaches the predetermined range is considered to be successfully converted, and enters the follow-up process. processing flow.

Preferably, in step 4, the gray value is increased by a preset value of 2000.

Preferably, the three indicator points are all on the bone structure.

Preferably, in step 1, a 64-slice spiral CT machine and a 1.5T superconducting magnetic resonance are respectively used for CT and MRI scans. For MRI scans, the T2 phase three-dimensional fast spin echo sequence is selected for sagittal scans, and the scan parameters are: TR 1300ms, TE39ms, resolution 320, matrix 320*224, excitation once, slice thickness 1mm, overlap 50%; CT scanning parameters: 120kV, 35mA, collimator width 0.6mm, pitch 0.9, slice thickness 1mm, overlap 50% , the scanning time of each layer is 500ms.

Preferably, in step 2, the tool used to convert and correct the spatial coordinate data corresponding to all points in the image according to the conversion function is matlab7.0 software.

Preferably, the predetermined range of the degree of overlap is: both lateral and longitudinal errors are less than 1mm.

Preferably, in step 4, the tool used to reconstruct the two-dimensional and three-dimensional images of the cruciate ligament of the knee joint with adjacent bone structures in CT is ImageJ 1.48 software.

Preferably, in step 5, the tool used to measure the structure of the cruciate ligament and its insertion in the reconstructed image is ImageJ 1.48 software.

Preferably, the tool used for synchronously reconstructing the two-dimensional images of CT and MRI is Xiphoid software.

The present invention can accurately digitally fuse the CT and MRI images of the ipsilateral knee joint, facilitate corresponding observation and measurement, provide accurate data reference for clinical services, especially ligament reconstruction or repair, and avoid relying solely on CT or MRI The resulting measurement deviation can improve the surgical effect and help restore the patient's limb function to the greatest extent; this technology can be extended to other joints and ligaments throughout the body, and can also provide imaging support for the later application of 3D printing technology in ligament surgery.

Description of drawings

Fig. 1 is a flowchart of the present invention.

detailed description

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.

As shown in Figure 1, the method for visually reconstructing the cruciate ligament of the knee joint disclosed by the present invention is specifically implemented in accordance with the following steps:

1. Data acquisition: Use 64-slice spiral CT machine and 1.5T superconducting magnetic resonance to obtain original imaging data, fix the target knee joint at 0° straight (straight plastic plate can be used to fix it), at 30 CT and MRI scans were performed consecutively within minutes. MRI uses special limb coils, and selects T2 phase three-dimensional fast spin echo sequence (sampling perfection with application-optimized contrasts by using different flip angle evolutions, SPACE) for sagittal scanning. Scanning parameters: TR 1300ms, TE 39ms, resolution 320, matrix 320*224, excitation once, slice thickness 1mm, overlap 50%. CT scan parameters: 120kV, 35mA, collimator width 0.6mm, pitch 0.9, slice thickness 1mm, overlap 50%, scan time per slice 500ms. After scanning, export the Dicom data through the built-in software of the imaging device.

2. Using the characteristic that each point on CT and MRI has unique three-dimensional coordinates, select 3 indication points with high recognition and clear display on CT and MRI images (preferably on the bone structure, To avoid point movement of soft tissue due to compression deformation), the coordinate positions of the three points are extracted after marking respectively. Then, according to the principle of 3-point surface determination, the transformation function between the two coordinate systems is obtained with reference to the surface determined by 3 points on MRI or CT. According to the conversion function, use matlab7.0 software (MathWorks, USA) to write a program to convert and correct the spatial coordinate data of all points in the corresponding image, so that the spatial coordinate systems of CT and MRI are completely unified, and the spatial positions of the resulting images are completely overlapped.

3. Theoretically, the spatial layout of the two images after the above transformation should be completely consistent, and the reconstructed images should be highly overlapped. In order to verify the effect of the first two steps, use Xiphoid software (used in medical image processing, written by Ning Jing and provided for free) to simultaneously reconstruct the two-dimensional images of CT and MRI, select the same layer, and overlap the two images through the pixel extraction function , images with a high degree of overlap (horizontal and vertical errors less than 1mm) are considered to be converted successfully and can enter the subsequent processing flow.

4. Use the imaging function of Xiphoid software to reconstruct the MRI image two-dimensionally. Use the value masking function of the software (prescribed lower threshold 0, upper threshold 250), roughly select the cruciate ligament image structure displayed on the sagittal plane, coronal plane and cross-sectional plane, and extract all the threshold ranges within the selected range The position coordinates of the points and export the coordinate data.

5. Increase the gray value of the extracted data by 2000 and re-import it into CT, and use ImageJ1.48 software (National Institute of Health, USA) to reconstruct the two-dimensional cruciate ligament of the knee joint with adjacent bone structures in CT and three-dimensional images.

6. Use the measurement function of ImageJ 1.48 software to measure the structure of the cruciate ligament and its insertion in the reconstructed image, and obtain individualized measurement data. .

Certainly, the present invention also can have other multiple embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes All changes and modifications should belong to the scope of protection of the appended claims of the present invention.

Claims (7)

1. A method for visually reconstructing the cruciate ligament of the knee joint, comprising the following steps: Step 1. Data collection: fix the target knee joint at 0° straight, conduct CT and MRI scans successively within 30 minutes, and export their respective Dicom data; Step 2. Unify the coordinate system: select 3 indication points on the CT and MRI images, mark them separately and extract the coordinate positions of the 3 points, and then use the 3 points on the MRI or CT to determine the coordinates according to the principle of 3-point surface determination. The surface is used as a reference to obtain the transformation function between the two coordinate systems, and according to the transformation function, the spatial coordinate data of all points in the corresponding image are transformed and corrected; Step 3. Cruciate ligament spatial coordinate extraction: frame-select the image structure of the cruciate ligament displayed on each level of the sagittal plane, coronal plane and transverse plane, and extract the position coordinates of all points within the selected range that meet the threshold range; Step 4. Visual image reconstruction of the cruciate ligament: increase the gray value of the extracted data at each point by a predetermined value and re-import it into the CT, and reconstruct the two-dimensional and three-dimensional images of the cruciate ligament of the knee joint with adjacent bone structures in the CT. The predetermined value of the increase of the gray value is 2000; Step 5. Image measurement: measure the structure of the cruciate ligament and its insertion point in the reconstructed image to obtain individualized measurement data; Verify the converted data before step 4, reconstruct the two-dimensional images of CT and MRI synchronously, select the same layer, and overlap the two images through pixel extraction. The image whose overlapping degree reaches the predetermined range is considered to be successfully converted, and enters the subsequent processing flow. The predetermined range of overlapping degree is: both lateral and longitudinal errors are less than 1mm. 2. The method for visually reconstructing the cruciate ligament of the knee joint according to claim 1, wherein the three indicator points are all on the bone structure. 3. the method for visual reconstruction knee cruciate ligament according to claim 1, is characterized in that, in step 1, carry out CT and MRI scan and adopt 64 rows of spiral CT machines and 1.5T superconducting magnetic resonance respectively, MRI scan selection T2 phase three-dimensional fast spin echo sequence for sagittal scan, scan parameters: TR 1300ms, TE 39ms, resolution 320, matrix 320*224, excitation once, slice thickness 1mm, overlap 50%; CT scan parameters: 120kV ,35mA, collimator width 0.6mm, pitch 0.9, slice thickness 1mm, overlap 50%, scanning time per slice 500ms. 4. The method for visually reconstructing the cruciate ligament of the knee joint according to claim 1, characterized in that, in step 2, the tool used for converting and correcting the spatial coordinate data of all points in the corresponding image according to the conversion function is matlab7. 0 software. 5. The method for visually reconstructing the cruciate ligament of the knee according to claim 1, wherein in step 4, the two-dimensional and three-dimensional images of the cruciate ligament of the knee with adjacent bone structures are reconstructed in CT. The tool used is ImageJ1.48 software. 6. The method for visually reconstructing the cruciate ligament of the knee joint according to claim 1, characterized in that, in step 5, the tool used to measure the structure of the cruciate ligament and its insertion point in the reconstructed image is ImageJ 1.48 software. 7. The method for visually reconstructing the cruciate ligament of the knee joint according to claim 1, wherein the tool used for the simultaneous reconstruction of the two-dimensional images of CT and MRI is Xiphoid software.