This study was to explore the application and effect of three-dimensional (3D) images of the esophagus in the treatment of atrial septal defect (ASD) combined with tricuspid regurgitation (TR) surgery under the processing of marching cubes (MC) image reconstruction algorithm. The MC image reconstruction algorithm was improved as the optimized MC image reconstruction algorithm. 100 patients who had successfully undergone the ASD combined with TR surgery in the hospital from January 2017 to December 2019 were selected as the research objects and grouped based on size of the defect. The preoperative and postoperative conditions of the patients were analyzed with the MC image reconstruction algorithm. Compared with the traditional MC image algorithm, the optimized MC was advanced with less running time and fewer fixed points (
About 10%–15% of patients with congenital heart disease suffer from ASD. As one of the most common congenital heart diseases, ASD accounts for about 1 : 2 in males and females. In adult congenital heart disease, the incidence of ASD accounts for about 35% to 40% [
Therefore, the conventional MC algorithm was improved as the optimized MC to construct a three-dimensional ultrasound heart model, so as to further study the therapeutic effect of occlusion on patients with ASD combined with TR.
A voxel was the basic unit in a three-dimensional data field. The
The most important step in the MC algorithm was to extract the contour surface, which mainly included the following three steps: determining the positional relationship between the contour surface and the voxel focus and determining the division method of the voxel contour surface; determining the focal coordinates of the edge and the contour surface; and calculating the normal vector of the contour surface. When the focal coordinates of the edge and the contour surface was determined, the three-dimensional data field was assumed to be continuous, and the linear interpolation between the two points was adopted to calculate the coordinates of the intersection point of the edge and the contour surface. The coordinates of the two vertices were set to be
In the vector calculation by the contour surface method, the gradient value of each vertex on the voxel was calculated by the gray difference method, then the normal direction of the intersection could be obtained by linear interpolation of the gradient between the two vertices, which referred to the normal vector of the contour surface. It was assumed that the gray value of a vertex was
The normal vector of contour surface
The traditional MC algorithm was to extract and draw the three-dimensional model based on the contour surface. The model was fitted by multiple triangular faces, and these three intersection points were obtained by linear interpolation among the vertices of the voxels. This type of approach required a long time, which affected the efficiency of model construction. In addition, analysis of previous studies revealed that the ambiguity of contour surface connection also affected the effect of model generation. Based on this, the optimized MC algorithm was constructed in this study.
Firstly, the linear interpolation was optimized by replacing the linear interpolation point with the median point, and the equations could be written as follows:
If the pixel at point
A total of 100 adult patients with ASD combined with TR admitted to hospital from January 2017 to December 2019 were selected, and they all met the following criteria: patients who were clinically confirmed as ASD combined with TR; patients aging over 18 years old and under 60 years old; patients with normal liver function and kidney function; and patients conforming to the indications for occlusion. Patients with the following conditions were excluded: patients with other types of heart diseases; patients suffering from mental diseases; patients suffering from hypertension or diabetes; patients suffering from Eisenmenger syndrome; patients who received other treatments including traditional Chinese medicine (TCM); and patients with poor compliance. All patients participating in the experiment had signed the informed consent forms, and this study was reviewed and approved by the Ethics Committee of the hospital.
In this experiment, ASD patients were grouped based on the size of the ASD into group A with large ASD (group A), group B with medium ASD for no smaller than 30 mm (group B), and group C with small ASD of no smaller than 10 mm and no larger than 30 mm (group C).
The right femoral artery and vein were punctured to the 6F and 7F arteriovenous sheaths, respectively; systemic heparinization was realized with the first dose of intravenous heparin 100 U/kg (if the operation exceeded 1 hour, half the initial heparin dose should be added). The right heart was catheterized firstly to measure the pressure of the right atrium, right ventricle, and pulmonary artery, and the blood oxygen saturation of each part was detected. The form and size of the atrial septal defect and the distance from the upper edge of the defect to the right coronary valve of the aorta were measured further. If necessary, the ascending aortic angiography was performed to determine whether there was aortic valve prolapse and regurgitation. The angiography catheter was selected based on the form of ASD in left ventricle angiography, and the catheter was rotated counterclockwise from the femoral artery to the left ventricle so that the tip points to the ASD could be open. The catheter was moved slowly so that the tip could jump through the ventricular septal defect opening to the right ventricle, and then the catheter was fixed. The occluder was selected according to the defect diameter measured by angiography. Generally, the diameter of the occluder should be 1-2 mm larger than the angiographic diameter. A suitable occluder was sent to the left ventricular surface along the delivery sheath, and the left ventricular surface umbrella was released firstly. It was not necessary to adjust the direction for the symmetrical occluder, and the mark of the left ventricular side umbrella of the eccentric occluder should point to the apex so that left ventricular umbrella of the occlude could be close to the interventricular septum. The position of the occluder could be determined through hand feel, fluoroscopy, ultrasound, or even ventriculography. If the position was appropriate and there was no obvious residual shunt displayed by the ultrasound image, the wire was fixed and the long sheath was withdrawn. The right ventricular umbrella of the occlude was released. The left ventricular angiography and ascending aorta angiography were repeated. Contrast and transthoracic ultrasound were adopted to confirm that the occluder was fixed and there was no obvious residual shunt; then the occlude could be completely released. The sheath was removed, the puncture port was pressurized, and then the surgery was completed.
Before the examination, the patient was instructed to refrain from eating for 12 hours. If the patient was nervous on the day of the examination, 2.5 mg of diazepam could be taken orally. Before the formal examination, the patient was required to take lidocaine glue orally, so that the oral cavity, pharynx, and esophagus of the patient were anesthetized by the topical anesthetic, so as to reduce and even avoid the response during intubation. The patient was placed in a lateral position, and the examiner stood on the left side of the patient. Dentures (if any) had to be removed before intubation. The patient was required to bite the mouth pad, and the glue was applied on the surface of the transducer. The curved probe was inserted along the middle of the oral tongue base, and moved rapidly after entering the esophagus to reach the middle of the esophagus (about 34 cm). The horizontal and vertical axis of the patient should be examined, respectively.
The SPSS 22.0 software was adopted for statistical analysis, and the counting results were expressed as the mean ± standard deviation. The
The collected transesophageal 3D ultrasound heart images were undertaken as the original dataset to test the traditional MC algorithm and the optimized MC algorithm under different sizes of dataset, and the calculation time of each algorithm and the number of fixed points of the constructed model were recorded and compared. The result is shown in Figure
Comparison of the original MC algorithm and the optimized MC algorithm. (a) The number of fixed points of the model; (b) the running time of the model.
The MC ultrasound images before and after optimization are shown in Figures
Ultrasound heart model based on traditional MC algorithm. (a) The ultrasound image; (b) the heart model.
Ultrasound heart model based on optimized MC algorithm. (a) The ultrasound image; (b) the heart model.
100 patients were included in the experiment, including 56 patients in group A (17 males and 39 females, with an average age of 35.17 ± 5.78 years old), 31 patients in group B (11 males and 20 females, with an average age of 36.45 ± 7.22 years old), and 13 patients in group C (5 males and 8 females, with an average age of 36.14 ± 6.17 years old). Comparison of the above information showed that the difference between the two groups was not statistically meaningful (
Comparison of basic information of patients in two groups. (a) Comparison results of gender; (b) comparison results of age.
The average RA, RV, and TR of patients with different sizes of defect were statistically analyzed, and the results are given in Figure
Comparison of RA, RV, and TR of three groups of patients. (a) Comparison results of TR; (b) comparison results of RA and RV. (
Correlations of RA, RV, and TR of three groups of patients were analyzed further, and the results are illustrated in Figure
Correlation analysis of RA, RV, and TR of patients in three groups.
Among all ASD patients, 13 patients had elevated pulmonary artery pressure (PAP), and 87 patients with ASD had normal PAP. The TRs of the patients with elevated PAP were compared with those of the patients with normal PAP, and the results are shown in Figure
Correlation between the pulmonary artery pressure and tricuspid regurgitation.
Surgery was performed only on patients in group A and group B, the changes in the amount of TR volume of patients before and one day after surgery were compared, and the results are illustrated in Figure
Comparison of tricuspid regurgitation before and after the surgery.
The amounts of TR of patients were detected at the 1st day, 7th day, 1st month, 3rd month, and 6th month after surgery. The results shown in Figure
Changes in the amount of tricuspid regurgitation of patients at different time points after the surgery.
ASD is caused by hypoplasia of the septum between the left ventricle and the RV of the patient. The atrioventricular septum has a defect that leads to a congenital disease in which the blood flow is connected [
Manuel et al. (2017) showed in the study that most adult ASD patients had different degrees of TR, and patients with moderate to severe TR accounted for about 20% of the total number [
The MC algorithm was explored and optimized to get the optimized MC algorithm, and a 3D heart model was successfully constructed. The efficacy of occlusion for patients with ASD and TR was further studied, and the results showed that the amount of TR in patients with large and medium ASD had been increased sharply after occlusion. However, this study only focused on the cardiac ultrasound images for the study of algorithm. Whether the algorithm is useful for other ultrasound images has to be further explored in future. In addition, the explored samples were too less and the patients with small ASD who do not need occlusion were not studied, which had to be further studied in depth in future. In summary, the results of this study can provide reliable basis for clinical treatment for ASD combined with TR.
No data were used to support this study.
The authors declare that they have no conflicts of interest.