IntroductionCongenital tracheal stenosis (CTS) is a rare but life-threatening disease that can lead to respiratory dysfunction in children. Obstructive sleep apnea syndrome (OSAS) in children is characterized by prolonged partial upper airway obstruction and/or intermittent complete obstruction. Both of the diseases require surgical intervention. Although respective treatments of these two diseases are clear, there is a lack of literature discussing the surgical treatment of patients with CTS complicated by OSAS.MethodsWe conducted a patient-specific study of patient with CTS complicated by OSAS. Computer-aided design was used to simulate surgical correction under different surgical sequences. Computational fluid dynamics was used to compare the outcomes of different sequences.ResultsAerodynamic parameters, pressure drop, velocity streamlines, wall shear stress (WSS), and the ratio of airflow distribution and energy loss rate were evaluated. An obvious interaction was found between the two diseases in different surgical sequences. The order of correction for CTS or OSAS greatly affected the aerodynamic parameters and turbulence flows downstream of tracheal stenosis and upstream of epiglottis. The CTS and OSAS had mutual influences on each other on the aerodynamic parameters, such as pressure drops and WSS.DiscussionWhen evaluating the priority of surgical urgency of CTS and OSAS, surgeons need to pay attention to the state of both CTS and OSAS and the physiological conditions of patients. The aerodynamic performance of the uneven airflow distribution and the potential impact caused by the correction of CTS should be considered in surgical planning and clinical management.

Background and objective: Surgical correction of pulmonary artery stenosis (PAS) is essential to the prognosis of patients with tetralogy of Fallot (TOF). The double -patch method of pulmonary arterioplasty is usually applied in case of multiple stenosis in TOF patients' pulmonary artery (PA) and when PAS cannot be relieved by the singlepatch method. The surgical planning for the double -patch design remains challenging. The purpose of this study is to investigate the double -patch design with different angulations between the left pulmonary artery (LPA) and the right pulmonary artery (RPA), and to understand postoperative hemodynamic alterations by the application of computer -aided design (CAD) and computational fluid dynamics (CFD) techniques. Methods: The three-dimensional model of the PA was reconstructed based on preoperative computed tomography imaging data obtained from the patient with TOF. Three postoperative models with different designs of doublepatch were created by "virtual surgery" using the CAD technique. Double -Patch 120 Model was created with double patches implanted in the main pulmonary artery (MPA) and the PA bifurcation and without changing the spatial position of PA. The angulation between the LPA and the RPA was defined as theta, which equaled to 120 degrees in Pre -Operative Model and Double -Patch 120 Model. Based on Double -Patch 120 Model, Double -Patch 110 Model and Double -Patch 130 Model were generated with theta equaled to 110 degrees and 130 degrees, respectively. Combined with CFD, the differences of velocity streamlines, wall shear stress (WSS), flow distribution ratio (FDR), and energy loss (EL) were compared to analyze postoperative pulmonary flow characteristics. Results: The values of velocity and WSS decreased significantly after virtual surgery. Obvious vortices and swirling flows were observed downstream of the stenosis of RPA and LPA in Pre -Operative Model, while fewer vortices developed along the anterior wall of the expanded lumens of RPA, especially in Double -Patch 110 Model. With the relief of PAS, two relatively higher WSS regions were observed at the posterior walls of RPA and LPA. The maximum WSS values in these regions of Double -Patch 110 Model were lower than those in DoublePatch 120 Model and Double -Patch 130 Model. Furthermore, the FDRs were elevated and the ELs were greatly reduced. It was found that Double -Patch 110 Model with the angulation between the LPA and the RPA equaled to 110 degrees showed relatively better properties of hemodynamics than other models. Conclusions: The angulation between the LPA and the RPA is an important factor that should be integrated in the double -patch design for TOF repair. Virtual surgery based on patient -specific vascular model and computational hemodynamics can be used to provide assistance for individualized surgical planning of double -patch arterioplasty.

In order to enhance the reconstruction of Tetralogy of Fallot (TOF) cardiovascular models and facilitate the development of individualized treatment strategies for clinical practitioners, this study employed the modeling outcomes from Materialise ® -Mimics as a reference point to investigate the modeling effectiveness of the existing automatic segmentation algorithm based on the U-Net model. We selected a single case and performed three-dimensional modeling using both the automatic segmentation algorithm and Mimics. Subsequently, we utilized Mimics to measure morphological parameters, including pulmonary artery diameter and angles, from the models generated by the two aforementioned methods, as well as from the two-dimensional images. The parameters acquired from the two-dimensional plane served as the standard reference. Discrepancies and relative errors between the parameters obtained from the two models and the reference values were calculated, while smaller discrepancies and parameter errors indicated greater model accuracy. Although the models generated through both methods exhibited substantial morphological similarity, the algorithmic models excluded image information at the juncture of the right ventricle and pulmonary artery. Furthermore, the data revealed that the discrepancies and relative errors in the algorithmic model's measurements were higher than those observed in the Mimics-generated models compared to the reference values. Consequently, it is inferred that the modeling efficacy of the automatic segmentation algorithm based on the U-Net model is promising, yet further model training is required to enhance modeling precision.

Tetralogy of Fallot (TOF) is one of the commonest cyanotic congenital heart diseases, characterized by the highly variable anatomy of pulmonary artery (PA), location and degree of obstruction. Subtle alterations in the geometry of PAs would cause changes of pulmonary hemodynamics, which are closely associated with the outcome of TOF patients. Hence, it is critical to understand the geometric characteristics of PA in TOF patients. This study was conducted to explored the differences of tortuosity of PAs between TOF patients and children with normal PAs. And there were twenty TOF patients and ten individuals with normal PA. The three-dimensional geometries of PAs were constructed based on preoperative computed tomography data. The tortuosity of pulmonary arteries were quantitatively measured and statistically analyzed. It was found that there were no obvious differences in the tortuosity of right pulmonary artery (RPA) between TOF and control groups (1.07 ± 0.044 vs. 1.07 ± 0.029, P = 0.977). Nevertheless, the tortuosity of main pulmonary artery (MPA) (1.07 ± 0.012 vs. 1.11 ± 0.038, P < 0.0001) and the tortuosity of left pulmonary artery (LPA) (1.10±0.022 vs. 1.18±0.070, P = 0.001) were relatively higher in the TOF group compared with the control group. The positive correlation was found between the tortuosity of MPA and the tortuosity of LPA (r=0.618, P < 0.0001). The area under the curve (AUC) of the MPA tortuosity and the LPA tortuosity was 0.945 and 0.935, respectively. They exhibit both high sensitivity and specificity in the diagnosis of TOF. The cutoff value of the MPA tortuosity was 1.092, and that of the LPA tortuosity was 1.117. It revealed that increased tortuosity of MPA and LPA in TOF patients compared with those of normal subjects, which might provide guidance for the diagnostic evaluation and prognostic prediction of TOF patients.