A new computational fluid dynamics based noninvasive assessment of portacaval pressure gradient.

Accurate assessment of portacaval pressure gradient (PCG) in patients with portal hypertension (PH) is of great significance both for diagnosis and treatment. This study aims to develop a noninvasive method for assessing PCG in PH patients and evaluate its accuracy and effectiveness. This study recruited 37 PH patients treated with transjugular intrahepatic portosystemic shunt (TIPS). computed tomography angiography was used to create three dimension (3D) models of each patient before and after TIPS. Doppler ultrasound examinations were conducted to obtain the patient's portal vein flow (or splenic vein and superior mesenteric vein). Using computational fluid dynamics (CFD) simulation, the patient's pre-TIPS and post-TIPS PCG was determined by the 3D models and ultrasound measurements. The accuracy of these noninvasive results was then compared to clinical invasive measurements. The results showed a strong linear correlation between the PCG simulated by CFD and the clinical invasive measurements both before and after TIPS (R2 = 0.998, P < 0.001 and R2 = 0.959, P < 0.001). The evaluation accuracy of this noninvasive method reached 94 %, and the influence of ultrasound result errors on the numerical accuracy was found to be marginal if the error was less than 20 %. Furthermore, the information about the hemodynamic environment in the portal system was obtained by this numerical method. Spiral flow patterns were observed in the portal vein of some patients. In a conclusion, this study proposes a noninvasive numerical method for assessing PCG in PH patients before and after TIPS. This method can assist doctors in accurately diagnosing patients and selecting appropriate treatment plans. Additionally, it can be used to further investigate potential biomechanical causes of complications related to TIPS in the future.

A streamlined controlled-expansion covered tapered stent for TIPS in the treatment of PHT.

Transjugular intrahepatic portosystemic shunt (TIPS) relieves cirrhotic complications by reducing portacaval pressure gradient (PCG), but it lacks precision in achieving a targeted post-TIPS PCG simply through diameter adjustment of equal diameter stents. This study aimed to present a controlled-expansion, streamlined, and covered tapered stent, and examined its effects on pressure reduction compared with equal- diameter stents. Twenty-four patients who underwent standardized 8-mm stent TIPS implantation at West China Hospital from December 2017 to February 2021 were included in the current study. Virtual equal-diameter stent graft with different diameter and streamlined tapered stents were created in the post-TIPS 3-dimentional models reconstructed based on computed tomography angiography data. The numerical simulation showed that only two patients achieved targeted post-TIPS PCG consistent with the clinical invasive measurement. When 6-mm and 10-mm equal-diameter stents were employed, simulated post-TIPS PCGs for most patients remained outside the safe range, and recirculating flow was observed at the stent-portal vein anastomosis. In contrast, the use of the new streamlined taper stent resulted in post-TIPS PCGs within the 10-12 mmHg range for 17 out of 24 patients, with no recirculating flow observed at the anastomotic sites. In conclusion, the streamlined tapered stent could pose an effective solution to the problem that the big jump depressurization between two different equal-diameter stents and it would improve the hemodynamics in the region near the PV-stent anchorage. Therefore, the streamlined tapered stent may present a superior alternative for TIPS procedure.

Evaluation of the effect of unilateral mastication on the morphology of temporomandibular joint from the perspective of dynamic joint space.

BACKGROUND: Unbalanced alterations of temporomandibular joint morphology were associated with unilaterally masticatory habits. OBJECTIVE: This study aimed to investigate the effect of unilateral mastication on the remodelling of the temporomandibular joint using dynamic joint space. METHODS: Twelve volunteers with non-maxillofacial deformity and healthy temporomandibular joints were recruited. The 3D models of the mandible and the maxilla were reconstructed according to computed tomography. The subjects were asked to masticate French fries and peanuts unilaterally, which was recorded by a 3D motion capture system. The dynamic joint space during unilateral mastication was analysed. RESULTS: During early closure, the joint space reduction on the non-masticatory side was significantly greater than on the masticatory side (p < .05). During later closure, the joint space reduction on the non-masticatory side was significantly lower than that on the masticatory side (p < .05). The difference in joint space reduction between both sides was greater than the French fries while masticating the peanuts. CONCLUSIONS: Unilateral mastication resulted in a different major pressure area on the bilateral TMJs. Therefore, unilateral mastication might be an essential factor in the bilateral asymmetrical remodelling of the TMJ.

The effect of splenic vein diameter on the diagnosis of portal vein thrombosis.

BACKGROUND: It was still controversial that whether the increase of splenic vein (SV) diameter increased the risk of portal vein thrombosis (PVT), which was a severe disease with high mortality, in the clinic. PURPOSES: This study, using computational fluid dynamics method, aimed to investigate how the increase of SV diameter affects the portal vein hemodynamics under different anatomical and geometric features of the portal venous system, thus how it induced to PVT. METHODS: The ideal models of the portal system, including different anatomical structures according to the location of left gastric vein (LGV) and inferior mesenteric vein (IMV), and different geometric morphological parameters models were established to carry out numerical simulation in this study. In addition, the morphological parameters of real patients were measured to verify the numerical simulation results. RESULTS: First, the wall shear stress (WSS) and helicity intensity, which were closely related to the occurrence of thrombosis, gradually decreased with the increase of SV diameter in all models. However, the degree of decrease was bigger in following models: (1) the models with LGV and IMV linking to SV compared with them linking to PV; (2) the models with big angle of PV and SV compared with small angle. In addition, the morbidity of PVT was higher when LGV and IMV linked to SV rather than them linked to PV in the real patients. Moreover, the angle of PV and SV was also different between PVT and non-PVT patients (125.53° ± 16.90° vs. 115.03° ± 16.10°, p = 0.01). CONCLUSION: Whether the increase of SV diameter will result in PVT is depended on the anatomical structure of portal system and the angle between PV and SV, this is also the reason leading to the clinical controversy that the increase of SV diameter is the risk factor of PVT.

Identification of high-risk patients for development of type B aortic dissection based on novel morphological parameters.

Background: Predicting the development of sporadic type B aortic dissection (TBAD) always remains a difficult issue. This study aimed to identify high-risk patients for development of TBAD based on morphological parameters. Methods: This propensity-score-matched case-control study collected and reconstructed the computed tomography angiography of acute TBAD patients and hospital-based control participants without aortic dissection from January 2013 to December 2016. Multivariate regression analysis was used to calculate the adjusted odds ratio (aOR) and 95% confidence interval (CI). Discriminant and reclassification abilities were compared between our model and a previously established model. Results: Our study included 76 acute TBAD patients and 79 control patients (48 cases and 48 controls after propensity-score matching). The degree of question mark (aOR 1.07, 95% CI 1.04-1.11), brachiocephalic trunk diameter (aOR 1.49, 95% CI 1.20-1.85), brachiocephalic trunk angle (aOR 0.97, 95% CI 0.94-0.99), aortic root diameter (aOR 1.31, 95% CI 1.15-1.48), and aortic width (aOR 1.12, 95% CI 1.07-1.17) were associated with a significantly increased risk of TBAD formation. Similar findings were observed in the propensity-score matching and sensitivity analysis only including hyperacute TBAD patients. A novel prediction model was established based on the aforementioned parameters. The new model showed significantly improved discriminant ability compared with the previously established model (c-index 0.78 [95% CI 0.71-0.85] vs. 0.67 [95% CI 0.58-0.75], p = .03), driven by increased reclassification ability in identifying TBAD patients (NRI for events 0.16, 95% CI 0.02-0.30, p = .02). Conclusion: Morphological predictors, including the degree of question mark, aortic width, aortic root diameter, brachiocephalic trunk angle, and brachiocephalic trunk diameter, may be used to identify patients at high risk of TBAD.

Rapid Morphological Measurement Method of Aortic Dissection Stent Based on Spatial Observation Point Set.

OBJECTIVES: Post-operative stent morphology of aortic dissection patients is important for performing clinical diagnosis and prognostic assessment. However, stent morphologies still need to be manually measured, which is a process prone to errors, high time consumption and difficulty in exploiting inter-data associations. Herein, we propose a method based on the stepwise combination of basic, non-divisible data sets to quickly obtain morphological parameters with high accuracy. METHODS: We performed the 3D reconstruction of 109 post-operative follow-up CT image data from 26 patients using mimics software. By extracting the spatial locations of the basic morphological observation points on the stent, we defined a basic and non-reducible set of observation points. Further, we implemented a fully automatic stent segmentation and an observation point extraction algorithm. We analyzed the stability and accuracy of the algorithms on a test set containing 8 cases and 408 points. Based on this dataset, we calculated three morphological parameters of different complexity for the different spatial structural features exhibited by the stent. Finally, we compared the two measurement schemes in four aspects: data variability, data stability, statistical process complexity and algorithmic error. RESULTS: The statistical results of the two methods on two low-complexity morphological parameters (spatial position of stent end and vascular stent end-slip volume) show good agreement (n = 26, P1, P2 < 0.001, r1 = 0.992, r2 = 0.988). The statistics of the proposed method for the morphological parameters of medium complexity (proximal support ring feature diameter and distal support ring feature diameter) avoid the errors caused by manual extraction, and the magnitude of this correction to the traditional method does not exceed 4 mm with an average correction of 1.38 mm. Meanwhile, our proposed automatic observation point extraction method has only 2.2% error rate on the test set, and the average spatial distance from the manually marked observation points is 0.73 mm. Thus, the proposed method is able to rapidly and accurately measure the stent circumferential deflection angle, which is highly complex and cannot be measured using traditional methods. CONCLUSIONS: The proposed method can significantly reduce the statistical observation time and information processing cost compared to the traditional morphological observation methods. Moreover, when new morphological parameters are required, one can quickly and accurately obtain the target parameters by new "combinatorial functions." Iterative modification of the data set itself is avoided.

The loss of helical flow in the thoracic aorta might be an identifying marker for the risk of acute type B aortic dissection.

BACKGROUND AND OBJECTIVE: The occurrence of acute type B aortic dissection (TBAD) remained unclear. This study aimed to investigate the association between flow features and hemodynamic parameters in aortas that demonstrated the risk of TBAD occurrence. METHODS: The geometries of 15 hyperacute TBAD and 12 control patients (with healthy aorta) were reconstructed from computed tomography angiography images. Pre-TBAD models were then obtained by eliminating the dissection flaps. Flow features and hemodynamic parameters, including wall shear stress-related parameters and helicities, were compared between pre-TBAD and control models using computational fluid dynamics. RESULTS: There were no significant differences in baseline characteristics and anatomical parameters between the two groups. Significant contralateral helical blood flow was present in the healthy thoracic aorta, while almost no helical flow was observed in the pre-TBAD group. In addition, the mean normal transverse wall shear stress (NtransWSS) was significantly higher in the pre-TBAD group (aortic arch 0.49±0.09 vs. 0.40±0.05, P = 0.04; descending aorta: 0.46±0.05 vs. 0.33±0.02, P<0.01). Moreover, a significantly negative correlation was found between helicity and NtransWSS in the descending aorta. Moreover, the location of primary tears in 12 pre-TABD subjects matched well with regions of high NtransWSS. CONCLUSIONS: Loss of helical flow in the aortic arch and descending aorta may be a major flow feature in patients with underlying TBAD, resulting in increased flow disturbance and wall lesions.

Hemodynamic analysis of hybrid treatment for thoracoabdominal aortic aneurysm based on Newtonian and non-Newtonian models in a patient-specific model.

The accuracy of the Newtonian model used in retrograde visceral revascularization (RVR) of hybrid surgery for thoracoabdominal aortic aneurysm (TAAA) hemodynamic simulation remains unclear. Noting that an appropriate blood viscosity model is a significant factor to capture hemodynamic changes in numerical studies. Therefore, both Newtonian and non-Newtonian blood viscosity models were adopted in this study to investigate the importance of hemodynamics when non-Newtonian blood property was accounted for in a patient-specific RVR simulation. The results revealed that disturbed flow and unfavorable WSS distribution can be observed in the anastomosis region under both blood viscosity models due to the retrograde flow pattern in the RVR model. However, although the non-Newtonian blood model has negligible effect on flow pattern and pressure drop, there were of significance quantitative and qualitative difference of local normalized helicity and wall shear stress distribution under pulsatile flow condition. In particular, the unfavorable WSS indicators distribution was better matched with a patient-specific follow-up report when non-Newtonian blood viscosity was accounted for. To conclude, the use of a Newtonian blood model is a reasonable approximation to obtain the general features of the flow field under steady flow condition. However, to study the hemodynamic parameters within retrograde flow under pulsatile flow condition, a non-Newtonian model may be more appropriate.

The pressure in the temporomandibular joint in the patients with maxillofacial deformities.

BACKGROUND: Temporomandibular disorder (TMD) symptoms were found to be common in the patients with maxillofacial deformities. The mandibular structure was in relation with the stress within temporomandibular joint (TMJ). However, the current studies on the TMJ stresses in the patients with different maxillofacial deformities are not comprehensive enough. PURPOSE: The aim of this study was to investigate the compression and morphology of the TMJ in the patients with different maxillofacial deformities under central occlusion. METHODS: 24 patients and 10 asymptomatic individuals were included in this study and divided into patient groups and control group. The 3D models were reconstructed. Muscle forces and boundary conditions corresponding to the central occlusion were applied. Nine morphological parameters of mandible were evaluated. RESULTS: The minimum principal stresses in the articular disc and condyle were significantly greater than those of the control group (P<0.05). For the articular disc, the compression on the non-deviation side was greater than those on the deviation side in patients with asymmetrical mandibles. There was difference between both sides in the mandibular prognathism and retrusion groups. The joint space of patients was significantly lower than that of the control group (P<0.05). CONCLUSIONS: Maxillofacial deformities might change the condylar position within the articular fossa, which decreased the joint space and increased the compression within TMJ. The patients with asymmetry mandible suffered greater pressure within TMJ on the non-deviation side. The bilaterally over-developed and under-developed mandible in patients might also increase the compression within TMJ.

Influence of severe neck angulation on hemodynamic and clinical outcomes following endovascular aneurysm repair: a hemodynamic analysis and a retrospective cohort study.

BACKGROUND: For patients with severe neck angulation (SNA), hemodynamic and clinical outcomes following endovascular aneurysm repair (EVAR) are still unclear. This study aimed to explore the influence of SNA on hemodynamic and clinical outcomes following EVAR. METHODS: This study included a hemodynamic analysis and a retrospective cohort study from West China Hospital of Sichuan University between January 2011 and December 2020. The Cox regression model, inverse probability of treatment weighting (IPTW) analysis, sensitivity analysis, and subgroup analysis were applied. Primary outcome was type IA endoleak (T1AEL). RESULTS: In this hemodynamic analysis, nine non-severe neck angulation (nSNA) and 16 SNA idealized models were constructed. We found a significant difference in drag force between SNA and nSNA models (7.016 ±â€Š2.579 N vs. 4.283 ±â€Š1.460 N, P = 0.008), and proximal neck angles were significantly associated with the magnitude of drag force (F = 0.082 × α-0.006 ×â€Šß + 2.818, α: 95% confidence interval [CI] 0.070-0.094; P = 0.001; ß: 95% CI -0.019 to 0.007; P = 0.319). In our cohort study, 514 nSNA patients (71.5 ±â€Š8.5 years; 459 males) and 208 SNA patients (72.5 ±â€Š7.8 years; 135 males) were included, with a median follow-up duration of 34 months (16-63 months). All baseline characteristics were well balanced after IPTW matching. We found that SNA was associated with a significant risk of adverse limb event (hazard ratio [HR] 2.18, 95% CI 1.09-3.12), yet was not associated with T1AEL, overall survival, or reintervention. In patients without proximal or distal additional procedures (DAP), subgroup analyses suggested a significant risk of T1AEL (Proximal: HR 5.25, 95% CI 1.51-18.23; Distal: HR 5.07, 95% CI 1.60-16.07) and adverse limb event (Proximal: HR 2.27, 95% CI 1.01-5.07; Distal: HR 2.91, 95% CI 1.30-6.54) in SNA patients. However, no noticeable difference was observed in patients with proximal or DAP. CONCLUSIONS: SNA has a critical influence on hemodynamic and clinical outcomes following EVAR. Appropriate additional procedures may be of great benefit to SNA patients.

A novel potential mechanism for the development of portal vein thrombosis in cirrhosis based on portal hemodynamics.

BACKGROUND: Marked changes in hemodynamics have been suggested to be a potential contributing factor to portal vein thrombosis (PVT) development. This study investigated the effect of portal hemodynamics based on the anatomical structure of the portal venous system on PVT development. METHODS: The morphological features of portal venous system in patients with PVT and those without PVT subgroups were compared. In addition, idealized PV models were established to numerically evaluate the effect of the variation in the angulation of superior mesenteric vein (SMV) and splenic vein (SV) on the hemodynamics of portal venous system. RESULTS: The angle α (angulation of SMV and SV) in patients with PVT was lower than that in patients without PVT (p < 0.0001), which was the only independent risk factor (odds ratio (OR), 0.90 (95% CI 0.84-0.95); p < 0.0001) for the presence of PVT. With the change in angle α, the flow pattern of blood flow changed greatly, especially the helical flow. When α = 80°, helical flow only appeared at the local PV near the intersection of SMV and SV. When α = 120°, most regions were occupied by the helical flow. In addition, the h2 gradually increased with increasing α, when α = 80°, h2 = 12.6 m/s2; when α = 120°, h2 = 29.3 m/s2. CONCLUSIONS: The angulation of SV and SMV was closely associated with PVT development. Helical flow changed following the varying angulation of SV and SMV. Therefore, angulation of SV and SMV may help to identify high-risk cohorts for future PVT development earlier.

Fast and Accurate Computation of the Displacement Force of Stent Grafts after Endovascular Aneurysm Repair.

Purpose: Currently, the displacement force of stent grafts is generally obtained using computational fluid dynamics (CFD), which requires professional CFD knowledge to perform the correct simulation. This study proposes a fast, simple, and clinician-friendly approach to calculating the patient-specific displacement force after endovascular aneurysm repair (EVAR). Methods: Twenty patient-specific post-EVAR computed tomography angiography images were used to reconstruct the patient-specific three-dimensional models, then the displacement forces were calculated using CFD and the proposed approaches, respectively, and their numerical differences were compared and analyzed. Results: Based on the derivation and simplification of the momentum theorem, the patient-specific displacement forces were obtained using the information of the patient-specific pressure, cross-sectional area, and angulation of the two stent graft ends, and the average relative error was no greater than 1.37% when compared to the displacement forces calculated by CFD. In addition, the linear regression analysis also showed good agreement between the displacement force values calculated by the new approach and CFD (R = 0.999). Conclusions: The proposed approach can quickly and accurately calculate the patient-specific displacement force on a stent graft and can therefore help clinicians quickly evaluate the post-EVAR displacement force.

Computational hemodynamic analysis for optimal stent position in the transjugular intrahepatic portosystemic shunt procedure.

Transjugular intrahepatic portosystemic shunt (TIPS) is an effective treatment for portal hypertension (PH). The current study aimed to investigate the effect of stent position on post-TIPS hemodynamic performance using computational fluid dynamics. Patient-specific pre- and post-TIPS models were reconstructed from CT images of two patients, then virtual TIPS models were created by shifting the portal vein (PV) entry site of the stent. Although there were marginal differences the effects of left-sided and right-sided TIPS on post-TIPS portal pressure and shunting flow, right-sided TIPS resulted in a greater proportion of superior mesenteric vein (SMV) flow diverting to stents compared to that for left-sided TIPS. The results also demonstrated that the nearer the entry site of stent to the portal venous bifurcation, the greater and more stable the shunting blood flow. These results suggest that the entry site of the stent should be as close to the portal vein bifurcation as possible during TIPS. TIPS on the right branch of the portal vein may be more likely to result in post-TIPS hepatic encephalopathy than that on the left branch.

[Comparison of stent displacement and displacement force after endovascular aneurysm repair with cross-limb or parallel-limb stent].

This study aims to investigate whether displacement force on stents can accurately represents the displacement of the stent after endovascular aneurysm repair (EVAR) by comparing the measured stent displacement with the displacement forces calculated by computational fluid dynamics (CFD). And the effect of cross-limb and parallel-limb EVAR on stent displacements is further studied. Based on our objective, in this study, ten cross-limb EVAR patients and ten parallel-limb EVAR patients in West China Hospital of Sichuan University were enrolled. Patient-specific models were first reconstructed based on the computed tomography angiography images, then the stent displacements were measured, and the displacement forces acting on the stents were calculated by CFD. Finally, the cosα value of the angle between the displacement force and the displacement vector was used to analyze the matching degree between the displacement and the displacement force. The results showed that the displacement forces on cross-limb stents and parallel-limb stents were (2.67 ± 2.14) N and (1.36 ± 0.48) N, respectively. Displacements of stent gravity center, stent displacements relative to vessel, and vessel displacements of cross-limb and parallel-limb stents were (4.43 ± 2.81) mm and (6.39 ± 2.62) mm, (0.88 ± 0.67) mm and (1.11 ± 0.71) mm, (3.55 ± 2.88) mm and (5.28 ± 2.52) mm, respectively. The mean cosα for cross-limb and parallel-limb stents were 0.02 ± 0.66 and - 0.10 ± 0.73, respectively. This study indicates that the displacement force on the stent can't accurately represent the displacement of the stent after EVAR. In addition, the cross-limb EVAR is probably safer and more stable than the parallel-limb EVAR.

The effect of mandibular movement on temporomandibular joint morphology while eating French fries.

BACKGROUND: The preferred masticatory side was reported to be almost always the same as the affected side of the temporomandibular disorder. Unbalanced alterations of temporomandibular joint morphology were found to be associated with unilaterally masticatory habits. The aim of this study was to investigate the effect of the mandibular movement on the remodeling of temporomandibular joint during eating French fries using a 3D motion capture system. METHODS: Twelve volunteers with non-maxillofacial deformity and a healthy temporomandibular joint were recruited. The 3D models of the mandible and the maxilla were reconstructed according to computed tomography. The subjects were asked to eat French fries by unilaterally mastication, which was recorded by a 3D motion capture system. The trajectories of the incisors and the condyles and the condylar acceleration during unilateral mastication were analyzed. RESULTS: During incisal biting, there was no significant difference in the condylar trajectories between the left and right sides (P > 0.05). During unilateral mastication, the average displacement and acceleration of the masticatory condyles were significantly lower than those of the non-masticatory condyles (P < 0.05). The trajectory angles of the masticatory condyles were significantly steeper than those of the non-masticatory condyle (P < 0.05). During swallowing, there was no obvious movement of the mandible. CONCLUSIONS: Between both temporomandibular joints, unilateral mastication resulted in significant differences in the regions of the condylar movement within the articular fossa, and then caused different compressive regions of the temporomandibular joints. Thus, unilateral mastication might result in a significantly different pattern of temporomandibular joint remodeling between the two sides.

Effects of different bypass surgeries on LSA revascularization in patients with left subclavian occlusion.

INTRODUCTION: Left subclavian artery (LSA) bypass surgery is mainly carried out for patients with severe left subclavian occlusion. This article aimed to evaluate the hemodynamic effects of different surgical bypass modes on LSA revascularization. METHODS: Three-dimensional models of the aorta were reconstructed from CTA images of a patient with LSA occlusion, a patient with type B aortic dissection with LSA coverage during thoracic endovascular aortic repair, and a healthy 74-year-old man, resulting in six modes for each person: healthy LSA mode, LSA occlusion mode and four bypass modes. Hemodynamic parameters, including flow field, flow distribution, pressure gradient, and wall shear stress, were calculated using computational fluid dynamics. RESULTS: After LSA bypass surgery, distal LSA blood flow resulting from left common carotid artery (LCCA) to distal LSA bypass was 100% of that in the healthy mode, while the other modes yielded flows at least 91%. Moreover, reversed flow only completely disappeared with LCCA to distal LSA bypass, whereas reverse flow was observed in the other three modes in early systole. CONCLUSION: Left common carotid artery to distal LSA bypass can effectively reduce reverse blood flow in the left vertebral artery, and it is a feasible, effective, and safe option for LSA revascularization in patients with left subclavian occlusion.

A Hemodynamic Analysis of the Thrombosis Within Occluded Coronary Arterial Fistulas With Terminal Aneurysms Using a Blood Stasis Model.

Objective: The aim of this study is to numerically evaluate thrombosis risk within occluded coronary arterial fistulas (CAF) with terminal aneurysms, and provide guidance in choosing occlusion positions, with clinical observations as reference. Method: Four patients with CAF were studied, with different occlusion positions in actual treatments. Hemodynamics simulations were conducted, with blood residue predicted using the blood stasis model. Three types of models (untreated model, aneurysm-reserved model and aneurysm-removed model) were studeid for each patient. Four metrics, i.e., proportion of high oscillatory shear index (OSI), area of high OSI, old blood volume fraction (OBVF)) and old blood volume (OBV) was obtained to distinguish the thrombosis risk of different treatments (proximal or distal occlusion), comparing with the follow-up CTA. Results: For all the postopertive models, the high OBVF, high OSI(>0.3) and low time-averaged wall shear stress (TAWSS) regions were mainly at the distal fistula, indicating these regions were prone to thrombosis. The regions where blood residue remains are roughly regions of high OSI, corresponding well with clinical observations. In contrast, TAWSS failed to distinguish the difference in thrombosis risk. Absolute values (area of high OSI, OBV) can better reflect the degree of thrombosis risk between treatment types compared with percentage values (proportion of high OSI, OBVF). By comparing with the actual clinical treatments and observations, the OBV is superior to the area of high OSI in determining treatment type. Conclusion: The OBV, a volumetric parameter for blood stasis, can better account for the CAF thrombosis and reflect the degree of blood stasis compared with OSI or TAWSS, is a more appropriate metric for thrombosis in the fistula. Together with morphological parameters, the OBV could guide clinicians to formulate more appropriate surgical plans, which is of great significance for the preoperative evaluation and treatment prognosis of CAF patients.

In vivo biomechanical effects of maximal mouth opening on the temporomandibular joints and their relationship to morphology and kinematics.

The temporomandibular joints (TMJs) are the only joints in the human skull and regulate all mandibular motions. The functions of TMJs are considerably influenced by their biomechanical surroundings. However, owing to the unique characteristics of TMJs, comprehending their kinematic and biomechanical mechanisms remains challenging. As a result, understanding how biomechanics relate to TMJ structures and motions is critical in subsequent therapies. The goal of this study is to investigate any links between morphological or kinematic factors and discal stresses during mouth opening. Our study included eight asymptomatic participants who did not show any signs or symptoms of temporomandibular disorders. The morphological parameters, kinematic properties, and stresses were determined using computed tomography (CT), magnetic resonance imaging (MRI), and subject-specific movements. Following the investigation, we discovered that the opening of the mouth was not the primary cause of TMJ stress. The stress on the discs is directly linked to condylar displacements during mouth opening. Furthermore, morphological characteristics related to the relative position of the condyles in the glenoid fossa at the intercuspal position have a limited effect on condylar displacements and stresses. In conclusion, the morphological parameters, which are commonly employed in clinics, show only static conditions in the TMJs. The kinematic parameters provide dynamic information regarding the TMJs, which can be used in the examination, diagnosis, and treatment of TMJ diseases to reduce stress.

Association Between Blood Flow Pattern and Rupture Risk of Abdominal Aortic Aneurysm Based on Computational Fluid Dynamics.

OBJECTIVES: This study aimed to derive a novel classification of blood flow pattern in abdominal aortic aneurysms (AAA) based on computational fluid dynamics (CFDs), and to determine the predictive value of flow patterns in AAA rupture. METHODS: This was an age and sex matched case control study. Cases were identified as patients who underwent emergency endovascular or open repair due to ruptured or AAA at risk of impending rupture. Controls were age and sex matched with patients with an AAA who were asymptomatic and had a confirmed unruptured AAA from computed tomography angiography images from the same period. Classification of blood flow pattern (type I: non-helical main flow channel with multiple vortices; type II: non-helical main flow channel with single vortices; and type III, helical main flow channel with helical vortices) and haemodynamic parameters (areas of low wall shear stress [AlowWSS], aneurysm pressure drop [Δ pressure], etc) were derived from CFD analyses. Multivariable regression was used to determine independent AAA rupture risk factors. The incremental discriminant and reclassification abilities for AAA rupture were compared among different models. RESULTS: Fifty-three ruptured and 53 intact AAA patients were included. Ruptured AAA showed a higher prevalence of type III flow pattern than intact AAA (60.4% vs. 15.1%; p < .001). Type III flow pattern was associated with a significantly increased risk of aneurysm rupture (odds ratio 10.22, 95% confidence interval 3.43 - 30.49). Among all predicting models, the combination of AAA diameter, haemodynamic parameters (AlowWSS or Δ pressure), and flow pattern showed highest discriminant abilities in both the overall population (c-index = 0.862) and subgroup patients with AAAs < 55 mm (c-index = 0.972). Compared with AAA diameter, adding the flow pattern could significantly improve the reclassification abilities in both the overall population (net reclassification index [NRI] = 0.321; p < .001) and the subgroup of AAAs < 55 mm (NRI = 0.732; p < .001). CONCLUSION: Type III flow pattern was associated with a significantly increased risk of AAA rupture. The integration of blood flow pattern may improve the identification of high risk aneurysms in both overall population and in those with AAAs < 55 mm.