Surgically relevant aortic arch mapping using computed tomography

Development of idealized human aortic models for in vitro and in silico hemodynamic studies

Background

The aorta, a central component of the cardiovascular system, plays a pivotal role in ensuring blood circulation. Despite its importance, there is a notable lack of idealized models for experimental and computational studies.

Objective

This study aims to develop computer-aided design (CAD) models for the idealized human aorta, intended for studying hemodynamics or solid mechanics in both in vitro and in silico settings.

Methods

Various parameters were extracted from comprehensive literature sources to evaluate major anatomical characteristics of the aorta in healthy adults, including variations in aortic arch branches and corresponding dimensions. The idealized models were generated based on averages weighted by the cohort size of each study for several morphological parameters collected and compiled from image-based or cadaveric studies, as well as data from four recruited subjects. The models were used for hemodynamics assessment using particle image velocimetry (PIV) measurements and computational fluid dynamics (CFD) simulations.

Results

Two CAD models for the idealized human aorta were developed, focusing on the healthy population. The CFD simulations, which align closely with the PIV measurements, capture the main global flow features and wall shear stress patterns observed in patient-specific cases, demonstrating the capabilities of the designed models.

Conclusions

The collected statistical data on the aorta and the two idealized aorta models, covering prevalent arch variants known as Normal and Bovine types, are shown to be useful for examining the hemodynamics of the aorta. They also hold promise for applications in designing medical devices where anatomical statistics are needed.

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.

Exploration of Simplified Intraluminal TEVAR Technique for the Treatment of Aortic Arch Disease

Objective:

The positional relationship between the three branches of the aortic arch was determined in normal people. This study provides data to support the customization of aortic arch stents and simplifies intraluminal treatment.

Methods:

From January 2019 to August 2019, 120 patients who met the inclusion criteria were examined by CT angiography. The ratio of the distance from the midpoint of the three-branch opening onto the anterior wall to the cross-sectional diameter of the aortic arch was calculated. The positional relationship among the three-branch openings was obtained and the data were analyzed statistically.

Results:

The three-branch openings were not in a straight line. The positional relationship among the three-branch openings was divided into four types, which were not statistically different between sex and age (P>0.05).

Conclusion:

By measuring the opening position of the three aortic branches, the positional relationship among the three branches was defined to provide a theoretical basis for the design of intraluminal stents and simplified intracavity thoracic endovascular aortic repair (TEVAR) technology.

The Position Relationship Between the Opening of the Three Branches of the Aortic Arch and the Aortic Arch Axis in Normal People

BACKGROUND

Due to the anatomical variability of the three branches of the aortic arch, interventional treatment of arch diseases becomes difficult. The aim of this study was to assess the position of three branches of the aortic arch in normal people and to provide reference data for the customization of aortic arch stents and simplified intraluminal treatment.

METHODS

A total of 120 patients who underwent computed tomography angiography examination of thoracic aorta in our institution were enrolled as per a set of inclusion and exclusion criteria from January 2018 to December 2018. Measurements were carried out using GEAW 4.6 workstation. The parameters recorded were the ratio of the distance from the point where the aortic branch opening intersects the aortic arch to the anterior wall of the aorta to the cross-sectional diameter of the aortic arch. Finally, the position relationship among the three branch openings was determined.

RESULTS

The position relationship among the three branches openings is divided into three categories. Type I: Two of the branch openings are completely surrounded by the boundary of the other branch. Type II: There is no inclusion relationship between the three branch openings. Type III: One branch opening is surrounded by the boundary of the other branch. In type I, there were 23 cases (19.2%); in type II, 37 cases (30.8%); and in type III, 60 cases (50%). These three position relationships were not significantly different between sexes and different ages (P > 0.05). These data were used to design a possible stent model.

CONCLUSIONS

This study reveals that the position of three aortic branches exhibits distinct patterns divided into 3 types. Based on measurements of the opening position of the three branches, the position relationship between the 3 branches can be obtained to provide a theoretical basis for the design of intraluminal stents and application of the simplified intracavity thoracic endovascular aneurysm repair technology.

The Role of Dual-Source Computed Tomography Angiography in Evaluating the Aortic Arch Vessels in Acute Type A Aortic Dissection: A Retrospective Study of 42 Patients

Background

This study aimed to investigate the role of dual-source computed tomography angiography (DSCTA) to evaluate the anatomy of the aortic arch vessels in patients with acute Type A aortic dissection (AD).

Material/Methods

A retrospective clinical study included 42 patients with acute Type A AD who underwent DSCTA and were treated in our hospital between January 2018 and December 2018. The findings were compared with a control group of 45 healthy individuals with hypertension and without aortic arch lesions.

Results

The diagnostic accuracy of DSCTA in patients with acute Type A AD was almost 100%. The innominate artery was most frequently affected. The mean DSCTA imaging measurements for the root of the innominate artery, the left common carotid artery, and the left subclavian artery, in the coronal plane of the aortic arch, were 17.7±3.7 mm, 17.7±3.7 mm, and 12.9±3.1 mm, respectively. The angles formed by the origin of the three aortic arch branches vessels and the aortic arch were 70.5±10.2°, 58.5±15.5°, and 90.2±22.7°, respectively. In the transverse plane of the aortic arch, the mean angles were 110.5±22.3°, 100.3±15.2°, and 95.4±10.6°, respectively. These DSCTA imaging findings were significantly different in the patient group compared with the control group.

Conclusions

DCTA demonstrated that patients with Type A AD showed anatomic differences in the aortic arch vessels. These findings may help surgeons to develop treatment strategies and select the most appropriate vascular grafts and stents.

A simple patient-tailored aortic arch tangential angle measuring method to achieve better clinical results for thoracic endovascular repair of type B aortic dissection

Background

To report a simple individual tailored aortic arch tangential angle (θ-AATA) measuring method and its clinical application efficacy in the endovascular treatment of type B aortic dissection (AD).

Methods

From January 2013 to December 2014, acute type B AD patients were prospectively enrolled and treated with endovascular therapy in our center. Among these patients, a specific method was applied to measure θ-AATA based on the axial images of the CT scan. The length of proximal landing zone (PLZ) of each patient was measured at the routinely applied left-anterior oblique (LAO) 45-degree and θ-AATA. Respective treatment strategies based on the length of the PLZ were planned accordingly, and the stent-graft was deployed under the fluoroscopy at θ-AATA. The occurrence of immediate type I endoleak was recorded during the completion angiogram, while the alignment of the proximal marks was determined under fluoroscopy at θ-AATA and at LAO-45-degree as well.

Results

Totally 76 patients with type B AD were prospectively enrolled. The average value of θ-AATA was 58.3±5.2 degrees, which was significantly larger than the routine 45 degrees (P<0.01). The mean landing zone length measured under θ-AATA (18.4±3.9 mm) was longer than that (15.9±3.1 mm) obtained at the routine LAO-45 degrees (P<0.05). Stent-grafts' deployment strategies were substantially changed accordingly. Alignment of the proximal marks was achieved in 72 patients (93.4%) under θ-AATA and only in two patients (2.7%) at LAO-45 degrees (P<0.01). All stent-grafts' implantation was successfully completed. No major type I endoleak was found in the immediate post-deployment angiography.

Conclusions

It is easy to apply this patient-tailored θ-AATA measuring method in clinical practice. This more precise measurement is benefit for more reasonable treatment strategy planning, more precise deployment, and therefore a better outcome.

Design and Experimental Validation of an Active Catheter for Endovascular Navigation

Endovascular techniques have many advantages but rely strongly on operator skills and experience. Robotically steerable catheters have been developed but few are clinically available. We describe here the development of an active and efficient catheter based on shape memory alloys (SMA) actuators. We first established the specifications of our device considering anatomical constraints. We then present a new method for building active SMA-based catheters. The proposed method relies on the use of a core body made of three parallel metallic beams and integrates wire-shaped SMA actuators. The complete device is encapsulated into a standard 6F catheter for safety purposes. A trial-and-error campaign comparing 70 different prototypes was conducted to determine the best dimensions of the core structure and of the SMA actuators with respect to the imposed specifications. The final prototype was tested on a silicon-based arterial model and on a 23 kg pig. During these experiments, we were able to cannulate the supra-aortic trunks and the renal arteries with different angulations and without any complication. A second major contribution of this paper is the derivation of a reliable mathematical model for predicting the bending angle of our active catheters. We first use this model to state some general qualitative rules useful for an iterative dimensional optimization. We then perform a quantitative comparison between the actual and the predicted bending angles for a set of 13 different prototypes. The relative error is less than 20% for bending angles between 100 deg and 150 deg, which is the interval of interest for our applications.

The path to personalized vascular therapy - We are closer than we think

The terms "personalized" or "precision" medicine are being used commonly in some branches of medicine but have yet to be widely adopted in vascular surgery. Despite this, personalized vascular therapy occurs on a daily basis in every vascular specialist's office as we strive to make informed recommendations at the individual patient level. The following is a description of several of the areas where advances in personalized vascular care have been achieved, including custom devices, personalized predictions, pharmacogenetics and surgicogenetics.

Current state in tracking and robotic navigation systems for application in endovascular aortic aneurysm repair

OBJECTIVE

This study reviewed the current developments in manual tracking and robotic navigation technologies for application in endovascular aortic aneurysm repair (EVAR).

METHODS

EMBASE and MEDLINE databases were searched for studies reporting manual tracking or robotic navigation systems that are able to manipulate endovascular surgical tools during abdominal or thoracic aortic aneurysm repair. Reports were grouped by the navigation systems and categorized into phantom, animal, and clinical studies. First, the general characteristics of each system were compared. Second, target registration error and deployment error were used to compare the accuracy of the tracking systems. Third, all systems were reviewed for fluoroscopy time (FT), radiation dose, and contrast volumes, if reported, in rigid and nonrigid studies. Fourth, vascular cannulation performance of the systems was compared, studying cannulation time, Imperial College Complex Cannulation Scoring Tool score, and the number of wall hits and catheter movements within rigid studies.

RESULTS

Of 721 articles and references found, 18 studies of four different navigation systems were included: the Aurora (Northern Digital, Waterloo, Ontario, Canada) tracking system, the StealthStation (Medtronic Inc, Minneapolis, Minn) tracking system, an ultrasound localization tracking system, and the Sensei (Hansen Medical, Mountain View, Calif) steerable remote-controlled robotic navigation system. The mean tracking accuracy averaged 1 mm for the three manual tracking systems measured in a rigid environment. An increase of target registration error reaching >3 mm was reported when measured in a nonrigid experimental environment or due to external distortion factors. Except within small-animal studies or case studies, no evidence was found on reduction of clinical outcome parameters, such as FT, radiation dose, and contrast volumes, within clinical EVAR. A comparison of vascular cannulation performance in rigid studies revealed that the Sensei robotic system might have an advantage during advanced cannulation compared with standard cannulation within complex cannulations tasks.

CONCLUSIONS

This review summarizes the current studies on manual tracking and robotic navigation systems for application in EVAR. The main focus of these systems is improving aortic vessel cannulation, required in complex EVAR, in which the robotic system with the improved steerability is favored over manual tracking systems or conventional cannulation. All reviewed tracking systems still require X-ray for anatomic imaging, stent graft deployment, and device registration. Although the current reviewed endovascular navigation systems have shown their potential in phantom and animal studies, clinical trials are too limited to conclude that these systems can improve EVAR outcomes or that they can systematically reduce FTs, radiation doses, and contrast volumes during (complex) EVAR.