Pre-procedural fit-testing of TAVR valves using parametric modeling and 3D printing

AI-Powered Multimodal Modeling of Personalized Hemodynamics in Aortic Stenosis

Aortic stenosis (AS) is the most common valvular heart disease in developed countries. High-fidelity preclinical models can improve AS management by enabling therapeutic innovation, early diagnosis, and tailored treatment planning. However, their use is currently limited by complex workflows necessitating lengthy expert-driven manual operations. Here, we propose an AI-powered computational framework for accelerated and democratized patient-specific modeling of AS hemodynamics from computed tomography (CT). First, we demonstrate that the automated meshing algorithms can generate task-ready geometries for both computational and benchtop simulations with higher accuracy and 100 times faster than existing approaches. Then, we show that the approach can be integrated with fluid-structure interaction and soft robotics models to accurately recapitulate a broad spectrum of clinical hemodynamic measurements of diverse AS patients. The efficiency and reliability of these algorithms make them an ideal complementary tool for personalized high-fidelity modeling of AS biomechanics, hemodynamics, and treatment planning.

Analysis of Fluid-Structure Interaction Mechanisms for a Native Aortic Valve, Patient-Specific Ozaki Procedure, and a Bioprosthetic Valve

The Ozaki procedure is a surgical technique which avoids to implant foreign aortic valve prostheses in human heart, using the patient's own pericardium. Although this approach has well-identified benefits, it is still a topic of debate in the cardiac surgical community, which prevents its larger use to treat valve pathologies. This is linked to the actual lack of knowledge regarding the dynamics of tissue deformations and surrounding blood flow for this autograft pericardial valve. So far, there is no numerical study examining the coupling between the blood flow characteristics and the Ozaki leaflets dynamics. To fill this gap, we propose here a comprehensive comparison of various performance criteria between a healthy native valve, its pericardium-based counterpart, and a bioprosthetic solution, this is done using a three-dimensional fluid-structure interaction solver. Our findings reveal similar physiological dynamics between the valves but with the emergence of fluttering for the Ozaki leaflets and higher velocity and wall shear stress for the bioprosthetic heart valve.

Dimensional Accuracy in 3D Printed Medical Models: A Follow-Up Study on SLA and SLS Technology

Background: With the rise of new 3D printers, assessing accuracy is crucial for obtaining the best results in patient care. Previous studies have shown that the highest accuracy is achieved with SLS printing technology; however, SLA printing technology has made significant improvements in recent years. Methods: In this study, a realistic anatomical model of a mandible and skull, a cutting guide for mandibular osteotomy, and a splint for orthognathic surgery were replicated five times each using two different 3D printing technologies: SLA and SLS. Results: The SLA group had a median trueness RMS value of 0.148 mm and a precision RMS value of 0.117 mm. The SLS group had a median trueness RMS value of 0.144 mm and a precision RMS value of 0.096 mm. There was no statistically significant difference in RMS values between SLS and SLA technologies regarding trueness. Regarding precision, however, the RMS values for SLS technology were significantly lower in the splint and cutting guide applications than those printed with SLA technology. Conclusions: Both 3D printing technologies produce modern models and applications with equally high dimensional accuracy. Considering current cost pressures experienced by hospitals, the lower-cost SLA 3D printer is a reliable choice for point-of-care 3D printing.

Three-dimensional modelling of aortic leaflet coaptation and load-bearing surfaces: in silico design of aortic valve neocuspidizations

OBJECTIVES

Three-dimensional (3D) modelling of aortic leaflets remains difficult due to insufficient resolution of medical imaging. We aimed to model the coaptation and load-bearing surfaces of the aortic leaflets and adapt this workflow to aid in the design of aortic valve neocuspidizations.

METHODS

Geometric morphometrics, using landmarks and semilandmarks, was applied to the geometric determinants of the aortic leaflets from computed tomography, followed by an isogeometric analysis using Non-Uniform Rational Basis Splines (NURBS). Ten aortic valve models were generated, measuring determinants of leaflet geometry defined as 3D NURBS curves, and leaflet coaptation and load-bearing surfaces were defined as 3D NURBS surfaces. Neocuspidizations were obtained by either shifting the upper central coaptation landmark towards the sinotubular junction or using parametric neo-landmarks placed on a centreline drawn between the centroid of the aortic root base and centroid of a circle circumscribing the 3 upper commissural landmarks.

RESULTS

The ratio of the leaflet free margin length to the geometric height was 1.83, whereas the ratio of the commissural coaptation height to the central coaptation height was 1.93. The median coaptation surface was 137 mm2 (IQR 58) and the median load-bearing surface was 203 mm2 (60) per leaflet. Neocuspidization multiplied the central coaptation height by 3.7 and the coaptation surfaces by 1.97 and 1.92 using the native coaptation axis and centroid coaptation axis, respectively.

CONCLUSIONS

Geometric morphometrics reliably defined the coaptation and load-bearing surfaces of aortic leaflets, enabling an experimental 3D design for the in silico neocuspidization of aortic valves.

Development and validation of 3-dimensional simulators for penile prosthesis surgery

BACKGROUND

The acquisition of skills in penile prosthesis surgery has many limitations mainly due to the absence of simulators and models for training. Three-dimensional (3D) printed models can be utilized for surgical simulations, as they provide an opportunity to practice before entering the operating room and provide better understanding of the surgical approach.

AIM

This study aimed to evaluate and validate a 3D model of human male genitalia for penile prosthesis surgery.

METHODS

This study included 3 evaluation and validation stages. The first stage involved verification of the 3D prototype model for anatomic landmarks compared with a cadaveric pelvis. The second stage involved validation of the improved model for anatomic accuracy and teaching purposes with the Rochester evaluation score. The third stage comprised validation of the suitability of the 3D prototype model as a surgical simulator and for skill acquisition. The third stage was performed at 3 centers using a modified version of a pre-existing, validated questionnaire and correlated with the Rochester evaluation score.

OUTCOME

We sought to determine the suitability of 3D model for training in penile prosthesis surgery in comparison with the available cadaveric model.

RESULTS

The evaluation revealed a high Pearson correlation coefficient (0.86) between questions of the Rochester evaluation score and modified validated questionnaire. The 3D model scored 4.33 ± 0.57 (on a Likert scale from 1 to 5) regarding replication of the relevant human anatomy for the penile prosthesis surgery procedure. The 3D model scored 4.33 ± 0.57 (on a Likert scale from 1 to 5) regarding its ability to improve technical skills, teach and practice the procedure, and assess a surgeon's ability. Furthermore, the experts stated that compared with the cadaver, the 3D model presented greater ethical suitability, reduced costs, and easier accessibility.

CLINICAL IMPLICATIONS

A validated 3D model is a suitable alternative for penile prosthesis surgery training.

STRENGTHS AND LIMITATIONS

This is the first validated 3D hydrogel model for penile prosthesis surgery teaching and training that experts consider suitable for skill acquisition. Because specific validated guidelines and questionnaires for the validation and verifications of 3D simulators for penile surgery are not available, a modified questionnaire was used.

CONCLUSION

The current 3D model for penile prosthesis surgery shows promising results regarding anatomic properties and suitability to train surgeons to perform penile implant surgery. The possibility of having an ethical, easy-to-use model with lower costs and limited consequences for the environment is encouraging for further development of the models.

The Application of Precision Medicine in Structural Heart Diseases: A Step towards the Future

The personalized applications of 3D printing in interventional cardiology and cardiac surgery represent a transformative paradigm in the management of structural heart diseases. This review underscores the pivotal role of 3D printing in enhancing procedural precision, from preoperative planning to procedural simulation, particularly in valvular heart diseases, such as aortic stenosis and mitral regurgitation. The ability to create patient-specific models contributes significantly to predicting and preventing complications like paravalvular leakage, ensuring optimal device selection, and improving outcomes. Additionally, 3D printing extends its impact beyond valvular diseases to tricuspid regurgitation and non-valvular structural heart conditions. The comprehensive synthesis of the existing literature presented here emphasizes the promising trajectory of individualized approaches facilitated by 3D printing, promising a future where tailored interventions based on precise anatomical considerations become standard practice in cardiovascular care.

Feasibility of 3-dimensional printed models in simulated training and teaching of transcatheter aortic valve replacement

In the study of TAVR, 3-dimensional (3D) printed aortic root models and pulsatile simulators were used for simulation training and teaching before procedures. The study was carried out in the following three parts: (1) experts were selected and equally divided into the 3D-printed simulation group and the non-3D-printed simulation group to conduct four times of TAVR, respectively; (2) another 10 experts and 10 young proceduralists were selected to accomplish three times of TAVR simulations; (3) overall, all the doctors were organized to complete a specific questionnaire, to evaluate the training and teaching effect of 3D printed simulations. For the 3D-printed simulation group, six proceduralists had a less crossing-valve time (8.3 ± 2.1 min vs 11.8 ± 2.7 min, P < 0.001) and total operation time (102.7 ± 15.3 min vs 137.7 ± 15.4 min, P < 0.001). In addition, the results showed that the median crossing-valve time and the total time required were significantly reduced in both the expert group and the young proceduralist group (all P<0.001). The results of the questionnaire showed that 3D-printed simulation training could enhance the understanding of anatomical structure and improve technical skills. Overall, cardiovascular 3D printing may play an important role in assisting TAVR, which can shorten the operation time and reduce potential complications.

3D Printing for Cardiovascular Surgery and Intervention: A Review Article

3D printing technology can be applied to practically every aspect of modern life, fulfilling the needs of people from various backgrounds. The utilization of 3D printing in the context of adult heart disease can be succinctly categorized into 3 primary domains: preoperative strategizing or simulation, medical instruction, and clinical consultations. 3D-printed model utilization improves surgical planning and intraoperative decision-making and minimizes surgical risks, and it has demonstrated its efficacy as an innovative educational tool for aspiring surgeons with limited practical exposure. Despite all the applications of 3D printing, it has not yet been shown to improve long-term outcomes, including safety. There are no data on the outcomes of controlled trials available. To appropriately diagnose heart disease, 3D-printed models of the heart can provide a better understanding of the intracardiac anatomy and provide all the information needed for operative planning. Experientially, 3D printing provides a wide range of perceptions for understanding lower extremity arteries' spatial geometry and anatomical features of pathology. Practicing cardiac surgery processes using objects printed using 3D imaging data can become the norm rather than the exception, leading to improved accuracy and quality of treatment. This study aimed to review the various applications of 3D printing technology in cardiac surgery and intervention.

Shaping the Future of Cardiovascular Disease by 3D Printing Applications in Stent Technology and its Clinical Outcomes

Cardiovascular disease (CVD) is a leading cause of death worldwide. In recent years, 3D printing technology has ushered in a new era of innovation in cardiovascular medicine. 3D printing in CVD management encompasses various aspects, from patient-specific models and preoperative planning to customized medical devices and novel therapeutic approaches. In-stent technology, 3D printing has revolutionized the design and fabrication of intravascular stents, offering tailored solutions for complex anatomies and individualized patient needs. The advantages of 3D-printed stents, such as improved biocompatibility, enhanced mechanical properties, and reduced risk of in-stent restenosis. Moreover, the clinical trials and case studies that shed light on the potential of 3D printing technology to improve patient outcomes and revolutionize the field has been comprehensively discussed. Furthermore, regulatory considerations, and challenges in implementing 3D-printed stents in clinical practice are also addressed, underscoring the need for standardization and quality assurance to ensure patient safety and device reliability. This review highlights a comprehensive resource for clinicians, researchers, and policymakers seeking to harness the full potential of 3D printing technology in the fight against CVD.

Generation of synthetic aortic valve stenosis geometries for in silico trials

In silico trials are a promising way to increase the efficiency of the development, and the time to market of cardiovascular implantable devices. The development of transcatheter aortic valve implantation (TAVI) devices, could benefit from in silico trials to overcome frequently occurring complications such as paravalvular leakage and conduction problems. To be able to perform in silico TAVI trials virtual cohorts of TAVI patients are required. In a virtual cohort, individual patients are represented by computer models that usually require patient-specific aortic valve geometries. This study aimed to develop a virtual cohort generator that generates anatomically plausible, synthetic aortic valve stenosis geometries for in silico TAVI trials and allows for the selection of specific anatomical features that influence the occurrence of complications. To build the generator, a combination of non-parametrical statistical shape modeling and sampling from a copula distribution was used. The developed virtual cohort generator successfully generated synthetic aortic valve stenosis geometries that are comparable with a real cohort, and therefore, are considered as being anatomically plausible. Furthermore, we were able to select specific anatomical features with a sensitivity of around 90%. The virtual cohort generator has the potential to be used by TAVI manufacturers to test their devices. Future work will involve including calcifications to the synthetic geometries, and applying high-fidelity fluid-structure-interaction models to perform in silico trials.

A Systematic Analysis of Additive Manufacturing Techniques in the Bioengineering of In Vitro Cardiovascular Models

Additive Manufacturing is noted for ease of product customization and short production run cost-effectiveness. As our global population approaches 8 billion, additive manufacturing has a future in maintaining and improving average human life expectancy for the same reasons that it has advantaged general manufacturing. In recent years, additive manufacturing has been applied to tissue engineering, regenerative medicine, and drug delivery. Additive Manufacturing combined with tissue engineering and biocompatibility studies offers future opportunities for various complex cardiovascular implants and surgeries. This paper is a comprehensive overview of current technological advancements in additive manufacturing with potential for cardiovascular application. The current limitations and prospects of the technology for cardiovascular applications are explored and evaluated.

CardioVision: A fully automated deep learning package for medical image segmentation and reconstruction generating digital twins for patients with aortic stenosis

Aortic stenosis (AS) is the most prevalent heart valve disease in western countries that poses a significant public health challenge due to the lack of a medical treatment to prevent valve calcification. Given the aging population demographic, the prevalence of AS is projected to rise, resulting in a progressively significant healthcare and economic burden. While surgical aortic valve replacement (SAVR) has been the gold standard approach, the less invasive transcatheter aortic valve replacement (TAVR) is poised to become the dominant method for high- and medium-risk interventions. Computational simulations using patient-specific models, have opened new research avenues for optimizing emerging devices and predicting clinical outcomes. The traditional techniques of generating digital replicas of patients' aortic root, native valve, and calcification are time-consuming and labor-intensive processes requiring specialized tools and expertise in anatomy. Alternatively, deep learning models, such as the U-Net architecture, have emerged as reliable and fully automated methods for medical image segmentation. Two-dimensional U-Nets have been shown to produce comparable or more accurate results than trained clinicians' manual segmentation while significantly reducing computational costs. In this study, we have developed a fully automatic AI tool capable of reconstructing the digital twin geometry and analyzing the calcification distribution on the aortic valve. The developed automatic segmentation package enables the modeling of patient-specific anatomies, which can then be used to simulate virtual interventional procedures, optimize emerging prosthetic devices, and predict clinical outcomes.

Soft robotic patient-specific hydrodynamic model of aortic stenosis and ventricular remodeling

Aortic stenosis (AS) affects about 1.5 million people in the United States and is associated with a 5-year survival rate of 20% if untreated. In these patients, aortic valve replacement is performed to restore adequate hemodynamics and alleviate symptoms. The development of next-generation prosthetic aortic valves seeks to provide enhanced hemodynamic performance, durability, and long-term safety, emphasizing the need for high-fidelity testing platforms for these devices. We propose a soft robotic model that recapitulates patient-specific hemodynamics of AS and secondary ventricular remodeling which we validated against clinical data. The model leverages 3D-printed replicas of each patient's cardiac anatomy and patient-specific soft robotic sleeves to recreate the patients' hemodynamics. An aortic sleeve allows mimicry of AS lesions due to degenerative or congenital disease, whereas a left ventricular sleeve recapitulates loss of ventricular compliance and diastolic dysfunction (DD) associated with AS. Through a combination of echocardiographic and catheterization techniques, this system is shown to recreate clinical metrics of AS with greater controllability compared with methods based on image-guided aortic root reconstruction and parameters of cardiac function that rigid systems fail to mimic physiologically. Last, we leverage this model to evaluate the hemodynamic benefit of transcatheter aortic valves in a subset of patients with diverse anatomies, etiologies, and disease states. Through the development of a high-fidelity model of AS and DD, this work demonstrates the use of soft robotics to recreate cardiovascular disease, with potential applications in device development, procedural planning, and outcome prediction in industrial and clinical settings.

Advanced 3D Visualization and 3D Printing in Radiology

Since the discovery of X-rays in 1895, medical imaging systems have played a crucial role in medicine by permitting the visualization of internal structures and understanding the function of organ systems. Traditional imaging modalities including Computed Tomography (CT), Magnetic Resonance Imaging (MRI) and Ultrasound (US) present fixed two-dimensional (2D) images which are difficult to conceptualize complex anatomy. Advanced volumetric medical imaging allows for three-dimensional (3D) image post-processing and image segmentation to be performed, enabling the creation of 3D volume renderings and enhanced visualization of pertinent anatomic structures in 3D. Furthermore, 3D imaging is used to generate 3D printed models and extended reality (augmented reality and virtual reality) models. A 3D image translates medical imaging information into a visual story rendering complex data and abstract ideas into an easily understood and tangible concept. Clinicians use 3D models to comprehend complex anatomical structures and to plan and guide surgical interventions more precisely. This chapter will review the volumetric radiological techniques that are commonly utilized for advanced 3D visualization. It will also provide examples of 3D printing and extended reality technology applications in radiology and describe the positive impact of advanced radiological image visualization on patient care.

Application of cardiovascular 3-dimensional printing in Transcatheter aortic valve replacement

Transcatheter aortic valve replacement (TAVR) has been performed for nearly 20 years, with reliable safety and efficacy in moderate- to high-risk patients with aortic stenosis or regurgitation, with the advantage of less trauma and better prognosis than traditional open surgery. However, because surgeons have not been able to obtain a full view of the aortic root, 3-dimensional printing has been used to reconstruct the aortic root so that they could clearly and intuitively understand the specific anatomical structure. In addition, the 3D printed model has been used for the in vitro simulation of the planned procedures to predict the potential complications of TAVR, the goal being to provide guidance to reasonably plan the procedure to achieve the best outcome. Postprocedural 3D printing can be used to understand the depth, shape, and distribution of the stent. Cardiovascular 3D printing has achieved remarkable results in TAVR and has a great potential.

The application of 3D printing in preoperative planning for transcatheter aortic valve replacement: a systematic review

BACKGROUND

Recently, transcatheter aortic valve replacement (TAVR) has been suggested as a less invasive treatment compared to surgical aortic valve replacement, for patients with severe aortic stenosis. Despite the attention, persisting evidence suggests that several procedural complications are more prevalent with the transcatheter approach. Consequently, a systematic review was undertaken to evaluate the application of three-dimensional (3D) printing in preoperative planning for TAVR, as a means of predicting and subsequently, reducing the incidence of adverse events.

METHODS

MEDLINE, Web of Science and Embase were searched to identify studies that utilised patient-specific 3D printed models to predict or mitigate the risk of procedural complications.

RESULTS

13 of 219 papers met the inclusion criteria of this review. The eligible studies have shown that 3D printing has most commonly been used to predict the occurrence and severity of paravalvular regurgitation, with relatively high accuracy. Studies have also explored the usefulness of 3D printed anatomical models in reducing the incidence of coronary artery obstruction, new-onset conduction disturbance and aortic annular rapture.

CONCLUSION

Patient-specific 3D models can be used in pre-procedural planning for challenging cases, to help deliver personalised treatment. However, the application of 3D printing is not recommended for routine clinical practice, due to practicality issues.

Imaging-Based, Patient-Specific Three-Dimensional Printing to Plan, Train, and Guide Cardiovascular Interventions: A Systematic Review and Meta-Analysis

BACKGROUND

To tailor cardiovascular interventions, the use of three-dimensional (3D), patient-specific phantoms (3DPSP) encompasses patient education, training, simulation, procedure planning, and outcome-prediction.

AIM

This systematic review and meta-analysis aims to investigate the current and future perspective of 3D printing for cardiovascular interventions.

METHODS

We systematically screened articles on Medline and EMBASE reporting the prospective use of 3DPSP in cardiovascular interventions by using combined search terms. Studies that compared intervention time depending on 3DPSP utilisation were included into a meta-analysis.

RESULTS

We identified 107 studies that prospectively investigated a total of 814 3DPSP in cardiovascular interventions. Most common settings were congenital heart disease (CHD) (38 articles, 6 comparative studies), left atrial appendage (LAA) occlusion (11 articles, 5 comparative, 1 randomised controlled trial [RCT]), and aortic disease (10 articles). All authors described 3DPSP as helpful in assessing complex anatomic conditions, whereas poor tissue mimicry and the non-consideration of physiological properties were cited as limitations. Compared to controls, meta-analysis of six studies showed a significant reduction of intervention time in LAA occlusion (n=3 studies), and surgery due to CHD (n=3) if 3DPSPs were used (Cohen's d=0.54; 95% confidence interval, 0.13 to 0.95; p=0.001), however heterogeneity across studies should be taken into account.

CONCLUSIONS

3DPSP are helpful to plan, train, and guide interventions in patients with complex cardiovascular anatomy. Benefits for patients include reduced intervention time with the potential for lower radiation exposure and shorter mechanical ventilation times. More evidence and RCTs including clinical endpoints are needed to warrant adoption of 3DPSP into routine clinical practice.

Mitral Valve-in-Valve Implant of a Balloon-Expandable Valve Guided by 3-Dimensional Printing

Background

Our goal was to explore the role of 3-dimensional (3D) printing in facilitating the outcome of a mitral valve-in-valve (V-in-V) implant of a balloon-expandable valve.

Methods

From November 2020 to April 2021, 6 patients with degenerated mitral valves were treated by a transcatheter mitral V-in-V implant of a balloon-expandable valve. 3D printed mitral valve pre- and post-procedure models were prepared to facilitate the process by making individualized plans and evaluating the outcomes.

Results

Each of the 6 patients was successfully implanted with a balloon-expandable valve. From post-procedural images and the 3D printed models, we could clearly observe the valve at the ideal position, with the proper shape and no regurgitation. 3D printed mitral valve models contributed to precise decisions, the avoidance of complications, and the valuation of outcomes.

Conclusions

3D printing plays an important role in guiding the transcatheter mitral V-in-V implant of a balloon-expandable valve.

Clinical Trial Registration

ClinicalTrials.gov Protocol Registration System (NCT02917980).

An impact of three dimensional techniques in virtual reality

Three dimensional (3D) imaging play a prominent role in the diagnosis, treatment planning, and post-therapeutic monitoring of patients with Rheumatic Heart Disease (RHD) or mitral valve disease. More interactive and realistic medical experiences take an advantage of advanced visualization techniques like augmented, mixed, and virtual reality to analyze the 3D models. Further, 3D printed mitral valve model is being used in medical field. All these technologies improve the understanding of the complex morphologies of mitral valve disease. Real-time 3D Echocardiography has attracted much more attention in medical researches because it provides interactive feedback to acquire high-quality images as well as timely spatial information of the scanned area and hence is necessary for intraoperative ultrasound examinations. In this article, three dimensional techniques and its impacts in mitral valve disease are reviewed. Specifically, the data acquisition techniques, reconstruction algorithms with clinical applications are presented. Moreover, the advantages and disadvantages of state-of-the-art approaches are discussed in detail.

Automatic Aortic Valve Cusps Segmentation from CT Images Based on the Cascading Multiple Deep Neural Networks

Accurate morphological information on aortic valve cusps is critical in treatment planning. Image segmentation is necessary to acquire this information, but manual segmentation is tedious and time consuming. In this paper, we propose a fully automatic aortic valve cusps segmentation method from CT images by combining two deep neural networks, spatial configuration-Net for detecting anatomical landmarks and U-Net for segmentation of aortic valve components. A total of 258 CT volumes of end systolic and end diastolic phases, which include cases with and without severe calcifications, were collected and manually annotated for each aortic valve component. The collected CT volumes were split 6:2:2 for the training, validation and test steps, and our method was evaluated by five-fold cross validation. The segmentation was successful for all CT volumes with 69.26 s as mean processing time. For the segmentation results of the aortic root, the right-coronary cusp, the left-coronary cusp and the non-coronary cusp, mean Dice Coefficient were 0.95, 0.70, 0.69, and 0.67, respectively. There were strong correlations between measurement values automatically calculated based on the annotations and those based on the segmentation results. The results suggest that our method can be used to automatically obtain measurement values for aortic valve morphology.

Three-dimensional virtual and printed models for planning adult cardiovascular surgery

BACKGROUND

The objective of this study was to explore the usefulness of virtual models and three-dimensional (3D) printing technologies for planning complex non-congenital cardiovascular surgery.

METHODS

Between July 2018 and December 2019, adult patients with different cardiovascular structural diseases were included in a clinical protocol to explore the usefulness of Standard Tessellation Language (STL)-based virtual models and 3D printing for prospectively planning surgery. A qualitative descriptive analysis from the surgeon's viewpoint was done based on the characteristics, advantages and usefulness of 3D models for guiding, planning and simulating the surgical procedures.

RESULTS

A total of 14 custom 3D-printed heart and great vessel replicas with their corresponding 3D virtual models were created for preoperative surgical planning. Six of 14 models helped to redefine the surgical approach, 3 were useful to verify device delivery, while the rest did not change the surgical decision. In all open surgery cases, cardiac and vascular anatomy accuracy of virtual and physical 3D replicas was validated by direct visualisation of the organs during surgery. Printing was achieved through an external provider associated with the Hospital, who printed the final prototype in 5-7 days. Printed production cost was between 100 and 500 USD per model.

CONCLUSIONS

In the current study, the selected 3D printed models presented different advantages (visual, tactile, and instrumental) over the traditional flat anatomical images when simulating and planning some complex types of surgery. Notwithstanding 3D printing advantages, STL-based virtual models were pre-printing useful tools when instrumentation on a physical replica was not required.

Clinical Applications of Patient-Specific 3D Printed Models in Cardiovascular Disease: Current Status and Future Directions

Three-dimensional (3D) printing has been increasingly used in medicine with applications in many different fields ranging from orthopaedics and tumours to cardiovascular disease. Realistic 3D models can be printed with different materials to replicate anatomical structures and pathologies with high accuracy. 3D printed models generated from medical imaging data acquired with computed tomography, magnetic resonance imaging or ultrasound augment the understanding of complex anatomy and pathology, assist preoperative planning and simulate surgical or interventional procedures to achieve precision medicine for improvement of treatment outcomes, train young or junior doctors to gain their confidence in patient management and provide medical education to medical students or healthcare professionals as an effective training tool. This article provides an overview of patient-specific 3D printed models with a focus on the applications in cardiovascular disease including: 3D printed models in congenital heart disease, coronary artery disease, pulmonary embolism, aortic aneurysm and aortic dissection, and aortic valvular disease. Clinical value of the patient-specific 3D printed models in these areas is presented based on the current literature, while limitations and future research in 3D printing including bioprinting of cardiovascular disease are highlighted.

Use of Patient-Specific 3-Dimensional Printed Models for Planning a Valve-in-Valve Transcatheter Aortic Valve Replacement and Educating Health Personnel, Patients, and Families

Background: Aortic stenosis is a common disease of the elderly. Valve replacement with open surgery is the preferred therapy for many patients with low surgical risk. Bioprosthetic valve failure occurs in up to 66% of patients and has a worse prognosis when the mechanism of failure is stenosis compared to regurgitation.

Case Report: An 80-year-old female with a medical history of surgical aortic valve replacement, diabetes, chronic back pain, coronary artery disease, and hypertension was referred to the interventional cardiology clinic for heart failure symptoms. A bioprosthetic valve placement that was small for the patient's size (effective orifice area/body surface area 0.75 cm²/m²) resulted in symptomatic improvement that lasted for 7 years. The patient underwent an aortic valve-in-valve transcatheter valve replacement with excellent outcomes. Preoperative planning involved a patient-specific 3-dimensional printed patient model.

Conclusion: In patients at high surgical risk, transcatheter aortic valve replacement is a fundamental pillar of treatment. However, valve-in-valve procedures have specific anatomic challenges, such as the risk of coronary artery obstruction and the limitation of valve expansion inside a rigid bioprosthetic valve frame. In those difficult cases, interventional cardiologists must make precise decisions regarding the approach. Three-dimensional models can be printed with the patient's specific measurements. This approach represents truly personalized medicine and can serve as a tool for procedural planning, education of the health personnel involved in the case, and patient and family engagement.

Three-dimensional printing for cardiovascular diseases: from anatomical modeling to dynamic functionality

Three-dimensional (3D) printing is widely used in medicine. Most research remains focused on forming rigid anatomical models, but moving from static models to dynamic functionality could greatly aid preoperative surgical planning. This work reviews literature on dynamic 3D heart models made of flexible materials for use with a mock circulatory system. Such models allow simulation of surgical procedures under mock physiological conditions, and are; therefore, potentially very useful to clinical practice. For example, anatomical models of mitral regurgitation could provide a better display of lesion area, while dynamic 3D models could further simulate in vitro hemodynamics. Dynamic 3D models could also be used in setting standards for certain parameters for function evaluation, such as flow reserve fraction in coronary heart disease. As a bridge between medical image and clinical aid, 3D printing is now gradually changing the traditional pattern of diagnosis and treatment.

Clinical situations for which 3D printing is considered an appropriate representation or extension of data contained in a medical imaging examination: adult cardiac conditions

BACKGROUND

Medical 3D printing as a component of care for adults with cardiovascular diseases has expanded dramatically. A writing group composed of the Radiological Society of North America (RSNA) Special Interest Group on 3D Printing (SIG) provides appropriateness criteria for adult cardiac 3D printing indications.

METHODS

A structured literature search was conducted to identify all relevant articles using 3D printing technology associated with a number of adult cardiac indications, physiologic, and pathologic processes. Each study was vetted by the authors and graded according to published guidelines.

RESULTS

Evidence-based appropriateness guidelines are provided for the following areas in adult cardiac care; cardiac fundamentals, perioperative and intraoperative care, coronary disease and ischemic heart disease, complications of myocardial infarction, valve disease, cardiac arrhythmias, cardiac neoplasm, cardiac transplant and mechanical circulatory support, heart failure, preventative cardiology, cardiac and pericardial disease and cardiac trauma.

CONCLUSIONS

Adoption of common clinical standards regarding appropriate use, information and material management, and quality control are needed to ensure the greatest possible clinical benefit from 3D printing. This consensus guideline document, created by the members of the RSNA 3D printing Special Interest Group, will provide a reference for clinical standards of 3D printing for adult cardiac indications.

Fabrication of a ceramic/metal (Al2O3/Al) composite by 3D printing as an advanced refractory with enhanced electrical conductivity

Fused deposition modelling (3D) printing is used extensively in modern fabrication processes. Although the technique was designed for polymer printing, it can now be applied in advanced ceramic research. An alumina/aluminum (Al₂O₃/Al) composite refractory can be fabricated by mixing metallic aluminum in a polymer to form an Al/polymer composite filament. The filament can be printed via a regular thermoplastic material extrusion printer with no machine modification. In this study, Al/polymer composite samples were printed in a crucible shape and sintered at different temperatures to form Al₂O₃/Al composite refractory specimens. The sintered samples were examined via several analytical techniques such as scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, compressive testing, hardness testing, XPS, and Hall measurement. Unlike other ceramic printing techniques that require expensive 3D printing machines and a very high temperature furnace (above 1500 °C) for post processing, this study demonstrates the viability of fabricating refractory items using a cost-effective fused deposition modelling 3D printer and a low temperature furnace (900 °C). The samples did not disintegrate at 1400 °C and were still sufficiently electrically conductive for advanced refractory applications.

An Al₂O₃/Al composite is fabricated by the 3D printing, sintering, and calcination processes that can be used in refractory applications.

Utility of Three-Dimensional (3D) Modeling for Planning Structural Heart Interventions (with an Emphasis on Valvular Heart Disease)

PURPOSE OF REVIEW

Advanced imaging has played a vital role in the contemporary, rapid rise of structural heart interventions. 3D modeling and printing has emerged as one of the most recent imaging tools and the implementation of 3D modeling is expected to increase with further advances in imaging, print hardware, and materials.

RECENT FINDINGS

3D modeling can be used to educate patients and clinical teams, provide ex vivo procedural simulation, and improve outcomes. Intra-procedural success rates may be improved, and post-procedural complications can be predicted more robustly with appropriate application of 3D modeling. Recent advances in technology have increased the availability of this tool, such that there can be more ready adoption into a routine clinical workflow. Familiarity with 3D modeling and its current utilization and role in structural interventions will help inform how to approach and adapt this exciting new technology.

3D printed patient-specific aortic root models with internal sensors for minimally invasive applications

Minimally invasive surgeries have numerous advantages, yet complications may arise from limited knowledge about the anatomical site targeted for the delivery of therapy. Transcatheter aortic valve replacement (TAVR) is a minimally invasive procedure for treating aortic stenosis. Here, we demonstrate multimaterial three-dimensional printing of patient-specific soft aortic root models with internally integrated electronic sensor arrays that can augment testing for TAVR preprocedural planning. We evaluated the efficacies of the models by comparing their geometric fidelities with postoperative data from patients, as well as their in vitro hemodynamic performances in cases with and without leaflet calcifications. Furthermore, we demonstrated that internal sensor arrays can facilitate the optimization of bioprosthetic valve selections and in vitro placements via mapping of the pressures applied on the critical regions of the aortic anatomies. These models may pave exciting avenues for mitigating the risks of postoperative complications and facilitating the development of next-generation medical devices.

3D printing in adult cardiovascular surgery and interventions: a systematic review

3D printing in adult cardiac and vascular surgery has been evaluated over the last 10 years, and all of the available literature reports benefits from the use of 3D models. In the present study, we analyzed the current applications of 3D printing for adult cardiovascular disease treated with surgical or catheter-based interventions, including the clinical medical simulation of physiological or pathology conducted with 3D printing in this field. A search of PubMed and MEDLINE databases were supplemented by searching through bibliographies of key articles. Thereafter, data on demographic, clinical scenarios and application, imaging modality, purposes of using with 3D printing, outcomes and follow-up were extracted. A total of 43 articles were deemed eligible and included. 296 patients (mean age: 65.4±14.2 years; male, 58.2%) received 3D printing for cardiac and vascular surgery or conditions [percutaneous left atrial appendage occlusion (LAAO), TAVR, mitral valve disease, aortic valve replacement, coronary artery abnormality, HOCM, aortic aneurysm and aortic dissection, Kommerell's diverticulum, primary cardiac tumor and ventricular aneurysm]. Eight papers reported the utility of 3D printing in the medical simulator and training fields. Most studies were conducted starting in 2014. Twenty-six was case report. The major scenario used with 3D printing technology was LAAO (50.3%) and followed by TAVR (17.6%). CT and echocardiography were two main imaging techniques that were used to generate 3D-printed heart models. All studies showed that 3D-printed models were helpful for preoperative planning, orientation, and medical teaching. The important finding is that 3D printing provides a unique patient-specific method to assess complex anatomy and is helpful for intraoperative orientation, decision-making, creating functional models, and teaching adult cardiac and vascular surgery, including catheter-based heart surgery.

Accuracy of cardiac magnetic resonance generated 3D models of the aortic annulus compared to cardiovascular computed tomography generated 3D models

To evaluate the accuracy of 3D models of the aortic-root generated from non-contrast cardiac magnetic resonance (CMR). Data were retrospectively collected from 30 consecutive patients who underwent surgical aortic valve replacement and had available records of both intra-operative assessment and pre-surgery annulus assessment by cardiovascular computed tomography (CCT) and CMR. The 3D models were independently segmented, modelled and printed by two blinded "manufacturers". The measurements on the models were carried out by two cardiac surgeons with Hegar dilator. Data were analyzed with non-parametric tests. There was no significant intra- or inter-observer variability (p ≥ 0.13). The agreement between the diameter of the 3D model derived from CMR images and either the anatomical reference of the intraoperative measurement (p = 0.10, r = 0.97) or the radiological reference of the 3D model generated from CCT (p = 0.71, r = 0.92) was very good. The process of segmentation plus the post-processing was about 17 ± 2 min for a model created by CMR, significantly higher than a model created from CCT (7 ± 2 min; p < 0.001). The printing time for a single model did not differ between the two modalities (p = 0.61) and was less than 60 min. The cost for a single model was approximately 0.5 €. 3D models generated from non-contrast CMR performed well when compared to the anatomical reference standard and are comparable to the pair CCT derived models.

3D Printing Applications for Transcatheter Aortic Valve Replacement

PURPOSE OF REVIEW

A combination of evolving 3D printing technologies, new 3D printable materials, and multi-disciplinary collaborations have made 3D printing applications for transcatheter aortic valve replacement (TAVR) a promising tool to promote innovation, increase procedural success, and provide a compelling educational tool. This review synthesizes the knowledge via publications and our group's experience in this area that exemplify uses of 3D printing for TAVR.

RECENT FINDINGS

Patient-specific 3D-printed models have been used for TAVR pre-procedural device sizing, benchtop prediction of procedural complications, planning for valve-in-valve and bicuspid aortic valve procedures, and more. Recent publications also demonstrate how 3D printing can be used to test assumptions about why certain complications occur during THV implantation. Finally, new materials and combinations of existing materials are starting to bridge the large divide between current 3D material and cardiac tissue properties. Several studies have demonstrated the utility of 3D printing in understanding challenges of TAVR. Innovative approaches to benchtop testing and multi-material printing have brought us closer to being able to predict how a THV will interact with a specific patient's aortic anatomy. This work to date is likely to open the door for advancements in other areas of structural heart disease, such as interventions involving the mitral valve, tricuspid valve, and left atrial appendage.

Improved co-registration of ex-vivo and in-vivo cardiovascular magnetic resonance images using heart-specific flexible 3D printed acrylic scaffold combined with non-rigid registration

BACKGROUND

Ex-vivo cardiovascular magnetic resonance (CMR) imaging has played an important role in the validation of in-vivo CMR characterization of pathological processes. However, comparison between in-vivo and ex-vivo imaging remains challenging due to shape changes occurring between the two states, which may be non-uniform across the diseased heart. A novel two-step process to facilitate registration between ex-vivo and in-vivo CMR was developed and evaluated in a porcine model of chronic myocardial infarction (MI).

METHODS

Seven weeks after ischemia-reperfusion MI, 12 swine underwent in-vivo CMR imaging with late gadolinium enhancement followed by ex-vivo CMR 1 week later. Five animals comprised the control group, in which ex-vivo imaging was undertaken without any support in the LV cavity, 7 animals comprised the experimental group, in which a two-step registration optimization process was undertaken. The first step involved a heart specific flexible 3D printed scaffold generated from in-vivo CMR, which was used to maintain left ventricular (LV) shape during ex-vivo imaging. In the second step, a non-rigid co-registration algorithm was applied to align in-vivo and ex-vivo data. Tissue dimension changes between in-vivo and ex-vivo imaging were compared between the experimental and control group. In the experimental group, tissue compartment volumes and thickness were compared between in-vivo and ex-vivo data before and after non-rigid registration. The effectiveness of the alignment was assessed quantitatively using the DICE similarity coefficient.

RESULTS

LV cavity volume changed more in the control group (ratio of cavity volume between ex-vivo and in-vivo imaging in control and experimental group 0.14 vs 0.56, p < 0.0001) and there was a significantly greater change in the short axis dimensions in the control group (ratio of short axis dimensions in control and experimental group 0.38 vs 0.79, p < 0.001). In the experimental group, prior to non-rigid co-registration the LV cavity contracted isotropically in the ex-vivo condition by less than 20% in each dimension. There was a significant proportional change in tissue thickness in the healthy myocardium (change = 29 ± 21%), but not in dense scar (change = - 2 ± 2%, p = 0.034). Following the non-rigid co-registration step of the process, the DICE similarity coefficients for the myocardium, LV cavity and scar were 0.93 (±0.02), 0.89 (±0.01) and 0.77 (±0.07) respectively and the myocardial tissue and LV cavity volumes had a ratio of 1.03 and 1.00 respectively.

CONCLUSIONS

The pattern of the morphological changes seen between the in-vivo and the ex-vivo LV differs between scar and healthy myocardium. A 3D printed flexible scaffold based on the in-vivo shape of the LV cavity is an effective strategy to minimize morphological changes in the ex-vivo LV. The subsequent non-rigid registration step further improved the co-registration and local comparison between in-vivo and ex-vivo data.

Three-dimensional printing in structural heart disease and intervention

Three-dimensional (3D) printing refers to the process by which physical objects are built by depositing materials in layers based on a specific digital design. It was initially used in manufacture industry. Inspired by the technology, clinicians have recently attempted to integrate 3D printing into medical applications. One of the medical specialties that has recently made such attempt is cardiology, especially in the field of structural heart disease (SHD). SHD refers to a group of non-coronary cardiovascular disorders and related interventions. Obvious examples are aortic stenosis, mitral regurgitation, atrial septal defect, and known or potential left atrial appendage (LAA) clots. In the last decade, cardiologists have witnessed a dramatic increase in the types and complexity of catheter-based interventions for SHD. Current imaging modalities have important limitations in accurate delineation of cardiac anatomies necessary for SHD interventions. Application of 3D printing in SHD interventional planning enables tangible appreciation of cardiac anatomy and allows in vitro interventional device testing. 3D printing is used in diagnostic workup, guidance of treatment strategies, and procedural simulation, facilitating hemodynamic research, enhancing interventional training, and promoting patient-clinician communication. In this review, we attempt to define the concept, technique, and work flow of 3D printing in SHD and its interventions, highlighting the reported clinical benefits and unsolved issues, as well as exploring future developments in this field.

Methods for verification of 3D printed anatomic model accuracy using cardiac models as an example

Background

Medical 3D printing has brought the manufacturing world closer to the patient’s bedside than ever before. This requires hospitals and their personnel to update their quality assurance program to more appropriately accommodate the 3D printing fabrication process and the challenges that come along with it.

Results

In this paper, we explored different methods for verifying the accuracy of a 3D printed anatomical model. Methods included physical measurements, digital photographic measurements, surface scanning, photogrammetry, and computed tomography (CT) scans. The details of each verification method, as well as their benefits and challenges, are discussed.

Conclusion

There are multiple methods for model verification, each with benefits and drawbacks. The choice of which method to adopt into a quality assurance program is multifactorial and will depend on the type of 3D printed models being created, the training of personnel, and what resources are available within a 3D printed laboratory.

The Role of 3D Printing in Medical Applications: A State of the Art

Three-dimensional (3D) printing refers to a number of manufacturing technologies that generate a physical model from digital information. Medical 3D printing was once an ambitious pipe dream. However, time and investment made it real. Nowadays, the 3D printing technology represents a big opportunity to help pharmaceutical and medical companies to create more specific drugs, enabling a rapid production of medical implants, and changing the way that doctors and surgeons plan procedures. Patient-specific 3D-printed anatomical models are becoming increasingly useful tools in today's practice of precision medicine and for personalized treatments. In the future, 3D-printed implantable organs will probably be available, reducing the waiting lists and increasing the number of lives saved. Additive manufacturing for healthcare is still very much a work in progress, but it is already applied in many different ways in medical field that, already reeling under immense pressure with regards to optimal performance and reduced costs, will stand to gain unprecedented benefits from this good-as-gold technology. The goal of this analysis is to demonstrate by a deep research of the 3D-printing applications in medical field the usefulness and drawbacks and how powerful technology it is.