Recent recognition of the poor prognosis of significant tricuspid regurgitation (TR) has resulted in increased indication for tricuspid valve interventions. TR can affect 65% to 85% of the population worldwide and has a 1-year mortality rate greater than 25% in patients with severe regurgitation. A key procedure for patient selection and intraoperative assessment of intervention involves determining the location of the vena contracta width and regurgitant jet area. Manual visualization of the vena contracta (VC) can be time consuming depending on its location. Decreasing the required time for VC visualization would potentially result in decreased time for patient assessment, device deployment and intraprocedural intervention evaluation thus reducing hospital costs. There is currently no commercially available automatic VC detection system. We present a method to automatically localize the VC using 3D intracardiac echocardiography (ICE) on a simplified anthropomorphic phantom as a proof of concept. A beating heart phantom was outfitted with a silicone flange containing a mechanical valve and an orifice to cause a regurgitant jet. We propose an image processing pipeline to segment the regurgitant jet from Doppler ultrasound, as acquired by ICE, to determine the location of the VC automatically. The VC locations output by the algorithm were validated both qualitatively and quantitatively by comparison to manually annotated VC locations. On average, the location of VC detected by the algorithm was within 1.52±35mm to the location of the ground truth VC. We envision that this study will play a major role towards the development of an automated system for VC localization during TV interventions.

All-optical ultrasound imaging, in which ultrasound is generated and received using light, is well-suited to minimally invasive surgical procedures. Here we present a device that can provide real-time M-mode ultrasound images, and demonstrate its use imaging a dynamic heart valve phantom. This device, comprising two optical fibres, one with a graphene-polydimethylsiloxane composite coating for ultrasound generation, and a second with a concave Fabry-Perot cavity for ultrasound reception, had a diameter of < 1 mm. This provided a wide ultrasound transmission bandwidth (> 30 MHz) that enabled imaging with high axial resolution (< 50 μm) and large imaging depths (> 2 cm). M-mode imaging with an A-line rate of 100 Hz was demonstrated on a heart valve phantom with realistic mitral valve motion. This work demonstrates the potential for all-optical ultrasound imaging to be used for guidance of intracardiac interventions.

C-Arm positioning for interventional spine procedures can often be associated with a steep learning curve. The current training standards involve using real X-rays on cadavers or via apprenticeship-based programs. To help limit excess radiation exposure, several radiation-free training systems have been proposed in the literature but there lacks a hands-on, cost-effective simulator that does not require access to a physical C-Arm. In order to expand the accessibility of radiation-free C-Arm training, we have developed a 10:1 scaled down C-Arm simulator using 3D-printed parts and wireless accelerometers for tracking. We generated Digitally Reconstructed Radiographs (DRRs) in real-time using a 1-dimensional transfer function operating on a ray-traced projection of a patient CT scan. To evaluate the efficacy of the system as a training tool, we conducted a user study in which anesthesiology and orthopedic residents were evaluated on the accuracy of their C-Arm placement for three standard views used in spinal injection procedures. Both the experimental group and control group were given the same evaluation task with the experimental group receiving 5 minutes of training on the system using real-time DRRs and a standardized two page curriculum on proper image acquisition. The experimental group achieved an angular error of 4.76±1.66° which was lower than the control group at 6.88±3.67° and the overall feedback of the system was positive based on a Likert scale questionnaire filled out by each participant. The results indicate that our system has high potential for improving C-Arm placement in interventional spine procedures and we plan to conduct a follow-up study to evaluate the long-term training capabilities of the simulator.

PURPOSE:Transcatheter, beating heart repair techniques for mitral valve regurgitation is a very active area of development. However, it is difficult to both simulate and predict the clinical outcomes of mitral repairs, owing to the complexity of mitral valve geometry and the influence of hemodynamics. We aim to produce a workflow for manufacturing dynamic patient-specific models to simulate the mitral valve for transcatheter repair applications.METHODS:In this paper, we present technology and associated workflow, for using transesophageal echocardiography to generate dynamic physical replicas of patient valves. We validate our workflow using six patient datasets representing patients with unique or particularly challenging pathologies as selected by a cardiologist. The dynamic component of the models and their resultant potential as procedure planning tools is due to a dynamic pulse duplicator that permits the evaluation of the valve models experiencing realistic hemodynamics.RESULTS:Early results indicate the workflow has excellent anatomical accuracy and the ability to replicate regurgitation pathologies, as shown by colour Doppler ultrasound and anatomical measurements comparing patients and models. Analysis of all measurements successfully resulted in t critical two-tail > t stat and p values > 0.05, thus demonstrating no statistical difference between the patients and models, owing to high fidelity morphological replication.CONCLUSIONS:Due to the combination of a dynamic environment and patient-specific modelling, this workflow demonstrates a promising technology for simulating the complete morphology of mitral valves undergoing transcatheter repairs.

A guidance system using transesophageal echocardiography and magnetic tracking is presented which avoids the use of nephrotoxic contrast agents and ionizing radiation required for traditional fluoroscopically guided procedures. The aortic valve is identified in tracked biplane transesophageal echocardiography and used to guide stent deployment in a mixed reality environment. Additionally, a transapical delivery tool with intracardiac echocardiography capable of monitoring stent deployment was created. This system resulted in a deployment depth error of 3.4mm in a phantom. This was further improved to 2.3mm with the custom-made delivery tool. In comparison, the variability in deployment depth for traditional fluoroscopic guidance was estimated at 3.4mm.

Objective: Transcatheter aortic valve implantation (TAVI) relies on fluoroscopy and nephrotoxic contrast medium for valve deployment. We propose an alternative guidance system using augmented reality (AR) and transesophageal echocardiography (TEE) to guide TAVI deployment. The goals of this study were to determine how consistently the aortic valve annulus is defined from TEE using different aortic valve landmarks and to compare AR guidance with fluoroscopic guidance of TAVI deployment in an aortic root model.Methods: Magnetic tracking sensors were integrated into the TAVI catheter and TEE probe, allowing these tools to be displayed in an AR environment. Variability in identifying aortic valve commissures and cuspal nadirs was assessed using TEE aortic root images. To compare AR guidance of TAVI deployment with fluoroscopic guidance, a TAVI stent was deployed 10 times in the aortic root model using each of the two guidance systems.Results: Commissures and nadirs were both investigated as features for defining the valve annulus in the AR guidance system. The commissures were identified more consistently than the nadirs, with intraobserver variability of 2.2 and 3.8 mm, respectively, and interobserver variability of 3.3 and 4.7mm, respectively. The precision of TAVI deployment using fluoroscopic guidance was 3.4 mm, whereas the precision of AR guidance was 2.9 mm, and its overall accuracy was 3.4 mm. This indicates that both have similar performance.Conclusions: Aortic valve commissures can be identified more reliably than cuspal nadirs from TEE. The AR guidance system achieved similar deployment accuracy to that of fluoroscopy while eliminating the use and consequences of nephrotoxic contrast and radiation.

Beating heart valve therapies rely extensively on image guidance to treat patients who would be considered inoperable with conventional surgery. Mitral valve repair techniques including the MitrClip, NeoChord, and emerging transcatheter mitral valve replacement techniques rely on transesophageal echocardiography for guidance. These images are often difficult to interpret as the tool will cause shadowing artifacts that occlude tissue near the target site. Here, we integrate ultrasound imaging directly into the NeoChord device. This provides an unobstructed imaging plane that can visualize the valve lea ets as they are engaged by the device and can aid in achieving both a proper bite and spacing between the neochordae implants. A proof of concept user study in a phantom environment is performed to provide a proof of concept for this device.

Trans-esophageal echocardiography (TEE) is a standard component of patient monitoring during most cardiac surgeries. In recent years magnetic tracking systems (MTS) have become sufficiently robust to function effectively in appropriately structured operating room environments. The ability to track a conventional multiplanar 2D TEE transducer in 3D space offers incredible potential by greatly expanding the cumulative field of view of cardiac anatomy beyond the limited field of view provided by 2D and 3D TEE technology. However, there is currently no TEE probe manufactured with MTS technology embedded in the transducer, which means sensors must be attached to the outer surface of the TEE. This leads to potential safety issues for patients, as well as potential damage to the sensor during procedures. This paper presents a standard 2D TEE probe fully integrated with MTS technology. The system is evaluated in an environment free of magnetic and electromagnetic disturbances, as well as a clinical operating room in the presence of a da Vinci robotic system. Our first integrated TEE device is currently being used in animal studies for virtual reality-enhanced ultrasound guidance of intracardiac surgeries, while the "second generation" TEE is in use in a clinical operating room as part of a project to measure perioperative heart shift and optimal port placement for robotic cardiac surgery. We demonstrate excellent system accuracy for both applications.

OBJECTIVE:: Optimal atrial septal defect (ASD) closure should combine off-pump techniques with the effectiveness and versatility of open-heart techniques. We report our experience with off-pump ASD closure using the Universal Cardiac Introducer (UCI) in a porcine model. The goal was to create an ASD over the fossa ovale (FO) and position a patch over the ASD under ultrasound (US) imaging and augmented virtual reality guidance.METHODS:: An US probe (tracked with a magnetic tracking system) was positioned into the esophagus (transesophageal echocardiographic probe) for real-time image-guidance. The right atrium (RA) of six pigs was exposed via a right lateral thoracotomy or medial sternotomy. The UCI was attached to the RA wall. A punching tool was introduced via the UCI, navigated and positioned, under US guidance, to create an ASD into the FO. A patch with its holder and a stapling device were introduced into the RA via the UCI. The patch was positioned on the ASD. Occlusion of the ASD was determined using US and Doppler imaging.RESULTS:: The FO membrane was excised successfully in all animals. US image-guidance provided excellent visualization. The patch was positioned in all cases with complete occlusion of the ASD. The stapling device proved too bulky, impeding circumferential positioning.CONCLUSIONS:: Using the UCI, ASD closure was safe and feasible. US imaging, combined with virtual and augmented reality provided accurate navigating and positioning. This study also provided valuable information on the future design of anchoring devices for intracardiac procedures.