Category Archives: Medicine

3D Printing Hearts with Valves

Improving Valve Representation in Cardiac Stereolithography by Spatially Registering Magnetic Resonance Imaging and Echocardiography Tyler Robert Moore MDa, Erin Janelle Madriago MDb, and Michael Silberbach MDb Introduction Additive manufacturing, a means of fabricating objects layer by layer though extrusion or sintering, has the potential to impact biomedical research, patient imaging, and medical therapies. One example is personalized anatomic modelling, the creation of tangible models representing the anatomy of an individual patient.1 Of particular interest is the creation of cardiac models in patients with congenital heart malformations.2 The benefits of such models include physician education,3 operative planning,4 and procedure simulation.5 Patient-specific heart models are readily created from cross-sectional data acquired through computed tomography (CT) and magnetic resonance (MR).6 Despite improvements in cardiac-gated CT and MR,7 the temporal resolution of fast moving cardiac structures such as the valve leaflets is limited. Standard three-dimensional echocardiography can acquire volumetric data up to 20 Hz, allowing superior resolution of the valve leaflets.8 Spatially constrained volumetric data is a more recent development in echocardiography that allows for its use in creating heart models through additive manufacturing.9–11 While echocardiography can be used to create very accurate models of the valves, its limited field of view precludes representation of the entire heart, great vessels, and adjacent thoracic structures in a single model. Integration of multiple modalities allows for more comprehensive modelling of the heart by exploiting both the larger field of view inherent to CT and MR as well as the detailed valve anatomy acquired with echocardiography. Combining modalities requires a means to spatially register the data sets. If there are several anatomic fiducials, corresponding points that are readily identifiable in both data sets, they can be used to determine a linear transformation between the coordinate systems of the two studies.12 Preliminary results have demonstrated the feasibility of combining cardiac MR and three-dimensional echocardiography to create such models.13 Materials and Methods Subjects Subjects are less than 18 years of age. Cardiac models are created from cardiac MR and three-dimensional echocardiography performed in the course of the subjects’ care. The Oregon Health and Science University Institutional Review Board approves maintenance of a cardiac imaging data repository for the creation of heart models for pediatric subjects. Source Data MR is performed using a 1.5 Tesla Philips Ingenia with Philips REV5 software. Sequences used directly for modelling include a pre-gadolinium Fast3D sequence, a pre-gadolinium BFFE cine sequence acquired in the short axis plane that included the atrioventricular valves, and a post-gadolinium angiographic sequence. Gadolinium enhanced sequences are performed using a bolus of Gadavist at 0.1 mmol/kg. Subjects under 12 years of age are routinely sedated by a pediatric anesthesiologist as part of the institutional routine. Three-dimensional echocardiography data are acquired using a Philips iE33 xMATRIX with an X7-2 probe. Volumetric data sets are acquired in 30 temporal phases per heartbeat with 208 slices per phase. Visual inspection allows retrospective selection of the temporal subset corresponding to the appropriate phase of the cardiac cycle. Software Mimics Innovation Suite v17.0 (Materialise, Belgium) is

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