A process called “rapid prototyping” allows interventionalists to produce 3D models of patients’ hearts to better facilitate pre-procedural planning for catheter-based structural heart interventions.
Previously limited to engineering and manufacturing, rapid prototyping initially helped create physical models of cars, planes and computers before their designs were sent to the production floor. The technique first entered the medical field to help surgeons—oral and maxillofacial, orthopedic and neurologic—with hands-on approaches to complex procedures. Three years ago, researchers from the University of Colorado Denver School of Medicine and physicians from the University of Colorado Hospital (UCH) in Aurora, Colo., began refining the technique for the cardiovascular realm.
“Rapid prototyping offers us an opportunity to take a patient’s medical image and transform it into a physical object,” says lead researcher John D. Carroll, MD, an interventional cardiologist and medical director of the Cardiac and Vascular Center at UCH.
Carroll works alongside other cardiologists, computer scientists and research fellows in the clinical science program, a collaboration with Philips Healthcare that combines clinical research and developmental approaches to 3D visualization.
While 2D and 3D computer images obtained from coronary CT scans have made great strides in visualizing heart conditions, these images can sometimes “misrepresent many of the features of the disease state of a patient,” says Carroll. Three-dimensional models help to better understand individual features and to provide better planning methods for the navigation of devices during an intervention (see sidebar).
UCH has created 40 patient heart models and is refining the process by which the models are handcrafted. Currently, the facility focuses on working with the most complex patient cases and those that deal with structural heart disease. These cases include ventricular septal defects with surgical patch dehiscence, fenestrated artrial septal defects with large atrial septal aneurysm and prosthetic mitral valve perivalvular leaks.
“Creating these models makes the most sense for patients who have unusual or complex anatomy that needs to be more fully understood before a therapeutic intervention,” says Carroll.
Research Assistant Adam R. Hansgen, adds, “When you look at a model instead of an image on a screen, you start understanding the anatomic relationships better and how you would potentially manipulate the catheter.”
The researchers say that models such as these may pave the way for medical device companies to customize catheter-based devices based on individual anatomic structure.
Putting it together
UCH is one of a handful of facilities in the U.S. working to create prototyped models of the whole heart, says S. James Chen, PhD, director of the 3D Lab and associate professor of medicine. “It’s a pretty small group, and most other researchers doing this type of work are looking only at specific chambers or vessels, not the whole heart.”
The intricate process begins with 2D cardiac CT angiography images (MRI and echocardiography images are sometimes used), which are then processed with the use of several software packages ranging from those used for DICOM viewing to others that were originally designed for applications in computer animation and video game creation.
The 3D datasets are broken down into cross-sectional slices of varying thickness, depending on the technology and model of the 3D printer being used. UCH researchers use a Z Corporation 3D printer equipped with Hewlett-Packard print heads. The heart’s cross-sections are printed from the ink-jet print head using a water-based adhesive. Researchers then use light adhesive and powder made of plaster or resins to coat and glue the model together, creating a porcelain-type feel, says Hansgen.
The model goes into its post-processing phase where it will cure and dry. The 3D printing process takes six to seven hours to complete, while the entire rapid prototyping process—imaging to complete model—takes three days. The plaster or resin-based powders allow color to be injected into the rapid prototyped model to create the contrast