Accurate Models Advance Artificial Heart

It has been almost 20 years since surgeons placed the country's first artificial heart in 61-year-old Barney Clark. The Washington dentist lived just 112 days after doctors implanted the Jarvik-7 device.

Since then, medical science has continued to strive for an alternative for those with heart disease. Just last year, a U.S. company introduced a newer-generation artificial heart. Two of the recipients have lived almost a year with the device.

Today, medical institutions such as the Cleveland Clinic Foundation (Cleveland, OH) are working to create a Total Artificial Heart (TAH) that will bring life to patients without access to a donor.

Advanced technology in materials such as polymers and metals, new 3-D photography, and rapid inspection software and traditional CAD/CAM software are bringing researchers closer to their goal.

A Heart-Filled History and Future

But the organization's most ambitious project is the MagScrew Total Artificial Heart, being developed in collaboration with Foster-Miller Inc. (Waltham, MA) - an engineering and technology development firm - which could eventually be implanted permanently.

"Our TAH is a device that replaces the sick natural ventricles and native valves of a patient," says Stephan Weber, senior research engineer in the Department of Biomedical Engineering at the Cleveland Clinic Foundation. "Applications for this system would exist for patients with end-stage heart failure who would not survive until a suitable heart donor is located for transplant or for patients who are not eligible for heart transplantation."

Going With the Flow

Cleveland Clinic researchers determined that the best way to ensure a proper flow pattern was to reverse engineer the complex geometries of the blood pump housings in the TAH.

Weber turned to Advanced Design Concepts (ADC) (Pewaukee, WI) - a 3-D modeling and CAD service bureau - to supply a surface model and a 3-D solid model representation of the chamber.

Ergonomical Precision

"The housing does not have a very mechanical shape," says Mark Schaefer, ADC president. "It flows more ergonomically than mechanically. A key feature in the housing design is the smooth transition from the inflow port to the main chamber and from the main chamber to the outlet port. This is what creates a smooth flow pattern for the blood. Modeling this as accurately as possible avoids dead zones of flow and blood clot formation."

ADC began by painting the housing white and scanning it with an Atos white-light scanner. Engineers then used Raindrop Geomagic, Inc.'s (Research Triangle Park, NC) - a developer of 3-D photography software - Geomagic Studio software to convert the resulting scanned data into a 3-D solid model.

Geomagic Studio provides precise dimensional geometry and photometric color information in one process. The result is a true-to-life, accurate 3-D model that can be imported into CAD/CAM software, used to drive a manufacturing device, or placed on the Internet for collaborative engineering and e-commerce applications. This automated process is called 3-D photography.

Ensuring Quality and Saving Time

At the click of a mouse, Geomagic Qualify automatically aligned the CAD model with scanned point cloud data from the plastic TAH model. After ADC specified the level of tolerance, Qualify displayed a detailed color map showing different deviation levels. The software also can produce a green and red display that acts as a "go/no-go" gauge. Results can be documented automatically in web-ready HTML reports with annotated notes.

"In Geomagic Qualify we were able to see errors in the Pro/E model relative to the original plastic model," Schaefer says. "We corrected those and were able to get the model to within 0.010 of an inch of the original, which is what the Cleveland Clinic team had requested. The whole process took less than one day as opposed to what might have been weeks using the Pro/E program alone."

A Large Hurdle Cleared

"Geomagic's precision helped us over one of the largest hurdles between the existing device and a TAH that can be manufactured accurately," says Weber. "The process ADC used saved both time and money. We had attempted to measure the geometry of the volume using a CMM machine, but this took too much time and the resulting model was not even close to being accurate enough."

With Geomagic Qualify, it was a quick and easy process to ensure that the 3-D model was accurate. "The ability to switch back and forth between Pro/E and Geomagic Qualify with little hesitation in processing time saved literally days," says Schaefer.

Weber thinks that the 3-D photography approach used by ADC brings the Cleveland Clinic a little closer to making its total artificial heart a reality. For heart patients, it could eventually mean the difference between life and death.