Originally Published March 2000
Affordable 3-D Printer Used in Clinical Application
Intended for design engineers, a system that generates fast, cost-effective models also improves surgical outcomes.
Karim Marouf, Managing Editor
Although advances in rapid prototyping have produced systems that can create highly accurate models in a fraction of the time used by conventional methods, these systems are costly and not always as fast as one might expect. Z Corp. (Burlington, MA) has stepped in to provide a solution with its Z402 3-D printer. The Z402 system is a relatively inexpensive modeling system that benefits anyone who wants to produce a model very quickly. Although it is targeted at medical device and other design engineers, the system recently found a unique application not in a design lab but in the clinic of a reconstructive surgeon.
The Z402 3-D printer allows design engineers to make multiple iterations early in the process.
A Difficult Procedure
Craniosynostosis describes a condition in which sutures separating the seven bones of an infant's skull prematurely close. Many craniofacial disorders have a component of craniosynostosis, which prevents the brain from expanding normally within the skull. This can result in increased intracranial pressure and lead to brain damage and vision loss in extreme cases.
Surgery to correct the condition is an extremely delicate operation, notes John Teichgraeber, MD, associate professor of surgery for the Division of Plastic and Reconstructive Surgery and the Division of Pediatric Surgery at the University of Texas Health Science Center in Houston. The procedure involves releasing the fused suture and reshaping the skull. It is generally done by a plastic surgeon with the help of a neurosurgeon and can take from 2 to 5 hours to perform, depending on the surgeons' expertise and the severity of the case.
For the surgeons, the difficulty resides in determining where to make the incisions that will allow the skull to develop symmetrically at a regular pace. Without careful planning, the cuts could expand too much or the skull could grow asymmetrically, causing the head to become misshapen. Unfortunately, there is little time to spare between the initial diagnosis and when surgery must take place.
These are the constraints under which Teichgraeber typically labors. While preparing to operate on a 9-month-old infant suffering from craniosynostosis recently, he enlisted the aid of a relatively inexpensive and fast 3-D printer. The result, according to Teichgraeber, was an optimization of resources and, most importantly, a successful outcome.
A New Tool for Surgery
The RapidView modeling system developed by Medical Modeling Corp. (Golden, CO) outputs 3-D models created from CT and MRI data using the Z402 3-D printer from Z Corp. Medical Modeling Corp. was able to import the CT-scan data provided by Teichgraeber into an MIM-ICS software package provided by Materialize (Ann Arbor, MI). An STL file was exported from MIMICS to the Z402 system. The software file was then imported and sliced within Z Corp.'s system software and prepared for modeling. Data preparation took just minutes.
A model of the baby's skull was created using Z Corp.'s proprietary starch-based material in less than 4 hours. This represented a time savings of more than 12 hours compared with rapid prototyping systems.
This model of the baby's skull was used to prepare for surgery.
"That's the beauty of the Z402 system," says Andy Christensen, general manager of Medical Modeling Corp. "It's just really fast, and this allows for receipt of a CT scan and model generation all in the same day."
A Great Outcome
The model was used by Teichgraeber in preparation for the surgery. It also was taken into the operating room nonsterile for reference during surgery. Using the model, Teichgraeber was able to significantly reduce the length of the surgery.
"This procedure was done in the least amount of time possible and provided the patient with a great outcome," says Teichgraeber. "The model provided more than enough accuracy and allowed for communication before the surgery between myself and the neurosurgeon."
With the Z402 system, Medical Modeling Corp. was able to provide a realistic 3-D model for the doctor at about one-third the cost of alternative rapid prototyping methods. With an accuracy of 0.5% (0.005 in./in.), the system is not as precise as more expensive systems but is still suitable for most modeling applications.
Reducing Time to Market
The speed of the Z402 system has great benefits for medical OEMs. It allows design engineers to make multiple iterations early in the design process. Part visualization and communication are improved, while creativity is enhanced and design flaws reduced. By enabling models with complex geometries to be generated quickly and inexpensively, the office-compatible Z402 system provides quick feedback and reduces time to market for new products.
"The benefits of the Z402 come down to time and cost," reiterates Christensen. "We can do applications for trauma, such as when someone is involved in a car crash and they need a model right away. We can get a CT scan in the morning and ship a model the same day, which is something that we never thought of doing before because in the past it took too long to build the model."
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