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Feature: Entering the titanium age 

01-15-2020 17:10

The potential for metal 3-D printing in IR

By Jennifer Stover  Winter 2020

Imagine a world with personalized stents, filters and catheters specially designed for each of your patients. It is a world that is not far off because of the emerging technology of metal 3-D printing, according to Rahmi Oklu, MD, PhD, FSIR, chair of the Mayo Clinic Arizona division of vascular and interventional radiology.

First conceived of in the 1980s, 3-D printing, also known as additive manufacturing, is already used to make resin and plastic dental and orthopedic prosthetics unique to each patient, as well as medical models that aid in surgical planning and preparation. While metal 3-D printing has been used in defense and aerospace for a number of years, its use in medicine is still emerging.

Research on personalized metal 3-D joint prosthetics, which would be more durable than today’s joints, is ongoing. Metal joints printed with 3-D technology would fit a patient precisely and could eliminate the need for joint reoperations due to sizing complications.

Customized IR devices with metal 3-D printing

The days of having a stent or other device shipped from a  manufacturer
will wane, says Dr. Oklu, who thinks metal 3-D printing will become commonplace in medicine within 10–5 years.

The customization benefits of metal 3-D printing for orthopedics would transfer well to IR, says Dr. Oklu, with metal-printed stents, IVC filters and even embolics all specially made for each patient. “Metal 3-D printing has started to become more prevalent in medicine,” notes Malia Kuo, an intern for Dr. Oklu and the lead author of a poster on the topic presented at the SIR 2019 Annual Scientific Meeting. “It’s so easy to customize and create nuances that traditional medicine can’t.”

The ability to create tailor-made cardiac prosthetic devices with metal 3-D printing could revolutionize IR, says Dr. Oklu, allowing for differences in individual anatomy far better than currently available stents (even with varying off-the-shelf size increments): “Maybe their vessel is narrow on one end and wider at the other end. Maybe it needs to be somewhat of a conical shape.”

With a CT scan and a metal 3-D printer, IRs could make a stent with an exact fit for a particular artery or vein. “Everyone’s anatomy is different. Contours are different. You can make a device based on the needs of that patient,” says Dr. Oklu. Another possible application is IVC filters. Filters designed specifically for each patient could reduce or even eliminate dislodged filters or other complications. “If you can custom design the filter to the patient’s IVC, you have personalized an IVC filter,” notes Dr. Oklu.

In addition to the benefits of personalization, 3-D printing uses less waste than traditional manufacturing processes and will become more cost effective as the cost of printers decreases. Today, a good metal 3-D printer might cost as much as $300,000, which does not include the price of specialized software and metal materials, both of which are expensive. Industrial resin-based printers, in contrast, can be as high as $100,000—and lower-end printers can be purchased for as little as a couple hundred dollars.

Only a very small number of manufacturers currently produce metal 3-D printers, most of them in Europe. Dr. Oklu hopes his department will purchase one within the next year.

The metal 3-D printing process

Whether using resin or metal, the 3-D printing process is similar. First, special software creates a three-dimensional file from a high-resolution CT scan, MRI or ultrasound. The file is segmented into thin layers, and the printer then uses the software to build the object, layer by layer.

The metal printing process is more complex than traditional resin 3-D printing. First, a metallic dust is sprayed on a platform and a high-temperature laser melts the small metal microparticles to create the 3-D structure. The excess metallic dust is removed and reused following sterilization. Because of the metallic dust, metal 3-D printers require a separate room and ventilation. While it can take a considerable amount of time to print with resin or plastic, small metal objects such as stents could take as little as a few hours, and printers could manufacture with the same metals in use today, including titanium and shape-metal alloys like nitinol, Dr. Oklu says.

The future is near

While metal 3-D printing is not ready for IR patients just yet, Dr. Oklu and his team already print resin medical models for surgical planning and education, both for their own use and for colleagues in urology, orthopedic surgery, cardiology and transplant surgery. He recently created a 3-D-printed resin model for consenting a patient and for preoperative planning of a prostate artery embolization (PAE). “The patient was nervous and did not understand PAE, so we made the model so he could better understand the steps involved in the procedure,” Dr. Oklu explains. The model shows the patient’s entire pelvis in three dimensions, including the artery going into the prostate.

Another model Dr. Oklu printed shows a patient with hereditary pulmonary arteriovenous malformation (AVM). During a typical procedure, Dr. Oklu might embolize a couple AVMs but, with the aid of the exact 3-D model, he was able to embolize seven. “The model facilitated getting into those vessels,” he explains. “It helped with the consenting, planning the procedure, educating the trainees with the approach and helped us use less contrast and radiation,” he says. “These are all win–win for the patient and for the team.”

It is eye-opening and educational for patients to see themselves in three dimensions as opposed to a two-dimensional scan on a computer. “Patients love it because knowledge is power,” Dr. Oklu says. “They may feel as if they don’t know what they’re getting into, but if you 3-D print the entire pelvis with the prostate and the arteries, suddenly they begin to understand what’s going on. You begin to discuss things you wouldn’t otherwise. It changes the discussion with the patient. It empowers the patient and takes it to another level.”

The days of having a stent or other device shipped from a manufacturer will wane, says Dr. Oklu, who thinks metal 3-D printing will become commonplace in medicine within 10–15 years. The technology is still developing and there is much progress to be made, plus Dr. Oklu stresses that more government oversight is needed to ensure accuracy and sterility. He sees 3-D technology as transformational for IRs, and anticipates trials within the next 3–5years. “I think IRs should embrace this. Everything we do is device related. I think IRs ought to lead it,” Dr. Oklu says. “This is the future. It’s going to happen, and we’re not that far from it.”

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