Ingrid Hein

December 05, 2016

CHICAGO — Virtual reality 3D fetal models created from MRI scans can be used to visualize the internal organs of a fetus, assess abnormalities, and give parents a way to better understand what is happening to their child, an expert said here at the Radiological Society of North America 2016 Annual Meeting.

The 3D visualizations are more detailed with MRI than with ultrasound, and can also be used to model the appearance of the fetus after birth, said Heron Werner Jr, MD, PhD, from the Clínica de Diagnóstico por Imagem in Rio de Janeiro.

Dr Werner started out using CT scans to make 3D prints of mummies for the Museum of Rio de Janeiro. Ancient mummies do not move and are not sensitive to radiation, so CT scans worked well, he explained. But when it comes to fetuses, it is not that simple.

Although CT scans can be performed in less than 1 second, they have a radiation dose significant enough to adversely affect a developing embryo or fetus, which means the only options for visualization are ultrasound and MRI.

"The secret to MRI is good quality," said Dr Werner. "That means you need the fetus to be perfectly still for 26 seconds, and babies are not very still. Sometimes we have to repeat the procedure several times, so it can take about half an hour to get 26 seconds."

Initially, Dr Werner and his colleagues scanned 6 mm "slices" and stitched them together. Today, they scan 1 mm slices, which contain far more information and provide higher-quality images. Once the data are captured, a physician can decide what parts of the scan need to be reconstructed in 3D. The slices are then sequentially put together to form the 3D model.

The original objective of the process was to use 3D printing to show students 3D representations of malformations of the fetus, but the method proved to be useful in practice.

"In postnatal discussions, when I would talk to a surgeon, we sometimes found it difficult to explain with a 2D image on the screen," said Dr Werner. They started to print in 3D, which made it easier, but the problem was the price. "We have lot of cases; to print them all is costly," he explained.

So Dr Werner connected with the 3D modeling lab at his university to find a new way of visualizing malformations of the fetus. He took his 3D model, which included the womb, umbilical, cord, placenta, and fetus, and had it programmed for the Oculus Rift 2, a virtual-reality headset. The researchers added the sound of the heartbeat to make the experience even more immersive.

Strap on a Headset

Now, by fastening on a headset and headphones, physicians can get a close look at the internal pathways of a fetus to identify issues.

Dr Werner was involved in the creation of a 3D model to help a fetal endoscopic surgeon visualize twin-to-twin transfusion syndrome, which left one twin at risk for starvation (Arch Gynecol Obstet. 2015;292:1183-1184). Using a 3D model, the team was able to simulate the surgery in virtual reality.

"We think this is especially interesting for training novice endoscopic surgeons," Dr Werner said.

In another case he was involved in, researchers used 3D ultrasound and MRI to create a 3D physical model of the airway of a fetus with a tumor in the thorax at 36 weeks (Congenit Anom [Kyoto]. 2016;56:46-47). They then created a simulated video of the fetus so the doctor could "travel" from the upper respiratory tract through the pharynx and down to the tracheobronchial tree.

"If a tumor is causing compression, you have to wait to cut the umbilical cord to stabilize the airway path first," said Dr Werner. "Virtual reality gives the surgeon another way of visualizing the problem and a way discuss it with the parents."

New ways of using the technology are emerging constantly, he added. Currently, he's working with physicians to study trisomy 11 and trisomy 18 syndromes. "You scan the face and print it in 3D so the parents can visualize it," he explained. "It's a way to help them calm their anticipations."

Dr Werner is also conducting the prenatal and postnatal visualizations for mothers infected with the Zika virus.

Although 3D printing will continue to be invaluable, Dr Werner said he sees a future in which 3D visualizations will be integrated directly with ultrasound and MRI.

"Then doctors can prepare the image in the way they want, in accordance with their particular discipline," he explained. "At that point, they might be able to manipulate the image on their own and might not even need to send it to us to clean up."

 
Most doctors still want something they can hold.
 

But not everyone is jumping into virtual reality just yet. A more hands-on approach with 3D-printed models is still preferable to Michael Itagaki, MD, a Seattle-based interventional radiologist and the owner of Embodi3D.com, a biomedical 3D printing company.

"Most doctors still want something they can hold and have an intuitive understanding of, and it's still better than what you can get with just visualization," he said.

When you look at something in virtual reality, it's just using one sense — your eyes. But if you're holding it and looking at it, you're using two senses, he explained. The sense of touch is strong and is one of the key reasons people who are blind have a very good understanding of things when they pick them up and feel them, Dr Itagaki added.

And with 3D models you can actually test devices. "You can take a catheter or a wire or something and put it in a model. You can understand how much torque is on it, how much bend it has, how much force it feels; there's no way you can simulate that in virtual reality," he explained. "Having something that is physical and solid is still more helpful."

Dr Werner has disclosed no relevant financial relationships. Dr Itagaki is the owner of Embodi3D.com.

Radiological Society of North America (RSNA) 2016 Annual Meeting: Abstracts PD230-SD-WEB1 and NR394-SD-WEB2. Presented November 30, 2016.

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