Hold me, turn me: 3D printed models help doctors rehearse tricky cerebrovascular procedures

Vein of Galen-3D-20140418_Orbach-croppedFour children with life-threatening malformations of blood vessels in the brain appear to be the first to benefit from 3D printing of their anatomy before undergoing high-risk corrective procedures.

The children, ranging from 2 months to 16 years old, all posed particular treatment challenges: cerebrovascular disease often entails complex tangles of vessels in sensitive brain areas.

“These children had unique anatomy with deep vessels that were very tricky to operate on,” says Boston Children’s neurosurgeon Edward Smith, MD, senior author of the paper and co-director of the hospital’s Cerebrovascular Surgery and Interventions Center. “The 3D-printed models allowed us to rehearse the cases beforehand and reduce operative risk as much as we could. You can physically hold the 3D models, view them from different angles, practice the operation with real instruments and get tactile feedback.”

3D printing cerebrovascular
The 3D printer at work.

As described last week in the Journal of Neurosurgery: Pediatrics, the models were based on the children’s actual brain scans. Data from the scans were used to program a 3D printer that laid down synthetic resins layer by layer. Prints were made not just of the cerebrovascular malformations, but also the normal vessels feeding and draining them, and, in some case, the surrounding brain anatomy. The prints each took less than 24 hours to make.

The kindest cuts

Three of the four children had arteriovenous malformations (AVMs), in which tangles of arteries and veins connect abnormally, and were treated surgically. One of them was Adam Stedman, a 16-year-old with an AVM in the visual processing area of his brain. He faced a risk of serious vision loss if the AVM was not promptly and correctly removed.

Adam's AVM print.
Adam’s AVM print.

“In AVMs, there’s a need to cut the cut the blood vessels in a very specific sequence, like defusing a bomb,” says Smith, who operated on Adam. “A lot of the vessels were deep, and we needed to get a sense of which were feeding the AVM and which were draining it. You want to turn the faucet off first before you close the drain; if not, the sink overflows. The 3D model allowed me to go directly to the right pipes as quickly and efficiently as possible and move in rapid progression because I’d practiced those steps ahead of time.”

But the surgery went off without complications, and last month Adam had a clean one-year follow-up angiogram. He has a small blind spot in his vision but has adjusted to it.

Adam’s mother, Amy, keeps a photo of his 3D-printed vessels on her smartphone. “I want to dip it in gold and wear it as a necklace,” she says.

3D printing cerebrovascular
A 3D-printed AVM as it appears in situ, embedded in brain tissue.

Darren Orbach, MD, PhD, codirector of the Cerebrovascular Surgery and Interventions Center, who treated the 2-month-old infant had a rare vein of Galen malformation in which arteries connect directly with veins, bypassing the capillaries. He used an interventional radiology technique called embolization to seal off the malformed blood vessels from the inside.

“Even for a radiologist who is comfortable working with and extrapolating from images on the computer to the patient, turning over a 3D model in your hand is transformative,” he says. “Our brains work in three dimensions, and treatment planning with a printed model takes on an intuitive feel that it cannot otherwise have.”

At left, a magnetic resonance angiogram of the baby’s vein of Galen malformation. At right, the 3D-printed model. The arrows indicate the arteries feeding the malformation (red arrows) and the vein draining it (blue arrow).
At left, a magnetic resonance angiogram of the baby’s vein of Galen malformation. At right, the 3D-printed model. The arrows indicate the arteries feeding the malformation (red arrows) and the vein draining it (blue arrow).

Greater precision, greater safety

The life-sized and enlarged 3D models, based on brain magnetic resonance (MR) and MR arteriography data from each child, were created in collaboration with the Boston Children’s Hospital Simulator Program (SIMPeds), directed by Peter Weinstock, MD, PhD, the paper’s first author. Measurements of the models showed 98 percent agreement with the children’s actual anatomy.

All four children’s malformations were successfully removed or eliminated with no complications. When two of the AVM patients were compared with controls who did not have 3D-printed models—matched for age, size and type of AVM, surgeon and operating room—those with 3D models had their surgical time reduced by 30 minutes, or 12 percent. That may sound modest, but even a 30-minute reduction is significant for children who are especially sensitive to anesthesia.

Process of creating a 3D printed model from patient image data Peter Weinstock simulation program
The making of a model (clockwise from top left): Importing a patient’s images into a 3D design program for printing; checking the print job; removing the model, embedded in a support material, from the printer; examining the cleaned and finished product (in this case, modeling a skull defect).

The SIMPeds program is tracking use of 3D-printed models across Boston Children’s Hospital, such as a recent high-profile case of a toddler with a severe skull defect cared for by the Craniofacial Anomalies Program. Melissa Burke, SIMPeds director of operations, cites several benefits of custom 3D models:

  • Safer procedures
  • More efficient procedures
  • Increased surgical confidence
  • Reduced time under anesthesia
  • Reduced blood loss during surgery

“Sometimes the prints are used to come to the conclusion that we don’t want to do a surgery, which is very valuable,” adds Burke.

Smith and Orbach are continuing to use 3D models for their trickier cases. “3D printing has become a regular part of our process,” says Smith. “It’s also a tool that allows us to educate our junior colleagues and trainees in a way that’s safe, without putting a child at risk.”