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Hold Me, Turn Me

Posted August 18, 2015

Four children with life-threatening malformations of blood vessels in the brain appear to be the first to benefit from 3-D printing of their anatomy before undergoing high-risk corrective procedures, according to a new paper.

Darren Orbach studies a 3-D printed model of a patient’s blood vessels to prepare for surgery. Image credit: Katherine Cohen, Boston Children's

Darren Orbach studies a 3-D printed model of a patient’s blood vessels to prepare for surgery. Image credit: Katherine Cohen, Boston Children’s

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,” said Edward R. Smith, Harvard Medical School associate professor of neurosurgery at Boston Children’s Hospital and senior author of the paper.

“The 3-D printed models allowed us to rehearse the cases beforehand and reduce operative risk as much as we could,” said Smith, who co-directs the Cerebrovascular Surgery and Interventions Center at Boston Children’s. “You can physically hold the 3-D models, view them from different angles, practice the operation with real instruments and get tactile feedback.”

As described 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 3-D printer that laid down synthetic resins layer by layer.

Prints were made not just of the cerebrovascular malformations but also from the normal vessels feeding and draining them, and, in some cases, the surrounding brain anatomy. Each print 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.

“In AVMs, there’s a need to cut the blood vessels in a very specific sequence, like defusing a bomb,” said 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 3-D 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.”

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 3-D-printed vessels on her smartphone. “I want to dip it in gold and wear it as a necklace,” she said.

Darren Orbach, HMS associate professor of radiology and co-director of the Cerebrovascular Surgery and Interventions Center at Boston Children’s, treated a 2-month-old infant who had a rare vein of Galen malformation in which arteries bypass capillaries to connect directly with veins. Orbach 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 3-D model in your hand is transformative,” he said. “Our brains work in three dimensions, and treatment planning with a printed model takes on an intuitive feel that it cannot otherwise have.”

A 3-D printed AVM as it appears in situ, embedded in brain tissue. Image: Katherine Cohen, Boston Children's

A 3-D printed AVM as it appears in situ, embedded in brain tissue. Image: Katherine Cohen, Boston Children’s

Greater precision, greater safety

The life-sized and enlarged 3-D models, based on brain magnetic resonance and magnetic resonance arteriography data from each child, were created in collaboration with the Boston Children’s Hospital Simulator Program (SIMPeds), directed by HMS associate professor of anesthesia Peter Weinstock, 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 3-D printed models—matched for age, size and type of AVM, surgeon and operating room—those with 3-D 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.

The SIMPeds program is tracking use of 3-D printed models across Boston Children’s Hospital, such as a recent high-profile case of a toddler with a severe skull defect. Smith and Orbach continue to use 3-D models for their trickier cases.

“3-D 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.”

Source: HMS

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