(CNN) In the past six months, Cassidy and Chad Lexcen have been too busy to look at the Google Cardboard images that saved their baby's life.

During that time they had to tend to their daughter, Teegan, who teetered on the brink of life and death at Nicklaus Children's Hospital in Miami, plus they had to fly back and forth to care for their other three children in Chaska, Minnesota.

But CNN recently brought the images of Teegan's heart to the Lexcens, and seeing them for the first time brought on deep emotions -- both happy and sad.

Google Cardboard looks like a set of big square goggles. Stick your iPhone inside and with the right app, you can see images in three-dimensional virtual reality.

Pediatric heart surgeons at Nicklaus used the Google Cardboard images to design a one-of-a-kind surgery for Teegan, who was born with half a heart and one lung.

The doctors in Miami had never seen a child with Teegan's anatomy, and went back and forth on what surgery could help her. Some of them thought it was hopeless.

But one member of the team, Dr. Juan Carlos Muniz, had the idea of looking at images of her heart in Google Cardboard, where it would be seen in virtual reality.

Muniz gave the contraption to Dr. Redmond Burke, director of cardiovascular surgery at Nicklaus. Using the device, Burke could move around and see the heart from every angle -- to almost be inside the heart, checking out its structure.

Parents Cassidy and Chad Lexcen, older daughter Harper, son Asher and the twin babies Teegan, right, and Riley.

Google Cardboard allowed Burke to map out the surgery , which she had in December.

In July, her parents got to see those images.

"Holy cow! This is so cool!" Chad said as he looked through Google Cardboard in his living room. "It's almost like a little video game."

"You don't picture doctors and surgeons looking through a piece of cardboard and some glasses to plan a major life saving surgery," Cassidy added. "It seems like a toy."

Seeing the images made the Lexcens appreciate even more the inventive surgery that saved Teegan -- but it also brought back memories of when her original doctors told them their baby was inoperable and they should take her home to die.

Cassidy said doctors in Minnesota told her and her husband to "make the best of our time with her and just prepare to say goodbye."

The worst moment was when they brought Teegan and her twin sister, Riley, home, and they had to tell their older daughter, Harper, then 6, that Teegan wasn't going to make it.

"We had to tell her that we have these two baby girls but one of them is going to be an angel baby -- and she was old enough to know what an angel baby was," Cassidy said.

But the Lexcens didn't give up. Instead, they searched around the country for a surgical team that might consider operating on Teegan.

They found their team at Nicklaus, and she had her surgery there in December when she was almost 4 months old.

But even after the surgery, Teegan's life was still in danger.

Teegen Lexcen

"We were on a constant roller coaster. There were good days and bad days, good weeks and bad weeks," Burke, the surgeon, said. "We were never sure if this was going to be it, if we were going to lose her."

Teegan spent six months in the hospital and needed two more surgeries, including a tracheostomy to help her breathe.

She was discharged in June.

Since then, except for a bad cold that landed her in the hospital for a few days, she's been doing well. The main goal now is for her to gain weight. At 10 months old she weighs only a little over 11 pounds.

Burke said it's impossible to make a prognosis for Teegan, given the uniqueness of her anatomy. But he says all the signs are good.

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"She's gaining weight, and that's a good predictor of how well she'll do," he said. "Plus she's got a resiliency, and that's really key. She's recovering from her cold, but if she'd caught that cold before the surgery, it would have killed her."

The Lexcens say they'll always be grateful to Burke and the other doctors and nurses who cared for Teegan, and for Google Cardboard.

"It's amazing for the fact that it gave him the exact path that he needed to get to her heart," Cassidy said.