Scanner gives surgeons real-time 'road map' of human body

Canadian surgeons may be a step closer to making virtual navigation of the human body – akin to a car’s GPS — a part of their surgical repertoire.

The 7D Surgical Navigation device was pioneered by a team of doctors and engineers from Sunnybrook Health Sciences Centre and Ryerson University in Toronto, and is being tested now. It gives surgeons a roadmap of what lies beneath human tissue – without having to make a cut.

If the device pans out, it could improve surgeries for patients worldwide by allowing surgeons to cut, dissect, and insert bone screws within half a millimetre of precision – which is a step above other available surgical navigation devices.

Being precise during brain and spine surgeries 'can mean the difference between a good outcome or coma and paralysis.'- Dr. Vincent Yang

And being precise during brain and spine surgeries “can mean the difference between a good outcome or coma and paralysis,” says Dr. Victor Yang, the device’s inventor and a neurosurgeon at Sunnybrook Health Sciences Centre.

No one understands the issue more than retired dentist and high school teacher Dr. Peter Salmon, whose life changed after a tragic fall last year. “I had a serious spinal cord injury and doctors said my chances of recovery were slim to none,” he says.

“We thought he might be on a breathing machine and completely paralyzed for the rest of his life,” says his wife Roslyn.

After two surgeries on his spine, Peter Salmon now breathes on his own and has been gaining strength in his arms and legs. Shortly after his operations, surgeons realized one of the screws in his spine wasn’t in the ideal position, but fortunately there have been no complications.

Others aren't so fortunate, though, and Dr. Yang says this is what inspired him to develop the 7D device in the hopes of minimizing surgical imprecision.

There’s a 3 per cent risk that screws inserted during spine surgery won’t be in the right place using current technology and techniques, Yang says. The existing navigation system used to guide certain parts of the operation aren’t always perfect, he adds.  

For years, surgeons have been using X-rays and CT scans to help guide their surgeries. Navigation systems that are currently used during operations have been shown to reduce the need for repeat surgery to fix mistakes – but they have their own set of issues.

The main challenge is to perfectly “match up” a patient’s CT or MRI scan – which could have been taken months earlier — to the patient’s body at the time of surgery. Adding to the complexity of that matchup, the contours of the body and underlying anatomy change depending on how the patient lies on the operating table, Yang says.

“It’s very difficult to look at a scan and know if the structures under the skin will be exactly where you expect,” he adds.

During brain and spine surgery, neurosurgeons try to match a patient’s CT or MRI scan to that patient’s body by using a pointer to mark specific anatomical landmarks. A navigation device then links each landmark to its corresponding position on the scan, giving surgeons a computerized 3D image of what is under the surface.

However, the accuracy of the match-up depends on the surgeon’s ability to place the landmarks in the right location and on the assumption that no change has occurred in the patient's body between the time of the scan and surgery.

“That’s a big assumption,” Yang says.

Navigation systems that overcome these issues do exist, but they rely on bulky CT machines in the operating room or special “hybrid” operating rooms with built-in CT scanners, which are expensive and few and far between.

Biophotonics

On top of this, most navigation devices require significant time to set-up, constant adjustment in the operating room, and have awkward designs that obscure a surgeon’s view, making them hard to use - not to mention disruptive to the surgery at hand.

 “We wanted to make a device that was precise, easy-to-use, and less expensive so that all patients could benefit,” Yang says.

Yang, along with his research team of engineers and scientists at 7D Surgical, may have found the answer with their new 7D Surgical Navigation device, which is in the early phase of human trials.

The 7D device looks like a special light that hangs over the surgical table. It uses the principle of biophotonics — the science of using light photons for imaging biological materials — to detect surface contours and underlying anatomy.

The device then perfectly matches up the surface that it sees with a patient’s CT or MRI scan, generating an accurate 3D map of what’s underneath. The anatomical roadmap is projected onto computer screens in the operating room so that surgeons can view the images in real-time as they operate.

By removing the guesswork that surgeons often have to rely on, the device’s ability to match up a scan to a patient’s body has an unparalleled level of precision. With every movement on the operating table the device generates new images.

“It essentially works in real-time, so you can watch as your screw goes into bone millimetre by millimetre,” Yang says.

Yang hopes that the 7D device will lead to safer surgeries and lower rates of revision surgery.

Cost savings

What’s more, given that the device itself is a light mounted above the table along with the regular operating-room lights, all surgeons need to do is move it into their surgical view to get the device to work. Since surgeons naturally direct the room lights toward the area where they’re operating, “using the device basically requires no extra movements,” Yang says.

The device’s ease of use and almost zero setup time mean that surgeries may become faster and cheaper.

Each minute in the operating room can cost anywhere from $100 to $200. If you add in the relatively inexpensive price tag of roughly $300,000 for the [7D] device itself, hospitals could save significant amounts of money.- Dr. Victor Yang

CT scanners used in the operating room can easily cost upwards of  $1 million and can take 30 minutes to set up, for example.

“Each minute in the operating room can cost anywhere from $100 to $200,” Yang says. “If you add in the relatively inexpensive price tag of roughly $300,000 for the [7D] device itself, hospitals could save significant amounts of money.”

Early testing of the 7D device suggests that drawbacks are limited.

There have, however, been issues with using the device at the same time that surgeons have their own forehead-mounted mini-headlights turned on. The added light can throw off the sensitive 7D device's image quality, Yang says.

Yang’s team is working to fix this by figuring out how to calibrate the device to accommodate the extra light, and is looking at special mini-headlights that won’t interfere.

Research will focus on testing how the 7D device compares to other techniques and whether it actually results in safer surgeries and fewer complications. The device will primarily be used in spine, brain, and head and neck surgeries for now.

So far, Yang and a number of his surgical colleagues at Sunnybrook Health Sciences Centre have used the 7D device on 10 patients during spine and brain surgeries.

For patients like Dr. Peter Salmon, taking away some of the risks associated with surgery could make all the difference. “I hope future patients in my position will have access to such a revolutionary tool,” he says.