Surgeons use augmented reality to ‘see inside’ the bones of patients
A team at Imperial College London has demonstrated how surgeons can use augmented reality in the operating theatre to improve the outcome of reconstructive surgery for patients.
In a series of trial procedures at St Mary’s Hospital in London, surgeons strapped on a Microsoft HoloLens headset while operating on patients undergoing reconstructive lower limb surgery.
The HoloLens is a self-contained computer headset that immerses the wearer in ‘mixed reality’, enabling them to interact with holograms – computer-generated objects made visible through the visor.
The Imperial team used the technology to overlay images of CT scans – including the position of bones and key blood vessels – onto each patient’s leg, in effect enabling the surgeon to ‘see through’ the limb during surgery.
According to the team trialling the technology, the approach can help surgeons locate and reconnect key blood vessels during reconstructive surgery, which could improve outcomes for patients.
“We are one of the first groups in the world to use the HoloLens successfully in the operating theatre,” said Dr Philip Pratt, lead author of the study.
“Through this initial series of patient cases we have shown that the technology is practical, and that it can provide a benefit to the surgical team. With the HoloLens, you look at the leg and essentially see inside of it. You see the bones, the course of the blood vessels, and can identify exactly where the targets are located.”
Following a car accident or severe trauma, patients may have tissue damage or open wounds that require reconstructive surgery using fasciocutaneous flaps. These flaps of tissue, which are taken from elsewhere on the body and include the skin and blood vessels, are used to cover the wound and enable it to close and heal properly.
A vital step in the process is connecting the blood vessels of the ‘new’ tissue with those at the site of the wound, so oxygenated blood can reach the new tissue and keep it alive.
The standard approach for this element of reconstructive surgery has been the use of a handheld scanner which uses ultrasound to identify blood vessels under the skin by detecting the movement of blood pulsing through them, enabling the surgeon to approximate where the vessels are and their course through the tissue.
“Augmented reality offers a new way to find these blood vessels under the skin accurately and quickly by overlaying scan images onto the patient during the operation,” explained Dr Pratt.
In the procedures used to trial the technology, five patients requiring reconstructive surgery on their legs underwent CT scans to map the structure of the limb, including the position of bones and the location and course of blood vessels.
Images from the scans were then segmented into bone, muscle, fatty tissue and blood vessels by Dr Dimitri Amiras, a consultant radiologist at Imperial College Healthcare NHS Trust (ICHNT), and loaded into intermediary software to create 3D models of the leg.
These models were then fed into specially designed software that renders the images for the HoloLens headset, which in turn overlays the model onto what the surgeon can see in the operating theatre. Clinical staff are able to manipulate these AR images through hand gestures to make any fine adjustments and correctly line up the model with surgical landmarks on the patient’s limbs, such as the knee joint or ankle bone.
Dr Amiras said: “Using the HoloLens, we can identify where the blood vessels are in 3D space and use virtual 3D arrows to guide the surgeon. Currently, data preparation is a time-consuming process, but in the future much of this could be automated, with the consultant radiologist checking the accuracy of the model against the original scan. I think this is a great example of what can be achieved in an Academic Health Science Centre.”
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