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LASER 2023: optics promises autonomy for surgical robots

29 Jun 2023

Full body scans of skin lesions, laser bone cutting, and craniotomies among the possibilities discussed at Munich technical forum.

by Mike Hatcher in Munich
What will the operating room of the future look like? Well, if the suggestions in an eye-opening technical forum on robotic surgery at LASER World of Photonics prove accurate then we will see some remarkable new techniques powered by optics and lasers.

Photonics technology is of course already used widely in surgery, a point underlined by the fact that cataract removal is the number-one surgical procedure performed worldwide, with some 25 million operations now carried out every year.

That is largely because the eye presents an ideal optical window for light-based interventions, and laser correction of visual defects is now a decades-old procedure. Development of the state-of-the-art robotic “SMILE” (SMall Incision Lenticule Extraction) Carl Zeiss system, using a femtosecond laser, began 20 years ago, and some 7 million corrections were carried out in 2022.

Outlining which kinds of optics technologies might appear on platforms in the future, Erik Markveg from the Jena-based surgical robot maker AvateraMedical highlighted that today’s surgical robots still all rely on a surgeon’s view down an eyepiece - they are not yet autonomous systems.

For that reason, AvateraMedical has added features like immersive eyepieces, haptic sensors, and stereoscopic optics to give the surgeon something approaching the “natural” kind of feedback that is lost from conventional hands-on surgery.

Markveg said that imaging would play a key role in the future development of robot-assisted surgery, ultimately enabling autonomous operation.

Techniques that might support that transition include autofluorescence for tissue discrimination, spectral imaging to identify tumors and blood perfusion, optical coherence tomography (OCT) to identify tissue layers and nerves, and even Raman techniques to provide molecular information.

Full-body OCT scan
OCT was a topic picked up by the University of Lübeck’s Robert Huber - one of the original pioneers of the technique. Huber’s team has now developed a system capable of 30 MHz operation - allowing tens of millions of depth scans per second.

It means that although OCT will always struggle to penetrate much beyond a millimeter of normal human skin, “MHz-OCT” offers the prospect of rapidly scanning large areas of skin, provided that the huge streams of data generated can be handled.

Huber showed an in vivo image of an entire human hand captured in this way, and said that in principle an entire body could be scanned for suspicious skin lesions in just three minutes.

“OCT for medical robots is like lidar for self-driving cars,” Huber told the forum, suggesting that the technique could be invaluable in the move towards more autonomous surgical robots.

Huber's Munich-based startup company OptoRes is looking to commercialize the technology, which is based around its patented Fourier-domain mode-locking (FDML) approach.

Bone machine
Another startup, Advanced Osteotomy Tools (AOT), is pursuing an even more radical idea. Summed up by the Basel-based company’s strapline “We Laser Bone”, AOT is seeking to reinvent bone surgery with the use of an erbium-YAG source.

Emitting microsecond pulses at 2490 nm, the wavelength matches an absorption peak of water, which is present in bones, and works by heating up water rather than bone tissue directly. CTO Tobias Wilken has overseen development of AOT’s “CARLO” (Cold Ablation Robot-Guided Laser Osteoplasty) system, which has gained CE Mark approval following a clinical study involving more than 100 patients.

Now deployed in around a dozen clinics - mostly in France and Germany - CARLO is said to remove bone tissue layer-by-layer in a far less traumatic manner than a conventional medical saw or drill, preserving more bone architecture and helping patients heal more quickly. Animal studies have also shown increased bone-regrowth, said Wilken.

Promising application areas are seen in knee surgery - where the much greater flexibility of the laser system could be used to help fix specific problems that would currently require a full knee replacement - as well as interventions to the cochlear and middle ear.

Likening the universal nature of the tool to that of a scalpel or a drill, Wilkens described the approach and its digital workflow as “the missing key to digitizing surgery”.

‘Awake’ laser craniotomy
The same session also heard a remarkable presentation from Freiburg neurosurgeon Peter Reinacher, who has been working with the Fraunhofer Institute for Laser Technology (ILT) on a laser for “awake” craniotomies.

Reinacher explained that the “awake” approach is known to offer better patient outcomes for interventions such as deep-brain stimulation to control serious tremors caused by Parkinson’s disease, or removal of low-grade glioma tumors - but that many patients are understandably put off by the prospect of having a hole drilled in their skull.

Conventional drills also carry a high risk of collateral damage, and so the team has set about developing an alternative laser approach that is safer and more patient-friendly.

The result, thus far, is a Q-switched carbon dioxide laser called “STELLA” that in animal tests has been able to remove skull tissue at a similar rate to that of a conventional tool, with efficient ablation and no heat damage when used alongside a water spray that is a typical feature in surgery.

Not yet tested on people, the laser craniotome is also monitored with OCT, which allows tissue removal to be stopped just before the laser fully pierces the skull. Instead, a layer of bone tissue a few hundred microns thick can be safely left in place, and then removed with a more conventional tool.

LaCroix Precision OpticsSPECTROGON ABUniverse Kogaku America Inc.ECOPTIKSchaefter und Kirchhoff GmbHTRIOPTICS GmbHHÜBNER Photonics
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