Heads-up surgery: Dr Robert Ibe discusses augmented reality in operating microscopes for neurosurgical interventions
Brain cancer is one of the most deeply feared diseases. Besides often killing with devastating speed, it can also profoundly affect the organ that most people associate with the mind and self, the seat of our emotions and fundamental controller of our bodies and behaviour. Glioma is the most common cancer that originates in the brain. It is a ‘primary’ rather than ‘metastatic’ brain tumour. Gliomas are more accurately described based on the type of cells from which the tumour originated, for example, glioblastomas, astrocytomas or oligodendrogliomas. The most common primary brain tumour in adults is glioblastoma multiforme, which is also unfortunately the deadliest.
Apart from management options to control the symptoms of the tumour, one treatment option is surgical intervention. However, brain surgery is notoriously difficult. The benefits need to be carefully considered against the risks of such surgery, and even then, successful recovery can be slow. But innovations are constantly being developed in multiple paradigms and new approaches pioneered. One such example is how microscopy is becoming increasingly facilitative of exoscopic microsurgery, especially in neurosurgery and neurovascular surgery.
Heads-up Surgery
Traditional surgical microscopes employ binocular eye pieces that necessitate a heads-down approach to surgery. Although such binocular microscopes offer excellent image quality, magnification and illumination while freeing up the surgeon’s hands, the heads-down approach means compromised ergonomics. Surgeons frequently need to adopt awkward body positions, which can put considerable strain on their necks and backs, especially if these positions are maintained for several hours during surgery.
“Keyhole surgery”, as laparoscopic surgery is often referred to in lay terms, redefined the field of surgery, providing minimally invasive procedures, which reduced pain, incision size, wound complications and post-operative recovery and hospital stay. However, laparoscopy can also reduce the surgeon’s range of movement through the incision, and depth perception due to the two-dimensional (2D) view.
Similarly, endoscopes facilitate minimally invasive brain surgery. They offer superior ergonomics when used with a high-resolution camera and a high-definition screen, to give surgeons an in-depth view of the brain. But endoscopy also has some limitations, such as short focal length and the lack of true depth perception with 2D images. Endoscopes also need to be operated by the surgeon, thereby occupying one hand throughout the surgery.
A new digital surgical microscope optimised for heads-up surgery, with the ability to incorporate augmented reality (AR) technologies to better inform surgeons in real-time, has been developed by Leica Microsystems to tackle these surgical challenges. The ARveo digital AR microscope and how it is being used by neurosurgeons, such as Professor Dr Raphael Guzman from the University Hospital and Children’s Hospital in Basel, Switzerland, highlights how technological advances in the digital imaging quality of surgical microscopes are paving the way for new surgical operating approaches. Not only does the ARveo deliver excellent resolution, depth-of-field and colour on ultra-high-definition 4K screens, the 3D depth perception is also comparable with that achieved with binocular microscopes.
This enables neurosurgeons to determine tissue characteristics, discern subtle changes and confidently manoeuvre their surgical instruments in and out of deep cavities. This gives the surgeon confidence in what he or she is assessing and reduces their physical strain and tiredness, allowing them to perform long surgeries in a more comfortable operating position. Particularly in conjunction with exoscopic surgery, neurosurgeons can now orient the microscope into any field at any angle, allowing the surgeon to stand or sit upright, look straight ahead and move only their hands rather than their entire body in the direction of work, throughout the operation.
This technology may even open up new or rarely used angles compared with conventional optical microscopy. For example, surgery performed in the posterior fossa, with a supracerebellar infratentorial approach to the pineal region to biopsy or resect pineal-region tumours, can traditionally be performed in either a prone or semi-sitting position. The semi-sitting position involves bending the neck to look upwards at the surgical site and raising the arms in an overhead position for long periods of time during the surgery. However, performing the same type of surgery using an exoscope with heads-up display avoids the unnecessary tiring of the neck and arms, while providing a caudal-to-cranial view of the patient and surgical site. Surgeons now have the advantage of being able to adapt the microscope image instantly, rather than their bodies to be able to visualise what they need to see in the surgical field of view.
Augmenting Reality for Integrated Insights
As a digital operating microscope, the information provided by the ARveo can be integrated with data from other devices and sources, for example, real-time information on the patient’s vitals. Connectivity can also be leveraged to integrate image guided surgery (IGS) and AR image overlays. For example, IGS with AR can reveal both the cortical surface as well as an in-depth view of a tumour. Another example is the intraoperative fluorescence imaging of tumours, using the active substance, 5 aminolevulinic acid (5-ALA) and the blue light fluorescence module, Leica FL400.5.
“When we talk about fluorescence imaging, intraoperative fluorescent angiography, intraoperative fluorescence for a tumour surgery with 5-ALA, I think the resolution and the perception of the fluorescence on the big screen is actually a little bit better than when it’s injected into the ocular,” says Guzman.
Moreover, fluorescent AR from the Glow platform can provide additional precise, real-time information that can prove critical for timely decision-making in the operating room. The latest Glow800 augmented reality fluorescence delivers impressive fluorescent visualisation both on-screen for heads-up neurovascular surgery and in the binocular view, via the CaptiView image injection module. The fluorescent signal appears to be truly within the blood vessel and not floating above or beside it, which is important as it allows surgeons to move the blood vessels to see what is behind them – a view that may previously been obstructed by a surgical clip, for example.
Given the ever-improving image quality available with digital microscopes and heads-up displays, there is a growing trend towards using this more comfortable, convenient and precise imaging technology in neurosurgery and neurovascular surgery. As these and other innovations continue to proliferate in the surgical field, it is hoped that surgical interventions for brain and other tumours can continue to improve, both in terms of operative ease and effectiveness for surgical teams and in terms of clinical outcomes for patients.
Dr Robert Ibe is with Leica Microsystems
