Purpose and aims
The technologies aim to facilitate minimally invasive surgery, i.e., operations via small surgical approaches with minimized wound size, blood loss and surgery time. The small incisions require the surgeon to operate without a direct view of the deep anatomical structures. Instead, surgical navigation based on modern imaging and visualization technologies must be employed to reveal the anatomy of the surgical area. These technologies let the surgeon see inside the patient and perform procedures with enhanced precision. In addition, they can be used to confirm that a surgical implant is placed correctly at the first attempt.
- Intraoperative navigation, a technique for guiding surgical instruments with high precision during an operation. We are developing a new and unique technology, based on augmented reality (AR), where radiological and real-time video images are merged, so that the surgeon can "see" inside the patient. We have published several studies on monitor-based AR technology in spinal navigation, and are now further developing that system for navigation in the brain during open and endoscopic surgery. We also intend to study eyeglass-based (Head Mounted Device, HMD) mobile AR for spinal and cranial procedures as well as various methods for registering the patient's position, so-called patient tracking.
- Tissue recognition, where "smart instruments" inform the surgeon of the tissue type facing the instrument. We use diffuse reflectance spectroscopy (DRS) for spinal surgery, surgery on brain tumors as well as interventional removal of blood clots in the brain to prevent stroke. Furthermore, we study Hyperspectral imaging (HSI) for non-invasive visualization of different tissue types such as tumor and healthy tissue.
The development of intracranial surgery has been dependent on technological advances. Imaging techniques such as DT and MRI, the surgical microscope and navigation systems have enabled detailed diagnostics and maintained surgical precision even deep within the brain. Interventional angiography, methods of navigating catheters inside blood vessels and examining and treating vascular diseases, have provided new possibilities. Parts of our project are performed in a hybrid operating room, i.e. an operating theatre equipped with advanced radiological equipment for angiographic intervention, in combination with newly developed navigation technology based on augmented reality technology. This unique combination allows the integration of the interventional radiological methods with navigated surgery.
An essential component of AR navigation is the user interface, i.e. how the superimposed image with information is presented to the surgeon. The user interfaces available today are monitor, projector, microscope and HMD. We have extensive experience in monitor and microscope-based AR. However, there is evidence suggesting that the future may lie in HMD-based solutions that are under continuous development. Aside from the fact that HMDs provide an opportunity to combine AR and virtual reality (VR) for better imaging and understanding of reality, they also provide the advantage that the surgeon never has to look away from the surgical field. A simple and portable piece of equipment that does not depend on large underlying infrastructure such as a hybrid OR and intraoperative radiology can lead to easier and more widespread use of the technology even if some benefits of the hybrid OR-based solutions are lost.
Spinal surgery is usually performed with only anatomical structures on the vertebrae as landmarks and with fluoroscopy of implants as a control. The anatomy of the vertebral column must therefore be exposed with large surgical openings and the surgical staff are repeatedly exposed to radiation. In minimally invasive techniques,small incisions or puncture holes are used and surgical trauma is minimized. However, this requires other methods to visualize deep lying structures. Our navigation technology provides that visualization without exposing the staff to radiation. We have published several studies on AR navigation in spinal surgery in the thoracic and lumbar spine.
In parallel with the navigation methods, we are developing two optical techniques, based on spectral analysis to give the surgeon more information about the tissues being operated on. These are DRS where a probe is built into a surgical instrument and used to differentiate between tissues or HSI where the tissue surface is photographed non-invasively for the same purpose. In several preclinical studies, we have demonstrated the ability of the DRS method to distinguish between cortical and cancellous bone, i.e. between the outer hard casing of a vertebrae and the inner softer core. This method has successfully been used in tumor surgery. We use DRS in an ongoing study to distinguish between brain tumor and healthy brain. At the same time, in a first clinical pilot study, we have shown that HSI technology can be applied for the same purpose. Studies to compare these two methods in tumor surgery are planned. The DRS technology will also be tested in clinical spinal surgery studies as soon as a commercial product has been launched. We have used DRS in an animal model to distinguish different blood clot types. Studies on human clots are ongoing.
Significance and scientific novelty
We intend to develop and improve different interfaces for AR navigation, as a novel approach to surgical navigation, with the aim that they would be the first choice in spine, as well as in open and endoscopic intracranial surgery. Furthermore, "smart instruments" with tissue recognition technology will be developed for spinal, cranial and interventional use. The non-invasive HSI technique will be adapted for guidance in tumor surgery. The combination of AR navigation, "smart instruments" and HSI may result in increased surgical precision, measured by both radiological and clinical outcome measures, thereby reducing patient injuries, intervention and hospital stay times, as well as preventing reoperations. At the macro level, socio-economic benefits are achieved by making optimal use of healthcare resources and minimizing patient harm.
The projects are conducted as a research collaboration between our group at the Karolinska University Hospital and the technical universities of Delft and Eindhoven in the Netherlands and of Las Palmas in Spain as well as Cincinnati Children's Hospital in the USA. The Karolinska University Hospital has an innovation partnership with Philips, and some of our projects are based within this partnership. Our research group at Karolinska designs and conducts preclinical and clinical studies and formulates the clinical problems, while Philips contributes with technical knowledge and technology development. Thus, we have a crucial role to play in the targeting and development of the new technologies, while conducting independent clinical studies. Our group receives no funding from Philips, but the collaboration with Philips on the described techniques is exclusive, no other hospitals or clinics are involved. At the same time, we have initiated a collaboration with Brainlab, the leading company in surgical navigation technology. Brainlab develops AR based on a platform other than Philips. In a tripartite collaboration, we intend to compare these techniques and study the possibilities of combining these to achieve the best clinical results.
Another industrial collaboration is with the company LightSpace3D, which develops multifocal AR glasses for work near the surgical field (<30cm).
Clinical studies: neurology, neurosurgery, radiology
In parallel with our projects aimed at developing new technological solutions, we also perform research within the neurological and neurosurgical fields, reflecting our clinical work.
- Spinal cord injury: where diagnostics, surgical and medical treatment, complications, epidemiology and molecular pathogenesis are studied. The aim is to improve diagnostics in the area, including complicated conditions such as spinal infarction and to map and find strategies for preventing complications such as thromboembolic events and posttraumatic spinal cord tethering, through studies of patients cared for at Karolinska as well as nationally. A comprehensive prospective mapping of protein expression and inflammatory response in spinal cord injury has been initiated.
- Spine surgery: Evaluating experiences and surgical outcomes using our own patient data as well as national registries we strive to address a number of questions in spine surgery. The aim is to improve patient care and surgical strategies and techniques. In anterior spinal procedures a recurring question is whether the anterior surgery is stable enough biomechanically or whether complementary posterior surgery should be performed. Adjacent segment disease occurs after fusion surgery, and reflects the increased strain on the tissues bordering a fused area. Degenerative changes in these areas is an unsolved issue in spine surgery. Another controversial topic is the need for fixation after laminectomy. In laminectomy, posterior elements are removed, which is considered to lead to an imbalance in the forces acting on the cervical spine and the development of kyphotic deformity. We plan to compare the outcome of laminectomy with and without fixation in a follow-up randomized multicenter study in patients with spinal stenosis.
- Imaging studies: To develop state of the art navigation solutions, high quality imaging solutions are essential. Ongoing studies investigate the best way to use cone beam CT in the hybrid OR as well as solutions to optimize intraoperative use of MRI and ultrasound. In parallel we examine the indications and clinical utility of different radiological investigations in neurology, neurosurgery and trauma care. For instance, a serious complication of cervical spine trauma is damage to blood vessels, mainly the vertebral arteries, which can result in stroke. As the radiological techniques for mapping vascular injuries have improved, questions are raised about when these examinations should be performed and whether early diagnosis benefits the patient and brings a health economic benefit.
- Pediatric neurosurgery: Systematic work is underway to develop and integrate modern navigation technology. The head of the small child cannot be fixed during neurosurgical procedures since the bone is soft. In addition, ionizing radiation carries increased risks for the child. The work is therefore driven towards developing alternative methods for intraoperative navigation. An ongoing research project is focused on three-dimensional ultrasound imaging in brain tumor surgery. Ultrasound allows for repeated imaging during surgery and can potentially improve patient outcomes by increasing the chance of achieving maximal tumor removal.
- Hydrocephalus is a disorder of the circulation of cerebrospinal fluid (cerebrospinal fluid), and can develop in both children and adults with a negative effect on brain function. In adults, dementia-like conditions are seen and in children a deterioration of brain development. By studying steroid acid metabolites in cerebrospinal fluid with special turnover in the brain tissue, we want to establish a standard to better predict which patients will benefit from neurosurgical treatment.