Scientific MIRACLE: lasers and augmented reality for better bone surgeries
Combining physics, engineering, and medicine to create a laser equipped robotic endoscope for bone surgeries.
The progress of technology and science is exponential. We currently live in an era of miniaturization, smartphones, and robots, relying more and more on latest technological inventions.
Yet, when it comes to bone surgeries, doctors still use conventional saws (some designs are centuries old), which have quite some restrictions. A group of scientists working at the University of Basel is trying to change this and give bone surgery a serious update.
Their project, entitled poetically The MIRACLE project (Minimally Invasive Robot-Assisted Computer-guided LaserosteotomE ), aims at the development of a modern robotic endoscope equipped with a bone-cutting laser— sounds pretty cool right?
Close collaboration with hospitals
The MIRACLE project is the flagship project of the Department of Biomedical Engineering. According to Dr. Lilian Witthauer, head of Planning and Navigation, one of the MIRACLE subgroups:
“The ultimate goal is to create a minimally invasive robot which cuts bones using a laser. This project lies at the intersection of natural sciences and medicine and requires close cooperation of both scientists and medical doctors.”
The scientists involved therefore often visit hospitals and attend surgeries to spot and understand issues and possible improvements, which helps them to design new techniques necessary for the innovative, flexible endoscope.
Knee and spine surgeries
Creating such a complicated device is no easy task. This is why there are in total four subgroups working on this big project, the Smart Implants group, the Bio-Inspired Robots for Medicine-Lab, the Biomedical Laser and Optics group, and the Planning and Navigation group.
The construction of the endoscope and its cooling system is in the hands of the robotics group. They will also develop a guidance and feedback system, and investigate interactions between the endoscope and tissue during the surgery.
“We aim at orthopedic surgeries, mainly replacement of the knee joint, later bone cancer treatments, spinal cord surgeries, and jaw reconstructive surgeries,” adds Witthauer.
Contact-free bone surgeries
The bone will be cut contact-free by a laser beam. To find the optimal parameters to cut bones with laser is the main challenge of the Biomedical Laser and Optics Group. Another task of this group is to find a way to guide the laser light through the approximately 25 cm long endoscope.
Compared to the traditional way of bone cutting which produces cuts of about 2 millimeters in width, this laser method has significant advantages.
The actual bone cutting process leads to the formation of a submicrometer-sized bubble of plasma that can ablate tissue in a controlled manner and induce cracks within the bone structure. Compared to the more traditional way of bone cutting producing cuts of about two millimeters of width, this laser method has significant advantages:
“The laser cut has a very small width. The cut is ten times thinner than with a conventional saw, which allows for higher precision. It has also been shown that cutting with laser yields a better healing process because it creates a different cutting surface. Higher precision also means that we can make functional cuts. We can cut bone pieces in angles and shapes that aren’t possible with conventional methods. These pieces fit into each other like pieces of a puzzle or velcro,” explains Witthauer.
The laser will be a part of an innovative, flexible endoscope. Due to the flexibility, standard optical markers cannot be used to determine the position of the endoscope, and hence new navigation methods have to be developed.
This is the aim of the Navigation and Planning group, led by Dr. Witthauer. One of the PhD students working on this issue is Lorenzo Iafolla, whose project deals with a new minimally invasive navigation technique using an optomechanical position sensor.
“I am developing a sensor, called ASTRAS, to determine the exact position of the endoscope tip inside the human body. The sensor contains a light source, an image sensor, and a shadow mask, which looks like a grid,” explains Iafolla.
“By changing the position of the light source, the shadow cast of the grid onto the image sensor changes too. From the changes of the image, the position of the light source can be calculated. In the endoscope, several of these sensors will be stacked to get the position of the tip.”
The sensor contains a shadow mask, which looks just like a grit. By changing the angle of the light source, the image seen by the sensor will change too. Based on the position of the lanes created by the grit, the researchers can then calculate the angle.
Another navigation technique under investigation in the Planning and Navigation group is based on optical fibers.
Samaneh Manavi, another PhD student in the Planning and Navigation subgroup, is working on something called fiber optic shape sensing, which allows reconstructing the entire shape of the endoscope.
“The fibers are glued to a special tube, which can be only bent, not twisted. Inside these fibers, there are sites where the refractive index changes periodically. When sending broadband light through the fibers, only a certain wavelength is reflected at these sites. Bending the fiber results in a change of the periodicity of the refractive index and hence in a change in the reflected wavelength. The change in wavelength is measured by a spectrometer and can be used to calculate the curvature of the fiber,” describes Manavi.
Augmented and virtual reality
Another exciting part of the MIRACLE project is “Planning.” Witthauer and her team will support the surgeon in planning and execute the surgery by a 3D visualization of the intervention.
“So far we have been using the virtual reality glasses to show medical imaging data sets from Computer Tomography (CT) scans to medical doctors,” explains Witthauer. “However, in the future, we want to use augmented reality glasses for that purpose.”
In contrast to virtual reality, augmented reality allows the surgeon to see the real world superimposed with computer-generated objects, such as a 3D visualization of CT images.
“Thanks to augmented reality, the physician will be able to monitor the endoscope cutting the bone inside the patient,” explains Witthauer. “At the end, we would also like to visualize the spread of tumors or positions of critical organs such as big blood vessels and nerves not to be cut into.”
The research team currently uses a virtual reality room, where they can visualize CT data sets of mummies, corpses and real patients. Internship student Marek Zelechowski explains:
“What is new is that the picture is being calculated in real time. 180 frames per second, so 90 per eye per second. Shadow cast gives you a real 3D impression.”
Future of Orthopedics
The MIRACLE project is still at its beginning, the technologies are still to be miniaturized, and the first prototype is to be developed. However, Lilian Witthauer already has clear plans about the first type of surgeries that could be performed.
“The first surgeries we want to aim at are the knee surgeries, during which a part of the knee joint is replaced by an implant. Other possibilities include the jaw region, or later even spinal cord surgeries.”
The part of the bone to be replaced or removed will be first cut into small pieces and sucked out — this process will also be implemented into the endoscope by the robotics group. After the intervention, the Smart Implants group will come into play, with their 3D printed bone implants made of biocompatible materials.
The laser operated endoscopes might still sound quite futuristic, but thanks to the work of researchers from the University of Basel, a true scientific MIRACLE could happen. And who knows, maybe your next orthopedic surgery will include only a few stitches and your surgeon wearing augmented reality glasses.
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