Gamma Knife radiosurgery is a type of radiation therapy used to treat tumors, vascular malformations, and other abnormalities in the brain. It uses specialized equipment to focus on 200 tiny beams of radiation on a tumor or other target with submillimeter precision.
The plans for this type of surgery are usually drawn up manually; neurosurgeons work with radio-oncologists and physicians to select the number, size, shape, and power of the beams to be used and map out exactly where they should be directed so that the entire treatment area is covered.
How effective the plans are, therefore, relies generally upon the doctor’s experience. To remove that from the condition, Intuitive Therapeutics set out to develop software that can calculate all of the criteria automatically. The startup started working with Professor Jean-Philippe Thiran at EPFL‘s Signal Processing Laboratory 5 (LTS5) in 2015, and together they built up a program called IntuitivePlan, which is currently available on the market.
The program uses an optimal inverse planning system whereby doctors specify the radiation dose to be applied to each area of the diseased tissue as well as the maximum dose that the surrounding tissue can be exposed to. Based on these inputs, the software generates a surgical plan that optimizes the various criteria along with a preprogrammed constraint on how long the procedure should last to minimize patients’ overall exposure time.
Professor Jean-Philippe Thiran at EPFL’s Signal Processing Laboratory 5 (LTS5) in 2015 said, “Developing the surgical plans involves a process of combinatorial optimization that is computationally expensive by nature. The calculation method we chose is called convex optimization.”
Professor Marc Levivier, head of neurosurgery at the CHUV and director of the CHUV’s Gamma Knife Center, said, “The program uses powerful processing techniques that can generate the optimal combination in under two minutes. It takes 20 or 30 minutes to develop a plan manually – sometimes even longer for complicated procedures. The software often comes up with plans that we never would have thought of ourselves, or wouldn’t have been able to map out by hand.”
Engineers successfully turned their idea into software that meets doctor’s expectations. What’s more, their software has obtained the CE Marking, it can be used in routine clinical procedures.
Levivier said, “I trust the program fully, but for the first few procedures. I also created some surgical plans by hand and compared them with those produced by the software. Then I selected the best option for each patient. The initial results have been auspicious.”
Currently, the IntuitivePlan is compatible only with Gamma Knife devices, but the engineers are already working on adapting their program to other kinds of radiotherapy equipment.
- Marc Levivier et al. “A real-time optimal inverse planning for Gamma Knife radiosurgery by convex optimization: description of the system and first dosimetry data,” J. Neurosurg. 2018. DOI: 10.3171/2018.7.GKS181572.