Fujitsu Laboratories, Ltd. in collaboration with researchers at the University of Toronto (U of T) today announced the development of a technology for dramatically streamlining the creation of radiation treatment plans for Gamma Knife(1) radiosurgery, leveraging Fujitsu’s quantum-inspired computing technology, the Digital Annealer, which rapidly solves combinatorial optimization problems.
Gamma Knife radiation therapies are used to
treat illnesses including brain tumors and arteriovenous malformations.
The process of creating treatment plans using conventional methods is
often laborious and time-consuming, and doctors must spend time making
painstaking and detailed adjustments to determine how much radiation
should be administered to a target while minimizing dose to surrounding
tissue. With the newly developed technology, however, medical
professionals can create treatment plans in roughly one
minute, maintaining the same level of accuracy as conventional methods,
while simultaneously calculating a huge number of possible combination
patterns of where and how much dose to deliver with the Digital
Annealer.
By easing the burden on medical professionals in creating fast and
accurate treatment plans, the new technology frees them to devote more
time and energy to ensuring patients receive the most effective and
humane care possible. Going forward, Fujitsu Laboratories
and U of T researchers will continue to test the effectiveness of this
technology based on additional patient data, and ultimately develop
technologies that actively contribute to improvement of medical science
and society at large.
Background
Gamma Knife surgery is used to treat brain tumors and other conditions
because of its relative non-invasiveness and highly precise method of
delivery of radiation. By using 192 different sources of gamma radiation
aimed at different points, the dose to the
affected area can be maximized while the dose to the surrounding
healthy organs is kept very low. Parameters including position, shape,
and dose of radiation must be considered to achieve optimal dosage to
the affected area. However, the number of potential
combination patterns is enormous, and in current medical practice,
doctors generate treatment plans by manually repeating parameter
adjustments based on their previous experience. This process can take
about 1.5 to 3 hours to generate a plan that meets the
patient’s individual needs, placing a heavy burden on medical
professionals.
While the physician is preparing the treatment plan, the patient may
also need to wait, frequently with a frame fixed to their head to limit
movement, which may cause some physical discomfort. It is also necessary
to secure medical personnel to help to prepare
patients for treatment and make sure the frame remains in place.
Recent years have witnessed the emergence of new tools to help ease this
process–for instance, software that automates the generation of
treatment plans. In the field, however, it often remains the case that
the generated plan still requires clinicians to
manually modify and adjust the plans.
Since 2017, Fujitsu and U of T have been collaborating in a strategic
partnership centered on research relating to quantum computing. With
this latest initiative, the parties have collaborated in the development
of technology to help apply the use of the Digital
Annealer for the generation of treatment plans for Gamma Knife
therapies. Researchers at U of T and its medical institutions studied
and developed methods to translate the Gamma Knife optimization to
combinatorial optimization, a format understandable by the
Digital Annealer technology developed by Fujitsu.
About the Newly Developed Technology
U of T researchers, through their methods and the use of Digital
Annealer technology by Fujitsu, has developed the following technology
to generate treatment plans at high speed while maintaining the same
accuracy as treatment plans created by experienced doctors.
1. Using the physical properties of the human body (Dose Profile), the shot shape during gamma irradiation is modeled.
In the past, shots (Concentrated area of gamma rays) formed by multiple
gamma rays were assumed to be perfectly spherical during the shot
position determination process. However, it has been found that the
sphere is not necessarily perfect due to the influence
of moisture in the human body. The newly developed technology
determines the position of shots utilizing shot shapes reflecting the
physical characteristics of gamma rays in the human body. This can
contribute to the generation of more accurate treatment plans.
2. Optimization of radiation parameters using the Digital Annealer
In the past, during shot position determination process, multiple gamma
ray radiation positions (Position of the shot) were determined
sequentially; the position of the first shot was determined and the
position of the second shot was determined after that
so as to include the remaining part of the affected tissue as much as
possible. However, this may not result to the optimal number of shots or
positions. By contrast, the Digital Annealer allows users to search for
the positions of all shots simultaneously
at the beginning, resulting in a more accurate overall optimized
treatment plan. It is also possible to obtain an optimized solution for
the parameters of the radiation shape, enabling the rapid generation of a
treatment plan that optimizes dosage for each
patient.
In a study of 49 cases of auditory nerve tumors, U of T researchers
compared the newly developed technology against the conventional method.
Referring to an index of radiation delivery accuracy, it was found that
the developed technology was as accurate as
manual planning. Additionally, while it took 1.5 to 3 hours to manually
generate a plan, it was possible to reduce this to about 2 minutes with
the newly developed technology.
By supporting plan generation with the newly developed technology, the
time required for Gamma Knife treatment, as well as the burden on
patients and medical professionals can be drastically reduced. Reduction
of personnel costs for hospitals can also be expected.
Future Plans
Going forward, Fujitsu Laboratories and U of T researchers will continue
to verify the effectiveness of this technology based on data from more
patients, and will continue to develop technologies that offer the
potential to contribute to medical science and
society at large. Future potential projects include shortening the time
required for Gamma Knife treatment processes themselves rather than the
treatment plans, or applying this technology to other radiotherapy
methods.
