Microwave based stroke diagnostics

Stroke diagnostics with a microwave-based system

In Sweden 30000 patients suffer a stroke every year. About 20 % of these patients perish and the other 80 % often face long term rehabilitation. Stroke is also the most expensive disease for the society. In a MedTech West project a microwave based diagnostic system is being developed allowing earlier and more successful treatment than today.

Our technique aims at determining if a bleeding or a blood clot causes a patient’s stroke. The preferred treatment for clot is thrombolysis, which should be given as early as possible for best effect. This treatment must not be given to bleeding patients. Our technique transmits microwave radiation through the skull in many different directions. It is then received on the other side and analyzed with advanced signal processing algorithms in order to perform the diagnostics. In the future, our technique will make it possible to start the thrombolysis already in the ambulance, thereby largely increasing the number of patients that receives this treatment and also the chances for successful treatment.

Our approach

Microwave technology for medical diagnostics is sensitive to variations in liquid and ion concentration between different tissues and disease-states. In the event of a stroke it is a pool of blood or a blood clot together with the decreased oxygenation of the tissue that alters the dielectric properties from that of a healthy brain. The propagation patterns of microwaves are however much more complex than that of for example x-rays, and this also makes the analysis of the measurements harder. In making the diagnosis the measured scattering pattern must be related to thecorresponding tissue properties, i.e. the dielectric properties. In mathematical terms this problem is both non-linear and ill-posed and this poses particular challenges on the algorithm in terms of the need for massive computational resources to reach the desired accuracy. The motivation for the research is on the other hand driven by the potential to develop a portabledevice for stroke detection, something that is not possible with conventional technique. Our solution utilizes a microwave antenna helmet, a microwave send-and-receive unit and a signal-processing algorithm, which can accurately and rapidly separate strokes caused by a bleeding or a clot already in the ambulance.

Current developments

We have developed a microwave helmet and a dedicated microwave unit together with the signal-processing algorithm. The system has been tested in clinical trials at Sahlgrenska with very encouraging results. The use of a statistical classification algorithm has proven itself to be a beautiful way to reduce the computational burden to ensure real time performance while retaining the accuracy in the diagnosis. Still much work remains to improve the performance in terms of user friendliness and to show that the diagnostic result is reliable and robust such that it can be safely used as the primary diagnostic tool on real patients in the ambulance. Experiences and results obtained inthis project will be very valuable also in our other research projects based on microwave technology.


The final system will be deployed in the ambulance and thanks to a rapid diagnosis of the stroke the thrombolytic treatment of clot patients can be started much earlier than today. The system can also be used at the hospital for monitoring of risk patients. In the future we can also foresee a large number of other application areas where the microwave technology can improve the diagnostics.

Research team

MedTech West partner 

Dr. Andreas Fhager, Department of Signal Processing and Biomedical Engineering, S2, Chalmers University of Technology.

Clinical partner

Prof. Mikael Elam, Institute of Neuroscience and Physiology, Clinical Neurophysiology, Sahlgrenska University Hospital.

Dr. Jan Erik Karlsson, Strokeenheten, Sahlgrenska University Hospital.

Industrial partners

Medfield Diagnostics


For more information on this project, contact Henrik Mindedal at henrik.mindedal@medtechwest.se