Scientists at Fraunhofer Research Institution for Modular Solid State Technologies EMFT, together with Ketek GmbH, have developed a novel, silicon-based optical sensor component called a silicon photomultiplier (SiPM). The module is immune against magnetic radiation, which is essential for combining PET and MRT, which is an efficient hybrid diagnosis method. The device also has  in other low light applications such as space exploration , high frequency physics, life sciences and, in general, detecting weak light signals in analytical instruments.

The sensor component developed by the scientists in Munich has several advantages compared to traditional technology. The lower operating voltage eases the device design. Due to improved temperature stability of the components, less cooling of the equipment is necessary. This results in reduced manufacturing complexity and cost. A low dark count rate eases the detection of the target signal, thus increasing the efficiency. The single components show very homogeneous properties, which facilitates the parallelization of several detector components into one block detector, quite unlike traditional photomultiplier.

Medical imaging is critical in modern medicine for reliable diagnostics of health problems such as  neurological illnesses, apoplexy and cancer. Such imaging technologies are used for x-ray and ultrasonic examinations, Magnet Resonance Tomography (MRT) as well as Positron-Emission-Tomography (PET).

MRT records only the morphology and function of a patient, whereas PET can show a body’s metabolism by means of minute radioactively marked particle. In the future, illnesses could be discovered in an earlier stage and their progress could be monitored more effectively using a hybrid MR-PET technology. Moreover, MR-PET could facilitate the understanding of such illnesses as Alzheimer’s disease, Parkinson’s disease, depression and schizophrenia, as well as help refining surgical techniques. Additionally the radiation stress to patients could be significantly reduced, compared to the currently used CT-PET technology.

The biggest obstacle in combining PET and MRT to one device so far has been, that traditional Photomultipliers could not operate in a magnetic field without significant loss of efficiency. Due to their small size, the SiPMs developed by Fraunhofer EMFT are not affected by the surrounding magnetic field. The small size also makes them more efficient and faster than the avalanche diodes used in the first MR-

Fraunhofer EMFT conducts research and development in open, modular, application oriented system technologies in the fields of micro electronics and micro system engineering with approximately 110 employees in Munich and Regensburg.

Caption: A Fraunhofer EMFT scientist with a Silicon Photomultiplier Wafer for medical applications.