Hyperion-IID: Pre-clinical PET/MR insert with digital SiPMs
In 2009 Philips presented a new fully digital sensor (dSiPM), that can be used for PET and PET/MRI applications. Directly on the sensor it counts the detected photons. This technology promises highest PET signal-to-noise performance, since there are no analog steps between the sensor and the digitization. For the same reason the vulnerability to the harsh electromagnetic environment of an MRI scanner is minimized. On the other hand the amount of digital circuits inside the MRI increases which enlarges the challenge of MRI silent integration. With Hyperion IID, the world’s first PET/MR insert was built that uses digital SiPMs. It bases on the system concept of Hyperion I (see below), which was largely improved with respect to MRI compatibility, MRI synchronization and usability.
The scanner was funded by the NRW Ziel 2-Programm (EFRE) 2007-2013, and the Wellcome Trust and EPSRC under grant number WT 088641/Z/09/Z. It was built in cooperation with Philips Research Aachen (system design and electronics), King’s College London (FPGA readout architecture and image reconstruction), Philips Digital Photon Counting (dSiPMs) and Irmato Industrial Solutions Aachen (mechanical design).
Publications about Hyperion-IID
- Weissler B, Gebhardt P, Dueppenbecker PM, Wehner J, Schug D, Lerche CW, Goldschmidt B, Salomon A, Verel I, Heijman E, Perkuhn M, Heberling D, Botnar RM, Kiessling F, and Schulz V. A Digital Preclinical PET/MRI Insert and Initial Results. IEEE Transactions on Medical Imaging. 2015;34(11):2258‑70.
PET/MR Simultaneous Operation
- Wehner J, Weissler B, Dueppenbecker P, Gebhardt P, Schug D, Ruetten W, Kiessling F, and Schulz V. PET/MRI insert using digital SiPMs: Investigation of MR-compatibility. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 2014;734:116‑21.
- Wehner J, Weissler B, Dueppenbecker PM, Gebhardt P, Goldschmidt B, Schug D, Kiessling F, and Schulz V. MR-compatibility assessment of the first preclinical PET-MRI insert equipped with digital silicon photomultipliers. Physics in Medicine and Biology. 2015;60(6):2231‑55.
- Schug D, Wehner J, Dueppenbecker PM, Weissler B, Gebhardt P, Goldschmidt B, Salomon A, Kiessling F, and Schulz V. PET performance and MRI compatibility evaluation of a digital, ToF-capable PET/MRI insert equipped with clinical scintillators. Physics in Medicine and Biology. 2015;60(18):7045‑67.
- Schug D, Wehner J, Dueppenbecker PM, Weissler B, Gebhardt P, Goldschmidt B, Solf T, Kiessling F, and Schulz V. ToF Performance Evaluation of PET Modules With Digital Silicon Photomultiplier Technology During MR Operation. IEEE Trans Nucl Sci. 2015;62(3):658‑63.
- Weissler B, Gebhardt P, Lerche CW, Soultanidis GM, Wehner J, Heberling D, and Schulz V. PET/MR Synchronization by Detection of Switching Gradients. IEEE Trans Nucl Sci. 2015;62(3):650‑7.
PET: Digital SiPM Data Processing
- Goldschmidt B, Schug D, Lerche CW, Salomon A, Gebhardt P, Weissler B, Wehner J, Dueppenbecker PM, Kiessling F, and Schulz V. Software-Based Real-Time Acquisition and Processing of PET Detector Raw Data. IEEE Transactions on Biomedical Engineering. 2016;63(2):316‑27.
- Schug D, Wehner J, Goldschmidt B, Lerche C, Dueppenbecker PM, Hallen P, Weissler B, Gebhardt P, Kiessling F, and Schulz V. Data Processing for a High Resolution Preclinical PET Detector Based on Philips DPC Digital SiPMs. IEEE Trans Nucl Sci. 2015;62(3):669‑78.
PET: Performance Evaluation
Hyperion I: Pre-clinical PET/MR insert with analog SiPMs and direct digitization
Hyperion I is a pre-clinical PET gantry with a built-in MRI transmit/receive coil. A normal clinical MRI scanner adds the rest of the MRI imaging chain, when the PET/RF insert is placed on its patient table. Like this PET and MRI data can be acquired simultaneously of objects up to the size of rabbits. Special to this insert is the use of silicon photo multipliers (SiPMs) and the direct digitization of their analog signals inside the MRI bore. This enables a scalable system architecture with highest PET performance, since the optical path and the analog electronic lines, where signal degradation accrues, are very short. The research challenge is to integrate the PET detector electronics into the MRI scanner with lowest unwanted interaction between the two modalities.
The scanner was built under the EU FP7 project HYPERImage, Grant agreement no. 201651 in cooperation with Philips Research Aachen (system design and electronics), Irmato Industrial Solutions Aachen (mechanical design), Foundation Bruno Kessler Trento (SiPMs), Heidelberg University (Digitization ASIC), Ghent University (simulations) and the King’s College London (clinical partner).
Magnetic Particle Imaging
Magnetic Particle Imaging (MPI) is a new tracer based imaging technology. In MPI, the space-resolved concentration of superparamagnetic iron oxide nanoparticles (SPIO) is imaged. The SPIOs are excited by an external magnetic field and the response is proportional to the concentration of the SPIOs in the voxel. The spatial encoding is done by superimposing a magnetic field with three orthogonal homogeneous fields so that the fields cancel out each other only at a single field free point (FFP) and all particles not inside the FFP are saturated. Therefore, only the particles in the FFP contribute to the signal.
Our group works with the world’s first MPI scanner developed by Philips Research Hamburg. The goals of our group are to increase its sensitivity to enhance the achievable spatial resolution into sub-millimeter domain.