Tandem 1: SAFIR (Small Animal Fast Insert for mRi): Benchmarking a Novel Preclinical PET/MR

Short Summary:

We are developing a novel small animal Positron Emission Tomography (PET) insert for use in the recently installed pre-clinical 7T Magnetic Resonance Imaging (MRI) scanner at ETH Hönggerberg. Using state-of-the-art silicone photo multipliers (SiPM) and application-specific integrated circuits (ASICs) the system is designed to cope with high tracer activities, yielding excellent statistics.

Scope:

Hybrid techniques are becoming increasingly important in biomedical imaging, as multivariate tissue characterization will significantly enhance the diagnostic value of traditionally imaging techniques. In a large collaborative effort between ETHZ and UZH, the planned high-performance PET-insert is highly innovative with respect to its technological approach and it opens new avenues in preclinical hybrid molecular imaging. The insert will have unprecedented temporal resolution allowing dynamic tracer concentration to be visualized within a few seconds. In order to compensate for the loss of statistics induced by the short acquisition duration without compromising the resolution of the images, the system must be capable of handling injected radiotracer activities of up to 500 MBq. This represents an order of magnitude increase in interaction rate compared to standard activities used in pre-clinical practice. By inserting the PET ring into a high-field MR scanner, the system opens new frontiers in biomedical diagnostics, particularly in fast dynamic imaging and kinetic modeling. The STIR open source software package for tomographic image reconstruction will be leveraged for access to state-of-the-art reconstruction techniques. STIR was the result of an EU-funded collaboration between 6 partners and facilitates direct parametric reconstruction. The preclinical PET/MR site will be one of the very few institutions worldwide where the PET/MRI integrated multimodal research is possible in small animals, with the potential of a significant impact in research fields such as neuroscience, cardiology and oncology.

Specific Aims:

This proposal addresses a number of tasks mandatory for benchmarking and performing initial experiments with the first prototype ring of the PET insert. While existing developments mainly aim at high sensitivity and improved spatial resolution (e.g. Wehrl et al., 2011; Ko et al., 2016), to our knowledge there has been no PET insert development aiming at significantly improving the temporal resolution. Its successful development and completion will impact on several other fields in PET instrumentation research. The access to an ultra-fast combined PET/MRI system will be particularly beneficial for studies with ultra-short lived isotopes (e.g. [15O], physical half-life of 122 seconds).

 

Molecular imaging techniques used:

Positron emission tomography; Magnetic Resonance Imaging.

PET Insert
PET Insert
Concept of the complete insert, designed to fit inside the MR scanner gradient system. Rings of detector modules occupy the central portion.

Added value of KFSP for this specific tandem project:

Since its conception, SAFIR has benefitted from the multidisciplinary networks now strengthened by KFSP MINZ. The project was conceived in 2013 as a collaboration between (i) the ETH Institute for Particle Physics (Prof. Dissertori) responsible for the development of the PET insert, (ii) the IBT with Prof. Rudin responsible for the MRI-related tasks, and (iii) the UZH Institute of Pharmacology and Toxicology (IPT) with Prof. Weber being the main user of the completed PET/MRI system and responsible for its specifications, prototype test support and practical application. Furthermore, strong links exist to the Department of Radiology (Prof. Hodler), who has significantly invested in the recently installed 7T preclinical MR setup. The PET insert will cover the full range of PET/MRI applications of the IBT facility, whilst being custom tailored to the research needs as defined by UZH IPT. Additionally, the proposed PET insert will perfectly complement the clinical PET/MR setup operated by the USZ Department of Nuclear Medicine in Schlieren.

References