(1) Background: Small Animal Fast Insert for MRI detector I (SAFIR-I) is a preclinical Positron Emission Tomography (PET) insert for the Bruker BioSpec 70/30 Ultra Shield Refrigerated (USR) preclinical 7T Magnetic Resonance Imaging (MRI) system. It is designed explicitly for high-rate kinetic studies in mice and rats with injected activities reaching 500MBq, enabling truly simultaneous quantitative PET and Magnetic Resonance (MR) imaging with time frames of a few seconds in length. (2) Methods: SAFIR-I has an axial field of view of 54.2mm and an inner diameter of 114mm. It employs Lutetium Yttrium OxyorthoSilicate (LYSO) crystals and Multi Pixel Photon Counter (MPPC) arrays. The Position-Energy-Timing Application Specific Integrated Circuit, version 6, Single Ended (PETA6SE) digitizes the MPPC signals and provides time stamps and energy information. (3) Results: SAFIR-I is MR-compatible. The system’s Coincidence Resolving Time (CRT) and energy resolution are between separate-uncertainty 209.0(3)ps and separate-uncertainty 12.41(02) Full Width at Half Maximum (FWHM) at low activity and separate-uncertainty 326.89(12)ps and separate-uncertainty 20.630(011) FWHM at 550MBq, respectively. The peak sensitivity is ∼1.6. The excellent performance facilitated the successful execution of first in vivo rat studies beyond 300MBq. Based on features visible in the acquired images, we estimate the spatial resolution to be ∼2mm in the center of the Field Of View (FOV). (4) Conclusion: The SAFIR-I PET insert provides excellent performance, permitting simultaneous in vivo small animal PET/MR image acquisitions with time frames of a few seconds in length at activities of up to 500MBq.

The SAFIR collaboration is currently developing a high-rate positron emission tomography (PET) insert to study fast kinetic processes in small animals. Our insert is designed for simultaneous image acquisition with a preclinical 7 T magnetic resonance (MR) imaging device. In contrast to existing preclinical PET scanners and inserts, our hardware is optimized for high-rate measurements with source activities up to 500 MBq. As a first step, the SAFIR Prototype insert was constructed. This already incorporates the final components, but has a reduced axial field-of-view (35.6 mm). We use lutetiumyttrium oxyorthosilicate crystals (2.12 mm × 2.12 mm × 13 mm) one-to-one coupled to silicon photomultipliers. All analog signals are digitized within the insert. We use 49 MR-compatible dc- dc converters in the insert to provide the power to all readout electronics. After shimming, no degradation of the homogeneity of the static B0 field in the MR scanner was observed. During full operation, we saw a minor reduction in the signal-to-noise ratio of the MR data of 4.9%. With a low activity point source (22Na 0.65 MBq) we obtained a coincidence energy resolution of 13.8% full width at half maximum (FWhM) and a coincidence timing resolution of 194 ps (FWhM). First PET/MR rat brain and high-rate mouse cardiac images (84.9 MBq) are shown in this article.

SAFIR is a high-rate PET insert for a preclinical 7 T MRI scanner, aiming at studying fast biological processes in small animals, using tracer activities up to 500 MBq. The full detector comprises 15360 channels, each composed of a LYSO crystal and a S iPM photo-sensor. A dedicated readout system, operating inside the MRI magnet of 200 mm inner diameter acquires 40 kHz of hits per channel. PETA6 ASICs digitize amplitude and time of the hits. FPGAs read, process and transfer, via optical links, the digital data. We present the readout system in detail, together with first test results.

The small animal fast insert for mRi (SAFIR) positron emission tomography insert was proposed for quantitative dynamic acquisition inside a preclinical 7T magnetic resonance imaging scanner to study kinetics of short-lived tracers. For this purpose, the SAFIR readout should be capable of handling high count rates and achieving excellent timing performance. We evaluated one of the available application specific integrated circuits (ASICs) for SiPM readout, namely SiPM timing chip (STiC) version 3.1. In this paper, we show the performances of the SAFIR PET detector with the STiC ASIC readout. The SAFIR PET detector consists of an 8 x 8 array of lutetium yttrium oxyorthosilicate 2.1 mm x 2.1 mm x 12 mm crystals coupled, with optical grease, to an 8 x 8 array of SiPMs with a 2.0 mm x 2.0 mm photo-sensitive area. Signals from the individual SiPM channels were digitized by the STiC ASIC. Hit's arrival time and time-over-threshold (TOT) were recorded into time stamps with 50.2-ps least significant bit. We obtained an average energy resolution of 18.5% full width at half maximum (FWHM) at 511-keV photopeak after TOT nonlinearity correction and an average coincidence resolving time resolution of 244-ps FWHM with time walk correction that satisfy our requirements specification on the detector performance.

The SAFIR development represents a novel Positron Emission Tomography (PET) detector, conceived for preclinical fast acquisitions inside the bore of a Magnetic Resonance Imaging (MRI) scanner. The goal is hybrid and simultaneous PET/MRI dynamic studies at unprecedented temporal resolutions of a few seconds. The detector relies on matrices of scintillating LSO-based crystals coupled one-to-one with SiPM arrays and readout by fast ASICs with excellent timing resolution and high rate capabilities. The paper describes the detector concept and the initial results in terms of simulations and characterisation measurements.

SAFIR (Small Animal Fast Insert for mRi) is an innovative, high rate, PET detector insert for MRI, to be used for quantitative dynamic pre-clinical imaging, with very high activities injected in the animals, up to 500 MBq. The PET detector will be designed to allow for ultra short acquisition periods (of the order of a few seconds) simultaneously with the MRI, permitting unprecedented temporal resolutions in preclinical dynamic multimodal imaging. High sensitivity (~ 6%), high spatial resolution (~1.5 mm FWHM), excellent coincidence timing resolution (CTR ~ 300 ps FWHM) and a fast DAQ system able to cope with the huge data throughput are required. Parallel with the hardware efforts, dedicated 4D algorithms for image reconstruction must be developed. The overall state of the project will be presented, including ongoing activities towards the choice and characterization of the detector components (crystals, SiPMs and readout chips), MonteCarlo simulations, and first reconstruction of various simulated sources. Special emphasis will be given to the results of a recent high rate test, where the TOFPET ASIC has been tested with Hamamatsu S12642-0404PB-50 SiPM arrays coupled to matrices of LYSO:Ce crystals (3.1x3.1x12 mm3 each), exposed to a 500 MBq activity of FDG radiotracer in a volume of about 0.5 cm3.

The Small Animal Fast Insert for mRi (SAFIR) will be a PET insert for the Bruker BioSpin 70/30. It aims at applications where fast processes such as blood perfusion in the rodent brain are to be monitored comprehensively and non-invasively. Employing electronics originally designed for time-of-flight applications, coincidence resolving times of less than a nanosecond can be achieved allowing for short coincidence time windows. Consequently, random contributions to the coincidence events are suppressed, making short acquisition frames with very high tracer concentrations possible. This will allow collecting sufficient count statistics in a few seconds. Geant4-based Monte Carlo simulations were used to characterize the performance of the reference design consisting of polished LSO-like crystals, one-to-one coupled to Silicon Photomultipliers. The crystals are grouped into 8×8 matrices, which are arranged into 24 modules and 10 rings. Similar methods as described in the NEMA NU 4-2008 standard were employed. The simulation results on NECR, sensitivity, and spatial resolution will be presented. Most notably, the NECR at 500 MBq is almost nine times higher than at 50 MBq for the given scanner. Combined with a very high sensitivity, this allows for short acquisition times using these very high injected doses. In addition, essentially random-free measurements at standard activities below 50 MBq are possible.

The Alpha Magnetic Spectrometer (AMS) is a particle detector designed to search for anti-matter, dark matter and the origin of cosmic rays in space. A superconducting magnet has been developed to generate 0.78 T field at the center. The magnet system consists of a pair of large "dipole" coils together with two series of six racetrack coils, arranged circumferentially in order to minimize the stray field. The coils, series connected, are wound with an aluminum-stabilized mono-strand NbTi conductor and are cooled by a superfluid helium circuit. The superconducting magnet was successfully tested up to the operating current of 410 A, however the decision was taken to equip the spectrometer with a NdFeB permanent magnet in order to maximize the experiment life. The paper describes the results of the superconducting magnet tests and in particular analyses an anomalous increasing of the coil temperature during magnet charging.