9.4T Animal Scanner for Translation Research with Binary Compatibility to Human Scanner and Clinical UI
Jörg Felder1, Chang-Hoon Choi1, Stefan Schwan1, A. Avdo Celik1, Seong Dae Yun1, Nuno Andre da Silva1, Ana Maria Oros-Peusquens1, and N. Jon Shah1,2

1INM-4, Forschungszentrum Jülich, Jülich, Germany, 22Faculty of Medicine, Department of Neurology, JARA, RWTH Aachen University, Aachen, Germany

Synopsis

In translational research going from animal model to in vivo human it is often desirable to change as few experimental parameters as possible. For this purpose a unique 9.4 T animal scanner has been assembled consisting of a dedicated small bore magnet and being operated with clinical software. Here we demonstrate an initial performance analysis of the system as well as some more advanced image acquisitions.

Purpose

In translational research going from animal model to in vivo human it is often desirable to change as few experimental parameters as possible. However, clinical and animal systems are currently not available from a single vendor. For this purpose a 9.4 T animal MRI system using clinical software platform has been constructed consisting of components from different vendors as well as home-built assemblies. It allows compiling MR pulse sequences once for the animal or the human scanner and running them on both machines. A further advantage of the system presented here is that tedious reprogramming of sequences for machines from different manufacturers can be avoided. Moreover, the huge library of MR pulse sequences available on the clinical platform becomes available for animal imaging on the dedicated, small-bore preclinical scanner.

Methods

As a platform the Siemens Syngo software (Siemens Healthcare GmbH, Erlangen, Germany) was chosen in combination with the TaTS acquisition system modified with extra RF mixing stages in order to operate at 400 MHz. It was connected to a 9.4 T, 210 mm bore actively shielded magnet and a 120 mm inner diameter gradient insert (maximum gradient strength 600 mT/m, slew rate 4000 mT/m/ms) including second order shim coils (both: Agilent Technologies, Santa Clara, USA). The gradient coils are driven from the clinical gradient amplifiers using reduced output power while the shim coils are connected to 10 A current sources (Resonance Research, Inc., Billerica, USA) and interfaced with the Siemens system using a CAN to serial interface converter. The RF system uses a proton amplifier set that delivers 1 kW peak output power on a single channel or alternatively 4 x 250 W when the system is operated in parallel transmit mode. For X-nuclei a broadband 1 kW amplifier is additionally available (both: Barthel HF-Technik GmbH, Aachen, Germany). RF coils available include a fixed birdcage driven in quadrature as a body coil, single-tuned birdcages for various X-nucleus imaging as well as a set of proton receive surface coils. These are either home-built or purchased (RAPID Biomedical GmbH, Würzburg, Germany). For triggering and animal supervision a small animal monitoring and anesthesia system (Small Animal Instruments, Inc., New York, USA/A.M. Bickford, Inc., New York, USA) is connected to the clinical software platform. Modification in the software include a scaling of 1:5 in gradient strength in order to mimic clinical dimensions as well as disabling SAR and peripheral nerve stimulation monitoring which is not required for animal investigations.

Results

Clinical quality assurance (QA) protocols were adapted to the smaller field-of-view of the animal system and tested on scaled down phantoms with the same solution as used in the human sized versions, however. All QA protocols were within specifications (except for the gradient regulator check which could not be prepared because of the modified hardware). Initial experiments included the investigations of spinal cord injuries in rats which were imaged using a turbo spin echo sequence, compare Fig. 1. More examples of imaging and quantitative acquisitions carried out in order to investigate system performance are shown in Fig. 2 and Fig. 3.

Discussion

The initial measurements indicate that the performance of the home-built scanner is comparable to that of commercial animal MRI systems. At the same time it operates with sequences that have been compiled on a clinical platform making reprogramming of sequences for animal purposes obsolete. This is a major factor since different software platforms tend to split staff into different groups. Further extension of the system is planned and currently integration of four channel parallel transmit capability is being addressed. The intention is to use the animal scanner as a test platform for parallel transmission with human applications in mind as well as to elaborate animal applications using pTX.

Conclusion

A unique translational platform for experiments from bench to bedside at 9.4 T has been created. It allows investigation of animal models and human in vivo data with identical imaging sequences.

Acknowledgements

No acknowledgement found.

References

[1] Zaitsev, M. et. al. Mag. Reson. Med. 2001;45:109-117.

[2] Oros-Peusquens. A. M. et. al., Proc. ISMRM 19 (2011), 2755

Figures

Figure 1: (left) Hardware components of the 9.4 T animal scanner and (right) clinical UI with rat spinal cord images acquired using a TSE sequence, the integrated birdcage for transmission and a surface coil for signal reception.

Figure 2: Basic imaging - (top row) MP-RAGE, T2* weighted EPI, T2 weighted TRUFI and (bottom row) non-proton MR imaging, CEST with the z-spectra of pixels indicated by the yellow arrows, comparison of artefacts created by EPI vs. EPIK [1].

Figure 3: Qunatitative images showing (left-right) T1 [400 2500] ms, T2* [0 50] ms, water content [40% 110%] and magnetic susceptibility [-0.03 0.2] ppm [2].



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
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