Small-animal MRI: signal-to-noise ratio comparison at 7 and 1.5 T with multiple-animal acquisition strategies.
OBJECTIVE
The purpose of this study was to compare the signal-to-noise ratio (SNR) of phantom and rat brain images performed at 1.5 T on a clinical MR system and at 7 T on a small-animal experimental system. Comparison was carried out by taking into account SNR values based on a single sample acquisition at 1.5 and 7 T as well as on simultaneous imaging of multiple samples at 1.5 T.


METHODS
SNR was experimentally assessed on a phantom and rat brains at 1.5 and 7 T using 25 mm surface coils and compared to theoretical SNR gain estimations. The feasibility of multiple-animal imaging, using the hardware capabilities available on the 1.5 T system, was demonstrated. Finally, rat brain images obtained on a single animal at 7 T and on multiple animals acquired simultaneously at 1.5 T were compared.


RESULTS
Experimentally determined SNR at 7 T was far below theoretical estimations. Taking into account chemical shift, susceptibility artifacts and modifications of T1 and T2 relaxation times at higher field, a 7-T system holds limited advantage over a 1.5-T system. Instead, a multiple-animal acquisition methodology was demonstrated on a clinical 1.5-T scanner. This acquisition method significantly increases imaging efficiency and competes with single animal acquisitions at higher field.


CONCLUSIONS
Multiple-animal imaging using a standard clinical scanner has a great potential as a high-throughput acquisition method for small animals.
Beuf
Olivier
O
Laboratoire de RMN, CNRS UMR 5012, Université Lyon1, ESCPE, 43 Boulevard du 11 Novembre 1918, 69616 Villeurbanne, France. olivier.beuf@univ-lyon1.fr
Jaillon
Franck
F
Saint-Jalmes
Hervé
H
D000818:Animals; D016477:Artifacts; D001921:Brain / Q000378:metabolism / Q000473:pathology*; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015233:Models, Statistical; D019047:Phantoms, Imaging; D051381:Rats; D013997:Time Factors