The higher sensitivity and spectral resolution of the 7T small animal MR system extends our capabilities in spectroscopy and spectroscopic imaging. The Biospec USR70/30 (Bruker Biospin MRI, Billerica, MA) is an experimental imaging system based on an actively-shielded 7T magnet with a 30-cm bore and cryo-refrigeration that minimizes the time and cost associated with magnet maintenance.
Four receiver channels enable the use of custom RF arrays that increase imaging efficiency, and two transmit channels support broadband imaging, spectroscopy and spectroscopic imaging. Three interchangeable gradient inserts are set according to the target measurement: the largest, with 20-cm ID bore, provide a maximum gradient amplitude of 200mT/m, while 11.6-cm and 6-cm gradients, optimized for rats and mice, deliver 400 mT/m and 950 mT/m, respectively.
Commercially available RF coils include a quadrature 1H birdcage-style resonator (15-cm ID, actively decoupled), two linear 1H birdcage coils (7.2 cm, 3.5 cm) and a dual-tuned 13C/1H actively-decoupled resonator (7.2-cm ID). Custom coils are developed in-house for applications with special requirements.
MRI is a powerful, non-invasive imaging modality that combines high spatial resolution with exquisite soft-tissue contrast. This instrument is routinely used for longitudinal evaluation of small animal models of cancer through anatomic or functional imaging, including dynamic, contrast-enhanced (DCE-) MRI. Simple anatomic imaging provides an accurate means to visualize disease, often even when the tumor can not be palpated or detected by other imaging methods. DCE-MRI, when paired with appropriate pharmacokinetic modeling, supplements anatomic data with information about microvascular function.
Higher sensitivity and spectral resolution make this the ideal instrument for spectroscopy and spectroscopic imaging of species involving MR-visible nuclei such as 1H, 13C, 19F, 23Na, 31P and others. Retrospectively gated cardiac cine imaging enables routine visualization of cardiac motion and robust evaluation of cardiac output. Close proximity to CT, ultrasound, optical and PET facilitates the use of registered imaging data from multiple modalities. This system is also commonly used for screening, and the evaluation of novel contrast agents, therapeutic agents and imaging methods.