Figure 4

ECG electrodes systems. (a) System BioVet™ (©m2m Imaging Corp, Newark, USA): the carbon fibre electrodes are applied directly in contact with the cleaned and shaved chest skin and applied with gel electrode so that a minimal impedance electrical connection is made with the electrode. (b) Model 1025 small animal monitoring and gating system (Small Animal Instruments, Inc., Stony Brook, NY, USA): the ECG system used for the MRI scanners uses sub-dermal needle electrodes, pads or surface electrodes. The placement of the electrodes is typically in or on the right forepaw and the left hind pore, or electrodes are placed in the forepaw as long as it is across the heart plane. All the wire bundles within the scanner should be taped to eliminate unwanted movement from the gradient vibration and/or air flow. (c) Schematic representation of the fMRI setting: all the equipment needs to be non-ferromagnetic, and it is connected to a module system which allows gated acquisition of images, avoiding interferences from motion due to breathing and /or heart beating. Body temperature is also regulated through a heating module (small rodent heater system; Small Animal Instruments, Inc.) to monitor and control the animal temperature during imaging. The system software continuously processes the temperature measurements and sends an optical control signal to the heater control module. The rate of change of temperature is monitored, and heater control is adjusted to regulate temperature changes. Mouse temperature variations of less than ±0.1°C can typically be obtained during magnetic resonance (MR) examination.