Phase Contrast Magnetic Resonance Imaging to Assess Blood Flow in the Arteries of a Rat

Take an anesthetized rat secured on the bed of a magnetic resonance imaging, or MRI, system.

Gauze pads on the rat maintain its body temperature while sensors on the body monitor respiration and cardiac activity, ensuring stable physiological parameters.

Position the rat inside the scanner. Using phase contrast MRI, scan the neck region to identify the common carotid artery or CCA.

The scanner detects fluctuations in MR signal intensity caused by moving protons in the blood.

During the phases of the cardiac cycle, the blood velocity changes along with the diameter of the artery due to periodic constriction and dilation.

Align the imaging plane perpendicular to the direction of blood flow to obtain a cross-sectional view of the arteries.

Obtain images at defined intervals to compute blood flow, a product of blood velocity and the cross-sectional area, and assess variations in blood flow throughout the cardiac cycle.

Once the animal is found to be physiologically stable, start the MRI scans. Select the localizer sequence from the console monitor of the MRI scanner, and acquire scout images along all three orientations using any fast image acquisition sequence, such as the fast spin echo, to create coronal, axial, and sagittal images.

Look at the scout images to ensure that the center of the animal's head and neck is at the center of the magnet. If necessary, adjust the animal's position until the correct position is reached.

If the animal is repositioned, repeat the scout image scans. Once the rat is properly positioned, select the time of flight angiogram sequence from the console monitor of the MRI scanner, and acquire a 2D time of flight angiogram first to ascertain the precise anatomical location of the common carotid artery. Ensure that the saturation band is on and is placed on the top to avoid interference from venous signals.

The saturation band usually comes with time of flight sequence. If the saturation band does not show on the monitor, please notify the service person.

After locating the common carotid artery using the time-of-flight angiogram, target the image plane of the phase contrast magnetic resonance imager to the center of the same artery and orient it such that the slice is perpendicular to the direction of blood flow.

Ensure that both respiration and ECG gating are connected to the MRI system, showing the clear signal on the monitor computer and set the trigger module to be on in the trigger mode from the console monitor of the MRI scanner. At this point, again, confirm that the animals physiological responses are stable and verify that the gating selections are on in both the monitor computer and the console monitor of the MRI scanner.

Please remember to make sure that installations are on in both monitor computer and monitor one of MRI scanner.

Next, select the sequence of PC MRI sequence from the console monitor of the MRI scanner and perform the gated PC MRI scans. Repeat this process for each region of interest. Once all of the regions have been imaged, remove the animal from the scanner and return it to its cage.