Name: phase contrast magnetic resonance imaging to assess blood flow in the arteries of a rat
Uploaded: 2025-04-28T11:59:42.000+00:00
Duration: 1 min 14 s
Description: Source: Chiu, S., et al. Phase Contrast Magnetic Resonance Imaging in the Rat Common Carotid Artery. J. Vis. Exp. (2018).This video demonstrates phase ...

 phase contrast magnetic resonance imaging to assess blood flow in the arteries of a rat

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

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.

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All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.&#160;1. Animal Preparation and Monitoring<ol><li>Leave all magnetically susceptible objects such as wallets, keys, credit cards,&#160;etc. outside the scanner room prior to commencing animal preparation for MRI scanning.</li><li>Initially anesthetize the rat (2-month-old male Sprague-Dawley (SD) rat, 280&#8211;350 g) in an induction box using a mixture of 5% isoflurane (ISO) and oxygen (2 L/min) for 3&#8211;5 min, as necessary.</li><li>When the animal is recumbent and exhibits no response to a tail or toe pinch, discontinue ISO administration and transfer the animal to the scanning room.</li><li>Place the rat in the MRI bed in a head-first prone position and deliver 2-3% ISO through a nose cone device for maintaining anesthesia.</li><li>Monitor respiration by placing a respiratory pillow sensor under the animal's torso.</li><li>Connect the sensor to a respiratory system and check for respiration rate between 40-50 beats per minute (bpm).</li><li>For cine-gated PC-MRI acquisition, place one electrode each on the right forepaw and the left hind paw, respectively (Figure 1a).</li><li>Twist the electrocardiography (ECG) cables together.</li><li>Use a head holder with ear bars and a bite bar to secure the animal to restrict head movement.</li><li>Use a warm air heating system or gauze pads to maintain body temperature while in the magnet.</li><li>Ensure that the R-wave is clear on the ECG monitor (Figure 1b) and place the animal in the scanner. There is no need to place the surface coil on the top of the animal's neck as images are acquired by the volume coil.</li></ol>2. MRI Acquisition<ol><li>Use 2&#8211;3% ISO to maintain anesthesia during the entire imaging procedure. Continuously monitor physiological responses and keep as constant as possible.</li><li>Start the MRI scans once the animal is placed inside the scanner and continues to be physiologically stable. In this study, use a 7 T small animal MRI system with a gradient strength of 630 mT/m, but other field strengths of small animal MRI systems can be used.</li><li>Select the&#160;"Localizer" sequence from the console monitor of the MRI scanner and acquire scout images along all three orientations using any fast image acquisition sequence,&#160;e.g., the fast spin echo, to create coronal, axial, and sagittal images. The purpose of these scout images is to determine the imaging planes.</li><li>Ensure that the center of the animal's head and neck are 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 scanning to obtain scout images.</li><li>Select the&#160;"Time-of-flight (TOF) angiogram"&#160;sequence from the console monitor of the MRI scanner and acquire a 2D TOF angiogram first to ascertain the precise anatomical location of the common carotid artery (CCA). Use the following scanning parameters: repetition time (TR)/ echo time (TE)=22/4.87 ms, flip angle = 90&#176;, field of view (FOV) = 40 &#215; 40 mm2, matrix size = 256 &#215; 256, slice thickness 0.6 mm, with the number of excitation (NEX) = 1. NOTE: The name of the TOF sequence could be vender specific. The user can insert these parameters in the console monitor.</li><li>Ensure that the saturation band is "on" and is placed on the top to avoid interference from venous signals. NOTE:&#160;For the saturation band, it usually comes with the TOF sequence. If the saturation band does not show on the monitor, please notify the service person.</li><li>After locating the CCA using the TOF angiogram, target the image plane of the PC-MRI to the center of the CCA and orient such that the slice is perpendicular to the direction of blood flow (Figure 2a).</li><li>Ensure that both respiration and ECG gating are connected to the MRI system, showing the clear signal on the monitor computer (Figure 1b), and set the trigger module to be "on" in the&#160;"Trigger Mode" from the console monitor of the MRI scanner.</li><li>Confirm that the animal's physiological responses are stable before initiating the PC-MRI scan from the monitoring computer (Figure 1b). Verify that gating selections are "on" in both the monitor computer and the console monitor of MRI scanner. NOTE: The physiology monitoring system used in this study is provided by the vender. For most animal scanners, similar physiology monitoring systems are provided and are vender specific.</li><li>Select the sequence of PC-MRI sequence from the console monitor of the MRI scanner and perform gated PC-MRI scans using the following parameters: TR/TE=15.55/4.51 ms (minimum TR and TE), flip angle=30&#176;, FOV = 40 &#215; 40 mm2, matrix size = 192 &#215; 192, slice thickness = 2 mm, velocity encoding (VENC) = 120 cm/s, with NEX=8. Unidirectional VENC is acquired in the through-plane direction. NOTE: The scan time is approximately 8.5 min, but the actual scan time may be slightly different among animals due to the variation in cardiac cycles.</li><li>Repeat steps 2.6&#8211;2.9 of image acquisition if the region of interest (ROI) is to be changed to another location in the CCA, such as at the bifurcation.</li><li>Remove the animal from the scanner and return it to its recovery cage when the scan is complete.</li><li>Warm the animal with a heating lamp to maintain body temperature. Keep the lamp at least 15 cm away from the animal to prevent overheating.</li><li>When the animal starts to move and exhibits a response to a tail or toe pinch, turn off the heating lamp.</li></ol>

<figure class='table' style='width:581pt;'><table class='ck-table-resized'><colgroup><col style='width:30.81%;'><col style='width:20.65%;'><col style='width:20.14%;'><col style='width:28.4%;'></colgroup><tbody><tr><td style='height:15.5pt;'>7T small animal MRI system</td><td>Bruker</td><td>&#160;</td><td>&#160;</td></tr><tr><td style='height:15.5pt;'>Isoflurane</td><td>Baxter</td><td>1001936040</td><td>Anesthetic</td></tr><tr><td style='height:15.5pt;'>ECG lead</td><td>3M</td><td>2269T</td><td>&#160;</td></tr><tr><td style='height:15.5pt;'>Monitoring and gating system</td><td>SA instruments, Inc</td><td>Model 1030</td><td>&#160;</td></tr></tbody></table></figure>

<a href='https://app.jove.com/v/57304/phase-contrast-magnetic-resonance-imaging-rat-common-carotid'>Source: Chiu, S., et al. Phase Contrast Magnetic Resonance Imaging in the Rat Common Carotid Artery. J. Vis. Exp. (2018).</a>This video demonstrates phase contrast magnetic resonance imaging (PC-MRI) to measure blood flow in the common carotid artery of a rat. After securing an anesthetized rat on the MRI bed and ensuring stable physiological parameters, the common carotid artery is scanned to capture images at defined intervals. Blood flow is then computed from these images to evaluate changes throughout the cardiac cycle.

<img src='https://cloudfront.jove.com/files/ftp_upload/23411/23411_Figure_1_editor_23411.jpg' alt='23411_Figure_1.jpg' />Figure 1: Animal monitoring. (a) ECG electrodes are placed on the right forepaw and the left hind paw, and the respiratory pillow sensor is placed under the animal's torso. (b) The ECG and respiratory signals are clearly visible on the monitor.<img src='https://cloudfront.jove.com/files/ftp_upload/23411/23411_Figur...

Source: Chiu, S., et al. Phase Contrast Magnetic Resonance Imaging in the Rat Common Carotid Artery. J. Vis. Exp. (2018).This video demonstrates phase ...

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.

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Vídeo:  Phase Contrast Magnetic Resonance Imaging to Assess Blood Flow in the Arteries of a Rat - Experimento

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Within neuroimaging research, a number of recent studies have discussed the impact of between-study differences in volumetric findings that are thought to ...

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Neurociência

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An EEG-fMRI multimodal imaging method, known as the spatiotemporal fMRI-constrained EEG source imaging method, is described here. The presented method employs conditionally-active fMRI sub-maps, or priors, to guide EEG source localization in a manner that improves spatial specificity and limits erroneous results.

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

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