The overall goal of this procedure is to generate multimodality magnetic resonance image data sets for the comprehensive assessment of both cardiac function and morphology in rats. This is accomplished by first attaching electrodes to the rat's foot pads. Next, the animal is positioned into the MRI.
Scanning is then initiated and multis slice, short access, small animal look. Locker inversion or Sally recovery stacks are required. Finally, the images are reconstructed both online or offline.
Ultimately, results can be obtained that allow the study of the function and morphology of the heart in a small animal model through cardiac magnetic resonance imaging. This method can help answer key questions in the field of function and morphological cardiac studies in small animals such as myocarditis or infarction. Mold in enrollments.
After anesthetizing, a rat in an induction chamber filled with 5%ISO fluorine, check the level of sedation with a toe pinch, then weigh it, attach a nose cone and deliver two to 3%ISO fluorine in oxygen to maintain anesthesia for the remainder of the procedure. With warm water and soap. Wash the rat's tail to make the blood vessels more visible.
Using a 22 to 24 gauge IV catheter, approximately one third of the distance from the tip of the tail cannulate either vein. If attempts are unsuccessful, cannulate more proximally. Take a blood sample for hematocrit analysis and use skin glue and tape to secure the IV catheter.
Next, using alcohol or soaped water, clean the animal's footpads. Then attach an electrode to the middle of each footpad and use adhesive tape to secure it in position to minimize the formation of loops that may cause interference with the ECG signal. Twist the ECG cables tightly around each other to maintain the rat's body temperature at 38 plus or minus one degree Celsius.
First place a warming mat into the imaging container. Then insert the sensor of the thermometer in the anal orifice about one to two centimeters used in this study is a Phillips Engenia 3.0 T clinical MRI system with a 70 millimeter inner diameter solenoid coil. Place the rat in a supine or prone position into the imaging container with its heart in the center of the coil.
Then connect the ECG electrodes and wait for a stable signal before beginning imaging. Begin with a survey to locate the heart in the center of the MRI field of view. Once the position is correct, continue with two chamber and four chamber Sydney MRI views to determine the geometry of the stack of short axis images for Sally position Amid cavity short axis slice on the two and four chamber images, use a combination of 4, 000 millisecond acquisition and 4, 000 millisecond relaxation durations to allow for sufficient recovery of magnetization along the Z axis and to prevent overheating of the gradients.
To enable functional analysis, set the phases to at least 12 with temporal under sampling at a factor of two to accelerate acquisition. Next, without moving the rat, inject the gadolinium based contrast agent into the indwelling catheter. Then wait five minutes to allow the blood pool signal in the LV cavity.
To decline. Establish Sally as a multis slice, shore axis stack consisting of at least seven slices, 2.4 millimeters in thickness. Position the slices so that the most distal is below the apex of the heart and the top level is just distal to the cardiac valves, ensuring that the short AEs are perpendicular to the septum.
After approximately three rounds of cell or in 30 minute intervals, inject additional doses of contrast agent. Finally, when image acquisition is complete, remove the rep from the scanner and allow it to recover from anesthesia before returning it to its cage. In the housing facility for performing offline reconstruction of images, choose the cardiac phase for which to extract the data.
For example, T one maps in the systolic or diastolic phase, adjust the definition of the end systole or end diastole for TT one by selecting the corresponding cine image. Use color maps to visualize T one that provide exact values by passing the mouse over an area of interest. Finally, store the images in various image formats for further analysis.
The Sally technique demonstrated in this video produces three types of images simultaneously. The first arsine images that can be used to study local and global LV function. LV parameters that are assessed using A CMR software package include systolic and end diastolic volumes, ejection fraction, and mass multiple IR images with different nominal tis are the second type of dataset acquired from which the images with optimal null of normal myocardium can be selected.
This ensures maximum enhancement of areas with focal myocardial fibrosis or scars as necessary for LGE imaging. Thirdly, as shown here, T one maps are generated that should demonstrate homogenous relaxation times over healthy myocardium before administration of gato penate DMA gluing myocardium has a shorter T one than blood within the LV cavity in the first minutes after administration of contrast, agent T one of blood shortens more than that of myocardium, while the presented data from a healthy animal shows homogenous T one behavior across the entire myocardium in the presence of myocardial injury, EG myocardial infarction, T one is shortened in the affected region. T one maps can be reconstructed for any phase of the cardiac cycle.
In this figure, the top panel shows a pulse sequence scheme after an atic inversion pulse of 180 degrees. Image data for the first radial segment represented by colored sectors of circles are continuously sampled for consecutive cardiac phases represented by circles of different sizes and heart cycles depicted by the different circle colors during a predefined ad. While magnetization recovers with a time constant T one star temporal resolution.
For example, the number of cardiac phases is theoretically limited by minimum repetition time after a predefined rd, during which magnetization recovers without any readout induced perturbations with a time constant T one. The process is repeated for the next radial segment and so on. In the first step of the reconstruction of T one maps, raw images for the number of cardiac cycles encompassed by AD are reconstructed from all available image data acquired during a predefined time window within the RRR interval.
For example, during systole as a second step, pixel wise, nonlinear curve fitting is performed and the resulting T one star values are corrected for readout induced deviation of the magnetization recovery curve to generate a T one map from these raw images for a predefined interval after inversion, for example, 100 to 300 milliseconds, a set of IR prepared images with predefined steps of inversion time, such as 25 milliseconds, is reconstructed from all image data available within the interval. As shown here, cine images for predefined number of cardiac phases are reconstructed from all image data available beyond the time point at which all longitudinal magnetization within the field of view have recovered by at least 90%Once mastered, this technique can be performed within about two hours, including animal preparation, scanning, and imagery construction. If done properly.
