Ultrasound imaging is based on the principle that mechanical waves pass through tissues of different densities with different reflectivity, resulting in superimposed imaging of different reflected waves. In mice, excellent resolution can be obtained using high-frequency ultrasound (15-50 MHz). Effective analysis of cardiac morphology and vascular function can be performed in anesthetized or awake mice within a short collection time. Nowadays, the mainstream echocardiography is still planar imaging, whereas the currently developed 3 D reconstruction based on 2 D imaging pictures provides accurate measurements in a more intuitive way, but with a possible loss of resolution.
Principle
The basic principle of the mouse heart ultrasonography experiment is that mechanical waves pass through tissues of different densities with different reflectivity, resulting in superimposed imaging of different reflected waves.
Operation method
Mouse heart ultrasonography experiment
Principle
The basic principle of the mouse heart ultrasonography experiment is that mechanical waves pass through tissues of different densities with different reflectivity, resulting in superimposed imaging of different reflected waves.
Materials and Instruments
Equipment: Move The basic procedure of mouse cardiac ultrasonography can be divided into the following steps: Caveat 1. Anesthetics need to be stored at 4 ℃, protected from light, and the dosage is 0.5-0.75 mg/g of anesthetics for injection. 2. The operating table of the mouse cardiac ultrasound instrument should not be wiped with ethanol, and only pure water should be used. 3. The RMV704 probe is used for the determination of cardiac function in newborn mice, the RMV711 probe is used for the determination of cardiac function in pregnant mice, and the RMV707B probe is used for the determination of cardiac function in adult mice. For more product details, please visit Aladdin Scientific website.
Vevo770 mouse cardiac ultrasound, depilatory, conductive adhesive.
Reagents:
① Tribromoethanol (avertin) anesthetic.
A Anesthetize the mice to be tested by intraperitoneal injection of tribromoethanol, and remove the hairs on the chest of the mice by using a hair remover or shaving razor blade.
B Turn on the hot plate and control the temperature at 40 ℃, place the mice with the chest hairs removed on the table with their abdomens facing upwards, dab the limbs with purified water (for conductive use), and fix them to the corresponding positions on the table with adhesive tapes. Adjust the operating table so that the head of the mouse is slightly higher than the tail, so that the apical part of the heart and the bottom of the heart are flush.
C Place two pieces of thick film on both sides of the chest of the mouse (to hold the conductive adhesive in place), and apply the conductive adhesive to the chest of the mouse, which is about 2 cm thick. The probe should be buried in the conductive adhesive during the measurements.
D Parasternal long-axis view
(1) B-mode ultrasound long-axis view
Anatomy: The left ventricle, the aorta, and the mitral leaflet are visible.
Positioning of the probe: the 'notch' on the probe should be oriented towards the head of the animal and rotated approximately 30°-45° counterclockwise. (2) M-mode ultrasound long-axis view
Probe positioning: same as 4(1).
Goal: If the anatomy is sufficiently clear and the axis is at the correct angle, M-mode ultrasound measurements can be obtained to better understand LV cardiac function.
(3) Left ventricular outflow tract measurement
Probe positioning: same as 4(2).
Anatomy: The left ventricular outflow tract is measured at the level of the aortic valve leaflets by measuring the markers from one side to the other.
(4) Pulmonary Artery Outflow (not commonly used)
Probe Positioning: With the probe angle turned slightly toward the animal's left shoulder, the pulmonary artery comes into view. A sampling volume (samplevolume) is obtained in this position and a pulsed Doppler image of pulmonary outflow can be obtained.
DISCUSSION: Maximum blood flow velocity in the pulmonary artery is measured to determine pulmonary outflow. After obtaining the Doppler waveform, the maximum pulmonary artery velocity is measured at the peak of the waveform, and the entire waveform is traced to measure the time integral of pulmonary artery velocity.
E Parasternal short-axis view
(1) Parasternal short-axis view B-mode ultrasound image
Probe positioning: from the paraspinal long-axis view, the probe is rotated 90° clockwise to the short axis. In effect, the position of the probe trace is shifted from towards the head of the mouse to towards the left side of the mouse, resulting in a complete circular image of the left ventricle. This image can be optimized by rotating or tilting the probe.
(2) M-mode ultrasound image in parasternal short-axis view
Probe positioning: same as 5(1).
Anatomy: Placement of the M-mode ultrasound cursor in the parasternal short-axis view is the best view for obtaining M-mode ultrasound images to measure the LV internal diameter. These measurements will provide information on ejection fraction, short-axis shortening rate, and calculated values of LV size.
(3) Other visible anatomy in short-axis views
PROBE POSITIONING: All aspects of the left ventricle can be analyzed by moving the probe and scanning down to the apex and up to the base of the heart.
Anatomy: If the short-axis view is moved to the level of the aortic valve, the aortic valve will appear in the center. The tricuspid valve is on its right (left side of the screen) and the pulmonary valve on its left (right side of the screen). In this view, pulsed Doppler can be located at the pulmonary or tricuspid valve. The coronary arteries may also be present in this view.
F Apical 4-chamber view The apical 4-chamber view is the most challenging of the cardiovascular views.
PROBE POSITIONING: Obtaining an apical four-chamber view from the lower left side of the animal's thorax involves slowly trying to locate it from the apex toward the base of the heart. The probe is placed on the transverse section with the notch facing the left side of the mouse, and the mouse is then rotated slightly head down. The probe will also rotate 60° to 70°. Move the probe to the lateral wall of the thorax. In this position, a slight fine-tuning will yield an apical four-chamber view.
Anatomy: Try to visualize the right and left ventricles, with the atria at the bottom of the screen. This view provides accurate angles for pulsed Doppler of the mitral and tricuspid valves. Doppler from the mitral valve allows measurement of mitral inflow.
G Aortic Arch Section The final cardiovascular section is the aortic arch. If imaged correctly, the ascending aorta, branches and descending aorta are visible.
PROBE POSITIONING: The aortic arch view is an adjusted view of the right side of the sternum. The tangent of the probe is directed toward the animal's lower jaw. The probe can be rotated slightly clockwise to obtain a perfect image.
Anatomical target: In this view the descending aorta can be analyzed with pulsed Doppler; the descending aorta is usually the location of the aortic ligation.
H Right Parasternal Long-Axis View The right parasternal long-axis view is used to evaluate the right ventricle. The probe position is the same as the long-axis view, except that it is placed on the right side of the sternum. Proper adjustment of the probe position may be required depending on the strain of mouse used. Proper rotation of the tail end of the probe will help to visualize the right ventricle. Once this image is obtained, the thickness of the ventricular wall can be measured. This section is useful for studying pulmonary hypertension or any other heart disease that affects the right ventricle.
I Suprasternal Section The suprasternal section is used to obtain the aortic valve blood flow velocity. This section is done to obtain the correct Doppler shift to get an accurate valve blood flow velocity. The probe is placed in the midline at the level of the thoracic inlet of the mouse and by rotating the tail end of the probe, a tubular structure, the ascending aorta, will be seen. At the caudal end of this tubular structure, the aortic valve can be seen. Aortic flow velocity is obtained by placing the pulsed Doppler sampling volume over the valve leaflet.
An example of the results is shown in Figure 8-5-1. 