High Frequency Echocardiography Using Small Animals


An impaired heart function and related structural differences are associated with several diseases. Repetitive and in vivo visualization of the heart and blood vessels is therefore necessary to detect these conditions, follow their progression and study the influence of medication. Echocardiography uses ultrasound waves which are sent to the underlying tissue. Due to the collision of these waves on tissue structures, the direction of the ultrasound changes. The redirected waves will be recaptured and give rise to one ultrasound line with a grey scale. By scanning the entire tissue and combining all these lines, we can create a 2D image of the underlying tissue. However, the heart of small animals such as mice and rats, is very small and their heart frequency is very rapid. As a consequence, it is not possible to use the classical (human) echocardiography equipment, but we need to utilize an apparatus with a higher scan frequency in order to obtain an image with a sufficiently high resolution. These 2D images make it possible to visualize the heart and its parts such as valves. In case of e.g. a heart attack we are able to see which part of the heart is contracting insufficiently. Also blood vessels and pathologies of the blood vessels (like presence of atherosclerotic plaques or enlargement of the aorta) can be shown in this way. By repetitive scanning of the same area and showing the results in function of time, we can study the mobility of the walls of the heart and blood vessels. Measurement of the thickness of the ventricular wall and the size of the chambers will give us important information concerning the heart function. Furthermore, we can apply the Doppler principle by which we can determine the velocity of moving targets, more precisely the velocity of red blood cells. As such, we can measure blood flow through valves and blood vessels. High frequency echocardiography makes it possible to measure non-invasively, in vivo and in real-time cardiovascular parameters and structures in small animals. This technique can therefore be applied repetitively on the same animal by which progression and regression of diseases can be followed easily, limiting the number of animals.