Cardiac CT with ECG triggering

 Cardiac CT with ECG triggering offers good image quality of the heart when compared to CT performed for other purposes. 

As in any other field of radiology, analysis of the acquired images requires a systematic approach. 

First of all, it is important to understand that the orientation of the heart in the human body differs from that of other anatomic structures: the right ventricle, for example, does not lie completely on the right, but more anterior. 

The left ventricle does not lie on the left, but more posterior. 

Also, the heart does not always maintain the same position within the mediastinum - in young people it tends to have a vertical orientation, whereas in older people it tends to rest on the diaphragm, a more horizontal orientation.

Cardiologists analyze the heart using cardiac axes. 

These axes are also used in cardiac CT/MR and must be reconstructed in order to assess the heart properly. 

Axial slices, such as those imaged on the left, are useful for a global assessment of the morphology of the heart and its relation to the pericardium.

4-chamber view

On the left is a 4-chamber view, achieved by rotating upwards from the apex of the heart on the axial slices. 

In this axis, the right ventricle is projected next to the right atrium, and the left ventricle next to the left atrium. 

The mitral valve comes into view and - depending on the contrast protocol - the tricuspid valve may also be visible. 

Another feature of this cardiac axis is that the apex of the heart is well demarcated. Note that the apex is formed by the left ventricle.

3-chamber view

When the border between the mitral and aortic valves is localized on the axial slices and the images are rotated from this point, a 3-chamber view like the image on the left can be reconstructed. 

On this image, the left atrium, left ventricle, mitral-, aortic valve and proximal aorta ascendens are visible.

5-chamber view

On the left is an image of a 5-chamber view, which is similar to the 4-chamber view, but additionally displays the aortic valve and left ventricular outflow tract. 

This view is achieved by rotating the 4-chamber view a little more cranially.

2-chamber view

The 2-chamber view in the image on the left is achieved by rotating the images perpendicularly to the mitral valve and parallel to the cardiac septum. 

This axis gives an overview of the left atrium ventricle and mitral valve. 

It is a good view for analyzing ventricular function, especially that of the inferior and anterior walls.

For attaining functional data, consecutive short axes must be reconstructed making use of the 3- and 4-chamber views.