1. Sectional Anatomy
Of the
The Chest

2. Objectives List structures found in the thoracic region
Differentiate between tissues and structures based on displayed density levels
Identify various anatomy within the thoracic region in sagittal, axial, and coronal planes
Identify the locations of and relationships between anatomic structures
After completing this topic, you should be able to:
List structures found in the thoracic region
Differentiate between tissues and structures based on displayed density levels
Identify various anatomy within the thoracic region in sagittal, axial, and coronal planes
Identify the locations of and relationships between anatomic structures

3. Window Levels
There are certain structures within the chest which require specific density and contrast settings known as “window levels” to be seen accurately. The image on the left shows ‘lung windows’ which allows for clear visualization of the lung tissue. In this view you can see the lung markings, but lose detail in the bone and soft tissue. The second image shows more visualization of the mediastinum; particularly the heart and major vessels. In this view you cannot see the lung markings, but the soft tissue and bone are clearly visible.

4. Coronal
Images
In these coronal chest images the ribs look like jelly beans lined up around the chest. This is because the plane is only catching the edges of the ribs. In the top left image, you can see the sternum. This in an indicator that this image is very anterior. The image at the bottom right shows the spine. This can help you determine that the image is more posterior.

5. Sagittal Images
These are sagittal images of the chest. Remember that sagittal images are side views. First notice that neither image show vertebral bodies. That’s because neither image is a midsagittal view. Think about where the spine is in the body, centered. The image on the left is closer to the left of the body because the heart is in view. The image to the right is closer to the right side of the body.

6. Axial Images Images are discussed top to bottom.
As you can see by the green line indicating scan level, this first axial CT image shows the lungs just coming into view. The lungs look like two large black circles. The small black circle between them is the trachea. The lungs will continue to get bigger as the scans progress from superior to inferior on the body.
In the second image the heart comes into view. The lungs are larger on this image. The small structure just anterior to the heart is the sternum. On this image you will notice two white circles on each side of the lungs. These are the humeri. These sectional images are of a cadaver and the option of bringing the arms above the head was not possible.
The last image is at the end of the lungs. Looking close to the spine you will notice two black crescent areas of the lungs. The liver takes up most of this image.

7. Aortic arch Superior vena cava Esophagus Trachea
Here are some important vascular structures in the chest that you should be able to identify. In this image, you can see the aortic arch. The superior vena cava is also coming into view. The trachea is faint here, but is still visible, as is the esophagus. <Fade in green circles>.
Esophagus
Trachea

8. Right pulmonary artery
Pulmonary trunk
Several slices down you get a good view of the pulmonary trunk and its branches. Just to the right of the pulmonary trunk and slightly anterior to the right pulmonary artery, the ascending aorta is clearly visible. <fade in green circles> Just posterior to the left pulmonary artery is the descending aorta.
Right pulmonary artery
Left pulmonary artery

9. Right ventricle Right atrium Left ventricle Left atrium Esophagus
Taking the express elevator to the mid-heart level, you can clearly view the chambers of the heart, with the aorta sandwiched in the middle <fade in green circle>. In this image, contrast is visible in the right atrium and right ventricle. Posterior to the heart, the descending aorta and esophagus are close neighbors.
Left ventricle
Left atrium
Esophagus
Descending aorta

10. windows make a difference
As mentioned earlier, different structures within the thoracic region require different “window levels” to be seen clearly. A window width and level setting referred to as “lung windows” is used to visualize lung tissue. Here are a some examples of some of the images we have just seen, and similar images shown in lung windows.
Animation notes: Maybe slowly fade in text as narration is read.