How is the thorax diagnosed?

An x-ray of the thorax is also called an x-ray thorax. It is used to assess the structures and organs located in the chest area and thus enables the diagnosis of some diseases. In an X-ray of the thorax, the radiologist can assess the lungs, the size of the heart, the pleura, the diaphragm and the mediastinum.In addition, particularly bony structures are clearly visible on X-rays.

For this reason, the X-ray thorax is also used to assess the ribs, collarbone, sternum and thoracic spine. Since X-rays are associated with a certain radiation exposure for the patient, they are only used to exclude certain clinical pictures. These include pneumonia (pneumonia), pneumothorax (collapsed lung due to air that has entered the space between the pleura and the lung), pleural effusion (accumulation of fluid between the pleura and the lung), hematothorax (accumulation of blood), chylothorax (accumulation of lymph fluid) and emphysema (over-inflation of the lungs).

In addition, pathological changes can be detected in the X-ray thorax, such as lung tumors, changes in the esophagus, changes in the aorta, heart disease or diseases of the trachea. When taking an X-ray image, there are different beam paths that can be selected depending on the indication for the image. One is the so-called p-a projection (posterior-anterior projection).

Here, the patient’s thorax is irradiated from behind while the detector plate is located in front of the patient. This is the most commonly used beam path for patients who can stand. In addition, a lateral image is usually taken so that the thorax can be assessed directly in several planes.

As an alternative to the p-a image, there is the a-p image (anterior-posterior projection), in which the patient is irradiated from the front and the detector is located behind the thorax. This method is mainly used for bedridden patients. This beam path results in an enlargement of the organs located at the front of the thorax, as they are closer to the radiation source.

This must ultimately be taken into account when evaluating the X-ray image. For some patients, however, there is no other option (e.g. in intensive care units), as the patients cannot get up. The images are usually taken using the so-called hard beam technique.

X-rays with an intensity of 100-150kV are used. A CT of the thorax (computed tomography) provides an even more detailed view of the thorax and the organs and structures located within it. While the X-ray thorax only provides a two-dimensional view in two planes, the CT images can also be combined to form three-dimensional images.

For this purpose, the patient is pushed on a couch through a kind of tube which, after emitting X-rays, detects and calculates the radiation attenuated by the body. The more radiation a piece of tissue allows to pass through, the darker it will ultimately appear on the images calculated by the computer. It is important that the patient does not move as much as possible, as this can result in blurred images.

Ultimately, this method produces many individual sectional images, which are then combined to form an overall image. In this way, the organs and structures of the thorax are displayed without overlapping and can be assessed for changes. A CT of the thorax can be particularly helpful in determining the exact location of a lung tumor.

It is also often used for the detection of a pulmonary embolism. Of course, the same structures are visible in the CT of the thorax as in the X-ray thorax. It is therefore suitable for assessing the esophagus, heart, mediastinum and the bony thorax.

In addition, lymph nodes are also clearly visible in the CT. This plays an important role, especially in malignant diseases. The reason why CT is not routinely used instead of X-rays is the significantly higher radiation exposure for the patient.

For this reason, CT is only requested if conventional methods such as X-ray thorax or ultrasound (sonography) cannot provide sufficient information about the patient’s disease. In order to obtain even better contrasted images, the patient can be administered a contrast medium prior to the examination. As this accumulates differently in the various organs, the structures can be better separated from each other in this way. A CT examination usually takes between 5 and 20 minutes.