Computed tomography (CT) - German Cancer Research Center

Computed tomography - a very powerful and modern X-ray procedure

Image of a computed tomography (CT) scanner in a bright clinic setting. The machine has a circular opening and a flat surface extending from it, indicating where patients lie during the scan. The surrounding area features light-colored cabinetry and a colorful mural on the wall. — 256-line CT Somatom Flash (Siemens) © dkfz.de

Computed tomography (CT for short) is a modern and informative examination using X-rays. It produces sectional images of the body. Computed tomography can produce very precise images of various organs such as the brain, lungs, liver, skeleton, pancreas and kidneys. This makes it easy to determine the location and extent of a disease focus.

Before a CT scan, the following must be taken into account...

A radiology technician sits at a computer workstation, smiling, while operating a CT scanner in the background. Two monitors display medical images, indicating the technician is analyzing scan results. The environment is a clinical setting designed for conducting computed tomography examinations. — Operation of the CT by the technical staff © dkfz.de

1. that computed tomography is an X-ray examination and should not normally be used in the case of pregnancy (a few exceptions with very strict indications). If you cannot rule out the possibility of pregnancy, please consult us before the examination begins.
2. All metallic objects cause strong image interference. We therefore ask you to remove all items of clothing and accessories in the examination area that contain metal (hair clips, dentures, bras, necklaces, etc.). However, belts and zippers on pants and skirts can remain.
3. Before the examination, kidney and thyroid values (creatinine and TSH value) are required (kidney values not older than 4 weeks, thyroid values not older than 3 months), as no iodine-containing CT contrast agent may be injected in the case of renal insufficiency or pronounced hyperthyroidism.
4If the required values are available, the patient is informed about the examination and provided with an indwelling venous access in the arm through which the contrast medium can flow during the examination.
5. Clarification of contraindications that speak against the administration of Buscopan (prostate enlargement, cardiac arrhythmia, glaucoma); see below.

During a CT scan, attention must be paid to...

1. that the injected contrast medium can be accompanied by a strong feeling of warmth and a metallic taste, this is completely normal and is reported by many patients. Both will subside on their own within a minute and are completely harmless.
2. As with any other medication, contrast media can also cause allergic reactions. However, this only happens in rare exceptional cases. Coughing and skin rashes are the main symptoms; allergic shock is very rare. A possible allergy usually occurs within a few minutes. Please report such symptoms to us, as the medication required for treatment is always available.
3. For some CT examinations, it may be necessary to inject you with a medication (Buscopan), which reduces stomach and bowel movements. After the injection, your vision and therefore your ability to react in traffic or when operating machinery may be affected. You should therefore not drive a motor vehicle for the following 24 hours. Contraindications to the application of the medication are Increased intraocular pressure/glaucoma/glaucoma, an enlarged prostate or cardiac arrhythmia.
The examination takes approx. 5-10 min and is painless. You lie on a couch that moves slowly. Body movements during the examination have a very negative effect on the image quality. You should therefore try to lie as still and relaxed as possible. As the internal organs move when you breathe, the examination must be carried out while you are not breathing. You will be asked to hold your breath several times via an intercom system. If you assist us conscientiously, a good quality examination is guaranteed. For examinations of the heart or blood vessels, it may be necessary to give you an ECG.

After a CT scan, it is important to note...

1. that possible late allergic reactions to the contrast medium (very rare) may still occur. In this case, please consult an emergency room or your family doctor.
2. that the venous access line will initially remain in the arm during a further examination at the DKFZ (e.g. MRI).

The Somatom Definition FLASH - 256 lines and CT all-rounder

At the end of February 2010, a modern dual-source computer tomograph (Somatom Definition Flash from SIEMENS), which sets new standards in terms of speed and dose reduction, was put into operation in the Radiology division at the German Cancer Research Center. During the examination with this computer tomograph, two X-ray tubes rotate around the body simultaneously, so that, for example, complete thorax images can be taken in just 0.6 seconds and images of the entire heart in just 250 ms. Whole-body images frequently used in cancer diagnostics can be taken in less than five seconds. This is particularly beneficial for seriously ill and elderly patients as well as children. The new technology can also be used to examine tissue perfusion, which is advantageous for characterizing tumours and assessing the course of therapy. Not only has the speed of the examination been significantly improved compared to older CT models, but the radiation exposure of patients has also been reduced. A special technical development selectively reduces the radiation exposure of particularly sensitive regions of the body, such as the female breast. The radiation is reduced during the rotation phase, when the relevant areas of the body are most exposed to radiation. This measure makes it possible to reduce the radiation exposure of individual body regions by up to 40 percent.