Computed Tomography
For two decades the English electrical engineer had been building prototypes together with the U.S. physicist Allan M. Cormack. Now at last, in Wimbledon, he was able to launch the second major chapter in the history of radiology. At the time the Deutsches Ärzteblatt, a German magazine for healthcare professionals, called the achievement "probably the most important fundamental advance in radiology since Wilhelm Conrad Röntgen discovered X-rays in 1895." Cormack and Hounsfield were awarded the Nobel Prize for Medicine in 1979 for their work.
Radiation source revolves around the body
The computer tomograph generates a narrow X-ray beam which penetrates the part of the body being targeted. Inside the patient's body the beam is weakened to different degrees by the various structures of skin, fat, muscles, organs and bones. A large number of detectors are positioned exactly opposite the X-ray tube. These sensors pick up the weakened signal, process it electronically, and pass it on to a computer for analysis. Unlike X-ray images, which are only taken from one direction, in a CT the radiation source revolves around the body. In this way different views can be generated of the same layer. The computer converts the data into a three-dimensional grayscale image. These days this happens very quickly. Whereas the first-generation devices took about five minutes to generate such a tomography (an image of a specific plane), the high-performance devices of today only need a fraction of a second. The great advantage of CT images is that they are much clearer than a normal X-ray image. Thanks to better contrast gradation, it is easier for the radiologist to distinguish between different types of tissue such as bone, muscle or fat.
The heart in 3D
Technological advances, ever-improving image quality and ever-shorter exposure times enabled CT to develop into one of the most important radiological diagnostic procedures within just a few years. It is used, for example if there is suspicion of bleeding, dilated/expanded blood vessels, a brain tumor or brain edema, or to check on degenerative or age-related changes/lesions, a possible stroke or a suspected fracture of the skull. Radiologists use the whole-body CT to search for tumors and cysts in the chest and abdomen – or to monitor the development of known tumors or changes in inner organs. Similarly, slipped discs, osteoporosis and other degenerative changes or bone fractures can be safely and quickly diagnosed with the help of computed tomography. A cardiac CT can generate a three-dimensional image of the coronary arteries and any changes in them. This method can be used to visualize calcifications and deposits in the coronary vessels, the first signs of atherosclerosis. A cardiac CT can show both the inside of the blood vessels and the walls. Further advantages stem from the three-dimensional nature of the image: the separate parts of the heart are shown in their true proportions. Moreover, the physician can turn the 3D object any way he or she wants. This makes it easier to recognize important details.
Virtual look into the colon
In the meantime, computed tomography has matured to the extent that virtual colonoscopies are possible. Unlike traditional optical procedures, in which an endoscope is inserted into the colon, virtual colonoscopy is not directly invasive at all. Instead, digital slice images are converted by special computer programs into a three-dimensional view of the colon. Even polyps in the intestines can be detected in this way. The CT examination is thus making an important contribution to the early detection of colon cancer.
Contrast agents improve diagnosis
Contrast agents from Bayer Schering Pharma can considerably improve the usefulness of a CT scan. They are also suitable for state-of-the-art examination techniques such as the dual-source CT, which uses two X-ray tubes fixed at an angle of 90 degrees with a detector system directly opposite each tube. The maximum rotational speed is 3 rps. This makes it possible to achieve a very high resolution – a great advantage, especially in non-invasive cardiac imaging.
