Computertomography

Computertomography, commonly called computed tomography (CT), is a medical imaging technique that uses X-ray measurements taken from multiple angles around the body to reconstruct cross-sectional images. A CT scanner rotates an X-ray tube and detectors, producing axial slices that can be combined into three-dimensional representations. CT provides detailed images of bone, air-filled spaces, and soft tissues.

Principle and data: Attenuation of X-rays by tissues is measured and reconstructed with algorithms, such as filtered back projection or iterative methods. Images are quantified on Hounsfield units, which relate radiodensity to water and air.

Advances include multi-detector (or multidetector) CT, helical scanning, CT angiography, perfusion CT, and dual-energy CT. These enable fast whole-body imaging and improved material differentiation.

Medical uses: CT is widely used in trauma and emergency care, chest and abdominal imaging, detection of pulmonary embolism, stroke assessment, cancer staging, and guiding biopsies or procedures. It also enables 3D reconstructions for surgical planning and CT colonography for colorectal screening.

Safety and limitations: CT involves ionizing radiation. Contrast agents, usually iodinated, may be required and can cause allergic reactions or kidney injury in at-risk patients. Limitations include radiation exposure, inferior soft-tissue contrast relative to MRI, and susceptibility to artifacts from motion or metal. Access and cost vary by setting.

History: CT was developed in the early 1970s by Godfrey Hounsfield and Allan Cormack, earning the 1979 Nobel Prize in Physiology or Medicine. Since then, scanners have become faster, with more detectors and advanced imaging techniques.