Computed tomography (CT), originally known as computed axial tomography (CAT or CT scan) and body section roentgenography, is a medical imaging method employing tomography where digital geometry processing is used to generate a three-dimensional image of the internals of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation. The word "tomography" is derived from the Greek tomos (slice) and graphia (to write). CT produces a volume of data which can be manipulated, through a process known as windowing, in order to demonstrate various structures based on their ability to block the X-ray beam. Although historically (see below) the images generated were in the axial or transverse plane (orthogonal to the long axis of the body), modern scanners allow this volume of data to be reformatted in various planes or even as volumetric (3D) representations of structures.Although most common in healthcare, CT is also used in other fields, for example nondestructive materials testing.Contents [hide]
1 History
1.1 Tomosynthesis
2 Diagnostic use
2.1 Cranial CT
2.2 Chest CT
2.3 Cardiac CT
2.4 Abdominal and pelvic CT
2.5 Extremities
3 Advantages and hazards
3.1 Advantages Over Projection Radiography (See Radiography)
3.2 Radiation exposure
3.2.1 Typical scan doses
3.3 Adverse reactions to contrast agents
4 Process
4.1 Windowing
5 Three dimensional (3D) reconstruction
5.1 The principle
5.2 Multiplanar reconstruction
5.3 3D rendering techniques
5.4 Image segmentation
5.5 Example
6 External links