Computed Tomography introduction
In April 1972, G. N. Housenfield, a senior scientist at EMI LIMITED of middlesex at the annual congress of the British Institute of Radiology, announced the invention of a new revolutionary imaging technique, which he called "Computrized Axial Transverse Scanning". Its theory was quite simple according to which -
A cross section of the head (a tomographic slice) is examined from multiple angles with the help of a pencil like x-ray beam. The transmitted X-ray Beam is counted with the help of a scintillation detector and the data is fed by analyzing it with a mathematical algorithm and reconstructing a tomographic image.
This image has many features that have never been seen before in a 2D X-ray image. It can produce radiographic diffrence in different tissues such as soft tissue, blood clots, gray matter, white matter, cerebrospinal fluid, tumor and cerebral edema etc. It is known as CAT (Computrized Axial Tomography) and CT (Computrized Tomography) etc.
As with other Great Discoveries, CT is the result of the work of many different explorers. In 1917, an Austrian Mathematician J. Radon worked on gravitational theory, stating that a two or three dimensional object can be reproduced by its set of infinite projection. Hence, the mathematical concept of CT Scan was established 55 years before commercial production.
In 1956, Bracewell worked on radioastronomy to produce a solar map with the help of ray projection.
Oldendrof in 1961 and Cromack in 1963, understanding the concept of computed tomography, designed its laboratory model.
In 1968 Kuhl and Edwords created a successful mechanical scanner for nuclear imaging, but did not extend their work to diagnostic radiology. Hosenfield designed CT Scan for diagnostic radiology and also demonstrated remarkable potential in diagnostic diagnostic radiology.
Further, this modality has evolved into a versatile 3D whole body imaging modality with many clinical applications such as onchology, vascualr radiology, cardiology, traumatology and interventional radiology etc. Nowadays dedicated CT scanner is also available for special clinical application like -
1. Radiotherapy Planning- In CT scanner has extra wide bore, so that CT scans can be made with large field of view (FOV).
2. CT scanner is integrated with other modality for multi modality imaging. For example, CT scanner is integrated with PET scanner or SPECT scanner.
3. Dual source CT scanner for dedicated diagnostic imaging which has two X-ray tubes and volumatric CT scanner with 320 detector row, which can scan the entire organ in single rotation, has been developed.
CT scan is perfectly suited for 3D imaging and is used for brain, cardiac, musculoskeletal and whole body imaging.
