This is a technology that uses computer-processed x-rays to produce tomographic images (virtual 'slices') of specific areas of the body, allowing a view to what is inside it without cutting it open. In Medical imaging CT cross-sectional images are used for diagnostic and therapeutic purposes in various medical disciplines.
There are several advantages that CT demonstrates over traditional X-Ray. First, CT completely eliminates the superimposition of images of structures outside the area of interest. Second, because of the inherent high-contrast resolution of CT, differences between tissues that differ in physical density by less than 1% can be distinguished. Finally, data from a single CT imaging procedure consisting of either multiple contiguous or one helical scan can be viewed as images in the axial, coronal, or sagittal planes, depending on the diagnostic task.
CT is regarded as a moderate- to high-radiation diagnostic technique. The improved resolution of CT has permitted the development of new investigations, which may have advantages; compared to conventional radiography, for example, CT angiography avoids the invasive insertion of a catheter. CT colonography (also known as virtual colonoscopy or VC for short) may be as useful as a barium enema for detection of tumours, but may use a lower radiation dose. CT VC is increasingly being used as a diagnostic test for bowel cancer and can eliminate the need for a colonoscopy.
The radiation dose for a particular diagnosis depends on multiple factors: volume scanned, patient build, number and type of scan sequences, and desired resolution and image quality. CT scan has been shown to be more accurate than radiographs in evaluating anterior inter-body fusion.
Usage of CT has increased dramatically over the last two decades. CT has become an important tool in medical imaging to supplement x-rays and medical ultrasonography. It is also used for preventive medicine or screening for disease, for example CT colonography for patients with a high risk of colon cancer, or full-motion heart scans for patients with high risk of heart disease. The main uses of CT in medical diagnostics are to examine: