Common use of Computed Tomography Clause in Contracts

Computed Tomography. Computed tomography is an imaging technique that utilises computer-processed X-rays to produce tomographic images or 'slices' of specific areas of the body. Digital geometry processing is used to generate a three-dimensional image of the inside of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation [347]. Computed tomography produces a volume of data that can be manipulated, through a process known as windowing, in order to demonstrate various bodily structures based on their ability to attenuate the X-▇▇▇ ▇▇▇▇. This information is interpreted as Hounsfield Units (HU). Although historically the images generated were in the axial or transverse plane, perpendicular to the long axis of the body, modern scanners allow this volume of data to be reformatted in various planes or as volumetric (3D) representations of structures. Electron beam computed tomography (EBCT) and multi detector computed tomography (MDCT) are well-validated, non-invasive imaging methods which do not require the administration of radio-opaque contrast dyes [348]. The methods are considered to be the gold-standard for assessing the extent of VC and its progression in the coronary arteries, the aorta and the cardiac valves [349, 350]. Both CT technologies are considered equivalent in accuracy and reproducibility even though they operate on different imaging platforms [351-353]. Electron beam computed tomography employs a rotating fan of X‑rays produced by the impact of a beam of electrons against a tungsten ring. Image acquisition is rapid, limiting patient exposure to radiation [348]. Multi detector computed tomography employs a paired X‑ray source-detector unit revolving in a spiral motion around the patient who lies on a movable bed that advances through the beam of X‑rays [348]. Although MDCT is slower than EBCT and provides a higher radiation dose, it has a higher spatial resolution (better image quality) than EBCT [354]. Despite the advantages of CT imaging techniques for the quantification of calcification, there are also substantial limitations. The method is unable to distinguish intimal from medial calcification and CT methods are expensive and provide increased exposure to ionized radiation. The lack of accessibility of scanners can present a major obstacle to its routine application and more importantly the method requires a clinician or highly trained and experienced reader to interpret the results.