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Positron emission tomography–computed tomography is a hybrid CT modality which combines, in a single gantry, a positron emission tomography (PET) scanner and an X-ray computed tomography (CT) scanner, to acquire sequential images from both devices in the same session, which are combined into a single superposed (co-registered) image.
CT is based on the same principles as X-ray projections but in this case, the patient is enclosed in a surrounding ring of detectors assigned with 500–1000 scintillation detectors [13] (fourth-generation X-ray CT scanner geometry). Previously in older generation scanners, the X-ray beam was paired by a translating source and detector.
Most radiation therapy is planned using the results of a 3D CT scan. A 3D scan largely presents a snapshot of the body at a particular point in time, however due to the time of the acquisition, in which the patient is likely to have moved in some way (even if only breathing), there will be an element of blurring or averaging in the 3D scan. [ 6 ]
Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object.Applications of radiography include medical ("diagnostic" radiography and "therapeutic radiography") and industrial radiography.
The data can be corrected for self-absorption artefacts using an X-ray absorption-contrast CT scan of the same sample. If the solid-state chemistry of the sample is changing during the XRD-CT scan, then other data acquisition approaches can be employed that can improve the temporal resolution of the method, such as the interlaced approach [13] [14]
Spectral imaging is an umbrella term for energy-resolved X-ray imaging in medicine. [1] The technique makes use of the energy dependence of X-ray attenuation to either increase the contrast-to-noise ratio, or to provide quantitative image data and reduce image artefacts by so-called material decomposition.
In a closed system, X-ray shielding is put around the scanner so the operator can put the scanner on a desk or special table. Although the scanner is shielded, care must be taken and the operator usually carries a dosimeter, since X-rays have a tendency to be absorbed by metal and then re-emitted like an antenna.
In conventional CT machines, an X-ray tube and detector are physically rotated behind a circular shroud (see the image above right). An alternative, short lived design, known as electron beam tomography (EBT), used electromagnetic deflection of an electron beam within a very large conical X-ray tube and a stationary array of detectors to achieve very high temporal resolution, for imaging of ...