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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 ...
Drawing of CT fan beam and patient in a CT imaging system CT scan of the thorax. The axial slice (right) is the image that corresponds to number 2/33 on the coronal slice (left). Spinning tube, commonly called spiral CT, or helical CT, is an imaging technique in which an entire X-ray tube is spun around the central axis of the area being ...
Electron beam CT scanners are considered a fifth generation CT scanner, with first generation being the pencil beam with translation and rotation, second generation being a fan beam with similar motion to its predecessor, third generation having both rotating fan beam and detectors and fourth generation being a fan beam with a rotating movement but fixed detector.
Coronary CT angiography (CTA or CCTA) is the use of computed tomography (CT) angiography to assess the coronary arteries of the heart.The patient receives an intravenous injection of radiocontrast and then the heart is scanned using a high speed CT scanner, allowing physicians to assess the extent of occlusion in the coronary arteries, usually in order to diagnose coronary artery disease.
The portable CT scanner does not replace the fixed CT suite. An example of this type of machine is the Siemens Healthineers SOMATOM On.site. In 2008 Siemens introduced a new generation of scanner that was able to take an image in less than 1 second, fast enough to produce clear images of beating hearts and coronary arteries.
Modern SPECT equipment is available with an integrated X-ray CT scanner. As X-ray CT images are an attenuation map of the tissues, this data can be incorporated into the SPECT reconstruction to correct for attenuation. It also provides a precisely registered CT image, which can provide additional anatomical information.
As an example, each mm 2 of a CT detector may receive several hundred million photon interactions per second during a scan. [ 4 ] To avoid saturation in areas where little material is present between the X-ray source and the detector, the pulse resolving time must be small compared to the average time between photon interactions in a pixel.