In
microtomography X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
scanners, cone beam reconstruction is one of two common scanning methods, the other being
Fan beam reconstruction
Fan commonly refers to:
* Fan (machine), a machine for producing airflow, often used for cooling
** Hand fan, an implement held and waved by hand to move air for cooling
* Fan (person), short for fanatic; an enthusiast or supporter, especially wit ...
.
Cone beam reconstruction uses a 2-dimensional approach for obtaining projection data. Instead of utilizing a single row of detectors, as fan beam methods do, a cone beam systems uses a standard
charge-coupled device
A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...
camera, focused on a
scintillator
A scintillator is a material that exhibits scintillation, the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate (i.e. re-emit the absorbed ...
material. The scintillator converts X-ray radiation to visible light, which is picked up by the camera and recorded. The method has enjoyed widespread implementation in
microtomography, and is also used in several larger-scale systems.
An X-ray source is positioned across from the detector, with the object being scanned in between. (This is essentially the same setup used for an ordinary X-ray
fluoroscope
Fluoroscopy () is an imaging technique that uses X-rays to obtain real-time moving images of the interior of an object. In its primary application of medical imaging, a fluoroscope () allows a physician to see the internal structure and function ...
).
Projections from different angles are obtained in one of two ways. In one method, the object being scanned is rotated. This has the advantage of simplicity in implementation; a rotating stage results in little complexity. The second method involves rotating the X-ray source and camera around the object, as is done in ordinary CT scanning and
SPECT
Single-photon emission computed tomography (SPECT, or less commonly, SPET) is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera (that is, ...
imaging. This adds complexity, size and cost to the system, but removes the need to rotate the object.
The method is referred to as cone-beam reconstruction because the X-rays are emitted from the source as a cone-shaped beam. In other words, it begins as a tight beam at the source, and expands as it moves away.
See also
*
Computed tomography
*
Industrial CT scanning
Industrial computed tomography (CT) scanning is any computer-aided tomographic process, usually X-ray computed tomography, that uses irradiation to produce three-dimensional internal and external representations of a scanned object. Industrial CT ...
*
Tomographic reconstruction
Tomographic reconstruction is a type of multidimensional inverse problem where the challenge is to yield an estimate of a specific system from a finite number of projections. The mathematical basis for tomographic imaging was laid down by Johann ...
References
{{Medical imaging
Medical imaging
Medical physics
X-ray computed tomography