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Thursday, 31 October 2024
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Searchterm 'Intensity' found in 2 terms [
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Diaphanography
Diaphanography is a noninvasive breast imaging technique used in diagnosis of breast disease. The breast is illuminated with low intensity light and the transmission pattern of red and near-infrared radiation is detected. After amplification and reconstruction, the images are displayed on a monitor.
Results from diaphanography tend to show lower sensitivities and specificities than are found in diagnostic mammography studies. Light scanning (diaphanography and transillumination) is not recommended for screening or diagnostic evaluation of the breast.
Display
A display is a computer monitor that shows the processed data from the scanned area. Displays can be black-and-white or color, small or large depending upon the model and price of the machine.

See also Display Field of View, Display Matrix, Window Width, Bit Range, Hounsfield Scale, Interpolation, Minimum Intensity Projection, and Printer.
Filtration
X-rays contain a range of energies (polychromatic photons), the higher energies pass through the patient, the lower energies are absorbed or scattered by the body. Ideally, the x-ray beam should be monochromatic or composed of photons having the same energy. Strong filtration of the beam results in more uniformity. The more uniform the beam, the more accurate the attenuation values or CT numbers are for the scanned anatomical region.
There are two types of filtration utilized in CT:
Inherent tube filtration and filters made of aluminum or Teflon are utilized to shape the beam intensity by filtering out the undesirable x-rays with low energy. Filtration of the x-ray beam is usually done by the manufacturer prior to installation. The half value layer provides information about the energy characteristics of the x-ray beam. Too much filtration produces a loss of contrast in the x-ray image.
A mathematical filter such as a bone or soft tissue algorithm is included into the CT reconstruction process to enhance resolution of a particular anatomical region of interest.
Gantry
The gantry is a ring-shaped structure, containing the x-ray tube, collimators, filters, data acquisition system (DAS), associated electronics such as gantry angulation motors, rotational components including slip ring systems and the detector array in a CT or radiation therapy system. The table control, to regulate the gantry tilt and laser (or high intensity) lights are included within, or mounted on the gantry serving as anatomical positioning guides. To scan the patient, the patient table is moved through the gantry aperture.
The rotating arm on which an accelerator head is mounted is also called gantry. This gantry can rotate 360 degrees around its axis.
Half Value Layer
The half value layer (also half value thickness) is the amount of absorbing material, which is needed to reduce the x-ray intensity by one half.
The half value layer provides important information about the energy characteristics of the radiation. A low (or thin) half value layer for a given x-ray beam indicates that the x-ray beam contains more low energy and less penetrating radiation. An x-ray beam containing high energy or highly penetrating radiation has a high (or thick) half value thickness.
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 [last update: 2023-11-06 02:01:00]