8. Glossary
Barracuda & QABrowser Reference Manual
2012-10/4.3A
202
Scattered radiation
See radiation.
Serial radiography
A radiographic procedure in which a sequence of radiographs is made rapidly by using
an automatic cassette changer, image intensifier/TV chain, etc.
Shutter
In beam therapy equipment, a device, attached to the X-ray or gamma-ray source
housing to control the "ON" or "OFF" condition of the useful beam.
Sievert (Sv)
The special name for the SI unit of dose equivalent. One sievert equals one joule per
kilogram. The previously used unit was the rem. One sievert is equal to 100 rem.
Signal-to-noise ratio
For video cameras, the ratio of input signal to background interference. The greater the
ratio, the clearer the image.
Simulator
Diagnostic energy X-ray equipment used to simulate a therapy treatment plan outside
the treatment room.
Slice
The single body section imaged in a tomography procedure.
Source
See radiation source.
Source-detector distance (SDD)
The distance measured along the central ray from the centre of the front surface of the
source (X-ray focal spot or sealed radioactive source) to the active surface of the
detector.
Source-to-image-distance (SID)
The distance measured along the central ray from the centre of the front of the surface
of the source (X-ray focal spot of sealed radioactive source) to the surface of the image
detector.
Source-surface distance (source-skin distance) (SSD)
The distance measured along the central ray from the centre of the front surface of the
source (X-ray focal spot or sealed radioactive source) to the surface of the irradiated
object or patient.
Spot film
A radiograph taken during a fluoroscopic examination for the purpose of providing a
permanent record of an area of interest of to verify the filling of a void with contrast
media.
Stray radiation
See radiation.
Survey
See radiation protection survey.
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