8. Glossary
2012-10/4.3A
201
Barracuda & QABrowser Reference Manual
accompanied by a decrease in energy.)
Stray radiation
The sum of leakage and scattered radiation.
Useful beam
The radiation which passes through the opening in the beam limiting device and which
is used for imaging or treatment.
Radiation protection survey
An evaluation of the radiation safety in and around an installation, that includes
radiation measurements, inspections, evaluations, and recommendations.
Radiation receptor
Any device that absorbs a portion of the incident radiation energy and converts this
portion into another form of energy which can be more easily used to produce desired
results (e.g., production of an image). See image receptor.
Radiation source
The region and/or material from which the radiation emanates.
Radiogram
A film or other record produced by the action of X-rays on a sensitized surface.
Radiography
The production of images on film/image detector by the action of X-rays transmitted
through the patient.
Receptor
See radiation receptor.
Receptor assembly
A radiation receptor in the specialized container necessary for the proper operation of
the receptor.
Rem
The previously used special unit of dose equivalent. One rem equals 10
-2
sievert (Sv).
Resolution
In the context of an image system, the output of which is finally viewed by the eye, it
refers to the smallest size or highest spatial frequency of an object of given contrast
that is just perceptible. The intrinsic resolution, or resolving power, of an imaging
system is measured in mm
-1
or line pairs per millimeter (lp/mm), ordinarily using a
resolving power target. The resolution actually achieved when imaging lower contrast
objects is normally much less, and depends upon many variables such as subject
contrast levels and noise of the overall imaging system.
Roentgen (R) (or Röntgen)
The previously used special unit of exposure. An exposure of one Roentgen will
produce 2,58 × 10-4 coulomb of ions of either sign per kilogram in air. Here the
previously used physical quantity exposure has been replaced by kerma in air. See
kerma. One R does not equal 1 cGy as the units C/kg and J/kg are different. To do this
conversion the ionization constant for air must be used, which is 33,97 J/C. This is how
its calculated: 1 Gy = 1 J/kg Û 1 J/kg/(2,58 × 10
-4
C/kgR × 33,97 J/C) = 114,1 R. An
exposure of 114,1 R thus equals an Air Kerma of 1 Gy. That also means that the value
in R should be multiplied by 8,76 to get the Air Kerma in mGy. (See also Exposure.)
To Next Page
Loading...