RTI Piranha, Справочное руководство, Страница: 170 / 181

8. Glossary
Piranha & QABrowser Reference Manual 2014-06/5.5C
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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. 1 R = 2.58 × 10
-4
C/kg. – Originally
(Stockholm 1928) defined as "international R." (Symbol: r) and later (Chicago 1937)
modified to: Roentgen- or -ray, that gives a charge of 1 esE from secondary emission
in 0,001293 g of air.
This means that 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has been replaced by kerma in air.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.)
Scattered radiation
Radiation that, during passage through matter is changed in direction. (It is usually
accompanied by a decrease in energy.)
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