8. Glossary
Barracuda & QABrowser Reference Manual
2012-10/4.3A
196
Effective dose equivalent (HE)
Quantity used to express the weighted DOSE EQUIVALENT to the whole body when it
is irradiated non uniformly or partially.
Exposure (X)
A measure of the quantity of X-ray or gamma radiation based upon its ability to ionize
air through which it passes. The SI unit of exposure is coulomb per kilogram. The
previously used special unit of exposure was röntgen (R). 1 R = 2.58 × 10
-4
C·kg-1
(exactly). The physical quantity exposure is now replaced by
the quantity kerma in air. An exposure of 114.1 R is equal to an Air Kerma of 1 Gy.
That means that the value in R should be multiplied by 8.76 to get the Air Kerma in
mGy.
SI unit: C/kg
Exposure rate (X')
Exposure per unit time. Exposure rate is determined as the quotient of dX by dt, where
dX is the increment of exposure in the time interval dt: X' = dX/dt. A unit of exposure
rate is any quotient of the unit of exposure or its multiples or submultiples by a suitable
unit of time ((C/kg)/s, (mC/kg)/h, etc.).
SI unit: C/kg·s
Filter
In radiological equipment, material or device provided to effect filtration of the radiation
beam.
SI unit: mm
Filter: Inherent filter
The filter permanently in the useful beam; it includes the window of the X-ray tube and
any permanent enclosure for the tube or source.
Filter: Added filter
Filter in addition to the inherent filtration.
Filter: Total filter
The sum of the inherent and added filters.
Firmware
General: The operating system and software installed on a small device. Sometimes
called embedded software.
Barracuda firmware: Program stored in cabinet and modules which handles all control
of measurement electronics. Can be updated, then a special part of the firmware called
bootloader, is used. See Bootloader.
Fluorography
The production of a photographic record of the image formed on the output phosphor
of an image intensifier by the action of X-rays transmitted through the patient.
Fluoroscopy
Technique of radioscopy by means of a fluorescent screen.
Focal spot, effective
The apparent size of the radiation source region in a source assembly when viewed
from the central axis of the useful radiation beam.
SI unit: dimensionless (corresponding to a dimension in mm)
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