UNIT 5A
Introduction to
Radiographic Equipment
General Radiographic, Fluoroscopic
Dedicated, Multipurpose &
Mobile
Conventional vs. Digital
General Radiographic Equipment
• Multi-purpose / general radiographic
equipment - a wide range of procedures
can be performed using this type of
equipment
• It is used for general and/or routine
radiography.
• Examples: orthopedic radiography, chest,
podiatric, abdomen, spine and skull
radiography
General Radiographic Equipment
• Multi-purpose
general
radiographic
equipment
– Stationary
• Conventional
(cassette-based
film)
• Digital (CR –
cassette-based)
DR (Direct Digital) Radiographic
Equipment
• Multipurpose
– stationary
• IR integrated into
the equipment
(cassetteless)
Terminology
• Conventional - Uses film in cassettes (film
holders)
• Digital - Filmless; image is viewed on
monitor
– CR – computed radiography – uses
conventional equipment with cassettes
– DR – Direct digital radiography – uses special
equipment; cassetteless
Image Receptors
• Defined as the device that receives the
energy of the x-ray beam and forms the
image of the body part
• Four types
– Cassette with film (conventional)
– Image plate (IP – used in CR)
– Direct radiography (detector)
– Fluoroscopic screen
The X-ray Tube
• X-rays are produced in a cathode ray
tube
• They are produced from a series of
energy conversions
Requirements for the production of
x-rays include:
• A source of
electrons (the
filament or cathode)
• A means to
accelerate the
electrons (kVp)
• A way to stop the
electrons (the
target or anode)
The x-ray tube
• Is an evacuated glass envelope
• Has a positive (anode) and negative
(cathode) electrode.
• The cathode (filament) serves as the source of
electrons
• High voltage is applied (kVp) to accelerate the
electrons across the tube
• The anode (target) stops the electrons suddenly
which results in the production of x-rays
X-ray production
• The energy conversion involves the
conversion of
– electrical energy to..
– heat energy to..
– kinetic energy to..
– x-ray energy and heat energy.
• >99% of the energy conversion results in
heat
• <1% of the energy conversion results in xrays
The x-ray tube
• Tube housing protects the
patient and operator from
radiation emanating in all
directions.
• The collimator decreases or
increases the size of the xray field (inc or dec pt. &
operator exposure.)
– PBL-positive beam
limitation-automatic
collimation – detects size
of image receptor and
automatically
reduces/increases beam
size to correspond.
Tube Stand
• The device that supports and permits
the x-ray tube to be moved in different
directions.
• Floor-mounted – runs along a track on
the floor.
• Floor-to-ceiling or Floor-to-wall - has
add’l tracks on wall or ceiling
• Ceiling-mounted – provides most
flexibility
X-ray tube
controls
*SID is the distance
between the source (anode)
and the image receptor (IR)
• Longitudinal lock locks tube into position
along the length of the
table
• Transverse locklocks tube into position
across the width of the
table
• Vertical lock-locks
tube vertically to set
the SID*
• Collimator controls
X-ray tube
controls
• Detent lock-locks the
tube into the center of
the bucky tray (where IR
is) transversely.
• Tube angulation lockallows angulation of the
tube cephalad (towards
the head) and caudad
(towards the feet)
• Tube angle indicatorindicates the degrees of
tube angulation
Radiographic
Tables
• The table is
designed to support
the patient in a
position that
enhances the
radiographic
examination
• It is not designed
for comfort!
Radiographic
Tables
• The table must be
uniformly
radiolucent (allows
x-rays to easily pass
through)
• It must be easily
cleaned.
• It must be hard to
scratch.
• Some tables are
stationary (ie.
They don’t move)
Radiographic Tables
• Tables must have a space for a tray (Bucky
tray) to hold image receptors (IR) and a
radiographic grid
IR
Bucky Tray
Image Receptors
• Image receptors
(IR) can either be
film cassettes or
• CR (computerized
radiography)
imaging plates
(IP).
IR Orientation
Radiographic Table Accessories
• Grid –is installed over the tray & consists of Pb strips and
is used to absorb scattered radiation which causes fog
that degrades the visibility of image detail.
– Some grids consist of a mechanism that automatically
moves the grid during exposure (reciprocating grid).
– Others use a stationary grid (one that does not move).
Radiographic Tables
• Tables can be “fixed” or “tilting”
• Fixed (stationary) tables do not
permit tilting of patient’s head or feet
• Tilting tables are used mostly for
radiographic/fluoroscopic applications
• Table height is typically 30-40” from the
floor.
– Some fixed tables have adjustable heights
to assist patients on and off the table
Radiographic Tables
• Tabletops are usually movable
– Some are motor-driven along their
length
– Some are “floating tops” which move
along length and width simultaneously
– Brakes can be controlled by hand, knee or
foot.
– Movable tables are an advantage in
moving/positioning large patients!
Radiographic Table Accessories
• Footboards are an accessory used to
support the patient in a standing position
when tilting tables are employed.
•
should be exercised to
assure the footboard is
attached correctly to prevent injury to the
patient!
Wall-Mounted Bucky System
and Cassette Holders
• Allows standing radiographs
• Cassette holder – adjustable;
holds various size cassettes.
• Wall-Mounted Bucky –
Cassette holder (tray) with grid.
• DR (Digital Radiography)
does not use a bucky tray;
image receptor does not have to
be changed between exposures
Generator or
Control panel
• KvP Selector
• mA Selector
• Exposure time
Selector
• Table bucky vs
upright Bucky
switch
• On/Off switch
• Exposure switch
kVp Selector
• Selects the kilovoltage applied to the x-ray tube
to produce x-rays
• Diagnostic Range 45kVp-150kVp
• Major/Minor (increments of 10 kV/1kV)
• KvP controls the penetrating power of the xray beam (and therefore the # of x-rays
reaching the film)
• KvP controls the energy of the beam
• KvP affects density (darkness/brightness) and
contrast of the image (more on this in a later
lesson)
mA selector
• Selects the milliamperage (mA;x-ray tube current)
• Heats the filament; boils off electrons
(thermionic emission)
• Controls the # of electrons flowing from
cathode to anode (ie. Tube current)
• Controls the amount of x-rays produced
• Controls the amount of exposure delivered to
the patient.
• Controls the density (darkness) or brightness
of the image
• Range 25mA-1200mA (varies with equipment)
Exposure time selector
• Selects the length of the exposure
• Range from milliseconds to 6 seconds
(varies with equipment)
• Controls the time electrons flow from
cathode to anode
• Controls the amount of exposure
• Controls the density or brightness of
the image
mAs
• mAs is the product of mA X exposure time
• It represents the quantity of radiation
exposure delivered.
• Ex: 100 mA @ 1/20 second = 5 mAs
• Ex: 500 mA @ .01 second = 5 mAs
Table bucky vs
upright Bucky
switch
• Available when room
has a table bucky and
an upright bucky
• Activates the
reciprocating bucky
in table or upright.
Other controls
• On/Off switch - turns power to controls on
or off
• Exposure switch - remote control switch
which controls exposure
– prep stage - heats cathode and rotates anode*
– exposure stage - makes exposure(applies kV)
– *Holding the “prep” or “rotor” down for an
extended time decreases the life of the xray tube!
Other controls
• AEC - Automatic Exposure Control Automatically terminates exposure when
predetermined amount of exposure is
reached.
• Determines the amount of exposure needed
to produce a diagnostic image.
• Actually controls the exposure time.
• Operator selects kVp (and sometimes the
mA) and appropriate cells (detectors)
AEC (Automatic Exposure Control)
Provides automatic
control of x-ray
exposure
exposure automatically
terminates when the film
has received desired
amount of film
AEC
Radiographic/Fluoroscopic Equipment
• Radiographic equipment produces static
images only.
• Fluoroscopic equipment produces static
AND dynamic images.
Radiographic/Fluoroscopic Equipment
• In addition to the
components already
discussed,
fluoroscopic
equipment has a
movable
fluoroscopic
carriage which
includes:
– Image intensifier
– An additional x-ray
tube under the table
Radiographic/Fluoroscopic Equipment
• Spot film device – permits the
radiologist to obtain static images
during the fluoroscopic exam.
– Uses various cassettes
– Allows one or more exposures/image
receptor.
• Digital fluoroscopy allows digital
acquisition of spot films (cassetteless)
– Stores static images on a computer.
Mobile Radiographic and Fluoroscopic
Equipment
• Used for radiography:
– At the patient’s bedside
– In the surgical suite
– In the emergency department
• Mobile equipment has similar controls
to stationary equipment but no table.
Mobile Radiographic and Fluoroscopic
Equipment
• A mobile
fluoroscopic unit is
sometimes called a
“c-arm”
Introduction to the
Darkroom
Cassettes
Radiographic Film
Storage and Handling
Essentials of the Darkroom
Automatic Processor
Cassettes
• Cassettes are a lighttight film holder.
• They have a
radiolucent (allows xrays to pass through)
front (tube side)
• The back side usually
has Pb (lead) or Al
(aluminum) to absorb
back scatter.
• Cassettes come in a
variety of standard
sizes.
Standard Cassette Sizes
English
• 14” X 17”
• 14” X 14”
• 11” X 14”
• 10” X 12”
• 9.5” X 9.5”
• 8” X 10”
• 7” X 17”
Metric
• 35 X
• 35 X
• 28 X
• 24 X
• 24 X
• 20 X
• 18 X
43cm
35cm
35cm
30cm
24cm
25cm
43cm
Cassettes
• Most cassettes have intensifying screens
mounted on the front and back inside
surface.
• An Intensifying screen is a fluorescent
material that converts x-ray energy to light
energy which exposes the film.
• The purpose of intensifying screens is to
reduce patient exposure.
• Some cassettes have a single intensifying
screen; some have two intensifying
screens.
Intensifying Screens
• An intensifying screen is composed of
fluorescent phosphors which give off light
when struck by x-rays.
• Different phosphors give off different colors
(spectra) of light
• In radiography, most emit blue, blue/violet
or green light.
• Radiography film is most sensitive to one of
these spectrum.
Luminescence: Fluorescence vs.
Phosphorescence
• Luminescence - emission of light
• Fluorescence - when a phosphor emits light
upon being struck by x-rays, and light
emission ceases when the x-ray source
ceases.
• Phosphorescence - (aka “screen lag”) when
a phosphor emits light upon being struck by
x-rays, but the light continues to glow after
the x-ray source ceases.
Radiographic Film
• Radiographic film is
the primary medium
of conventional
radiography.
• It is composed of a
polyester base
which is tinted blue,
• And a coating of
emulsion (the light &
x-ray sensitive
component of film)
which is composed
of AgBr crystals
suspended in gelatin
• Film can either have
Radiographic Film emulsion coated on
one side (single
emulsion)
• or can be coated on
both sides (duplitized).
• Single emulsion film is
used with cassettes
with single screens.
• Duplitized film is used
with dual-screen
cassettes.
Radiographic Film Classifications:
• Speed - reflects the sensitivity (response)
of the emulsion to x-ray and light
exposure.
– ex: 100, 200, 400, 800 speed; the higher the
number, the more sensitive the emulsion
(requires less exposure)
• Contrast - how the film exhibits the
relationships between blacks and whites.
• Resolution (detail) - how the film
reproduces details of the subject.
Film Storage and Handling
• Ideal storage temperature - 68o
• Ideal humidity - 30-60%
• Stored film must be protected from:
– radiation
– light
– age
– pressure
– high temperatures
– too high/low humidity
Artifacts-foreign marks on the film
• Fog – gray/black appearance of film
– Caused by: Exposure to radiation, light or age
– Fog destroys visibility of details.
• Static-black “lightening”-like artifacts
– Caused by: Static discharge in the darkroom
due to low humidity & electrification by friction.
• Crescent (“crinkle”) marks- black moonshaped artifact.
– Caused by: Bent film (mishandling)
Darkroom
• Should be a safe environment for handling
radiographic film.
• Safelight-allows visibility in the darkroom
without fogging the film!
– Maximum intensity of bulb- 15 watts
– Safelight filters
• GBX - red light (for green or blue sensitive films
• Wratten 6B amber light for blue sensitive only (not
used today)
– Safelight can be direct or indirect .
Darkroom - film storage
• Film bins provide various sizes of film a lighttight & radiation proof storage .
• Films are stored largest film to smallest film
(front to back)
• Boxes of film are stored on end to prevent
pressure artifacts.
• The FIFO method (First in; first out) of film
usage prevents film from being used after it’s
expiration date.
• Expiration dates are stamped on each box
Darkroom –
The Automatic
Processor
• There are four racks
in an automatic
processor:
Developer Fixer,
Wash, Dryer
• Processing
temperature is 9095o F.
• Most processors
process films in 90
seconds.
Automatic Processor
Identify the following in the Darkroom:
• Main switch ( on wall)
• Power on/off (on processor)
• Film tray
• Water valve
• Replenishment tanks
– One for developer; one for fixer
– hoses
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