6. Cassettes Flashcards
is any type of holder used to
protect and transport the radiographic film as it travels
through the medical imaging department & other parts
of the medical facility.
radiographic cassette
CONVENTIONAL RADIOGRAPHY CASSETTES
conventional or computed
use standard radiographic film
Conventional cassettes
use no film
Computed radiography cassettes
With conventional cassettes, an image is projected onto
a sheet of film, and for this reason the process is referred to as
projection radiography (or sometimes as conventional radiography)
Conventional cassettes can be either
grid or nongrid
A grid in the ____ of the cassette absorbs
scattered & secondary radiation emitted from the
patient
front panel
are the most common type
found in medical imaging departments
Conventional cassettes
Since the sensitivity of radiographic film to direct x-ray exposure is ____, a very large exposure and
radiation dose to the patient is necessary to produce an adequate image
very low
The x-rays coming from the x-ray tube, carrying
anatomical information from the patient, either are
converted into _____ the film
light energy or directly expose
Approximately ____ of the image is produced from light exposure, and less than ____ is produced by direct x-ray exposure
90-99%,
1-10%
Cassettes have 3 main purposes:
- ) Keep the intensifying screens and film in close contact with one another
- ) Protect the screens and film from physical damage
- ) Protect the film from being exposed externally
X-ray cassette parts
- Lead blocker
- Front intensifying screen
- Sliding shutter for use with patient identification cameras
- Back intensifying screen
- Lead foil
- Foam pressure pad
- Hinge
In a typical radiographic cassette, the frame is
made of ____, or in some models, heavy ____
aluminum, steel,
plastic
The front & back panels are ___ on one side to allow the cassette to be opened and closed, similar to a book.
hinged
Common front panel materials include ______ of the x-rays
absorption
•Common front panel materials include
plastic, carbon fiber, bakelite, aluminum & magnesium
The back panel of the cassette is commonly made of
aluminum, stainless steel, or plastic
The inside wall of the back panel is lined with a ____ that allows primary x-rays to exit from the tube but inhibits the entry of weaker, scattered x-rays emanating
from objects behind the cassette
lead foil
That the primary beam can pass through this lead shield is apparent when the cassette is inadvertently placed in
its holder _____ when a radiographic image is
produced, generally during portable radiography.
upside down
This incorrect positioning of the cassette produces some rather obvious _____ on the radiographic image,
showing the structural components of the back of the cassette within the anatomical image
artifacts
Causes _____: Poor processing conditions, improper
film handling, patient clothing and jewelry, and dirt or other foreign matter on cassette screens and film
artifacts
There are 2 types of conventional radiographic cassettes:
Dual-screen and single-screen
are designed for use with
radiographic film having 2 emulsions, or dual-emulsion film
Dual-screen cassettes
are designed for use with film having 1 emulsion, or single-emulsion film.
Single-screen cassettes
the front and back panels are lined with a felt, plastic foam, or rubber material that serves as a backing to which the screens are attached
Dual-screen cassette
there is only 1 screen attached
to the inside of the front panel
Single-emulsion cassette
Another function of the _____ material is to exert a gentle, even pressure on the screens as they touch the film
backing
A small door that slides open and shut is commonly located in __ corner of the back panel of the cassette
1
The device opens the door & flashes a light that passes through the patient’s identification card, exposing that
corner of the film to the _____
pertinent information
The area of the sliding door is completely devoid of _____ material, as it must allow visible light from the patient identification camera to enter and expose the
film
screen
To avoid light exposure to this corner of the film from
the front screen during a radiographic exposure, the
corresponding corner of the front screen is devoid of _____ & is covered instead by a small strip of the _____
phosphor material,
lead
Radiographers should orient the cassette in such a way so as to avoid placing the ____ under important anatomy or identification markers.
lead blocker
Instead of a sliding door, some cassettes have a small slot in one corner into which is inserted the illuminating tab, covered by an ______ , of a light flashing device
identification card
Cassettes that are loaded with film in a darkroom have _____ to allow the cassette to be opened or closed
metal hinges
the speed at which the screens or screens convert x-rays to visible light
screen speed
Cassettes are usually labeled to indicate their
screen speed
To provide easy identification of speed, some manufacturers provide a _____ on cassettes used for specific applications such as extremity radiography
colored edge
Other labeling includes the size of the cassette and an
______ to produce a radiographic image, the technologist sees to it that the cassette’s identification number is repeated on the film used to record the image
identification number
_____ the film this way is accomplished either by
placing adhesive numerals corresponding to the
cassette’s identification # on the front screen of the
cassette or handwriting the numerals on the screen using a permanent black marker
Marking
Characteristics of a Good Cassette
- ) Lightweight, durable
- ) Smooth, washable surfaces
- ) Not easily bent
- ) Lightproof
- ) Capable of maintaining good screen-film contact
- ) Can be opened and closed easily
- ) Smooth, rounded edges and corners
are designed to decrease the distance between a body part and the film when the body-part plane & film plane are not parallel
Curved Cassettes
a curved cassette includes a convexly curved ______
and a concavely curved
front panel,
back panel
are used with rotational dental units to provide a
panoramic view of the entire mandible and teeth
Flexible Cassettes
The cassette is actually a black plastic envelope with a flap at one end that is fastened with plastic snaps or Velcro
Flexible Cassettes
Are those that are used with daylight film systems
Daylight Cassettes
Needs special type of cassettes, which can be opened by the mechanical system of the machine
Kodak daylight processor
Has a barcode attached to indicate the size of the film to be used
Kodak daylight processor
The construction of a ______ is similar to that of a cassette that must be handled in a darkroom
daylight cassette
are generally used with a daylight film-loading unit attached to a wall inside or directly outside a radiographic room
Daylight cassettes
This type of cassette is inserted into an automatic
daylight-processing unit, the cassette is mechanically opened, the film retrieved, and a new film inserted
Daylight cassettes
In some daylight cassettes, small release buttons located
on the end corners allow the film to ______
slide out
Differ from all other types of conventional nongrid
cassettes in one respect: have only 1 screen
Mammography Cassettes
Some mammography cassettes have a ______ front panel to minimize absorption of the x-ray beam
polycarbonate-polystyrene
Another unique characteristic of mammography cassettes is the _____ of their frames
width
Another less commonly used type of mammography cassette is called a
vacuum cassette
the air is drawn out of the
cassette after the film has been inserted to provide
optimal screen-film contact
vacuum cassette
There are 2 types of vacuum cassettes:
1.) It has a built-in vacuum valve and an internal
envelope that holds the film
2.) The second type of vacuum cassette is polyethylene
bag that can be loaded with a film, evacuated, and
heat-seated
The ____ of conventional grid cassettes is similar to
the design of conventional nongrid cassettes with 1 main exception
design
A grid of lead strips, arranged either ______ in the front panel is used to absorb wide angle scattered and secondary radiation coming from
the patient
linearly or crosshatched
Grids are classified according to their
ratio, frequency, & focal range
are typically heavier & slightly deeper
than nongrid cassettes
Grid cassettes
Most _____ do not provide a way to flash patient identification data on the film while it is still in the cassette
grid cassettes
can also be used with nongrid cassette
Slip-on grids
These grids have a slotted frame into which a cassette is inserted
Slip-on grids
is a relatively new technology that has been adopted by
many health care facilities throughout the world
Computed Radiography Cassettes
A cassette is used, but there are no screens or
radiographic film
Computed Radiography Cassettes
A cassette is used, but there are no screens or
radiographic film
-Instead, a ______ is
used
photostimulable-phosphor image plate
The main purpose of the cassette is to
protect the image
plate from damage
The frame of the computed radiography cassette is made of
lightweight aluminum, plastic or steel
With ______, radiographic
cassettes can provide many years of service
proper handling & treatment
If handled in a ____, the frame may be dent,
the hinges may be sprung or bent, and the front or back panel may be dented
rough manner
There are several causes of poor screen-film contact, which presents on the finished radiograph as an area of ______
poor detail or a blurred area
The cause is usually misuse or dropping of the cassette, resulting in either a sprung frame or in loosened or broken hinges or latched
poor screen-film contact
Other causes are a warped front panel, warped screens
due to excessive moisture, worn screen backing, and
foreign particulate matter between the screens & film
poor screen-film contact
Some causes of poor screen-film contact are
transient
Included in this category : air trapped between the film and a screen & the temporary bending of the cassette under the weight of heavy patients
transient poor screen-film contact
Air may be trapped between a screen & the film as a radiographer hurriedly loads a film & slams the cassette
shut
transient poor screen-film contact
Bending of the cassette under a heavy patient is
_____ because once the cassette is removed, it will return to its normal shape
transient
Cassettes may be tested for poor screen-film contact using a _____ enclosed in a thin sheet of _____
wire mesh (usually 3/16 in. squares), Plexiglas
The radiographic image of the wire mesh will appear _____ in areas where screen-film contact is poor
ill-defined (unsharp)
If the screens are damaged, they can be _____ and the cassette salvaged
replaced
Another problem encountered with cassettes is radiographer error in selecting the ______
correct speed
