Unit 1 (Preliminary Steps)
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Image Receptor (IR)
The device that receives the energy of the x-ray beam and forms the image of the body part
Common IR devices:
- Cassette with film
- Image Plate (cassette with phosphor plate)
- Fluoroscopic screen
- Direct Radiography (DR)
- (Solid-state detectors)
Cassette with film
we will use them some in the lab, but not in the clinical hospitals. The cassette holds film you process in the dark room.
Image Plate (IP)
Also called a cassette with phosphor plate. This is used in CR (computerized radiography). The whole cassette goes into a reader which feeds the info to the computer monitor.
The image is formed and transmitted to a television monitor via a camera and is shot and viewed in "real time."
This created still images that are viewed on a computer screen, and they are digital, with no cassette.
Common film sizes (4):
- 8" x 10"
- 10" x 12"
- 11" x 14"
- 14" x 17"
How do you convert inches to centimeters?
(for use in common film sizes)
Multiply inches x 2.54 to convert to cm
What is the most common large cassette size?
- 14" x 17"
- PA Chest, abdomen, etc.
What is the most common small cassette size?
- 10" x 12"
- hands, feet, etc.
The relationship of the anatomic superimposition to size, shape, position, and angulation must be reviewed.
Adjacent structures (critique)
Each anatomic structure must be compared with adjacent structures and reviewed to ensure that the structure is present and properly shown; varies from patient to patient.
Optical Density (OD)
The degree of Black/White
the difference in density between any two areas on a radiograph, must be sufficient to allow radiographic distinction of adjacent structures with different tissue densities; the shades of gray
short contrast vs. long contrast
- short contrast: more black/white, more penetration
- long contrast: more gray, less penetration
Recorded detail (critiquing radiograph)
the ability to visualize small structures, must be sufficient to show clearly the desired anatomic part
Magnification (Critiquing Radiograph)
this must be evaluated, sometimes it's desirable, sometimes not...many factors contribute to the level of magnification.
Shape distortion (critiquing radiograph)
This can be caused by angling the tube in ways that distort the image. Distortion is defined as the misrepresentation of the size or shape of any anatomic structure.
The patient is standing, facing you with palms of the hands facing forward, feet slightly apart, toes facing forward.
In what way are radiographs positioned for display on the viewbox/screen?
as though the person looking at the image sees the body part in anatomic position
Exceptions to the rule that the radiograph is displayed in anatomical position:
- Digits up for the following:
laterals - in the direction patient was actually facing
How are laterals displayed/hung?
in the position the patient was during the x-ray
What is an oblique radiograph?
a radiograph that is angled somewhere between a front shot and a back shot
How is an oblique radiograph hung/displayed?
Ways to assess a clinical history:
- "eyeball" patient for obvious symptoms
- note anything that might affect radiograph (tattoo, scar, external mass, etc.)
- conversationally question the patient about their condition
When to give the diagnosis to the patient:
NEVER, UNDER NO CIRCUMSTANCES
In general, how should the equipment be cleaned?
daily (at least), with a damp cloth (from top to bottom)
What is the most contaminated area of the hospital?
How do you clean the electrical parts of the machinery?
with alcohol or a dry cloth
When do you clean the tabletop and other patient contact areas?
after EACH patient, discarding ALL linens
What is the central dogma of OSHA's Standard Precautions?
treat EVERY patient as if they have a serious contagious illness (in terms of safety precautions)
What is prophylactic treatment?
treatment after an exposure has occured
What is the standard disinfectant solution approved by the CDC?
1 part bleach to 10 parts water
What do disinfectants (and germicides) do?
kill only those microorganisms which are pathogenic (not their spores)
What do antiseptics do?
- inhibit the growth of pathogenic microorganisms (does not kill)
- ex. alcohol
the complete removal of microorganisms and their spores; necessary for any invasive procedures
as clean as reasonably possible short of complete sterilization
Where will you find a procedure book?
usually in every exam room
What type of information might you find in a procedure book?
- what images should be taken for a procedure
- what equipment to use
- specific doctor preferences
What are the two main types of motion?
What is voluntary motion, and what type of muscle controls it?
- motion that can be prevented or controlled by the patient (ex. breathing, moving extremities, etc)
- striated muscle (skeletal muscle)
How can the radiographer strive to control voluntary motion?
- give clear breathing and position instructions
- provide for patient comfort
- use support and immobilization devices
What is involuntary motion and what type of muscle controls it?
- motion that the patient cannot control
- smooth muscle and cardiac muscle
What are some conditions that may cause involuntary motion?
- muscle spasm
- tremors (trauma, shock)
- peristalsis (intestines)
- heart palpitations
How can a radiographer best control involuntary motion?
by using the shortest exposure time possible (the quicker the exposure, the better chance of avoiding the movement)
Specific types of x-ray tables:
For the table, the cassette tray:
pulls our from underneath the table and includes a bucky-type moving grid
What is the name of the instrument used to measure the thickness of the body part?
caliper (measure thickness in cm)
What is the first step in the proper positioning sequence?
General position (ex. help the patient onto the table)
In proper positioning sequence, what do you do after attaining the general position?
measure the part to be radiographed and set the control panel
In proper positioning sequence, after measuring the part and setting the control panel, the next two steps are interchangeable. What are they?
- center the part to the CR (central ray)
- center the film to the CR
In proper positioning sequence, what do you do after aligning the patient and the film to the central ray (CR)?
In proper positioning sequence, what do you do after you adjust the collimation?
correctly place the anatomical marker
In proper positioning sequence, what do you do after you place the anatomical marker?
gonadal shield placement
In proper positioning sequence, what do you do after you place the gonadal shielding?
breathing instructions (as needed) to the patient
In proper positioning sequence, what do you do after giving breathing instructions to the patient?
make the exposure
What is the name of the list of radiographic projections and their factors, etc?
technique chart (also, exposure chart)
What are some factors that might need to be adapted from the technique charts?
- muscle tone
- congenital and developmental factors
- pathologic conditions
What does "inspiration" refer to?
- breath in and hold breath
- moves diaphragm to its lowest point
What does "expiration" refer to?
- breath out and hold air out
- holds the diaphragm up
how many and what types of markers must be imprinted on every image?
- patient id and date
- anatomic marker
What type of marker is admissible in court?
only the type that is imprinted on the image from being placed on the cassette before the image is taken (the type that can't be moved/changed)
Specifics required for anatomical marker placement:
- never obscure anatomy
- never placed over patient identification marker
- always on the edge of the collimation field
- placed on outside of any lead shielding
patient ID should include:
- patient's name
- identification number (important for follow-ups; legal)
- institution identity
additional markers/IDs that may be used:
- radiographer initials
- time indicators
- decub markers
- upright/erect markers
How large should the film be?
just large enough to cover the part imaged
What is OID? and what is desirable?
- object-to-image distance
- a minimal OID; get as close to actual size as possible
How should a long axis be positioned in relationship to film direction?
- it should run with the long axis of the film
- ex. the forearm should run along the length, not the width of the cassette
Beware CR, as it has two radiologic meanings...always note the context it is used in. What are its two meanings?
- Central Ray: the central or principal beam of radiation
- Computerized Radiography: non-analog
What is the general goal when it comes to CR centering to the IR?
to place the CR at right angles (90°) to the part being imaged
What SID is the most traditional for examinations?
40" - 48"
What SID is used for chest radiographs and why?
- true size of the part is essential to the diagnosis, so distance must be increased
If you increase the SID, what happens to the Recorded Detail?
it also increases
What is the SID, specifically?
from the anode to the image receptor
If you increase the SID, what happens to magnification?
What is the rule to follow to maintain the desired SID when you have to angle the xray tube?
the SID must be LOWERED 1" for every 5 degrees the tube is angled
Does collimation increase or decrease patient dose?
Does collimation increase or decrease scatter?
Does collimation improve or worsen recorded detail?
Does collimation make a longer or shorter scale of contrast?
shorter scale of contrast
When should you use gonadal shielding (3):
- use if gonads lie within 5 cm of primary beam
- if pertinent anatomy will not be covered
- if the patient has a reasonable reproductive potential (9-90)
Types of gonad shielding (3)
- shadow shielding
- contact shield
- large part area shields (lead aprons, etc.)
What is a routine projection?
- projections commonly taken on all average patients who can cooperate fully
- usually a minimum of 2 projections, 90° apart
those who can walk in themselves and cooperate voluntarily
Special (Alternate) projections:
- usually necessary for patients who cannot cooperate fully
- usually only one projection due to patient difficulties
Exceptions to the rule of taking at least two projections:
3 reasons for the 2 projection minimum rule:
- to combat problems of anatomic structures being superimposed
- localizations of lesions or foreign bodies
- determination of alignment of fractures
How many projections when joints are of primary interest?
- a minimum of three:
What is the exception to the joint projection number rule?
hip joints are usually only two projections, instead of the normal three for a joint
In CR, how do you know if your image is of diagnostic quality?
check the exposure control index
Use a grid to control scatter if the kVp goes over ____.
Are phosphor plates used in CR more or less sensitive to scatter as compared to analog film?
more sensitive to scatter
Are phosphor plates (CR) more or less sensitive to white light as compared to analog film?
- less sensitive
- takes 15-20 seconds to become exposed
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