Mobile Radiography (Portables)
8/29/2012 Class ed.
Principles of Mobile Radiography
You bring imaging services to pt using transportable x-ray equipment
Where are they commonly used?
pt room
ER
ICU
surgery and recovery rooms
nursery and neonatal units
When was mobile x-ray equipment first used?
battlefield WW1 -units were carried to field sites
Mobile X-Ray Machines
• True or false? Portables are
as sophisticated as stationary
units?
– False
• Typical unit has what 2
controls?
– kVp and mAs
• What is the mAs range?
– Generally 0.04 to 320 mAs
What is the kVp range?
-generally 40 to 130 kVp
Two basic types of Mobile X-Ray Machines
1. Battery powered
• Uses two different sets of batteries (lead-acid, or nickel-cadmium )
– One powers driving of machine
– One set provides power to x-ray tube
• Fully charged batteries:
- can make 10 to 15 exposures
- be driven reasonable distances
2. Capacitor discharge (obsolete)
• No batteries
• Carries two metal plates that hold electrical charge
• Capacitor units must be charged prior to each use
Battery-operated Unit
Advantages:
– Cordless
– Provide constant kVp and mAs
Disadvantages:
- Heavy
- hard to control
What is “Deadman” type of brake?
– stops machine instantly when push-handle released
Capacitor Discharge Units
Advantages?
lightweight, smaller and easier
to maneuver
require much less time to
charge than battery units
Disadvantages?
can’t handle thick body parts
due to voltage drop during
exposure
must be charged prior to each
use
The Nomad
For places with no electricity or chemical processors
Mainly for dental x-rays
3 important technical factors that must be clearly
understood to perform optimum mobile
examinations:
Grid
Anode-heel effect
Source–to–image receptor (SID)
Grid
Must be level!
X-ray beam must be properly centered to grid
Correct focal distance must be used
(Best grids for mobile radiography have ratios of 6:1 or 8:1 and a focal range of 36 - 44 inches)
Make sure grid is fastened to cassette properly (tape)
Anode Heel Effect
•
Correctly place anode-cathode (marked
on tube housing) with respect to
anatomy
–
•
Anode should be on thinner part (T-spine)
Heel effect increases with short SID,
larger field sizes (more common in mobile
radiography)
Beam travels through
thicker part of target on
anode side, thus
attenuating beam more
SID- Mobile Units
What is standard SID?
40
Possible problems with greater SID?
Need increased mAs, thus longer exposure time
Increases risk of imaging motion
Increased drain on battery
Possible grid cut-off
Performing Mobile Examinations
Plan ahead!
Gather all necessary devices to take with you
IR (bring extras!)
Grid
Tape
Markers
Sponges
Before Beginning Examination
• Find pt’s x-ray order
• Let nurse’s station know of your presence and purpose
• Identify pt and introduce yourself with your title
• Explain exam and ensure it is appropriate and correct
• Politely ask any visitors to leave
• Obtain assistance when necessary!
Interfering Devices
• Watch out for orthopedic beds,
fracture frames, tubes, wiring,
etc., producing artifacts
• Know which objects can be
moved and which ones you
have to work around
• May have to perform with
object in image
• Ask if unsure whether an
object can be moved
Portable Position
• If exam in supine position, move base of
machine to middle of bed
• If seated upright, base at end of bed
• Lateral and decubitus positions, place
base parallel or perpendicular to bed
Performing Mobile Examinations
Make sure collimation is not open larger than IR size
Check CR and IR alignment to prevent distortion
Use consistent system for keeping exposed and unexposed
IRs separate
Keep log of procedures, time of examination, technical factors
for image ID
Technique Charts and Logs
Exposure for optimum exam!
Should be available for every machine
Should display standard technical factors for all projections
performed with machine
Logbook of all recent pt exams and technique
Caliper should also be available for accurate patient
measurement
Scatter Radiation and Mobile Radiography
Mobile radiography produces some of highest
occupational radiation exposure for radiographers!
Wear a lead apron!
Wear film badge at collar or waist outside lead
protection
What is single most effective radiation protection
measure?
Distance!
What is minimal safe distance ?
6 feet
Safest Place to Stand
Least exposure is
at what angle to pt
and primary
beam?
Right angle
When should you shield pt’s gonads?
– X-raying children
- Person is of reproductive age
– Pt requests
– Gonads lie in or near useful beam
– When shield will not interfere with anatomy of interest
Radiation Safety cont’d
What is minimum source-to-skin distance?
– 12
Have visitors leave area
Warn other personnel when you are about to
make an exposure
Patient Mobility
Never move pt or part without:
Assessing ability to move or ability to tolerate movement
Checking with staff obtain assistance and permission to move a
part that has had surgery or fractured
Inappropriate movement can further injure pt!
Warn pt of potential discomfort from IR
Cold
Hard
IR can damage skin of older patient
Use cloth or paper cover to reduce risk of injury
Protect IR from contamination by use of
appropriate impermeable cover
Assess Patient Condition
Be aware of any limitations to procedure!
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Alertness
Respiration
Ability to cooperate
Language comprehension
Mobility
Fractures
Interfering devices
If in OR, don’t break sterile field!
Isolation Considerations
What are two types of pts in isolation?
Those who have contagious infectious microorganisms
you want to avoid them!
Those who must be protected from exposure to infectious
microorganismsthey want to avoid you!
This known as?
Reverse isolation!
Isolation Considerations cont’d
• Wear all required protective apparel for specific
situation
• Wash hands before gloving
• Protect IR with protective cover
Isolation Considerations cont’d
After procedure:
Discard of protective apparel according to protocol
Wash hands!
Wear clean gloves to clean equipment and use
appropriate aseptic technique
Wash hands again after removing gloves
Most Common Portable Radiographic Exams
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Chest
Abdomen
Pelvis
Femur
Cervical spine
Neonate
AP Chest
• Elevate head of the bed as pt
condition permits
• Pull pt to head of bed before
elevating if condition permits
• Make sure pt is not rotated
What if pt has respiration
assistance?
• watch pt chest to determine
inspiratory phase (or
respirator)
AP or PA Chest
Lateral Decubitus Position
• Place firm support under
pt to elevate body and
keep pt from sinking
down in bed
• Protect pt from rolling
off of bed!
Lateral Decubitus Position Considerations
• Fluid levels best imaged with?
– affected side down
• Air levels seen best with?
– affected side up
• How long should pts be in this position before exposure?
– 5 minutes
• Why?
– to allow fluid or air to settle
Orthopedic Examinations
How many images required?
at least 2 films at right angles to each other
Who do you obtain permission from prior to
moving an injured pt?
pt’s nurse or physician
How do you position pts?
very carefully!
Lateral Cervical Spine
– Dorsal decubitus position
– CR horizontal
– If there is a immobilization
device when should you
remove it?
• NEVER or until Dr.
gives permission
Neonate
• Move arms out of anatomy of interest
• Bring legs down
• Who should hold infant in position?
• Nurse- (provide lead apron)
• Why do you leave head rotated?
– to avoid advancing endotracheal tube too far
• Collimate closely
• Shield gonads
Neonate
• AP projection of chest and
abdomen often ordered and
shot in one exposure
• Infant is supine
• Some bassinets equipped with
tray to hold IR
• If IR placed directly under
infant- wrap with soft cover