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)

GridMust 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 timeIncreases 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!)GridTapeMarkersSponges

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 IRCold

Hard

IR can damage skin of older patientUse 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!

• 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 microorganisms-

they 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

• 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