Radiographic Procedures 2 (155) Mobile Radiography

Chapters 20 Mobile Radiography

Mobile radiography

• use of transportable x-ray equipment to bring imaging services to the patient

• commonly performed in:

  • patient rooms

  • ER

  • ICU

  • OR

  • PACU

  • nursery and NICU

Mobile units

• not as sophisticated as stationary units

• typical unit has controls for setting kVp and mAs

  • mAs controls automatically adjusts mA and time

  • typical mAs range: 0.04-320

  • kVp: 40-130

• power varies between 15-25 kW

• anatomic programs (APRs)

Digital Mobile units

• mobile units with direct digital capability

  • acquire image within seconds after exposure

  • uses a flat-panel detector

  • wirelessly transfer images to PACS

  • lower radiation doses possible

Technical considerations

• grid, anode heel effect, source-to-image receptor distance (SID)

• exposure technique charts are essential to optimize exams

Grid considerations

• sensitivity of CR imaging plates to scatter radiation leads to image degradation

• optimum performance:

  • level: use of grid on unstable surface may cause “off level” grid cutoff

  • centered to CR: midline of a grid more than 1-1½ inches off transversely from the CR causes “off level” grid cutoff

  • used at recommended focal distnace or radius: exposures outside the recommended focal range may produce cuttoff on the lateral margins

Anode heel effect

• causes decreased image density under the anode side of the x-ray tube

• more pronounced with:

  • short SID

  • larger field sizes

  • small anode angles

• short SID and large field sizes are common in mobile

• proper placement of anode-cathode axis with anatomy is essential

Source to image distance (SID)

• should be maintained at 40 inches (102 cm)

• standardized distance ensures consistent images

• longer SIDs:

  • requires increased mAs resulting in longer exposure times

  • increased risk of motion artifacts

Radiation safety in mobile x-ray

• produces some of the highest occupational radiation exposure to radiographers

• protection for self, patient, and other personnel:

  • wearing a lead apron

  • standing as far away from patient, tube, and beam as possible

    • recommended minimal distance is 6ft

    • standing at a right angle (90 degrees) to the primary beam

Mobile x-ray in isolation

• two types of patients in isolation:

  • those who have contagious infectious microorganisms

  • those who must be protected from exposire to infectious microorganisms (reverse isolation)

• wear all required protective apparel for specific situation

Equipment used in mobile

• IR

• grid

• protective covers

• tape

• caliper

• markers

• positioning blocks

• lead

• requisition

Initial mobile x-ray procedure

• preliminary steps for the radiographer prior to performing mobile radiography:

  • announce presence to nursing staff

  • ask for assistance if needed

  • confirm patient identity

  • introduce yourself to patient and family

  • explain the examination

  • observe medical equipment in room and move if necessary

  • ask family members and visitors to step out of the room

Mobile unit placement

• supine position: middle of bed

• seated upright position: foot of the bed

• lateral and decubitus positions: parallel or perpendicular to bed

Patient considerations

• assessment of patient condition

  • altertness

  • respiration

  • ability to cooperate

  • limitations to procedure

• patient mobility

  • never move a patient or part without assessment of ability to move or ability to tolerate movement

  • check with nursing staff or physician to obtain assistance and permission to move a part that has had surgery or is fractured

  • inappropriate movement can further injure the patient

• fractures

  • various fractures and fracture types

  • patient ability to assist

  • key is to be cautious and gentle for both patient safety and comfort

  • work in accordance with the patient’s condition and pain tolerance

• interfering devices

  • orthopedic beds, fracture frames, tube, and wiring produce artifacts

  • some objects can be moved and some require procedure modification to obtain the image

  • some procedures have to be performed with the object in the image

  • get assistance if unsure an object can be moved

• positioning and aspesis

  • warn patietn of potential discomfort of IR

  • IR can damage skin of older patient

  • protect Ir from contamination by use of cover

  • disinfect IR for asepsis and infection control

AP chest

• patient position:

  • dependent on condition

  • seated upright, semi upright, or supine

    • greatest upright angle the patient can tolerate, whenever possible

    • use the supine position for critically ill or injured patients

• part position:

  • center MSP to IR

  • top of IR 2 inches above relaxed shoulders

  • internally rotate patient’s arms (if not contraindicated)

  • no leaning or rotation of upper torso

• CR:

  • perpendicular to long aixs of sternum and center of IR

  • enters approximately 3 inches below jugular notch at level of T7

• respiration:

  • inspiration, unless otherwise requested

  • if respiration assistance is provided, watch patient’s chest to determine inspiratory phase

• collimation:

  • 14 × 17 in

AP chest image criteria

• structures shown:

  • anatomy of thorax:

    • heart

    • trachea

    • ribs

    • diaphragmatic domes

    • entire lung fields

    • vascular markings

  • evaluation criteria:

    • no motion; well-defined diaphragmatic domes and lung fields

    • lung fields in their entirety including costophrenic angles

    • pleural markings

    • ribs and thoracic intervertebral disk spaces faintly visible through heart shadow

    • no rotation; medial portion of clavicles and alteral border of ribs equidistant from vertebral column

AP/PA chest lateral decubitus

• patient position:

  • right or left lateral recumbent

    • affected side down for fluid levels

    • unaffected side down for air levels

  • remain for 5 minutes for air/fluid levels

  • knees flexed

  • place firm support under body to elevate 2-3 inches

  • raise arms over head or out of anatomy of interest

  • protect patient from rolling off bed

• part position:

  • ensure lateral position without rotation

  • IR behind patient and below support

  • top of IR 2 inches above relaxed shoulders

• CR:

  • horizontal and perpendicular to IR

  • enters approx. 3 inches below jugular notch at level of T7

• respiration:

  • inspiration unless otherwise requested

• collimation:

  • 14 × 17 in

AP/PA chest lateral decubitus image criteria

• structures shown:

  • anatomy of thorax

  • air or fluid levels

• evaluation criteria:

  • no motion or rotation

  • affected side in its entirety

    • upper lung for free air

    • lower lung for fluid

  • arms out of region of interest

AP abdomen

• patient position:

  • supine

  • adjust bed in horizontal position

• part position:

  • place grid under body centered to MSP and level of iliac crests

    • for upper abdomen, center grid 2 inches above iliac crests

  • use draw sheet to roll patient and as barrier between skin and IR

  • ensure grid does not tip to prevent cutoff

  • align shoulders and hips in same plane

  • place arms out of anatomy of interest

• CR:

  • perpendicular to center of grid

  • enters at MSP at level of iliac crests or 10th rib laterally

• respiration:

  • expiration

• Collimation:

  • 14 × 17 inches

AP abdomen image criteria

• structures shown:

  • inferior margin of liver

  • spleen

  • kidneys

  • psoas muscles

  • calcifications

  • evidence of tumor masses

  • size and shape of liver if upper abdomen and diaphragm included

• evaluation criteria:

  • no motion

  • outlines of abdominal viscera

  • abdominal region including ppubic symphysis or diaphragm

  • vertebral cloumn centered

  • psoas muscles, lower margin of liver, and kidney margins

  • no rotation

    • symmetric appearance of vertebral column and iliac wings

AP/PA abdomen left lateral decubitus

• patient position:

  • left lateral recumbent position

  • flex knees for stability

  • place firm support under patient to elevate body

  • raise both arms out of anatomy of interest

  • ensure patient cannot roll out of bed

  • leave in position for 5 minutes to allow air to rise and fluid to settle

• part position:

  • true lateral without rotation

  • place vertical grid centered at 2 inches above iliac crests to demonstrate diaphragm

  • ensure patient has been in position for at least 5 minutes to allow air to rise and fluid to settle

• CR:

  • horizontal and perpendicular to center of grid

  • enters at MSP at level 2 inches above iliac crests

• respiration:

  • expiration

• collimation:

  • 14 × 17 inches

AP/PA abdomen left lateral decubitus image criteria

• structures shown:

  • air or fluid levels

  • right border of the abdominal region must be visualized

• evaluation criteria:

  • no motion

  • well-defined diaphragm and abdominal viscera

  • air or fluid levels

  • right and elft abdominal wall and flank structures

  • no rotation

    • symmetric appearance of vertebral column and iliac wings

AP pelvis

• patient position:

  • supine

  • adjust bed to horizontal

  • move arms out of anatomy of interest

• part position:

  • place grid under pelvis

    • centered to MSP at level midway between ASIS and pubic symphysis

  • no rotation of pelvis

  • rotate legs medially approx. 15 degrees, when not contraindicated

• CR:

  • perpendicular to IR center

  • enters patient at MSP at 2 inches above pubic symphysis and 2 inches below ASIS

• respiration:

  • suspended

• collimation:

  • 14 × 17 inches

AP pelvis image criteria

• structures shown:

  • pelvis with both hip bones

  • sacrum and coccyx

  • proximal femora including head, neck, and trochanters

• evaluation criteria:

  • entire pelvis, including proximal femora and hip bones

  • no rotation

    • symmetric appearance of iliac wings and obturator foramina

    • femoral necks no foreshortened

    • greater trochanters in profile

AP femur

• patient position:

  • supine

  • patient generally has limited mobility

• part position:

  • carefully place grid lengthwise under femur

  • centered to midline of femur

  • distal end of grid low enough to include fracture site, pathology, and knee joint

  • ensure grid aligned parallel with CR and femoral condyles

• CR:

  • perpendicular to long axis of femur and center of grid

  • CR and grid must be aligned to prevent cutoff

• respiration:

  • suspended

• collimation:

  • top of ASIS for hip, bottom at tibial tuberosity for knee, 1 inch on side of the shadow of the femur, and 17 inches in length

AP femur image criteria

• structures shown:

  • distal 2/3 of femur

  • knee joint

• evaluation criteria:

  • most of femur including knee joint for distal

  • no rotation of knee

  • adequate penetration

  • orthopedic appliance in its entirety

Lateral femur

• patient position:

  • dorsal decubitus

• part position:

  • use either mediolateral or lateromedial projection

  • mediolateral projection preferred because it provides more visualization of proximal femur

  • mediolateral projection:

    • place vertical grid along lateral aspect of femur

    • distal edge of grid low enough to include knee joint

    • support unaffected leg with patient’s support or support block

    • elevate unaffected leg until femur is near vertical

  • lateromedial projection:

    • place vertical grid along medial aspect of femur (between patient’s legs)

    • make sure knee joint is included

    • ensure grid is perpendicular to the epicondylar plane

• CR:

  • perpendicular to long axis of femur

  • centered to femur

  • CR and grid must be aligned to prevent cutoff

• respiration:

  • suspended

• collimation:

  • radiation field at top of ASIS for hip, bottom at tibial tuberosity for knee, 1 inch on side of the shadow of the femur, and 17 inches in length

Lateral femur image criteria

• structures shown:

  • distal 2/3 of femur

  • knee joint

  • no superimposition of opposite thigh

• evaluation criteria:

  • most of femur with knee joint

  • patella in profile

  • superimposition of femoral condyles

  • oppposite femur and soft tissue out of area of interest

  • adequate penetration of proximal femur

  • orthopedic appliance if present

Lateral C-spine

• patient position:

  • right or left dorsal decubitus

  • arms extended alongside of body

  • do not remove any immobilization device without physician consent

• part position:

  • no rotation of upper torso, cervical spine, and head

  • grid lengthwise on right or left side, parallel to neck

  • top of grip approx. 1 inch above external acoustic meatus (EAM) and centered to C4

  • raise chin slightly, if not contraindicated

  • relax shoulders and reach for feet, if possible

• CR:

  • horizontal and perpendicular to center of grid

  • enters level of C4

  • increased OID; SID of 60-72 inches recommended to show C7

• respiration:

  • full expiration for depression of shoulders

• collimation:

  • radiation feild at top of ear attachment (TEA), bottom to jugular notch, and 1 inch on the sides of the neck

Lateral C-spine image criteria

• structures shown:

  • seven cervical vertebrae

  • base of skull

  • soft tissue of neck

• evaluation criteria:

  • all seven cervical vertebrae

  • neck extended when possible, so mandibular rami are no superimposing C1 or C2

• C4 centered

• superimposed posterior margins of each vertebral body

Best practices

• speed

• knowledge

• positioning accuracy

• practice standard precautions

• immobilizations

• equipment

• attention to detail

• attention to department protocol and scope of practice

• professionalism

AP chest/abdomen neonate

• infant is supine

• move arms out of anatomy of interest

• bring legs down

• leave head rotated to avoid advancing endotracheal tube too far

• collimate closely

• shield gonads

• CR is perpendicular to IR

• infant respirations are rapid

AP chest/abdomen neonate image

Lateral chest/abdomen neonate

• obtained using dorsal decubitus position

• elevate infant on blcok wrapped in soft cover

• place IR lengthwise and vertical beside infant and immobilize

• center infant’s chest and abdomen to IR

• have nurse hold arms and legs out of collimated field

• CR is horizontal and perpendicular to IR

  • enters on MCP

• exposure made on inspiration

Lateral chest/abdomen neonate image