Mobile Radiography and X-Ray Machines

Mobile Radiography

• Mobile radiography uses transportable X-ray equipment to bring imaging services to the patient.
• Common locations for mobile radiography include patient rooms, emergency departments, intensive care units, surgery and recovery rooms, and nurseries and neonatal units.
• Mobile X-ray was initially used in the military, with units carried to field sites.

Mobile X-Ray Machines

• Mobile X-ray machines are less sophisticated than stationary units.
• Power sources (generators) and exposure controls vary.
• Typical units have controls for setting kVp and mAs, with mAs ranging from 0.04 to 320 and kVp from 40 to 130.
• Power ranges between 15 and 26 kilowatts.
• Some mobile units have preset anatomic programs (APRs), similar to stationary units.
• Automatic exposure control (AEC) is also available on some mobile units.
• Mobile units with direct digital capability use flat panel detectors connected by a cord or wireless technology.

Technical Considerations

• Key technical factors for optimal mobile examinations include the grid, anode heel effect, and source-to-image-receptor distance (SID).
• Exposure technique charts are also crucial for optimum examinations.

Grid

• For optimal grid performance, it must be level, centered to the central ray (CR), and used at the recommended focal distance.
• Using a grid on an unstable surface may cause absorption of the primary beam, known as grid cutoff.

Anode Heel Effect

• The anode heel effect is more pronounced with shorter source-to-image distances (SID) and larger field sizes.
• Smaller anode angles also increase the effect.
• Proper placement of the anode-cathode axis in relation to the anatomy being imaged is essential.

SID

• Source-to-image-receptor distance (SID) should be maintained at 40 inches (102cm).
• A standardized distance ensures consistent images.
• Longer SID requires increased mAs, resulting in longer exposure time, and an increased risk of imaging motion.

Technique Charts

• Technique charts should be available for every mobile X-ray machine.
• The charts display standard technical factors for all projections performed with the machine.

Radiation Safety

• Mobile radiography procedures often expose radiographers to higher levels of occupational radiation.
• Wearing a lead apron is critical for protection of the radiographer, patient and other personnel.
• Standing as far away from the patient, X-ray tube, and beam as possible reduces exposure.
• A safe minimum distance is 6 feet (2 meters).
• The least exposure occurs when the beam is at a right angle to the patient.
• Distance is the most effective radiation protection measure.
• Inform all persons in the area that exposure is going to be made and advise everyone to move back at least 6 feet (2 m) from the patient and/or tube.
• Provide lead aprons for those who cannot leave the room.
• To avoid exposure to reproductive organs, shield patients' gonads.
• Consider using patient shields for children or persons of reproductive age. Shield only when the shield does not interfere with the area of interest.
• Minimum source-to-skin distance is 12 inches (30cm).

Isolation Considerations

• Two types of patients requiring isolation: those with contagious infectious microorganisms, and those who must be protected from infectious microorganisms (reverse isolation).
• Wear all required protective apparel(gloves/gown/safety glasses) for specific situations.
• Wash hands before gloving and use appropriate disposal procedures for gowns and gloves.
• Protect the image receptor (IR) with a protective cover if necessary.
• After every procedure, discard protective apparel according to protocol.
• Wash hands.
• Clean equipment.
• Use appropriate aseptic technique.
• Wash hands after removing gloves.

Performing Mobile Examinations

• Plan the trip out of the department.
• Gather necessary equipment (image receptor, grid, tape, caliper, markers, sponges).
• Check battery charge on battery-operated units.
• Verify patient identity and the procedure to be performed before entering the room.
• Communicate with nursing staff for proper patient care and obtain assistance, if needed.
• Introduce yourself and explain the procedure to the patient.
• Observe medical equipment (IVs, chest tubes, catheterbags)
• Ask family and visitors to leave the room until the examination is complete.
• Move chairs, IV poles, and other items out of the way to avoid blocking the machine's access/path.
• Position the mobile machine according to the patient's position.
• Ensure collimation is not open larger than the image receptor (IR) size.
• Check the alignment of the CR and IR to avoid distortion.
• Use a consistent system to keep exposed and unexposed image receptors (IRs) separate.
• Log procedures, time of examination and technical factors of image identification (ID).

Patient Considerations

• Assess patient's condition before and during the examination.
• Assess patient mobility and ability to tolerate movement.
• Check with the nursing staff or physician for assistance and permission if moving patients or body parts.
• Assess the presence of fractures and take necessary precautions.
• Assess and account for the presence of interfering devices like orthopedic beds, fracture frames, etc.
• Adhere to positioning and asepsis procedures.
• Inform the patient about potential discomfort from the IR, using cold compression or paper covers if necessary to reduce risk of damage to sensitive skin.
• Cover the image receptor to protect it from contamination, using an appropriate impermeable cover, if necessary.

Assessment of Patient Condition

• Allows necessary adaptation of procedure for quality patient care and image.
• Alertness, Respiration, Ability to Cooperate, and Limitations to procedure.

Patient Mobility

• Never move a patient or part without assessment.
• Check with the nursing staff for assistance and permission if needed.

Fractures

• Be cautious and gentle, and obtain plenty of assistance to ensure patient safety and comfort.

Interfering Devices

• Be aware that orthopedic beds, fracture frames, tubes, and wiring produce artifacts.
• Experienced radiographers know which objects can be moved and which require procedure modification to obtain the image.
• Some procedures may need to be performed with the object in the image.

Positioning and Asepsis

• Warn the patient about potential discomfort
• Use precautions against damage to older patient's skin.
• Use cloth or paper covers to reduce risk of injury and contamination.
• Use an impermeable cover to protect the image receptor from contamination.
• The image receptor cover makes positioning easier.

Mobile Chest X-Ray

• No specific details regarding the machine are provided.

Learning Outcomes

• List the requirements of an AP Mobile Chest X-ray.
• Discuss positioning requirements of AP Mobile Chest X-rays.
• Understand the different radiographic techniques used in mobile chest radiography.
• Discuss radiation protection needs for mobile chest radiography.
• Understand and describe infection control requirements for mobile chest radiography.

Lecture Outline

• Indications
• Radiation Protection
• Adjusting Your Technique
• Taking a mobile X-ray
• Positioning
• Exposure Technique
• Infection Control
• Image processing
• Follow-up

Indications

• Mobile CXR is used for critically ill patients who cannot be moved to a standard imaging area.
• Patients undergoing trauma/surgery.
• Patients in the emergency department (ED), intensive care unit (ICU), recovery rooms, and cardiac care units (CCUs) are common.
• Patients on wall suction.

Radiation Protection

• Average annual radiation dose per person in the USA is 6.2mSv.
• Chest X-Ray is 0.04mSv.

Radiation Protection - ALARA

• Minimize risks by asking unnecessary individuals to leave.
• Ensure all staff are at least 2 meters away.
• Alert staff before taking the exposure.

Positioning away from the beam

• Radiographers should stay as far away as possible from the X-ray beam.
• Stand behind a lead shield or protective barrier if possible.
• Maintain a distance of at least 2 meters from the X-ray source and an angle of 90 degrees or more to the direction of the primary beam.

Scattered Radiation

• Stand at least 2 meters away.
• Best place to stand for mobile scatter will be looked at in the practical.

Adjusting Your Technique

• Ideal CXR is PA Erect at 180cm with a grid.
• Portable CXRs may not deal with the ideal patient.
• Consideration for deviations from the ideal patient.

PA versus AP

• Heart closer to film, Pt fully erect, even beam, grid, scapulae removed for PA.
• heart further from film, Pt not fully erect, limited SID, no grid, scapulae cover lungs for AP.

AP vs PA Projection

• Comparison of pneumonia on patients taken one day apart.
• Consider heart size, rib and clavicle positioning, scapulae, use of grid.

Aiming for ERECT Position

• Allows air to rise and fluid to fall.
• Provides a good indication of heart size, mediastinal width, and a true inspiratory effort.

AP Erect Chest Requirements

• The medial portion of the clavicles should be equidistant from the vertebral column.
• Ribs should be symmetrical.
• Trachea should be seen midline.
• Lung fields should be clearly demonstrated.
• The faint shadow of ribs and thoracic vertebrae should pass through the heart shadow.
• 3 posterior ribs should be visible above the clavicles.

Taking a Mobile Radiograph

• Ensure a valid request.
• Confirm that this is the correct patient.
• Introduce yourself to the nursing staff/support personnel.
• Inquire if their assistance is needed.

Taking a Mobile Radiograph

• Confirm the patient's condition with the nursing staff.
• Determine if the patient is allowed to sit up
• Review the previous image.

Positioning

• Prepare the patient for the mobile examination.
• Remove any artifacts (necklaces, buttons).
• Ensure the patient's chin is positioned correctly.
• Position the patient's arms out of the way.
• Ensure that Oxygen tubing is not obscuring the area of interest.

Erect - Patient Positioning

• True AP projection.
• Minimize rotation of the patient.
• Ask the patient to relax their shoulders.
• Use pillows to reduce rotation.
• Patient position, typically upright on the bed.

AP Erect - Positioning the IR

• Align the center of cassette with vertebral prominence (C7).
• Ensure ~3-5cm of cassette is visible above the patient's shoulders.

AP Erect - Positioning the Tube

• Angle the tube to the patient's sternum, especially for more recumbent patients.
• Start with the tube level and then adjust angle until it's parallel with the patient's sternum, the angle is easiest to judge from a parallel to the floor plane.

AP Erect - Positioning the Tube

• For an AP erect projection, position the tube straight.
• Angle the tube to the patient's sternum, especially if the patient is more recumbent.
• Start with the tube in a horizontal position to judge the angle more effectively.

AP Erect - Positioning the Tube

• Position the tube at approximately 5–10 degrees caudal for a patient in an upright position.

Central Ray Placement

• When performing an AP chest x-ray, the tube angle increases, the C.R. placement must be adjusted higher.
• Ensure alignment between the central ray (CR) and the center of the lungs.

Central Ray Placement

• Align the Central Ray (CR) with the vertebra prominens (C7), jugular notch, and xiphoid tip.
• Semi-erect patients require adjustments to the CR to avoid unnecessary exposure of the abdomen.

AP Erect - Collimation

• Improve image quality and reduce patient and radiographer dose by using collimation.
• Cone in side-to-side to the gleno-humeral joint.
• Avoid irradiating areas outside the image receptor.

AP Supine - Patient Positioning

• Use a slide board (wipe it down after use) for support.
• Centre the slide board over the sternum.
• Watch out for arms rolling up.

AP Supine - Positioning the Tube & Exposure

• May require a small caudal angle (5°).
• Lower the bed as far as possible.
• If SID is less than 180cm, decrease exposure.

AP Supine – Common Positioning Error

• Possible false understanding about the apex placement.

Supine CXR examples

• Illustrations of different supine chest X-ray examples are available.

Exposure Technique - AP Erect

• Computed Radiography (CR): Use 90 kV (no grid), and the 180cm SID.
• Use a measuring tape to measure your own arm span for determining mAs.
• Adjust mAs if there are changes in SID, for an average patient 2.5–3.2 mAs is typically appropriate.

Exposure Technique – AP Erect

• Digital Radiography: Use higher kV. Determine kVp and mAs as necessary.
• Account for use or lack of grid.
• Maintain 180 cm SID.
• Adjust mAs for an average patient (or less).
• Adjust for changes in SID.
• Be prepared to adjust techniques from CR to DR.

Exposure Technique - Examples

• High exposure needed with NGT placement. Exposure reduced for situations like emphysema or muscle versus fat, etc..

Taking the Exposure

• Explain breathing techniques to the patient before the X-ray.
• If the patient is intubated, observe the ventilator.
• Call out to surrounding staff before, during and after the procedure.

Infection Control

• Standard precautions must be followed for all body fluids.
• Use gloves, gowns, and safety glasses.
• Change gloves/gown between each patient.
• Cover the cassette/clean after each use.
• Be careful not to touch the patient, then the X-ray beam, and then another patient without cleaning the tube first.

Infection Control

• Clean surfaces with alcohol wipes.
• Dispose of gowns and gloves in the appropriate bins.
• Practice hand hygiene.

Image Processing

• Process CR images as soon as you return to the department.
• Provide necessary annotations(Time of X-ray, degree of elevation, AP or PA, exposure factors/SID).
• Avoid placing annotations over important anatomy.

Follow-up

• Understand and address urgent readings on mobile CXR.
• Document and report urgent findings to the referring clinician or radiologist.

Summary

• Mobile CXR differs from standard X-ray.
• Patient position is critical.
• Teamwork with nursing and support staff is a must.
• Tube angles need to be adjusted.
• Adjust exposure factors.

This quiz explores the principles and technical considerations of mobile radiography and X-ray machines. It covers the use of mobile X-ray units in various healthcare settings, their operational specifications, and advancements in technology. Test your knowledge of the vital role that mobile imaging plays in patient care.