Common Positioning Errors

Avoiding Mistakes in Radiography: A Deep Dive into Common Positioning Errors

Radiographic positioning plays a vital role in obtaining accurate diagnostic images. Even minor errors in patient positioning can significantly impact image quality, interpretation, and ultimately patient care. Let’s take a deeper look at common positioning errors—what causes them, what happens in the image, and how to prevent them.

1. Rotation Errors

What Happens?
When the patient’s body or the region of interest is rotated off-axis, it leads to asymmetrical appearance of anatomical structures. For example:

  • In a PA chest X-ray, rotation causes the medial ends of the clavicles to appear unequally spaced from the spine.
  • In spinal X-rays, vertebral bodies may appear wedge-shaped or the spinous processes may shift laterally.
  • In pelvis X-rays, the obturator foramina appear asymmetrical—one may look narrowed or closed while the other appears wide.

Consequences:

  • Can mimic or hide pathology (e.g., scoliosis, fractures)
  • Leads to repeat exposures
  • Misinterpretation by radiologists

How to Fix It:

  • Check the midsagittal plane is aligned and perpendicular or parallel to the image receptor as needed.
  • Use positioning sponges, alignment lights, or grid markers.
  • Ask the patient to stay still and hold their position once aligned.

2. Poor Centering of the Central Ray (CR)

What Happens?
Improper CR placement results in cut-off anatomy, where the region of interest is partially or completely missed. Examples:

  • A lateral cervical spine X-ray may exclude C7-T1, a crucial junction.
  • In abdominal films, the diaphragm or bladder might be cropped out if the CR is placed too high or low.

Consequences:

  • Missing pathology or areas of clinical concern
  • Repeat imaging and unnecessary radiation exposure
  • Delayed diagnosis or incomplete clinical data

How to Fix It:

  • Know the anatomical landmarks and the area of clinical concern.
  • Use a CR checklist or “finger-width” method for palpation.
  • Reassess after patient movement or table adjustments.

3. Incorrect Tube Angle

What Happens?
Improper angulation causes foreshortening, elongation, or joint space distortion:

  • In clavicle X-rays, insufficient cephalad angulation may obscure the midshaft under the ribs.
  • In the AP axial cervical spine, incorrect angle may blur intervertebral disk spaces.
  • In knees, a wrong angle can make the joint appear closed or malformed.

Consequences:

  • Misjudgment of bone length or alignment
  • Inability to assess joint spaces or fractures
  • Unnecessary follow-up imaging

How to Fix It:

  • Understand required standard tube angles for each projection.
  • Adjust based on patient’s body habitus (e.g., more cephalad angle for large thighs in knee X-rays).
  • Always double-check tube head and collimator settings.

4. Inadequate Inspiration or Expiration

What Happens?
The image fails to capture the full lung field or organ expansion:

  • In chest radiography, taking the image during shallow breathing results in crowded lung fields, elevated diaphragm, and underexpanded lungs.
  • In abdominal X-rays, failing to capture expiration may cause overlapping of bowel loops, hiding pathology like free air.

Consequences:

  • Inaccurate lung assessment (e.g., hiding pneumothorax or effusion)
  • Diaphragm obscures lung bases or liver border
  • Diagnostic value of the image is reduced

How to Fix It:

  • Clearly instruct patients: “Take a deep breath in and hold it.”
  • Use visual cues or practice breaths for uncooperative patients.
  • For abdomen, shoot during quiet expiration unless otherwise indicated.

5. Overlapping of Structures

What Happens?
Multiple anatomical parts project over one another, obscuring critical features:

  • In a hand X-ray, fingers may overlap if not spread properly.
  • In pelvic radiographs, femoral heads may overlap the acetabulum.
  • In lateral skull views, improper head tilt causes mandibular rami to superimpose over cervical spine.

Consequences:

  • Hides fractures, dislocations, or pathology
  • Makes anatomical evaluation difficult or impossible
  • Radiologist may request repeat views or CT scan unnecessarily

How to Fix It:

  • Position each body part separately as required (e.g., fan lateral hand).
  • Use oblique views or angulated beams to separate overlapping bones.
  • Communicate with the patient to hold specific limb or digit positions.

6. Motion Blur

What Happens?
Any movement during exposure—either from the patient or the X-ray tube—results in a blurred image, lacking definition:

  • Spinal films may show blurred vertebral outlines.
  • In pediatric imaging, motion can render the image useless.
  • In portable X-rays, poor stabilization or long exposure times increase motion risk.

Consequences:

  • Loss of diagnostic detail
  • Mimics soft tissue abnormalities or pathology
  • Requires repeat exposures, especially dangerous in vulnerable populations

How to Fix It:

  • Use short exposure times, especially for mobile or pediatric patients.
  • Immobilize using positioning aids or parental assistance (with shielding).
  • Reassure the patient and explain the importance of staying still.

7. Incorrect Collimation

What Happens?

  • Over-collimation includes unnecessary anatomy, reducing contrast and increasing radiation dose.
  • Under-collimation excludes part of the anatomy of interest, risking diagnostic loss.

Examples:

  • Including both shoulders in an AP clavicle view leads to scatter and poor detail.
  • Cropping out part of the lung field in a chest X-ray may miss a lesion.

Consequences:

  • Legal and safety concerns (due to excessive radiation)
  • Poor contrast resolution
  • Rejection of the image in audits or accreditation reviews

How to Fix It:

  • Know the area of interest and collimate just enough to cover it.
  • Adjust collimation borders after positioning but before exposure.
  • Use light beam diaphragm or digital collimation for review.

8. Marker Errors

What Happens?
Markers (e.g., "L" or "R") are:

  • Missing
  • Placed on the wrong side
  • Positioned inside anatomy or overlapping key features

Consequences:

  • Legal implications in mislabeling body sides
  • Diagnostic errors in lateralization (e.g., treating left lung for a right-lung issue)
  • Surgical misplanning

How to Fix It:

  • Always use lead anatomical markers during setup.
  • Place them outside anatomy but within the collimated area.
  • Never rely solely on digital post-processing labels.

Final Thoughts: Quality Starts with Positioning

Every radiograph tells a story—but only if it’s captured correctly. Positioning errors not only compromise image quality but can also lead to clinical misjudgment, increased patient dose, and avoidable repeats.

Prevention is simple:

  • Follow positioning protocols
  • Communicate effectively with the patient
  • Double-check your centering, angles, and markers before pressing the button

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