Week 4: Session 8 – Image Evaluation and Error Correction

Text Explanation for Session 2

1. Common Radiographic Errors

• Positioning Errors:
  One of the most frequent errors in radiography is incorrect patient positioning. This can lead to images that are not diagnostic, requiring repeat exposures. For example:

  • Rotation: In chest radiography, if the patient is rotated, the clavicles will not appear equidistant from the spine, and the image may not accurately depict the heart and lungs.

  • Oblique Positioning: This occurs when a patient is unintentionally positioned at an angle, which can obscure important anatomical structures.

• Incorrect Exposure:
  Overexposure and underexposure are common issues:

  • Overexposure: Results in a dark image where details are lost, particularly in soft tissues.

  • Underexposure: Results in a light image that lacks sufficient contrast and detail, making it difficult to assess anatomical structures.

• Artifacts:
  Artifacts are unwanted objects or distortions on the image that are not part of the anatomy. Common causes include:

  • Patient Motion: Blurring of the image due to the patient moving during the exposure.

  • Foreign Objects: Jewelry, buttons, or other metal objects can interfere with the image.

  • Double Exposure: Occurs when two images are accidentally taken on the same film or digital receptor.

2. Image Evaluation and Diagnostic Quality

• Evaluating Positioning:
  Ensure that the patient is correctly positioned to avoid rotation or obliqueness. In chest radiography, check the position of the clavicles relative to the spine and ensure the diaphragm is visible. In extremity radiography, assess whether the joint space or fracture site is adequately visualized.

• Evaluating Exposure:

  • Contrast: Contrast refers to the difference between light and dark areas of the image. For chest X-rays, the lung fields should appear darker, and the heart and bones should have enough contrast to be easily distinguished.

  • Density: The image should not be too dark (overexposed) or too light (underexposed). The exposure settings should be adjusted based on the patient’s size and the body part being imaged.

• Evaluating Artifacts:
  Check for any unwanted objects, such as metal buttons, necklaces, or motion artifacts that could obscure the image. Ensure the image is free from any motion blur or electronic interference.

3. Error Correction Strategies

• Positioning Correction:
  If positioning is incorrect, reposition the patient and retake the image. For example, if the patient is rotated in a chest X-ray, ensure that they are standing straight with their shoulders equally distant from the image receptor.

• Adjusting Exposure Settings:
  If the image is overexposed (too dark), reduce the mAs or kVp for the next exposure. If the image is underexposed (too light), increase the mAs or kVp. Always refer to the technique chart to determine the appropriate settings.

• Removing Artifacts:
  Before taking the image, ensure the patient has removed all metal objects, such as jewelry or clothing with metal buttons. Make sure the patient is still during the exposure to avoid motion artifacts.