Chest X-ray Quality
Penetration

Key points

  • Digital correction may compensate for an incorrectly penetrated X-ray
  • Always check the structures behind the heart

Penetration is the degree to which X-rays have passed through the body. Assessment of penetration is traditionally a standard part of assuring chest X-ray quality. With modern digital viewing systems, over or under penetrated images are rarely a problem. Image data can be 'windowed' to optimise visibility of anatomical structures. This is often performed by radiographers after they have acquired the image or can be performed using the windowing tool in the viewing system.

A well penetrated chest X-ray is one where the vertebrae are just visible behind the heart. Although X-rays are still occasionally over or under exposed, a discussion of penetration now best serves as a reminder to check behind the heart. The left hemidiaphragm should be visible to the edge of the spine. Loss of the hemidiaphragm contour or of the paravertebral tissue lines may be due to lung or mediastinal pathology.

Under penetration

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Under penetration

  • The left hemidiaphragm is not visible to the spine
  • Lung tissue behind the heart cannot be assessed
  • Re-windowing the image using digital software can compensate

Re-windowing (hover over image)

  • The diaphragm (long arrows) is visible to the spine.
  • The left paravertebral soft tissues are visible (short arrows) , and the right side of the spine is clear (arrowheads).
  • There is no abnormality of lung tissue behind the heart.

Page author: Salisbury NHS Foundation Trust UK (Read bio)

Last reviewed: September 2016