Radiographic Artifacts: Recognition and Source Identification

What Is a Radiographic Artifact?

A radiographic artifact is any density or structure that appears on an image but does not correspond to a real anatomical structure in the patient. Artifacts can mimic disease, obscure pathology, or simply reduce diagnostic quality. Because an unrecognized artifact can lead to misdiagnosis or a repeated exposure, identifying and eliminating artifacts is a core radiographer skill and a direct patient-safety responsibility.

Artifacts fall into four major source categories: patient-related, equipment-related, detector-related, and processing-related. Learning to classify an artifact by its source tells you both why it occurred and how to prevent it.

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Patient-Related Artifacts

Patient-related artifacts originate with the patient's body or actions before or during the exposure.

• Motion artifact appears as blurring or streaking of anatomical edges. It results from voluntary or involuntary patient movement during the exposure. Short exposure times and clear patient instructions reduce motion.
• Jewelry and external objects (earrings, necklaces, snaps, zippers, hearing aids, hair braids with metallic clips) appear as sharp, high-density opacities superimposed on anatomy. Always ask patients to remove removable metallic objects and document anything that cannot be removed.
• Contrast media residue from a prior exam (e.g., retained barium in the colon) can appear as dense material overlying abdominal anatomy on a subsequent image.
• Positioning sponges or immobilization devices left in the field appear as low-density or mottled areas.

Safety point: Before every exposure, perform a thorough patient assessment and ask about implants, piercings, and recent contrast studies. Never assume the patient knows what must be removed.

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Equipment-Related Artifacts

Equipment artifacts arise from the X-ray tube, generator, Bucky, or grid.

• Grid lines appear as fine parallel stripes across the image when the grid is stationary or the Bucky mechanism fails. They can obscure fine detail.
• Grid cutoff produces a symmetric or asymmetric darkening (underexposure of the periphery) caused by misaligning the tube to the grid's focus distance or angle. Off-centering, off-level, or off-focus positioning all cause cutoff.
• Double exposure results in two sets of anatomy superimposed on one image, typically from accidentally re-exposing a cassette or detector that was not cleared.
• Collimation artifacts from secondary radiation at the beam edge may appear as lighter borders if the collimator leaves are damaged or misaligned.
• Tube-side artifacts: a cracked or damaged anode can produce irregular density patterns.

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Detector-Related Artifacts

In computed radiography (CR) and digital radiography (DR), the image receptor itself can be the source.

• Phosphor plate scratches in CR appear as thin, sharply defined lines running in the direction the plate was fed through the reader.
• Dead pixels or dead detector elements in DR panels appear as bright or dark dots, clusters, or lines that remain in exactly the same position on every image from that detector.
• Plate fogging occurs when a CR cassette is exposed to background radiation (e.g., stored near the X-ray room) before use. The image shows overall increased density with reduced contrast.
• Ghosting (residual image) in CR happens when a plate is not fully erased between uses; a faint prior image appears superimposed on the new image.
• Lead marker artifacts: placing a lead marker on the wrong side of the cassette (between the plate and the table) creates a reversed or distorted marker appearance.
• Pressure artifact in CR results from mechanical stress on the phosphor plate, showing as localized density changes.

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Processing-Related Artifacts

In facilities that still use film-screen or wet-processor systems, processing artifacts occur.

• Guide-shoe marks are small, regular crescent-shaped marks at consistent intervals caused by worn guide shoes in the film processor roller system.
• Pick-off artifacts appear as clear or light spots from emulsion torn away by sticky rollers.
• Chemical fog is uniform or non-uniform increased density from contaminated developer or improper replenishment.
• Pi lines are thin, evenly spaced lines across the film at intervals equal to the circumference of a processor roller, caused by a dirty or damaged roller.
• Static artifacts appear as tree-like or branching black marks from static electricity discharge during film handling in low-humidity environments.

In digital environments, PACS display settings (incorrect window/level, monitor artifacts) can create pseudo-artifacts. Always evaluate images on a calibrated diagnostic monitor or PACS workstation.

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Distinguishing Artifacts from Pathology

The key questions to ask:

1. Does the finding follow anatomical boundaries? True pathology usually does. A perfectly straight line crossing bone and soft tissue is almost certainly an artifact.

2. Does the finding repeat position-to-position? A dead detector element appears in the same pixel location on every image from that detector.

3. Is the finding outside the patient's body outline? Artifacts from external objects may project partially outside the collimated field.

4. Can the finding be explained by a known artifact mechanism? If yes, check the source and repeat if clinically necessary.

Safety point: When in doubt, consult the supervising radiologist or radiographer before repeating. Do not repeat exposures on your own authority without following your facility's repeat/reject protocol.

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Key Takeaway

Artifact recognition protects patients from unnecessary repeat exposures, prevents misdiagnosis, and ensures image quality. Classify first (source category), then identify the mechanism, then correct the cause. Document all repeated exposures in the facility's reject analysis log.