16.3 Artifacts, Markers & Annotation
Key Takeaways
- RTR.6.5 requires accurate laterality markers and annotations; physical radiopaque markers remain best practice, and digital labels can be wrong, flipped, or copied forward.
- Never release an image when side identification is uncertain—wrong-side documentation is a critical safety event.
- RTR.6.6 artifacts include motion, grid cutoff, clothing/foreign objects, CR/DR processing defects, double exposure, scatter fog, moiré, and detector hardware faults.
- Correct the root cause (geometry, collimation, gowning, detector hygiene, exposure time) rather than only windowing over the problem.
- If an artifact obscures the region of interest or laterality is compromised, reject/correct under ALARA and escalate equipment failures through QC/service pathways.
16.3 Artifacts, Markers & Annotation
Quick Answer: Correct laterality markers and accurate annotation are patient-safety requirements (RTR.6.5). Artifacts (RTR.6.6)—motion, grid cutoff, foreign objects/clothing, CR/DR processing problems, double exposure, scatter fog—must be recognized, explained, and corrected. Digital tools make annotation errors easier, not rarer. If an artifact obscures the clinical region or laterality is uncertain, do not release until fixed or properly escalated.
Image analysis is incomplete if you only judge mAs and rotation. Legal identification and artifactual densities decide whether an image is usable and whether the wrong side of a patient could be treated.
Markers & Annotation Accuracy (RTR.6.5)
Physical lead markers remain the gold standard habit
Best practice in Canadian departments still emphasizes radiopaque side markers placed in the primary beam (outside essential anatomy when possible) at exposure:
| Rule | Why it matters |
|---|---|
| Correct side (R / L) | Wrong-side surgery and treatment risk |
| Correct patient contact side | Marker on the side being imaged, not the opposite cassette edge by habit alone |
| Not over critical anatomy | Marker over fracture line or lung apex can force a repeat |
| Visible after collimation | Tight collimation that clips the marker creates incomplete legal image |
| Supplemental markers as protocol | Erect/supine, weight-bearing, inspiration/expiration, minutes post-contrast, mobile |
Digital annotation risks
Electronic annotation is useful for add-on labels (portable, upright, post-void) but creates unique failure modes:
- Post-exposure side labels applied to the wrong side after the fact
- Copy-forward annotations from a prior study on the wrong patient
- Image flip/rotate after annotation so the “R” no longer matches anatomy
- Missing annotation on stitched or reformatted secondaries
- Over-reliance on default laterality from the worklist without visual confirmation
Exam principle: A digital “R” is not automatically trustworthy if the physical marker is absent and anatomy is ambiguous (e.g., AP supine abdomen, unilateral extremity without landmarks). When laterality is uncertain, investigate before release.
Annotation content that supports care
- Projection (PA/AP/lateral/oblique) when not obvious
- Patient position (erect, semi-erect, supine, decubitus with side down)
- Behavioral/technique notes required by protocol (inspiration/expiration)
- Time-sensitive series labels (pre/post void, post-reduction)
Avoid cluttering the image with redundant text that covers pathology.
Artifacts (RTR.6.6): Recognition Table & Corrective Response
| Artifact | Appearance / cues | Common causes | Corrective response |
|---|---|---|---|
| Motion | Blur, ghosting of edges, repeated contours | Long exposure, patient pain/tremor, kids, respiration, equipment vibration | Shorten exposure time (↑ mA), immobilize, coach breath-hold, supports; pediatric distraction; check tube/stand locks |
| Grid cutoff (lateral decentering) | Overall or unilateral density loss; underexposed look across field | CR angled across lead strips; grid upside-down; off-level; wrong focal range SID | Re-center, match SID to grid focal distance, verify grid orientation, use appropriate ratio |
| Grid cutoff (upside-down focused grid) | Severe density loss laterally both sides or characteristic pattern | Focused grid inverted | Flip grid to correct orientation; repeat |
| Grid lines | Fine parallel lines | Stationary grid visible; wrong grid use; moving grid failure | Use moving Bucky when indicated; check mechanism; accept only if lines do not hide ROI and protocol allows |
| Clothing / buttons / zippers | Opaque shapes, fabrics, sparkles | Incomplete gowning | Remove radiopaque objects from FOV; re-gown; explain to patient |
| Jewelry / hair pins / ECG leads | High-density discrete objects | Not removed/relocated | Remove or reposition leads outside ROI when safe |
| Foreign objects on IR/detector | Dust, cracks, scratches, glue | Dirty plate, damaged detector | Clean per manufacturer; take QC flat field; remove from service if hardware defect |
| Double exposure | Superimposed anatomies, dark/overexposed combined image | Cassette reused (CR); wrong detector assignment; procedural error | Reject; QC process; re-image once with clear detector workflow |
| Scatter fog | Reduced contrast, gray veil | Poor collimation, no grid when needed, high kVp large field, open back of cassette (film era concepts still tested), patient scatter | Collimate, grid when indicated, optimize kVp, control field size |
| CR plate reader artifacts | Lines, skip, plate erasure incompleteness | Reader rollers, incomplete erase, light leak | Reprocess/erase plate; service if persistent; do not keep sending bad plates |
| DR processing / flat-field issues | Coring, dropout, structured noise, dead pixels clusters | Calibration overdue, dropped detector, software LUT errors | Recalibrate; service; alternate detector; do not “fix” hardware failure with edge enhance |
| Moire / aliasing | Wavy interference pattern | Grid frequency vs sampling; electronic interference | Adjust grid/processing; change orientation if protocol allows; service evaluation |
| Saturation / clipping | Pure white/black loss of data in regions | Extreme overexposure or processing | Cannot recover lost data; repeat with corrected technique |
| Quantum mottle | Grainy noise | Underexposure | Repeat with increased exposure as needed—not just windowing |
| Pajama folds / skin folds | Linear densities | Soft tissue | Reposition, smooth skin, note portable limitations |
| Cast / splint / backboard | Uniform or structured opacity | Trauma immobilization | Increase exposure appropriately; annotate; do not remove unstable immobilization without clinical order |
Motion Artifact — Special Emphasis
Motion is still one of the most common avoidable repeats.
Types:
- Voluntary — breathing, movement (coaching, supports, clear instructions)
- Involuntary — tremor, spasm, cardiac (minimize time, stabilize)
- Equipment — unlocked tube arm, moving table, grid mechanism
Pediatric tip: immobilization devices and caregiver assistance per policy beat multiple failed “please hold still” exposures. ALARA prefers one good immobilized image over three blurred ones.
Grid Cutoff Patterns Worth Memorizing
| Error | Typical density pattern |
|---|---|
| Off-level grid | Overall decrease in exposure across image |
| Lateral decentering | More density loss toward one side |
| Upside-down focused grid | Severe bilateral lateral underexposure |
| Wrong SID outside focal range | Density loss toward periphery |
Do not compensate solely by raising mAs without fixing geometry—you increase dose and may still fail.
Foreign Objects & Clothing: Workflow Discipline
Build a pre-exposure checklist into muscle memory:
- Gown / remove artifacts from region
- Empty pockets
- Move oxygen tubing, NG slack, monitor cables when safe
- Explain why metal must move (“it can hide a fracture”)
- Document non-removable objects (jewelry that cannot come off, permanent medical devices)
Piercings and religious items: use culturally safe communication; if item cannot be removed, annotate and collimate/angle when possible without losing required anatomy.
Double Exposure & Workflow Mix-ups
Modern DR reduces classic double exposure but it still appears in stems and in CR-heavy sites:
- Two body parts on one image
- “Ghost” of previous anatomy
- Unexpected darkness
Response: reject image, secure correct detector/plate, re-identify patient, single controlled re-exposure, report system issues if persistent.
Scatter Fog vs Pathology Veil
A gray, low-contrast image may be:
- Scatter fog (collimation/grid problem)
- Correct technique on a large soft-tissue patient
- True pathologic veil (edema, effusion layering)
Fix what you control first (collimation, grid, kVp, field size), reassess, then consider pathology recognition (16.2).
Corrective Response Hierarchy
- Identify artifact type (do not guess randomly)
- Decide impact: Does it obscure ROI or create wrong-side risk?
- Correct cause (not only symptoms)
- Repeat or add image under ALARA if needed (16.4)
- Escalate equipment problems to service/QC
- Document when non-removable artifacts remain
CAMRT-Style Stems
Expect items such as:
- “Density loss on both lateral margins after using a focused grid—most likely?” → upside-down grid
- “Electronic L marker placed after exposure on a hand without physical marker—risk?” → wrong laterality annotation
- “Wavy pattern over lumbar spine with stationary grid—what is it?” → moiré/grid-line interference
- “Blurred trabeculae with correct EI—cause?” → motion, not mAs
Master tables above until recognition is automatic under exam timing.
A focused grid produces an image with severe loss of density on both lateral sides of the field. What is the most likely cause?
Which practice best reduces wrong-side errors in digital radiography?
Trabecular detail is blurred on a wrist image, yet the exposure indicator is within acceptable range and there is no grid cutoff. What is the most likely problem?
A CR cassette is accidentally exposed twice with different projections. What is the appropriate technologist response?