How-To: Test if a Bright Point is “Real” (not artefact)

Goal: decide if a compact bright point on CT is a true object (e.g., fragment) or a single-slice artefact using the Evidence Viewer.

Step-by-step

  1. Open the slice in the Evidence Viewer with metadata enabled:
    /evidence-map/view.php?series=SE000013&i=45&img=/evidence-map/docs/images/_thumbs/SE000013_IM000045.thumb.png
  2. Hover the bright point with your mouse and read the Probe line (bottom of metadata panel). Note:
    Pixel: x,y
    Patient coords: L,P,S in mm
    Slice position: from Image Position (Patient) → S
  3. Navigate to adjacent instances (±2–3 slices) of the same series and repeat the hover:
    • Real object: similar L,P with small changes across S (appears on ≥2 slices)
    • Artefact: present on 1 slice, absent on neighbours or rides along a streak from dense bone/teeth
  4. Left–Right sanity: check the line that reads “Display sanity: row(+x) → Left/Right”. If it disagrees with overlay letters, trust the numeric L coordinate (Left = negative L in DICOM LPS).
  5. Record good candidates: copy series, instance, x,y, L,P,S into your notes and label the category (e.g., “foreign body candidate”).
T1 focus: after you identify a T1 midline slice, set the gallery filter to a narrow S range (≈ T1 ± 12 mm for 1 mm slices). Examine at L ≈ −100 mm if you’re testing for a fragment ~10 cm to the left of midline (Left is negative).
Reminder: This workflow flags objects of interest for your GP/radiologist. It does not diagnose.

Shortcuts

Files involved: partials/meta_panel.php, js/imp_probe.js, docs/data/_indexes/

Next (optional)

  1. Mark points button to save picks into docs/data/_annotations/<series>.json
  2. Fit trajectory (server): upload 3–6 points → returns a best-fit 3D line to overlay
  3. Region presets (e.g., “T1 focus”): auto-fills gallery S-range and viewer options