Infographics / Digital Radiography

Anti-Scatter Grid Geometry

Cross-section of an anti-scatter grid. Primary rays pass straight through the radiolucent interspaces to the image receptor, while obliquely travelling scattered rays strike the thin lead strips and are absorbed. An inset defines grid ratio r as strip height h divided by interspace width D, with construction facts (0.05 to 0.07 mm lead strips, radiolucent spacer not air, 40 to 60 lines per cm, typical ratio 6 to 12 to 1). A note summarises the contrast gain versus dose (Bucky factor) trade-off and moving versus stationary grids.

Anti-scatter grid: primary transmitted, oblique scatter absorbed Cross-section of an anti-scatter grid. Primary rays pass straight through the radiolucent interspaces to the image receptor, while obliquely travelling scattered rays strike the thin lead strips and are absorbed. An inset defines grid ratio r as strip height h divided by interspace width D, with construction facts (0.05 to 0.07 mm lead strips, radiolucent spacer not air, 40 to 60 lines per cm, typical ratio 6 to 12 to 1). A note summarises the contrast gain versus dose (Bucky factor) trade-off and moving versus stationary grids. primary beam patient grid strips image receptor primary beam transmitted scattered rays absorbed by lead strips grid geometry h D lead strip radiolucent spacer grid ratio r = h / D construction • lead strips 0.05–0.07 mm thick • interspaces: radiolucent spacer, not air • line density ≈ 40–60 lines / cm • typical grid ratio 6:1 – 12:1 effect on image and dose Higher grid ratio → more scatter removed → higher contrast (improvement factor ≈ 2–4). But more primary is absorbed, so mAs / dose rise (Bucky factor) — grids are often avoided in children. Moving (Potter–Bucky) grid blurs the strips; stationary grids risk grid-line / moiré artefact.
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