Infographics / Digital Radiography

Digital Image Matrix, Pixels & Sampling

Two square grids cover the same field of view. A coarse 4 by 4 matrix has large pixels; a finer 8 by 8 matrix has smaller pixels, giving higher spatial resolution but more data. A formula states pixel size equals field of view divided by matrix size, with the Nyquist limiting resolution equal to one over twice the pixel pitch. A row of discrete swatches shows that bit depth sets the number of grey levels, 2 to the power n.

Digital image sampling: pixel size equals field of view divided by matrix size Two square grids cover the same field of view. A coarse 4 by 4 matrix has large pixels; a finer 8 by 8 matrix has smaller pixels, giving higher spatial resolution but more data. A formula states pixel size equals field of view divided by matrix size, with the Nyquist limiting resolution equal to one over twice the pixel pitch. A row of discrete swatches shows that bit depth sets the number of grey levels, 2 to the power n. A digital image is a matrix of pixels — same field of view, sampled two ways 4 × 4 matrix 8 × 8 matrix finer sampling field of view field of view (same) pixel size = FOV ÷ 4 — larger pixels pixel size = FOV ÷ 8 — smaller pixels Larger matrix (or smaller FOV) → smaller pixels → higher spatial resolution, but more data. pixel size = field of view ÷ matrix size limiting resolution (Nyquist): f_N = 1 ÷ (2 × pixel pitch) Bit depth sets the number of grey levels: n bits → 2ⁿ discrete values each pixel stores one value → a grey level (e.g. 12-bit = 4096 levels)
Practise Digital RadiographyDownload SVG

More in Digital Radiography

Practice the Physics paper

FRCRX is a Part 1 Physics question bank: true/false items with explanations, timed mocks and topic analytics.

Start question practiceSee plans