CT Scan Reconstruction Simulator

CT Gantry

Gantry speed 60°/s

Tissue contrast (tumor density) 0.55

Gantry angle

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Projections

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Reconstruction fidelity

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How it works

An X-ray source and a detector array sit on opposite sides of a rotating gantry. At each angle θ the beam passes straight through the slice; denser tissue absorbs more photons, so each detector reads a line integral of attenuation along its ray. Sweeping θ from 0° to 360° produces one projection per angle — the scanner never "sees" the cross-section directly, only these projections.

p(θ, s) = ∫ μ(x,y) dl        along ray at angle θ, offset s
f(x,y) ≈ ∫₀^π p(θ, x·cosθ + y·sinθ) dθ   (back-projection)

Smearing every projection back along its ray and summing (back-projection) reconstructs the slice, but plain summation over-weights low spatial frequencies and produces a soft, star-shaped blur. Filtered back-projection first convolves each projection with a ramp (Ram-Lak) filter that boosts high frequencies before smearing, sharpening edges — the standard reconstruction used in real CT scanners.

Gantry speed — how fast the source/detector pair rotates; faster sweeps finish sooner but each frame still contributes one exact projection, so fidelity depends on total angles covered, not speed itself.
Tissue contrast — the attenuation coefficient of the embedded lesion relative to the surrounding soft tissue; low contrast is the hardest case for any reconstruction to resolve.
Filtered back-projection — toggle the ramp filter on the projections before smearing; compare the sharp edges against the unfiltered blur.
Reconstruction fidelity — correlation between the live reconstruction and the true phantom, updated every frame as more angles accumulate.

X-ray source Detector array Attenuation ray

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