Infographics / Fluoroscopy

DSA mask subtraction, log processing and post-processing

Three aligned frames. The pre-contrast mask shows only bone and soft tissue. The live frame adds contrast-filled vessels over the same bone. The live frame minus the mask leaves a subtracted image of vessels only, the stationary bone and soft tissue having cancelled. A lower panel shows that patient motion between frames leaves residual bone edges, the misregistration artefact, corrected by mask pixel shift.

Digital subtraction angiography: mask, live and subtracted frames Three aligned frames. The pre-contrast mask shows only bone and soft tissue. The live frame adds contrast-filled vessels over the same bone. The live frame minus the mask leaves a subtracted image of vessels only, the stationary bone and soft tissue having cancelled. A lower panel shows that patient motion between frames leaves residual bone edges, the misregistration artefact, corrected by mask pixel shift. Digital subtraction angiography — building a vessel-only image mask (pre-contrast) live (contrast-filled) subtraction (vessels only) subtracted image = live − mask (signals log-transformed): stationary bone and soft tissue cancel, iodine-filled vessels remain Patient motion between frames causes misregistration artefact subtraction after patient motion Stationary bone and soft tissue no longer cancel, so residual high-contrast edges (rust) remain — the misregistration artefact, worst at bone–soft-tissue boundaries. Mask pixel shift re-aligns the mask (small in-plane motion only).
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