ct圖像質(zhì)量講義(存儲版)
【正文】 amples: ?prostheses ?dental fillings ?surgical clips ?Electrodes ?bone ? Metal absorbs all radiation in ray ?causes starshaped artifact ? Artifact can be reduced by software Gee David ?Increase in mean energy of polychromatic beam as it passes through patient ?Can cause broad dark bands or streaks ? cupping artifact ?Minimized using beam hardening correction algorithms CT Artifacts: Beam Hardening MARS：減除金屬和硬化偽影 Gee David CT Artifacts: Partial Volume Effect ? CT ’s based on linear attenuation coefficient for tissue voxels ? If voxel nonuniform (contains several materials), detection process will average ? Can appear as ? incorrect densities ? Streaks and bands ? Minimizing ? Use thinner slices Gee David Gee David 謝 謝！ Gee David ?描述 CT 圖像質(zhì)量的三個主要參數(shù) : 空間分辨率、密度分辨率、噪聲 ?對比度 (密度 )分辨率 : 指當(dāng)細(xì)節(jié)與背景之間具有低對比度時，將一定大小的細(xì)節(jié)從背景中辨別出來的能力。 內(nèi)插算法的 Z軸分辨率會下降 30％ Gee David Gee David CT 對比度 Gee David Components of image contrast 對比度構(gòu)成 Contrast present in a medical image is the result of a number of different steps that occur during image acquisition, processing, and display image contrast Radiograhic contrast detector contrast display contrast Elemental Composition of subject Subject mass attenuation coefficient
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