The Common Vein

Copyright 2009

Introduction

Most artifacts can be attributed by the limitations of spatial resolution, temporal resolution, noise, or reconstruction algorithms.

The manifestation is reflected as blooming, blurrring, missing data.

Spatial resolution

Partial Volume Artifact

Partial volume artifact is caused by inadequate spatial resolution as a result of voxel size that is too large, commonly seen when two structures with different density are juxtaposed, and the average of their densities is assigned to the voxels at the interface so that their difference is not accurately reflected.

Blurring and blooming are both considered partial volume artifacts, and both are made worse by motion.

Blooming artifacts are caused when high contrast objects like calcium and metal appear larger than they really are due to partial volume artifact

Temporal Resolution

Temporal Resolution is the ability to resolve structures that are moving such as the heart, but temporal resolution has improved to such an extent with MDCT that this problem has mostly been solved .  The challenge now is the movement of the coronary arteries, and most specifically by the right coronary artery at the margin of the right heart border.  The blurring of the coronary artereies is the major cause of non diagnostic coronary CTA..

Stair Step Artifact

The stair step artifact is causes by malalignment of pixels during prospective trigger acquisition or retrospective reconstruction where phase misregistratiuon occurs and two side by side images are incorrecly aligned.  This commonly occurs due to arrhythmias, breathing, or inconsistent ECG gating.

Misregistration when extreme difference in densist yy is present

Ring Artif1acts

tube malfunction

Noise artifact

Caused by low signal to noise ratio

Motion artifact

Blurring or streaking caused by movement eg respiration heart shivering coufghing

Beam hardening

Gives a cupped appearance due to more ttenuation ion the centre than on the periphery of a structure