Understand 3D Image Quality Factors

Understand 3D Image Quality Factors

What is a Voxel?

If you combine the word “volumetric” and “pixel,” you get the word “voxel”.    A pixel is a two-dimension shape whereas a voxel is a three-dimensional element shaped like a cube.  Typically the smaller the voxel size the more detail is captured in the image.  Voxel determination is often a balance between the size of the area radiating, detail needed and acceptable dose to the patient to achieve the ALARA principle.

What is a voxel diagram

What is a Focal Spot?

The focal spot is the point where the electrons strike the tube’s anodes and result in the x-ray beam being emitted. The size of the focal spot has a direct influence on the resolution of the image.  The smaller the focal spot, the better the image quality. A small focal spot is generally used at relatively lower power settings (KV & MA) resulting in a lower dose to the patient.

What is a focal spot diagram

Rotation – 180° vs. 360°

Note the increased streak artifacts in the half-scan images. Artifacts appeared as streaks radiating from the titanium rods in the phantom due to photon starvation. The streaking is more pronounced in the half-scan 180° images. The half-scan 180° images exhibit an oblong artifact, in contrast to the full 360° images, where the rods appeared as continuous round circles.

Image rotation diagram