Three Dimensional Basics: Pixels and Voxels

Most of us are already familiar with pixels; after all, one of the first questions that we may ask when picking out a digital camera or computer monitor is how many pixels it has.  When it comes to digital radiography, the pixels still apply, but are limited to two dimensional images, such as intraoral and extraoral radiographs. In three-dimensional radiography, such as CBCT imaging, the complimentary unit is referred to as voxel.

A combination of the words “volumetric” and “pixel,” voxels are the measure of the dimensions of a perceptible cube in a 3D image. Unlike pixels, which have length and breadth, voxels have the third dimension, which is depth. This allows us to view volumetric patient anatomy, thus minimizing artifacts such as superimposition of anatomical structures.

pixels vs voxels

This volumetric data is arranged to represent specific anatomical regions using complicated mathematical algorithms as a process of reconstruction of the scan. This also allows doctors to view multiplanar views: axial, coronal and sagittal. Further reconstruction of panoramic and cross sectional views can also be achieved from this data.

Voxels and Resolution

The three-dimensional resolution of an image is based on the dimensions of the voxel, which is equal in all three dimensions, and, hence referred to as isotropic voxels. Measured in millimeters, voxel sizes used in CBCT imaging can range from 76 microns (highest in the industry as of now) and above. One important consideration to make is the resolution of images while considering a scan on patient, as the smaller the voxel size, higher the resolution. For appropriately diagnostic images to be achieved, this resolution should be decided depending on the task, factoring in diagnostic information from the scan and responsible consideration of patient exposure.

If you are currently looking for a CBCT unit, are voxels playing a role in your decision process? I look forward to interacting in the comment section below.

Shailesh Kottal, D.D.S. Contributor