CT Numbers - Video Lesson

This lesson is about CT numbers. CT imaging really does get its own numbers. Have you ever heard of MRI numbers or sonography numbers? Of course not. Because CT imaging is awesome, and the other modalities are not as awesome. During CT image reconstruction, each pixel in the digital image is assigned its own CT number. And these CT numbers have units that are called Houndsfield units. These numbers represent the physical density of the tissues within that pixel, and there is a specific scale that's used. All physical densities and CT numbers are calibrated based on water. So water actually has a CT number that's equal to zero houndsfield units. Tissues that have a physical density greater than water will have a CT number that is greater than zero and tissues with a physical density less than water will have a CT number less than zero. So