What is the number of bits per pixel required in a CT image to represent the full range of CT numbers?

In computed tomography (CT), the range of CT numbers, also known as Hounsfield units, typically spans from -1000 (representing air) to +3000 (representing dense bone). This wide range necessitates a sufficient number of bits per pixel to accurately represent the varying densities of tissues in medical imaging.

To calculate the number of bits needed, you can use the formula that relates the number of levels of gray (or distinct values) that can be represented by a certain number of bits. The number of distinct values is given by 2 raised to the power of the number of bits. For example, 8 bits yields 256 levels (2^8), while 10 bits yields 1024 levels (2^10), and so forth.

For a CT image that needs to represent values from -1000 to +3000, the total range is 4001 distinct values (3000 - (-1000) + 1). To find the minimum number of bits required to encompass this range, you calculate 2^n ≥ 4001.

• 2^12 equals 4096, which comfortably covers this range.

• On the other hand, 2^11 equals 2048,