What determines pixel size in a CT image?

The correct choice is based on the relationship between matrix size, display field of view (DFOV), and pixel size in a CT image. The matrix size refers to the number of pixels in each dimension (width and height) that compose the CT image. When the matrix size increases, the number of pixels in the image increases, thereby decreasing the pixel size for a given DFOV.

The display field of view (DFOV) is the actual area displayed in the image. If the DFOV is fixed and the matrix size increases, the pixel dimensions must decrease to accommodate the increased number of pixels over the same area. This relationship shows that pixel size is definitively influenced by the combination of the matrix size and DFOV, making this the best explanation for pixel size in a CT image.

In contrast, the other options, while related to imaging, do not accurately determine pixel size. Slice thickness influences the amount of tissue represented in each pixel but does not directly affect pixel size. Generator power impacts image quality and acquisition speed but doesn't dictate pixel dimensions. Lastly, the field of view and patient positioning are crucial for image acquisition and quality but are not the primary determinants of pixel size.