What does increasing slice thickness do to the image quality?

Increasing slice thickness in computed tomography affects the overall image quality by introducing changes to the clarity and sharpness of the structures being imaged. Thicker slices tend to average out information from a broader range of tissues, which can lead to a more homogenous appearance and a reduction in the detail visible in the image. This averaging effect can enhance image noise because the increased thickness includes contributions from multiple adjacent voxels, potentially blending structures that should be distinct from one another.

As a result, while the general signal-to-noise ratio may improve due to a larger volume of tissue being sampled, the actual perceived noise in the image can become more variable, leading to less clear delineation of anatomical details. Thicker slices can also mask small lesions or fine structures that would be more readily apparent in thinner slices, thereby impacting diagnostic capability.

In contrast, increasing slice thickness does not increase spatial resolution, as resolution is primarily influenced by pixel size and reconstruction algorithms, nor does it decrease partial volume effects, which tend to become more pronounced with thicker slices. Making slices thicker may not inherently affect exposure time directly, as that depends on other factors such as scan timing and parameters set by the technologist.