Which imaging technique would yield the least spatial resolution?

The choice of a 256x256 matrix size would yield the least spatial resolution among the given options. Spatial resolution in imaging is determined by the matrix size: a larger matrix size usually indicates a higher resolution image.

When analyzing spatial resolution, the matrix size directly affects the number of pixels that can represent the area being imaged. In a 256x256 matrix, there are fewer pixels available to depict the details of the image compared to larger matrices, such as 512x512, 1024x1024, or 2048x2048. Each increase in matrix size allows for finer detail representation because the same area is divided into a greater number of smaller pixels.

Therefore, while larger matrices provide more pixels for reconstructing images and can show finer details, the 256x256 matrix size is limited in its ability to capture that detail, leading to lower spatial resolution. This is why the selection of 256x256 is correctly identified as yielding the least spatial resolution.