Which of the following factors would produce a radiographic image with the highest spatial resolution?

Increasing the matrix size enhances spatial resolution in a radiographic image because a larger matrix means that there are more pixels available to represent the image. Each pixel captures information from a smaller area of the anatomy being imaged, allowing for finer detail and greater clarity in the representation of small structures. This results in a sharper and more well-defined image, making it easier to distinguish between closely situated tissues or structures.

In contrast, while increased exposure time can improve image quality by reducing noise and enhancing overall exposure, it does not inherently increase spatial resolution. Decreasing the source-to-image distance may impact the geometric sharpness and may introduce more magnification effects rather than improving resolution itself. Increasing grid ratio can help reduce scatter and improve contrast, but does not specifically enhance spatial resolution; it is primarily a factor in contrast improvement rather than detail resolution.