American Registry of Radiologic Technologists (ARRT) Practice Exam

When the object-to-film distance (OFD) increases, the image resolution decreases due to the geometric factors involved in radiographic imaging. As the distance between the object being imaged and the film plate increases, the x-ray photons diverge more before they reach the film. This divergence causes a blurring effect, leading to a loss of detail in the image.

This phenomenon is linked to the principles of image sharpness and spatial resolution in radiography. The spatial resolution is largely dependent on how closely the x-ray photons can converge on the film. An increased OFD results in a larger area on the film being exposed to the same point of the object, causing a diffusion of the x-ray signal and producing a less defined image.

In contrast, reducing the OFD allows for the x-rays to travel a shorter distance and maintain a more precise alignment with the film, thereby enhancing the resolution. Understanding this relationship is crucial for radiologic technologists aiming to optimize image quality in their work.