What should the FFD be set to for a Lateral Foot X-ray?

For a Lateral Foot X-ray, the recommended focal-film distance (FFD), also known as the source-to-image distance (SID), is typically set to 40 inches. This distance is standard as it helps in producing a high-quality image with adequate detail while minimizing distortion. Setting the FFD to 40 inches optimizes the balance between image sharpness and the size of the radiographic beam, thus facilitating clear visualization of the foot's anatomy.

This choice is particularly relevant because a shorter distance, like 40 inches, is generally preferable for extremities such as the foot, where increased detail is essential to accurately assess bone structures and soft tissues. Longer distances can lead to an increased magnification effect and potential blurring, reducing the diagnostic quality of the image.