According to the line focus principle in radiology, how does the effective focal spot size compare to the actual focal spot size?

The effective focal spot size is indeed smaller than the actual focal spot size due to the line focus principle. This principle is based on the angle at which the x-ray beam hits the anode of the x-ray tube. When the anode is angled, the actual focal spot (where the x-rays are produced) is larger, but the geometry of the system causes the effective focal spot to be smaller when projected onto the image receptor.

This smaller effective focal spot improves image sharpness and resolution, which is particularly important in mammography where fine details of breast tissue need to be visualized clearly. The distinction between the actual and effective focal spots is crucial in optimizing image quality while managing heat production and source life in the x-ray tube.

Through the use of angling the target, radiographers can achieve better image quality while still allowing for efficient use of the x-ray tube. Thus, in practice, understanding and applying the concept of effective versus actual focal spot size is critical for obtaining high-resolution diagnostic images.