Radiologic Technologist Practice Exam

Which factor will NOT affect the effective focal spot size?

1. Filament size

2. Anode angle

3. Target material

4. Actual focal spot size

The correct answer is: Target material

The effective focal spot size is influenced by several factors in radiologic imaging, but the target material is not one of them. The effective focal spot is determined by the geometry of the x-ray tube, particularly the filament size and the anode angle. A larger filament size will create a larger actual focal spot, which in turn can affect the effective focal spot when combined with the angle of the anode. The anode angle itself is crucial because a steeper angle leads to a smaller effective focal spot, while a shallower angle enlarges it. In contrast, the target material, while it influences the quality and quantity of x-rays produced, does not affect the effective focal spot size directly. It is essentially the materials used in the target that determine the efficiency of x-ray production through atomic structures and interactions, but not the size of the focal spot that is projected onto the imaging detector. Thus, the correct choice indicates a factor that is irrelevant to changes in effective focal spot size.