ARRT Fluoroscopy Exam 2026 – 400 Free Practice Questions to Pass the Exam

The highest mA possible for a small focal spot is 150 mA. This limitation is primarily due to the heat generation associated with the small focal spot size. A small focal spot is designed to provide high spatial resolution, which is essential for imaging detail, particularly in fluoroscopy procedures. However, because of its size, it can only dissipate heat effectively up to a certain point.

Exceeding 150 mA can lead to an increase in the thermal load on the anode, which can cause damage to the x-ray tube, such as melting or pitting of the target area. This is why, although higher mA settings are usually available for larger focal spots, small focal spots are restricted to a maximum of 150 mA to maintain both image quality and equipment safety. Understanding this limitation is crucial for radiologic technologists when selecting appropriate parameters for imaging to balance patient safety, image quality, and equipment longevity.