American Society of Radiologic Technologist (ASRT) Practice Exam

In the context of x-ray production, what is the primary purpose of the filament?

1. To reduce the exposure time

2. To provide a source of electrons

3. To filter the x-rays

4. To cool the anode

The correct answer is: To provide a source of electrons

The primary purpose of the filament in the context of x-ray production is to provide a source of electrons. When the filament is heated, typically by passing an electric current through it, it undergoes a process called thermionic emission. This process allows the filament to emit electrons, which are essential for generating x-rays. These emitted electrons are then accelerated towards the anode, where they collide with the target material, resulting in the production of x-rays. The efficiency and effectiveness of x-ray production depend heavily on the number of electrons emitted by the filament. Therefore, its role as a source of electrons is critical to the x-ray generation process. In contrast, the other options pertain to different aspects of x-ray machine operations but do not accurately represent the filament's primary function. For instance, while reducing exposure time is important for patient safety, it is influenced by other factors such as mA (milliamperage) and kVp (kilovolt peak). Filtering x-rays is carried out to remove low-energy, non-penetrating radiation, which is done using specific materials placed in the path of the x-ray beam, rather than by the filament. Cooling the anode is also vital to prevent overheating of the target material during the